WO2010059107A1 - Pneumatic actuator, and system and method for controlling the same - Google Patents

Pneumatic actuator, and system and method for controlling the same Download PDF

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Publication number
WO2010059107A1
WO2010059107A1 PCT/SE2009/051278 SE2009051278W WO2010059107A1 WO 2010059107 A1 WO2010059107 A1 WO 2010059107A1 SE 2009051278 W SE2009051278 W SE 2009051278W WO 2010059107 A1 WO2010059107 A1 WO 2010059107A1
Authority
WO
WIPO (PCT)
Prior art keywords
pulses
piston
pneumatic actuator
gaseous medium
space
Prior art date
Application number
PCT/SE2009/051278
Other languages
French (fr)
Inventor
Ortwin SCHLÜTER
Johan Nordkvist
Original Assignee
Scania Cv Ab (Publ)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scania Cv Ab (Publ) filed Critical Scania Cv Ab (Publ)
Priority to CN2009801479824A priority Critical patent/CN102227565A/en
Priority to EP09827820.3A priority patent/EP2359012A4/en
Priority to BRPI0916016A priority patent/BRPI0916016A2/en
Priority to RU2011124921/06A priority patent/RU2473824C1/en
Publication of WO2010059107A1 publication Critical patent/WO2010059107A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/06—Servomotor systems without provision for follow-up action; Circuits therefor involving features specific to the use of a compressible medium, e.g. air, steam
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/042—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the feed line, i.e. "meter in"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/046—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed depending on the position of the working member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/22—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/08—Servomotor systems incorporating electrically operated control means
    • F15B21/087—Control strategy, e.g. with block diagram
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/3057—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve having two valves, one for each port of a double-acting output member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/30575—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve in a Wheatstone Bridge arrangement (also half bridges)
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • F15B2211/328—Directional control characterised by the type of actuation electrically or electronically with signal modulation, e.g. pulse width modulation [PWM]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6653—Pressure control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6656—Closed loop control, i.e. control using feedback
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/75—Control of speed of the output member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/885—Control specific to the type of fluid, e.g. specific to magnetorheological fluid
    • F15B2211/8855—Compressible fluids, e.g. specific to pneumatics
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/26—Generation or transmission of movements for final actuating mechanisms
    • F16H61/28—Generation or transmission of movements for final actuating mechanisms with at least one movement of the final actuating mechanism being caused by a non-mechanical force, e.g. power-assisted
    • F16H61/30—Hydraulic or pneumatic motors or related fluid control means therefor

Definitions

  • the present invention relates to a pneumatic actuator according to the preamble of claim 1.
  • the present invention also relates to a system for controlling the pneumatic actuator according to the preamble of claim 7.
  • the present invention also relates to a motor vehicle.
  • the present invention further relates to a method for controlling a pneumatic actuator according to the preamble of claim 9.
  • the present invention also relates to a computer programme and computer programme product.
  • Pneumatic actuators or cylinders are used in a number of applications.
  • pneumatic actuators are used to control gear shifts in a gear box of a motor vehicle.
  • a pneumatic actuator comprises a cylinder in which a piston is arranged to reciprocate, said piston being arranged to actuate a gear shift of said gear box by means of a stroke.
  • the piston divides the cylinder into a first space and a second space.
  • the piston is reciprocated by introducing pressurized air from air valves via a first and a second passageway of the cylinder into the first or the second space depending on which direction of movement of the piston is intended.
  • a problem with this kind of arrangement is that the piston will move too fast, which may result in destruction of the transmission. Therefore chokes or constrictions are arranged at the air passageways such that the pressurized air is introduced and the speed of the movement of the piston throughout the stroke is reduced. This has the disadvantage that the speed of the piston is limited throughout the stroke, which is basically only needed in the middle or end of the stroke.
  • An object of the present invention is to provide a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
  • Another object of the present invention is to provide a system for controlling a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
  • Yet another object of the present invention is to provide a method for controlling a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
  • a pneumatic actuator a system for controlling a pneumatic actuator, a motor vehicle, a method, a computer programme and computer programme product, which are of the type stated by way of introduction and which in addition exhibits the features recited in the characterising clause of the appended claim 1 , 7, 8, 9, 16 and 17.
  • Preferred embodiments of the inventive pneumatic actuator are defined in appended dependent claims 2-6, and 10-15.
  • a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into or out of said first space, and a second space having a second port for passing a second gaseous medium into said second space, so as to move said piston, wherein said first gaseous medium is arranged to be provided as a first set of pulses, and said second gaseous medium is arranged to be provided as a second set of pulses, said sets being arranged to provide an impact difference for moving said piston.
  • the resulting force thus achieved facilitates control of the piston, and at least one position sensor arranged to sense the position of the piston, said control of the pneumatic actuator being based upon the position of the piston.
  • This facilitates easy and accurate control of the piston.
  • a desired predetermined movement may be imparted to the piston of the pneumatic actuator.
  • fast change of the force or impact is possible and ability to apply high forces is given.
  • Said pulses are achievable by means of simple air valves and thus costs may be kept low.
  • said first set of pulses and said second set of pulses are provided with substantially the same frequency. This facilitates continuous operation.
  • said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses.
  • said first set of pulses and said second set of pulses are arranged to be triggered at the same time. This is easy to programme and thus facilitates easy control of piston.
  • said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses.
  • This provides an alternative way of achieving said impact difference, i.e. said resulting force.
  • An advantage is that the control is independent of the pulse length. Here control is performed by means of feed pressure which may be easier in certain applications.
  • the first gaseous medium and/or the second gaseous medium are/is air. Air is easily accessible and thus usable in many applications and cost effective.
  • a system for controlling a pneumatic actuator comprising a pneumatic actuator according to any of the embodiments above, at least one gas source, a first valve member arranged to receive said first gaseous medium from said air source, said first valve member being connected to said first space for providing said first set of pulses, and a second valve member arranged to receive said second gaseous medium from said air source, said second valve member being connected to said second space for providing said second set of pulses, and means for controlling said pulses.
  • a system where the resulting force thus achieved controls the pneumatic actuator is achieved, said system facilitating fast change of the force or impact, and ability to apply high forces.
  • Said valve members for providing said pulses may be simple air switches and thus costs may be kept low.
  • a method for controlling a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into said space, and a second space having a second port for passing a second gaseous medium into said space, so as to move said piston, comprising the step of providing said first gaseous medium as a first set of pulses, and said second gaseous medium as a second set of pulses, said sets providing an impact difference for moving said piston, and determining the position of said piston and providing said sets as a function of said position.
  • This improves control of the piston.
  • the resulting force thus achieved facilitates control of piston.
  • the first set of pulses and the second set of pulses are provided with substantially the same frequency. This facilitates continuous operation.
  • said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses.
  • said first set of pulses and said second set of pulses are triggered at the same time. This is easy to programme and thus facilitates easy control of piston.
  • said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses.
  • the step of providing said sets is based upon the position of the piston, said impact difference being a function of said position. This improves control of the piston.
  • the first gaseous medium and/or the second gaseous medium is/are air. Air is easily accessible and thus usable in many applications and cost effective. BRIEF DESCRIPTION OF THE DRAWINGS
  • Fig. 1 schematically illustrates a pneumatic actuator according to an embodiment of the present invention
  • Fig. 2 schematically illustrates a system for controlling the actuator in fig. 1 according to an embodiment of the present invention
  • Fig. 3 schematically shows a motor vehicle according to an embodiment of the present invention
  • Fig. 4 schematically illustrates a computer according to an embodiment of the present invention
  • FIG. 5a and 5b schematically illustrates methods for controlling a pneumatic actuator according to embodiments of the present invention
  • Fig. 6a and 6b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a first embodiment
  • Fig. 7a and 7b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a second embodiment;
  • Fig. 8a and 8b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a third embodiment
  • Fig. 9 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fourth embodiment
  • Fig. 10 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fifth embodiment
  • Fig. 11 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a sixth embodiment
  • Fig. 12 schematically illustrates a detail of the set of pulses according to the first embodiment
  • Fig. 13 schematically illustrates a detail of the set of pulses according to a seventh embodiment.
  • link refers to a communication link which could be a physical line, such as an opto-electronic communication line, or a non- physical line such as a wireless connection, for example a radio- or microwave link.
  • Fig. 1 schematically illustrates a pneumatic actuator 100 according to an embodiment of the present invention.
  • the pneumatic actuator 100 comprises a cylinder 110 and a piston 120 arranged to reciprocate within said cylinder 110.
  • the piston 120 divides the cylinder 110 into a first space 112 and a second space 114.
  • the cylinder comprises a first port 116, passageway 116 or opening 116 for passing a first gaseous medium, for example air, into and/or out of the first space 112.
  • the cylinder further comprises a second port 118, passageway 118 or opening 118 for passing a second gaseous medium, for example air, into and/or out of the second space 114.
  • Said first gaseous medium is according to the invention arranged to be provided as a first set of pulses P1
  • said second gaseous medium is arranged to be provided as a second set of pulses P2, said sets being arranged to provide an impact difference for moving said piston.
  • said sets P1 , P2 are arranged to provide a resulting force for moving said piston.
  • the piston 120 comprises according to this embodiment a piston stem 122, which is arranged to be used for actuation in a desired application.
  • first gaseous medium P1 and the second gaseous medium P2 are the same. According to an embodiment the first and/or second gaseous medium are/is air.
  • Fig. 2 schematically illustrates a system 200 for controlling the actuator in fig. 1 according to an embodiment of the present invention.
  • the system 200 comprises a pneumatic actuator 100 e.g. according to fig. 1 , said pneumatic actuator 100 comprising a cylinder 110, a piston 120 arranged to reciprocate within said cylinder 110, the piston 120 dividing the cylinder 110 into a first space 112 and a second space 114.
  • the cylinder 110 comprises a first port 116 for passing a first gaseous medium, for example air, into and/or out of the first space 112, and a second port 118 for passing a second gaseous medium, for example air, into and/or out of the second space 114.
  • the system 200 further comprises a gas source 210 comprising said first and second gaseous medium, here illustrated as a common source.
  • the system further comprises a first valve member 220 arranged to receive said first gaseous medium from said gas source 210, and a second valve member 230 arranged to receive said second gaseous medium from said gas source 210.
  • the first valve member 220 is gas connected to the first port 116
  • the second valve member 230 is gas connected to the second port 118.
  • the system further comprises a position sensor 240 arranged to sense the position of the piston 120.
  • the system further comprises an electronic control unit 250.
  • the electronic control unit 250 is signal connected to the first valve member 220 via a link 225.
  • the electronic control unit 250 is further signal connected to the second valve member 230 via a link 235.
  • the electronic control unit 250 is signal connected to the position sensor via a link 245.
  • the first valve member 220 is arranged to provide said first gaseous medium as a first set of pulses P1 to the first space 112 via said first port 116
  • the second valve member 230 is arranged to provide said second gaseous medium as a second set of pulses P2 to the second space 114 via said second port 118.
  • Said first set of pulses P1 and said second set of pulses P2 are arranged to provide an impact difference for moving said piston 120.
  • the difference in impact of the first and second set of pulses P1 , P2 imparts an impulse to the piston 120 such that the piston 120 is moving, i.e. the piston is arranged to perform a stroke due to the resulting force provided by said sets of pulses P1 , P2.
  • Fig. 6-13 discloses different ways of achieving this impact difference by means of said first and second set of pulses P1 , P2.
  • the electronic control unit 250 is arranged to receive a signal via the link 245 from the position sensor 240 representing piston position data.
  • the electronic control unit 250 is arranged to process said piston position data so as to provide a signal via the link 225 representing a first set of pulses to the first valve member 220, such that the first valve member 220 provides said first gaseous medium to the first space 112 as said first set of pulses P1.
  • the electronic control unit 250 is further arranged to process said piston position data so as to provide a signal via the link 235 representing a second set of pulses to the second valve member 230, such that the second valve member 230 provides said second gaseous medium to the second space 114 as said second set of pulses P2.
  • the electronic control unit 250 is thus arranged to control said first valve member 220 and second valve member 230 based upon the position of the piston 120 such that the first and second set of pulses P1 , P2 are provided to the first and second space 112, 114, respectively, such that said difference in impact for moving said piston is achieved, the position of the piston 120 being arranged to be sensed by means of said position sensor 240.
  • the impact difference between the first and second set of pulses P1 , P2 needed to move the piston 120 may be determined by means of the electronic control unit 250.
  • the impact difference is according to an embodiment varied based upon the movement of the piston 120, i.e. the position of the piston 120, such that a desired movement of the piston 120 is achieved. This is according to an embodiment done by means of a feedback loop, where the position of the piston is determined after a certain number of the first and second set of pulses P1 , P2, e.g. after each pulse of the first and second set of pulses P1 , P2.
  • the first and second sets of pulses are according to an embodiment fed continuously based on said feedback for determining the position of the piston, i.e. both during a stroke or movement of the piston, and after an actuation application is completed, where the piston is supposed to be in a non-moving position or rest position.
  • the first and second sets of pulses P1 , P2 are provided such that the impact difference is zero, i.e. the piston is kept in the resting position by means of said sets of pulses P1 , P2.
  • the first and second sets of pulses are fed until the actuation is completed, where the sets of pulses are terminated.
  • means for holding the piston is provided, said means e.g. being a spring loaded ball. See fig. 5a and 5b, which show flow charts for performing such methods.
  • the electronic control unit 250 is programmed to control the piston 120 according to the specific application.
  • the position sensor 240 makes control of the piston 120 easy and reduces the risk of errors and malfunctioning since it gives an accurate result of the position.
  • the control of the piston 120 of the pneumatic actuator 100 is achievable without said position sensor.
  • varying parameters such as temperature, wear, tolerance, lubrication and run of the pneumatic actuator may influence the performance, and hence it is more difficult to achieve a satisfactory result by modelling of the pneumatic actuator 100.
  • the impact difference generated by means of the first and second set of pulses should be such that there is an impact of the first gaseous medium in the first space and vice versa.
  • the piston 120 When the piston 120 is moving in e.g. the direction towards the second space 114 due to said impact difference, the second gaseous medium is discharged from the second space 114.
  • the first gaseous medium is introduced as said first set of pulses P1 into the first space 112
  • the second gaseous medium is introduced as said second set of pulses P2 into the second space 114 and gas of said second gaseous medium is discharged from said second space 114.
  • the piston 120 When the piston 120 is moving in the direction towards the first space it is the opposite way around.
  • the first valve member 220 thus comprises means for discharging said first gaseous medium from said first space 112 when the piston 120 is moving towards said first space 112
  • the second valve member 230 comprises means for discharging said second gaseous medium from said second space 114 when the piston 120 is moving towards said second space.
  • the first and second valve members 220, 230 may vary due to application and due to the embodiment of the first and second set of pulses P1 , P2 achieving said impact difference.
  • each of the first and second valve member 220, 230 comprises a 3/2 valve which comprises a port for receiving gas from said gas source and a supply port from which the gaseous medium is arranged to be supplied as a set of pulses, and a discharge port to which gas is arranged to be discharged.
  • each of the first and second valve member 220, 230 comprises two valves, one for providing said set of pulses and a discharge valve to which gas is arranged to be discharged.
  • each of the first and second valve member 220, 230 comprises two valves, one for providing said set of pulses with a first amplitude, i.e. a first pressure, and one for providing said set of pulses with a second amplitude, i.e. a second pressure, different from said first amplitude/pressure.
  • the valve members may also comprise a proportional valve in order to vary the pressure of said sets of pulses.
  • Fig. 3 schematically shows a motor vehicle 300 according to an embodiment of the present invention.
  • the exemplified vehicle 300 comprises a tow car 310 and a trailer 312.
  • the vehicle 300 may be a heavy vehicle such as a truck or a buss.
  • the vehicle may alternatively be a car.
  • the pneumatic actuator 100 in fig. 1 is arranged in the vehicle 300.
  • the system 200 shown in fig. 2 is a subsystem of the vehicle 300.
  • the pneumatic actuator 100 in fig. 1 , 2 is a pneumatic gear shift cylinder arranged to actuate the gear shift of a gear box of the vehicle 300.
  • Fig. 4 schematically illustrates a computer according to an embodiment of the present invention.
  • Non-volatile memory 420 has a first memory portion 430 wherein a computer program, such as an operating system, is stored for controlling the function of apparatus 250.
  • apparatus 250 comprises a bus controller, a serial communication port, l/O-means, an A/D-converter, a time date entry and transmission unit, an event counter and an interrupt controller (not shown).
  • Non-volatile memory 420 also has a second memory portion 440.
  • a computer program P comprising routines for controlling a pneumatic actuator may be stored in an executable manner or in a compressed state in a separate memory 460 and/or in the read/write memory 450.
  • the memory 460 is a non-volatile memory, such as a flash memory, an EPROM, an EEPROM or a ROM.
  • the memory 460 is a computer program product.
  • the memory 450 is a computer program product.
  • the data processing device 410 performs a certain function it should be understood that the data processing device 410 performs a certain part of the program which is stored in the separate memory 460, or a certain part of the program which is stored in the read/write memory 450.
  • Data processing device 410 may communicate with a data communications port 499 by means of a data bus 415.
  • the non-volatile memory 420 is adapted for communication with the data processing device 410 via a data bus 412.
  • the separate memory 460 is adapted for communication with the data processing device 410 via a data bus 411.
  • the read/write memory 450 is adapted for communication with the data processing device 410 via a data bus 414.
  • data received on the data port 499 comprises piston position data information received from the position sensor associated with the piston. This information can be used by the system so as to control the pneumatic actuator, i.e. control the piston of the pneumatic actuator.
  • Parts of the methods described herein can be performed by apparatus 250 by means of the data processing device 410 running the program stored in the separate memory 460 or the read/write memory 450. When apparatus runs the program, parts of the methods described herein are executed.
  • Fig. 5a schematically illustrates a method for controlling a pneumatic actuator according to an embodiment of the present invention.
  • the method for controlling the pneumatic actuator 100, or rather the piston of the pneumatic actuator comprises a first step S510.
  • the position of the piston 120 of the pneumatic actuator 100 is determined.
  • the position of the piston is determined by means of the position sensor 240.
  • the method further comprises a second step S520.
  • a first set of pulses P1 are provided to the first space 112 and a second set of pulses P2 are provided to the second space 114, said pulses being provided based on said position, so as to provide an impact difference for moving said piston.
  • the pulses are provided by means of the first and second valve member respectively.
  • said valve members are controlled by means of an electronic control unit which is arranged to receive piston position data from said position sensor. This is described in relation to fig. 2.
  • the method further comprises a third step S530. In this step it is checked whether the piston is at a desired position, e.g.
  • the piston is provided to a rest position, e.g. by holding means.
  • Fig. 5b schematically illustrates a method for controlling a pneumatic actuator according to an embodiment of the present invention.
  • This method for controlling the pneumatic actuator 100, or rather the piston of the pneumatic actuator comprises a first step S510.
  • the position of the piston 120 of the pneumatic actuator 100 is determined.
  • the position of the piston is determined by means of the position sensor 240.
  • the method further comprises a second step S520.
  • a first set of pulses P1 are provided to the first space 112 and a second set of pulses P2 are provided to the second space 114, said pulses being provided based on said position, so as to provide an impact difference for moving said piston.
  • the pulses are provided by means of the first and second valve member respectively.
  • said valve members are controlled by means of an electronic control unit which is arranged to receive piston position data from said position sensor. This is described in relation to fig. 2.
  • the first and second sets of pulses are fed continuously based on said feedback for determining the position of the piston, i.e. both during a stroke or movement of the piston, and after an actuation application is completed, where the piston is supposed to be in a non-moving position or rest position.
  • the first and second sets of pulses P1 , P2 are provided such that the impact difference is zero, i.e. the piston is kept in the resting position by means of said sets of pulses P1 , P2.
  • Fig. 6a and 6b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a first embodiment.
  • Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
  • Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
  • said first set of pulses P1 and said second set of pulses P2 are arranged to be triggered at the same time, i.e. each pulse of the first and second set of pulses P1 , P2 start at the same time.
  • the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2.
  • the second set of pulses P2 end before the first set of pulses P1.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2.
  • the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact, i.e.
  • the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114 due to the resulting force achieved.
  • the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1.
  • the first set of pulses P1 end before the second set of pulses P2.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
  • An advantage with this embodiment is that it is easy to programme, e.g. when using the electronic control unit, as the pulses are triggered to start at the same time, thus simply needing two timers to start at the same time.
  • Fig. 7a and 7b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a second embodiment.
  • Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
  • Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
  • said first set of pulses P1 and said second set of pulses P2 are arranged to end at the same time.
  • the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2.
  • the first set of pulses P1 start before the second set of pulses P2.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2.
  • the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact.
  • the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114, this due to the resulting force thus achieved.
  • the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1.
  • the second set of pulses P2 begin before the first set of pulses P1.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
  • Fig. 8a and 8b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a third embodiment.
  • Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
  • Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
  • the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2.
  • said first set of pulses P1 start before and end after the second set of pulses P2.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2.
  • the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact.
  • the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114, this due to the resulting force thus achieved.
  • the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1.
  • the second set of pulses P2 begin before and end after the first set of pulses P1.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
  • Fig. 9 schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fourth embodiment.
  • Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
  • Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
  • the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2.
  • each pulse of said first set of pulses P1 begin and end before each pulse of said second set of pulses P2.
  • the frequency of the first and second set of pulses P1 , P2 is such that the piston moves only due to the difference in pulse width of the first set of pulses P1 and the second set of pulses P2 due to the inertia of the piston.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2.
  • the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114.
  • the piston By having the second set of pulses with a longer duration than the first set of pulses instead, the piston will move in the opposite direction.
  • each pulse in one of the sets of pulses could start within each pulse of the other sets of pulses and end after that each pulse in that set of pulses (not shown), thus achieving said impact difference, i.e. the resulting force for moving the piston.
  • Fig. 10 schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fifth embodiment.
  • each pulse is constituted by a pair of pulses.
  • Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
  • each pair of pulses of the second set of pulses P2 has the same frequency as each pulse in the first set of pulses P1.
  • Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
  • the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2.
  • Each first pulse of each pair of pulses of the second set of pulses P2 here starts at the same time as each pulse of the first set of pulses P1 , and each second pulse of the pair of pulses of the second set of pulses P2 ends before each pulse of the first set of pulses P1.
  • the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2.
  • the longer duration of the first set of pulses P1 compared to the second set of pulses P2 rendering a difference in impact.
  • the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114.
  • each pulse of the second set of pulses comprises more than two pulses, e.g. three pulses.
  • Each pulse of the first set of pulses could also comprise more than one pulse according to an alternative.
  • Fig. 11 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a sixth embodiment.
  • Said first set of pulses and said second set of pulses are provided with substantially the same frequency.
  • Said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses.
  • said first set of pulses and said second set of pulses are arranged to be triggered at the same time, i.e. each pulse of the first and second set of pulses start at the same time and end at the same time, the duration of the first and second set of pulses thus being the same.
  • the amplitude of the first set of pulses is higher than the amplitude of the second set of pulses.
  • the piston of the pneumatic actuator in fig. 1 or 2 will move in the direction towards the second space narrowing the same. This is due to the difference in amplitude between the first and second set of pulses.
  • the higher amplitude of the first set of pulses compared to the second set of pulses rendering a difference in impact, i.e. the resulting force.
  • the difference in amplitude, i.e. the difference in pressure the first gaseous medium being constituted by a portion of each of the first set of pulses of this difference in pressure imparts an impulse to the piston which moves in the direction towards the second space, this thus due to the resulting force.
  • Fig. 12 schematically illustrates a detail of the set of pulses according to the first embodiment.
  • said impact difference is provided by means of a difference x in pulse duration between the first and second set of pulses, said difference x constituting said impact difference, i.e. rendering the resulting force.
  • the first and second pulse starts at the same time and the second pulse ends before the first pulse.
  • Fig. 13 schematically illustrates a detail of the set of pulses according to a seventh embodiment.
  • said impact difference is provided by means of a combination of difference x in pulse duration between the first and second set of pulses, and a difference y in pulses amplitude between the first and second set of pulses, said differences constituting said impact difference, i.e. rendering the resulting force.
  • the first and second pulse ends at the same time and the second pulse starts before the first pulse, said pulse having higher amplitude than the second pulse.
  • a number of em bod i merits for providing the first and second set of pulses for controlling a piston of an actuator, e.g. an actuator according to fig. 1 and 2 have been described.
  • the sets are arranged to provide an impact difference for moving said piston.
  • the invention is not limited to these embodiments, but is within the scope of a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into or out of said space, and a second space having a second port for passing a second gaseous medium into or out of said space, so as to move said piston, wherein said first gaseous medium is arranged to be provided as a first set of pulses, and said second gaseous medium is arranged to be provided as a second set of pulses, said sets being arranged to provide an impact difference for moving said piston.
  • the pneumatic actuator according to the embodiments above comprises a piston having a piston stem. Said piston stem takes up space in said second space, and this should be considered when providing said sets of pulses.
  • the first gaseous medium is arranged to be introduced to and discharged from the first space through the first port
  • the second gaseous medium is arranged to be introduced to and discharged from the second space through the second port.
  • a first inlet port for introducing the first gaseous medium to the first space
  • a second port for discharging the first gaseous medium from the first space.
  • amplitude and duration difference may be combined.
  • Other suitable combinations are also possible such as combining pairs of pulses providing a duration difference with the other set of pulses as well as amplitude difference.
  • Other types of pulses apart from rectangular pulses are of course achievable, such as saw toothed pulses, needing a more sophisticated type of valve member, e.g. a proportional valve.
  • the pneumatic actuator 100 may be applied to any suitable application, e.g. applications within a vehicle such as gear shift, break system, suspension but also other industries where pneumatic actuators are used.

Abstract

The present invention relates to a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into said first space, and a second space having a second port for passing a second gaseous medium into said second space, so as to move said piston, wherein said first gaseous medium is arranged to be provided as a first set of pulses, and said second gaseous medium is arranged to be provided as a second set of pulses, said sets being arranged to provide an impact difference for moving said piston, and at least one position sensor arranged at said pneumatic actuator to sense the position of the piston, said control of the pneumatic actuator being based upon the position of the piston. The present invention also relates to a system for controlling a pneumatic actuator. The present invention also relates to method for controlling a pneumatic actuator. The present invention also relates to a computer programme and computer programme product.

Description

PNEUMATIC ACTUATOR, AND SYSTEM AND METHOD FOR CONTROLLING THE SAME
TECHNICAL FIELD
The present invention relates to a pneumatic actuator according to the preamble of claim 1. The present invention also relates to a system for controlling the pneumatic actuator according to the preamble of claim 7. The present invention also relates to a motor vehicle. The present invention further relates to a method for controlling a pneumatic actuator according to the preamble of claim 9. The present invention also relates to a computer programme and computer programme product.
BACKGROUND ART
Pneumatic actuators or cylinders are used in a number of applications. For example pneumatic actuators are used to control gear shifts in a gear box of a motor vehicle. Such a pneumatic actuator comprises a cylinder in which a piston is arranged to reciprocate, said piston being arranged to actuate a gear shift of said gear box by means of a stroke. The piston divides the cylinder into a first space and a second space. The piston is reciprocated by introducing pressurized air from air valves via a first and a second passageway of the cylinder into the first or the second space depending on which direction of movement of the piston is intended.
A problem with this kind of arrangement is that the piston will move too fast, which may result in destruction of the transmission. Therefore chokes or constrictions are arranged at the air passageways such that the pressurized air is introduced and the speed of the movement of the piston throughout the stroke is reduced. This has the disadvantage that the speed of the piston is limited throughout the stroke, which is basically only needed in the middle or end of the stroke.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
Another object of the present invention is to provide a system for controlling a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
Yet another object of the present invention is to provide a method for controlling a pneumatic actuator in which the stroke of the piston is controllable in an efficient and cost effective way.
SUMMARY OF THE INVENTION
These and other objects, apparent from the following description, are achieved by a pneumatic actuator, a system for controlling a pneumatic actuator, a motor vehicle, a method, a computer programme and computer programme product, which are of the type stated by way of introduction and which in addition exhibits the features recited in the characterising clause of the appended claim 1 , 7, 8, 9, 16 and 17. Preferred embodiments of the inventive pneumatic actuator are defined in appended dependent claims 2-6, and 10-15.
Specifically an object of the invention is achieved by a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into or out of said first space, and a second space having a second port for passing a second gaseous medium into said second space, so as to move said piston, wherein said first gaseous medium is arranged to be provided as a first set of pulses, and said second gaseous medium is arranged to be provided as a second set of pulses, said sets being arranged to provide an impact difference for moving said piston. The resulting force thus achieved facilitates control of the piston, and at least one position sensor arranged to sense the position of the piston, said control of the pneumatic actuator being based upon the position of the piston. This facilitates easy and accurate control of the piston. Thus, in this way a desired predetermined movement may be imparted to the piston of the pneumatic actuator. Further, fast change of the force or impact is possible and ability to apply high forces is given. Said pulses are achievable by means of simple air valves and thus costs may be kept low.
According to an embodiment of said pneumatic actuator said first set of pulses and said second set of pulses are provided with substantially the same frequency. This facilitates continuous operation.
According to an embodiment of said pneumatic actuator said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses. By providing the difference in pulses as a difference in duration of the pulses, i.e. difference in pulse width, easy programming and thus control of pulses and hence the piston is achievable.
According to an embodiment of said pneumatic actuator said first set of pulses and said second set of pulses are arranged to be triggered at the same time. This is easy to programme and thus facilitates easy control of piston.
According to an embodiment of said pneumatic actuator said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses. This provides an alternative way of achieving said impact difference, i.e. said resulting force. An advantage is that the control is independent of the pulse length. Here control is performed by means of feed pressure which may be easier in certain applications.
According to an embodiment of said pneumatic actuator the first gaseous medium and/or the second gaseous medium are/is air. Air is easily accessible and thus usable in many applications and cost effective.
A system for controlling a pneumatic actuator comprising a pneumatic actuator according to any of the embodiments above, at least one gas source, a first valve member arranged to receive said first gaseous medium from said air source, said first valve member being connected to said first space for providing said first set of pulses, and a second valve member arranged to receive said second gaseous medium from said air source, said second valve member being connected to said second space for providing said second set of pulses, and means for controlling said pulses. Hereby a system where the resulting force thus achieved controls the pneumatic actuator, is achieved, said system facilitating fast change of the force or impact, and ability to apply high forces. Said valve members for providing said pulses may be simple air switches and thus costs may be kept low.
A method for controlling a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into said space, and a second space having a second port for passing a second gaseous medium into said space, so as to move said piston, comprising the step of providing said first gaseous medium as a first set of pulses, and said second gaseous medium as a second set of pulses, said sets providing an impact difference for moving said piston, and determining the position of said piston and providing said sets as a function of said position. This improves control of the piston. The resulting force thus achieved facilitates control of piston. Thus, in this way a desired predetermined movement may be imparted to the piston of the pneumatic actuator. Further fast change of the force or impact is possible, and ability to apply high forces is given. Said pulses are achievable by means of simple air switches and thus costs may be kept low.
According to an embodiment of the method the first set of pulses and the second set of pulses are provided with substantially the same frequency. This facilitates continuous operation.
According to an embodiment of the method said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses. By providing the difference in pulses as a difference in duration of the pulses, i.e. difference in pulse width, easy programming and thus control of pulses and hence the piston is achievable.
According to an embodiment of the method said first set of pulses and said second set of pulses are triggered at the same time. This is easy to programme and thus facilitates easy control of piston.
According to an embodiment of the method said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses. An advantage is that the control is independent of the pulse length. Here control is performed by means of feed pressure which may be easier in certain applications.
According to an embodiment of the method the step of providing said sets is based upon the position of the piston, said impact difference being a function of said position. This improves control of the piston.
According to an embodiment of the method the first gaseous medium and/or the second gaseous medium is/are air. Air is easily accessible and thus usable in many applications and cost effective. BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention will be had upon the reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which:
Fig. 1 schematically illustrates a pneumatic actuator according to an embodiment of the present invention;
Fig. 2 schematically illustrates a system for controlling the actuator in fig. 1 according to an embodiment of the present invention;
Fig. 3 schematically shows a motor vehicle according to an embodiment of the present invention;
Fig. 4 schematically illustrates a computer according to an embodiment of the present invention;
Fig. 5a and 5b schematically illustrates methods for controlling a pneumatic actuator according to embodiments of the present invention;
Fig. 6a and 6b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a first embodiment;
Fig. 7a and 7b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a second embodiment;
Fig. 8a and 8b schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a third embodiment; Fig. 9 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fourth embodiment;
Fig. 10 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fifth embodiment;
Fig. 11 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a sixth embodiment;
Fig. 12 schematically illustrates a detail of the set of pulses according to the first embodiment; and
Fig. 13 schematically illustrates a detail of the set of pulses according to a seventh embodiment.
DETAILED DESCRIPTION
Herein the term "link" refers to a communication link which could be a physical line, such as an opto-electronic communication line, or a non- physical line such as a wireless connection, for example a radio- or microwave link.
Fig. 1 schematically illustrates a pneumatic actuator 100 according to an embodiment of the present invention.
The pneumatic actuator 100 comprises a cylinder 110 and a piston 120 arranged to reciprocate within said cylinder 110. The piston 120 divides the cylinder 110 into a first space 112 and a second space 114. The cylinder comprises a first port 116, passageway 116 or opening 116 for passing a first gaseous medium, for example air, into and/or out of the first space 112. The cylinder further comprises a second port 118, passageway 118 or opening 118 for passing a second gaseous medium, for example air, into and/or out of the second space 114.
Said first gaseous medium is according to the invention arranged to be provided as a first set of pulses P1 , and said second gaseous medium is arranged to be provided as a second set of pulses P2, said sets being arranged to provide an impact difference for moving said piston. Thus said sets P1 , P2 are arranged to provide a resulting force for moving said piston.
The piston 120 comprises according to this embodiment a piston stem 122, which is arranged to be used for actuation in a desired application.
According to an embodiment the first gaseous medium P1 and the second gaseous medium P2 are the same. According to an embodiment the first and/or second gaseous medium are/is air.
Fig. 2 schematically illustrates a system 200 for controlling the actuator in fig. 1 according to an embodiment of the present invention.
The system 200 comprises a pneumatic actuator 100 e.g. according to fig. 1 , said pneumatic actuator 100 comprising a cylinder 110, a piston 120 arranged to reciprocate within said cylinder 110, the piston 120 dividing the cylinder 110 into a first space 112 and a second space 114. The cylinder 110 comprises a first port 116 for passing a first gaseous medium, for example air, into and/or out of the first space 112, and a second port 118 for passing a second gaseous medium, for example air, into and/or out of the second space 114.
The system 200 further comprises a gas source 210 comprising said first and second gaseous medium, here illustrated as a common source.
The system further comprises a first valve member 220 arranged to receive said first gaseous medium from said gas source 210, and a second valve member 230 arranged to receive said second gaseous medium from said gas source 210. The first valve member 220 is gas connected to the first port 116, and the second valve member 230 is gas connected to the second port 118.
The system further comprises a position sensor 240 arranged to sense the position of the piston 120.
The system further comprises an electronic control unit 250. The electronic control unit 250 is signal connected to the first valve member 220 via a link 225. The electronic control unit 250 is further signal connected to the second valve member 230 via a link 235. The electronic control unit 250 is signal connected to the position sensor via a link 245.
The first valve member 220 is arranged to provide said first gaseous medium as a first set of pulses P1 to the first space 112 via said first port 116, and the second valve member 230 is arranged to provide said second gaseous medium as a second set of pulses P2 to the second space 114 via said second port 118. Said first set of pulses P1 and said second set of pulses P2 are arranged to provide an impact difference for moving said piston 120. Thus, the difference in impact of the first and second set of pulses P1 , P2 imparts an impulse to the piston 120 such that the piston 120 is moving, i.e. the piston is arranged to perform a stroke due to the resulting force provided by said sets of pulses P1 , P2. Fig. 6-13 discloses different ways of achieving this impact difference by means of said first and second set of pulses P1 , P2.
According to one embodiment the electronic control unit 250 is arranged to receive a signal via the link 245 from the position sensor 240 representing piston position data. The electronic control unit 250 is arranged to process said piston position data so as to provide a signal via the link 225 representing a first set of pulses to the first valve member 220, such that the first valve member 220 provides said first gaseous medium to the first space 112 as said first set of pulses P1. The electronic control unit 250 is further arranged to process said piston position data so as to provide a signal via the link 235 representing a second set of pulses to the second valve member 230, such that the second valve member 230 provides said second gaseous medium to the second space 114 as said second set of pulses P2.
The electronic control unit 250 is thus arranged to control said first valve member 220 and second valve member 230 based upon the position of the piston 120 such that the first and second set of pulses P1 , P2 are provided to the first and second space 112, 114, respectively, such that said difference in impact for moving said piston is achieved, the position of the piston 120 being arranged to be sensed by means of said position sensor 240.
Thus, based on the information of the position of the piston 240 the impact difference between the first and second set of pulses P1 , P2 needed to move the piston 120 may be determined by means of the electronic control unit 250. The impact difference is according to an embodiment varied based upon the movement of the piston 120, i.e. the position of the piston 120, such that a desired movement of the piston 120 is achieved. This is according to an embodiment done by means of a feedback loop, where the position of the piston is determined after a certain number of the first and second set of pulses P1 , P2, e.g. after each pulse of the first and second set of pulses P1 , P2.
The first and second sets of pulses are according to an embodiment fed continuously based on said feedback for determining the position of the piston, i.e. both during a stroke or movement of the piston, and after an actuation application is completed, where the piston is supposed to be in a non-moving position or rest position. Thus, according to such an embodiment, when the piston is in its rest position, the first and second sets of pulses P1 , P2 are provided such that the impact difference is zero, i.e. the piston is kept in the resting position by means of said sets of pulses P1 , P2. According to another embodiment the first and second sets of pulses are fed until the actuation is completed, where the sets of pulses are terminated. In this embodiment, in order to keep the piston in its rest position, means for holding the piston is provided, said means e.g. being a spring loaded ball. See fig. 5a and 5b, which show flow charts for performing such methods. The electronic control unit 250 is programmed to control the piston 120 according to the specific application.
The position sensor 240 makes control of the piston 120 easy and reduces the risk of errors and malfunctioning since it gives an accurate result of the position.
According to an alternative embodiment, by modelling the pneumatic actuator 100, the control of the piston 120 of the pneumatic actuator 100 is achievable without said position sensor. Here varying parameters such as temperature, wear, tolerance, lubrication and run of the pneumatic actuator may influence the performance, and hence it is more difficult to achieve a satisfactory result by modelling of the pneumatic actuator 100.
In order to move the piston 120 in the direction towards the second space 114 the impact difference generated by means of the first and second set of pulses should be such that there is an impact of the first gaseous medium in the first space and vice versa.
When the piston 120 is moving in e.g. the direction towards the second space 114 due to said impact difference, the second gaseous medium is discharged from the second space 114. Thus, when the piston 120 is moving towards the second space 114 the first gaseous medium is introduced as said first set of pulses P1 into the first space 112, and the second gaseous medium is introduced as said second set of pulses P2 into the second space 114 and gas of said second gaseous medium is discharged from said second space 114. When the piston 120 is moving in the direction towards the first space it is the opposite way around.
The first valve member 220 thus comprises means for discharging said first gaseous medium from said first space 112 when the piston 120 is moving towards said first space 112, and the second valve member 230 comprises means for discharging said second gaseous medium from said second space 114 when the piston 120 is moving towards said second space.
The first and second valve members 220, 230 may vary due to application and due to the embodiment of the first and second set of pulses P1 , P2 achieving said impact difference. According to one embodiment each of the first and second valve member 220, 230 comprises a 3/2 valve which comprises a port for receiving gas from said gas source and a supply port from which the gaseous medium is arranged to be supplied as a set of pulses, and a discharge port to which gas is arranged to be discharged. According to an alternative embodiment each of the first and second valve member 220, 230 comprises two valves, one for providing said set of pulses and a discharge valve to which gas is arranged to be discharged. According to yet another embodiment each of the first and second valve member 220, 230 comprises two valves, one for providing said set of pulses with a first amplitude, i.e. a first pressure, and one for providing said set of pulses with a second amplitude, i.e. a second pressure, different from said first amplitude/pressure. According to an embodiment the valve members may also comprise a proportional valve in order to vary the pressure of said sets of pulses.
Fig. 3 schematically shows a motor vehicle 300 according to an embodiment of the present invention. The exemplified vehicle 300 comprises a tow car 310 and a trailer 312. The vehicle 300 may be a heavy vehicle such as a truck or a buss. The vehicle may alternatively be a car.
According to an embodiment the pneumatic actuator 100 in fig. 1 is arranged in the vehicle 300. According to an embodiment the system 200 shown in fig. 2 is a subsystem of the vehicle 300. According to an embodiment the pneumatic actuator 100 in fig. 1 , 2 is a pneumatic gear shift cylinder arranged to actuate the gear shift of a gear box of the vehicle 300. Fig. 4 schematically illustrates a computer according to an embodiment of the present invention.
With reference to Figure 4, a diagram of one embodiment of the electronic control unit 250 is shown. The electronic control unit 250 is also referred to as apparatus and as computer. The apparatus comprises a non-volatile memory 420, a data processing device 410 and a read/write memory 450. Non-volatile memory 420 has a first memory portion 430 wherein a computer program, such as an operating system, is stored for controlling the function of apparatus 250. Further, apparatus 250 comprises a bus controller, a serial communication port, l/O-means, an A/D-converter, a time date entry and transmission unit, an event counter and an interrupt controller (not shown). Non-volatile memory 420 also has a second memory portion 440.
A computer program P comprising routines for controlling a pneumatic actuator may be stored in an executable manner or in a compressed state in a separate memory 460 and/or in the read/write memory 450. The memory 460 is a non-volatile memory, such as a flash memory, an EPROM, an EEPROM or a ROM. The memory 460 is a computer program product. The memory 450 is a computer program product.
When it is stated that the data processing device 410 performs a certain function it should be understood that the data processing device 410 performs a certain part of the program which is stored in the separate memory 460, or a certain part of the program which is stored in the read/write memory 450.
Data processing device 410 may communicate with a data communications port 499 by means of a data bus 415. The non-volatile memory 420 is adapted for communication with the data processing device 410 via a data bus 412. The separate memory 460 is adapted for communication with the data processing device 410 via a data bus 411. The read/write memory 450 is adapted for communication with the data processing device 410 via a data bus 414.
When data is received on the data port 499 it is temporarily stored in the second memory portion 440. When the received input data has been temporarily stored, the data processing device 410 is set up to perform execution of code in a manner described above. According to a preferred embodiment of the invention, data received on the data port 499 comprises piston position data information received from the position sensor associated with the piston. This information can be used by the system so as to control the pneumatic actuator, i.e. control the piston of the pneumatic actuator.
Parts of the methods described herein can be performed by apparatus 250 by means of the data processing device 410 running the program stored in the separate memory 460 or the read/write memory 450. When apparatus runs the program, parts of the methods described herein are executed.
Fig. 5a schematically illustrates a method for controlling a pneumatic actuator according to an embodiment of the present invention.
According to an embodiment the method for controlling the pneumatic actuator 100, or rather the piston of the pneumatic actuator, comprises a first step S510. In this step the position of the piston 120 of the pneumatic actuator 100 is determined. According to an embodiment the position of the piston is determined by means of the position sensor 240.
The method further comprises a second step S520. In this step a first set of pulses P1 are provided to the first space 112 and a second set of pulses P2 are provided to the second space 114, said pulses being provided based on said position, so as to provide an impact difference for moving said piston. The pulses are provided by means of the first and second valve member respectively. According to an embodiment said valve members are controlled by means of an electronic control unit which is arranged to receive piston position data from said position sensor. This is described in relation to fig. 2. The method further comprises a third step S530. In this step it is checked whether the piston is at a desired position, e.g. has performed a stroke or the like, and if the desired position has been reached end the method, or if not continue to determine position of piston in accordance with step S510, provide impact difference according to step S520 and check again according to step S530 until the desired position is reached, i.e. the actuation of the pneumatic actuator 100 is completed. If the actuation is completed the method ends, i.e. the feed of the first and second sets of pulses P1 , P2 are terminated. Here, according to an embodiment not illustrated in fig. 5a, the piston is provided to a rest position, e.g. by holding means.
Fig. 5b schematically illustrates a method for controlling a pneumatic actuator according to an embodiment of the present invention.
This method for controlling the pneumatic actuator 100, or rather the piston of the pneumatic actuator, comprises a first step S510. In this step the position of the piston 120 of the pneumatic actuator 100 is determined. According to an embodiment the position of the piston is determined by means of the position sensor 240.
The method further comprises a second step S520. In this step a first set of pulses P1 are provided to the first space 112 and a second set of pulses P2 are provided to the second space 114, said pulses being provided based on said position, so as to provide an impact difference for moving said piston. The pulses are provided by means of the first and second valve member respectively. According to an embodiment said valve members are controlled by means of an electronic control unit which is arranged to receive piston position data from said position sensor. This is described in relation to fig. 2.
According to this embodiment the first and second sets of pulses are fed continuously based on said feedback for determining the position of the piston, i.e. both during a stroke or movement of the piston, and after an actuation application is completed, where the piston is supposed to be in a non-moving position or rest position. Thus, when the piston is in its rest position, the first and second sets of pulses P1 , P2 are provided such that the impact difference is zero, i.e. the piston is kept in the resting position by means of said sets of pulses P1 , P2.
Fig. 6a and 6b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a first embodiment.
Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2. In the embodiment according to fig. 6a and 6b said first set of pulses P1 and said second set of pulses P2 are arranged to be triggered at the same time, i.e. each pulse of the first and second set of pulses P1 , P2 start at the same time.
In fig. 6a the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2. In fig. 6a the second set of pulses P2 end before the first set of pulses P1. Thus, in the example according to fig. 6a the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2. Thus, the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact, i.e. the resulting force. Thus, during this difference in duration the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114 due to the resulting force achieved. In fig. 6b the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1. In fig. 6b the first set of pulses P1 end before the second set of pulses P2. Thus, in the example according to fig. 6b the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
An advantage with this embodiment is that it is easy to programme, e.g. when using the electronic control unit, as the pulses are triggered to start at the same time, thus simply needing two timers to start at the same time.
Fig. 7a and 7b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a second embodiment.
Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2. In the embodiment according to fig. 7a and 7b said first set of pulses P1 and said second set of pulses P2 are arranged to end at the same time.
In fig. 7a the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2. In fig. 7a the first set of pulses P1 start before the second set of pulses P2. Thus, in the example according to fig. 7a the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2. Thus, the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact. Thus, during this difference in duration the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114, this due to the resulting force thus achieved.
In fig. 7b the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1. In fig. 7b the second set of pulses P2 begin before the first set of pulses P1. Thus, in the example according to fig. 7b the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
Fig. 8a and 8b schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a third embodiment.
Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2.
In fig. 8a the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2. In the embodiment according to fig. 8a said first set of pulses P1 start before and end after the second set of pulses P2. Thus, in the example according to fig. 8a the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2. Thus, the longer duration of the first set of pulses P1 compared to the second set of pulses P2 renders a difference in impact. Thus, during this difference in duration the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114, this due to the resulting force thus achieved.
In fig. 8b the duration of the second set of pulses P2 is longer than the duration of the first set of pulses P1 , i.e. the pulse width of the second set of pulses P2 is broader than the pulse width of the first set of pulses P1. In fig.
8b the second set of pulses P2 begin before and end after the first set of pulses P1. Thus, in the example according to fig. 8b the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the first space 112 narrowing the same.
Fig. 9 schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fourth embodiment.
Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency.
Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2. In the embodiment according to fig. 9 the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2. In fig. 9 each pulse of said first set of pulses P1 begin and end before each pulse of said second set of pulses P2.
In this embodiment the frequency of the first and second set of pulses P1 , P2 is such that the piston moves only due to the difference in pulse width of the first set of pulses P1 and the second set of pulses P2 due to the inertia of the piston. Thus, due to the inertia of the piston and a sufficiently high frequency of the set of pulses the piston will move in one direction due to said difference in pulse width. Thus, in the example according to fig. 9 the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2. Thus, the longer duration of the first set of pulses P1 compared to the second set of pulses P2 rendering a difference in impact. Thus, given the frequency is sufficient so that the inertia of the piston prevents the piston from moving back and forth, during this difference in duration the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114.
By having the second set of pulses with a longer duration than the first set of pulses instead, the piston will move in the opposite direction.
Alternatively each pulse in one of the sets of pulses could start within each pulse of the other sets of pulses and end after that each pulse in that set of pulses (not shown), thus achieving said impact difference, i.e. the resulting force for moving the piston.
Fig. 10 schematically illustrates a first and second set of pulses P1 , P2 for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a fifth embodiment.
In said second set of pulses P2 each pulse is constituted by a pair of pulses. Said first set of pulses P1 and said second set of pulses P2 are provided with substantially the same frequency. Thus, each pair of pulses of the second set of pulses P2 has the same frequency as each pulse in the first set of pulses P1.
Said impact difference is provided by means of a difference in pulse duration between the first and second set of pulses P1 , P2. In the embodiment according to fig. 10 the duration of the first set of pulses P1 is longer than the duration of the second set of pulses P2, i.e. the pulse width of the first set of pulses P1 is broader than the pulse width of the second set of pulses P2. Each first pulse of each pair of pulses of the second set of pulses P2 here starts at the same time as each pulse of the first set of pulses P1 , and each second pulse of the pair of pulses of the second set of pulses P2 ends before each pulse of the first set of pulses P1.
Thus, in the example according to fig. 10 the piston of the pneumatic actuator 100 in fig. 1 or 2 will move in the direction towards the second space 114 narrowing the same. This is due to the difference in duration between the first and second set of pulses P1 , P2. Thus, the longer duration of the first set of pulses P1 compared to the second set of pulses P2 rendering a difference in impact. Thus during this difference in duration the first gaseous medium being constituted by a portion of each of the first set of pulses P1 of this difference in duration imparts an impulse to the piston which moves in the direction towards the second space 114.
According to an alternative the pulses do not start at the same time. According to another alternative instead of a pair of pulses, i.e. two pulses, each pulse of the second set of pulses comprises more than two pulses, e.g. three pulses. Each pulse of the first set of pulses could also comprise more than one pulse according to an alternative. These variants could naturally be combined in a suitable manner for achieving said impact difference, i.e. the resulting force for moving said piston.
Fig. 11 schematically illustrates a first and second set of pulses for controlling a piston of the actuator in fig. 1 and 2, said pulses being provided according to a sixth embodiment.
Said first set of pulses and said second set of pulses are provided with substantially the same frequency.
Said impact difference is provided by means of a difference in pulse amplitude between the first and second set of pulses. In the embodiment according to fig. 11 said first set of pulses and said second set of pulses are arranged to be triggered at the same time, i.e. each pulse of the first and second set of pulses start at the same time and end at the same time, the duration of the first and second set of pulses thus being the same.
In the embodiment according to fig. 11 the amplitude of the first set of pulses is higher than the amplitude of the second set of pulses. Thus, in the example according to fig. 11 the piston of the pneumatic actuator in fig. 1 or 2 will move in the direction towards the second space narrowing the same. This is due to the difference in amplitude between the first and second set of pulses. Thus, the higher amplitude of the first set of pulses compared to the second set of pulses rendering a difference in impact, i.e. the resulting force. Thus the difference in amplitude, i.e. the difference in pressure, the first gaseous medium being constituted by a portion of each of the first set of pulses of this difference in pressure imparts an impulse to the piston which moves in the direction towards the second space, this thus due to the resulting force.
Fig. 12 schematically illustrates a detail of the set of pulses according to the first embodiment. In the first embodiment said impact difference is provided by means of a difference x in pulse duration between the first and second set of pulses, said difference x constituting said impact difference, i.e. rendering the resulting force. In this example the first and second pulse starts at the same time and the second pulse ends before the first pulse.
Fig. 13 schematically illustrates a detail of the set of pulses according to a seventh embodiment. In this embodiment said impact difference is provided by means of a combination of difference x in pulse duration between the first and second set of pulses, and a difference y in pulses amplitude between the first and second set of pulses, said differences constituting said impact difference, i.e. rendering the resulting force. In this example the first and second pulse ends at the same time and the second pulse starts before the first pulse, said pulse having higher amplitude than the second pulse. Above a number of em bod i merits for providing the first and second set of pulses for controlling a piston of an actuator, e.g. an actuator according to fig. 1 and 2, have been described. In all these embodiments the sets are arranged to provide an impact difference for moving said piston. The invention is not limited to these embodiments, but is within the scope of a pneumatic actuator comprising a cylinder and a piston arranged to reciprocate within said cylinder, said piston dividing said cylinder into a first space having a first port for passing a first gaseous medium into or out of said space, and a second space having a second port for passing a second gaseous medium into or out of said space, so as to move said piston, wherein said first gaseous medium is arranged to be provided as a first set of pulses, and said second gaseous medium is arranged to be provided as a second set of pulses, said sets being arranged to provide an impact difference for moving said piston.
The pneumatic actuator according to the embodiments above comprises a piston having a piston stem. Said piston stem takes up space in said second space, and this should be considered when providing said sets of pulses.
In the embodiments according to fig. 1 and 2 the first gaseous medium is arranged to be introduced to and discharged from the first space through the first port, and the second gaseous medium is arranged to be introduced to and discharged from the second space through the second port. According to an alternative there is a first inlet port for introducing the first gaseous medium to the first space and a second port for discharging the first gaseous medium from the first space. There could of course be one port for introduction and discharge in one of the spaces and two separate ports, one for introduction and one for discharge in the other space.
In fig. 6-13 different ways of achieving the impact difference by means of said first and second set of pulses P1 , P2 are disclosed in embodiments. As discloses in fig. 13 amplitude and duration difference may be combined. Other suitable combinations are also possible such as combining pairs of pulses providing a duration difference with the other set of pulses as well as amplitude difference. Other types of pulses apart from rectangular pulses are of course achievable, such as saw toothed pulses, needing a more sophisticated type of valve member, e.g. a proportional valve.
The pneumatic actuator 100 according to the present invention may be applied to any suitable application, e.g. applications within a vehicle such as gear shift, break system, suspension but also other industries where pneumatic actuators are used.
The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.

Claims

1. A pneumatic actuator (100) comprising a cylinder (110) and a piston (120) arranged to reciprocate within said cylinder (110), said piston dividing said cylinder into a first space (112) having a first port (116) for passing a first gaseous medium into said first space (112), and a second space (114) having a second port (118) for passing a second gaseous medium into said second space (114), so as to move said piston (120), characterized in that said first gaseous medium is arranged to be provided as a first set of pulses (P1 ), and said second gaseous medium is arranged to be provided as a second set of pulses (P2), said sets being arranged to provide an impact difference for moving said piston (120), and at least one position sensor (240) arranged at said pneumatic actuator (100) to sense the position of the piston (120), said control of the pneumatic actuator being based upon the position of the piston (120).
2. A pneumatic actuator according to claim 1 , wherein said first set of pulses (P1 ) and said second set of pulses (P2) are provided with substantially the same frequency.
3. A pneumatic actuator according to claim 1 or 2, wherein said impact difference is provided by means of a difference (x) in pulse duration between the first and second set of pulses (P1 , P2).
4. A pneumatic actuator according to any of claims 1 -3, wherein said first set of pulses (P1 ) and said second set of pulses (P2) are arranged to be triggered at the same time.
5. A pneumatic actuator according to any of claims 1 -4, wherein said impact difference is provided by means of a difference (y) in pulse amplitude between the first and second set of pulses (P1 , P2).
6. A pneumatic actuator according to any preceding claim, wherein the first gaseous medium and/or the second gaseous medium are/is air.
7. A system for controlling a pneumatic actuator comprising a pneumatic actuator according to any of claims 1 -6, at least one gas source (210), a first valve member (220) arranged to receive said first gaseous medium from said air source, said first valve member (220) being connected to said first space (112) for providing said first set of pulses (P1 ), and a second valve member (230) arranged to receive said second gaseous medium from said air source (210), said second valve member (230) being connected to said second space (114) for providing said second set of pulses (P2), and means (250) for controlling said valve members (220, 230), and at least one position sensor (240) arranged to sense the position of the piston (120), said control of the pneumatic actuator being based upon the position of the piston (120).
8. Motor vehicle comprising a pneumatic actuator according to any of claims 1 -6, or a system according to claim 7.
9. A method for controlling a pneumatic actuator (100) comprising a cylinder (110) and a piston (120) arranged to reciprocate within said cylinder (110), said piston dividing said cylinder into a first space (112) having a first port (116) for passing a first gaseous medium into said space, and a second space (114) having a second port (118) for passing a second gaseous medium into said space, so as to move said piston (120), characterized by the step of providing said first gaseous medium as a first set of pulses (P1 ), and said second gaseous medium as a second set of pulses (P2), said sets (P1 , P2) providing an impact difference for moving said piston (120), and determining the position of said piston (120) and providing said sets (P1 , P2) as a function of said position.
10. A method according to claim 9, wherein the first set of pulses (P1 ) and the second set of pulses (P2) are provided with substantially the same frequency
11. A method according to claim 9 or 10, wherein said impact difference is provided by means of a difference (x) in pulse duration between the first and second set of pulses (P1 , P2).
12. A method according to any of claims 9-11 , wherein said first set of pulses (P1 ) and said second set of pulses (P2) are triggered at the same time.
13. A method according to any of claims 9-12, wherein said impact difference is provided by means of a difference (y) in pulse amplitude between the first and second set of pulses.
14. A method according to any of claims 9-13, wherein the step of providing said sets (P1 , P2) is based upon the position of the piston, said impact difference being a function of said position.
15. A method according to any of claims 9-14, wherein the first gaseous medium and/or the second gaseous medium are/is air.
16. Computer programme (P) comprising a programme code for performing the method steps of claim 9-15 when said computer programme (P) is run on a computer (250).
17. Computer programme product comprising a program code stored on a, by a computer readable, media for performing the method steps of claim 9-15 when said computer programme (P) is run on the computer (250).
18. Computer programme product directly storable in an internal memory into a computer, comprising a computer programme (P) for performing the method steps according to claim 9-15, when said computer programme (P) is run on the computer.
PCT/SE2009/051278 2008-11-18 2009-11-10 Pneumatic actuator, and system and method for controlling the same WO2010059107A1 (en)

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CN2009801479824A CN102227565A (en) 2008-11-18 2009-11-10 Pneumatic actuator, and system and method for controlling same
EP09827820.3A EP2359012A4 (en) 2008-11-18 2009-11-10 Pneumatic actuator, and system and method for controlling the same
BRPI0916016A BRPI0916016A2 (en) 2008-11-18 2009-11-10 "pneumatic actuator, and system and method for controlling it"
RU2011124921/06A RU2473824C1 (en) 2008-11-18 2009-11-10 Air actuator, system and method of its control

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RU2011124921A (en) 2012-12-27
EP2359012A1 (en) 2011-08-24
SE0802422A1 (en) 2010-05-19
SE533131C2 (en) 2010-07-06
RU2473824C1 (en) 2013-01-27
EP2359012A4 (en) 2014-02-26
BRPI0916016A2 (en) 2015-11-03
CN102227565A (en) 2011-10-26

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