WO1995004327A9

WO1995004327A9 - Electronic control of portable devices and equipment

Info

Publication number: WO1995004327A9
Application number: PCT/GB1994/001704
Authority: WO
Filing date: 1994-08-03
Publication date: 1995-03-30

Abstract

Portable apparatus or device having a computerised controller (24) interfaced therewith to assist control of the apparatus or device by the user, wherein a motion sensor (20) is also provided on the apparatus or device, together with processing circuitry (22) which is interfaced with the controller (24) to enable the controller to utilise information relating to motion of the portable means in control thereof. The sensor may also be linked with a video tile (14).

Description

Title Electronic Control of Portable Devices and Equipment

Field of the invention

This invention relates generally to the electronic control of portable devices and equipment, where the term "devices and equipment" refers to any portable device, appliance, machine or equipment which is moved or movable to assist the user in performing a particular job or task, and which is generally referred to herein as "portable means".

Background to the invention

Increasingly, in devices and equipment as aforesaid, mini-computers are being incorporated. These computers act as controllers interfaced with the device or equipment at least to receive inputs therefrom and commonly to exchange information therewith, and also commonly have a facility for user inputs. Inputs may also be received from external systems with which the device or equipment is co-acting.

The invention

According to the present invention, there is provided a portable means as aforesaid equipped with a computerised controller, wherein the portable means also incorporates a motion sensor in communication with the controller.

A suitable motion sensor is an accelerometer for acceleration measurement, and/or a piezo-electric vibrating gyroscope for measurement of angular speed.

Typically, a motion sensor is employed which produces a small analogue voltage proportional to the parameter, i.e. acceleration or velocity or speed, being sensed.

Generally, sufficient sensors will be employed to enable sensing of motion in three coordinate directions.

Depending on application, the analogue voltage output of each sensor may be converted, as by integration over a selected interval, into a stream of pulses the frequency of which is representative of the magnitude of the input voltage. These pulses will be synchronised to an external digital clock, so that the integral of the pulse frequency is an accurate representation of the integral of the analogue input voltage, regardless of the selected clock frequency. Sampling and counting the pulses thus provides accurate measurements of the parameter being sensed. For example, the signal pulses can themselves be integrated, in order to obtain a parameter-representative signal. A sufficiently high sampling rate is employed to avoid inaccuracies, as the accuracy of this second integration is dependent on the relationship between the sampling period, the means of integration and the parameter/time curve. When the pulses are counted and sampled at intervals to obtain parameter measurements, counting can be performed by a programmable logic array, such as a XiLinx XC4005 chip. The programmable logic array is preferably designed to sample six channels simultaneously, which can be read sequentially by a microprocessor. Six channels enable the parameter, for example positions and orientations, to be computed in three dimensions.

The same programmable logic array is preferably also employed for calibration, to compensate for cross-channel sensitivities, and for integration, as well as for pulse counting. Additionally, this array may perform differentiation of velocity or speed measurements to obtain acceleration measurements.

It is possible to employ algorithms for auto-calibration when the device or equipment incorporating the sensor or sensors is stationary, for re-scaling of input data when a new calibration occurs and for modelling the system so that data is accompanied by error bounds.

As far as accelerometers are concerned, it is to be noted that silicon micromachined accelerometers for linear acceleration measurement and providing digital outputs are currently available and can be made use of in practice of the present invention. Detection of a constant acceleration by the accelerometers which is similar in magnitude to gravity indicates that the sensors are stationary.

The sensor for use in accordance with the invention can be produced as a single chip complete with a memory and interface which cooperates directly with the controller in the device or equipment, thus adding just one chip to the system.

The use of accelerometers provides two degrees of orientation information but cannot detect rotation about the gravity vector Vg, ie rotation in a plane tangential to the earth's surface.

A magnetic field sensor may be employed for measurement of the local magnetic field vector so as to detect the magnetic field direction and magnitude. This allows for detection of rotation about the gravity vector Vg.

It will be appreciated that the complexity of signal processing required in practice of the invention will depend on the application to which the invention is put. For some applications, any one of acceleration, velocity and position measurements alone may be sufficient, while measurement of two or even all three parameters may be necessary for other applications. The accuracy with which measurements have to be made and/or computed will also vary with application.

For example, in the case of a portable machine tool such as a soldering iron, where heating control and power conservation is practised by means of an in-built mini-controller, the invention may be incorporated to cause the machine tool to be switched on when it starts to move and/or switched off when it is laid to rest. In such an application, only a relatively imprecise detection of acceleration in three dimensions is required. If the motion of the machine tool is guided, detection of acceleration in only one or two dimensions may be sufficient.

On the other hand, if the invention is applied to a route guidance system, it will be necessary to follow the position of the user with a high degree of accuracy in at least two and possibly three dimensions.

Guidance as to possible applications of the invention can be gained from the following table, where these possible applications are grouped by parameter and accuracy.

Accuracy Acceleration Velocity Position

Low Movement alarm User walking, Location

Communications aid running, guidance (X)

Auto power control driving Auto power

Reaction to tapping

Safety shutdown

Correlated tapping

Medium Display adaption User gesturing Alarm

Steering/throttle scheduling (X) control Inertial mouse

User gesture control response

Free-fall protection

Correlation of accelerations

High Tilting of mouse Motion of Route guidance mouse (X)

User pointing Measurements

Microphone (X) control Virtual reality (X)

In the above table, applications marked with the letter X require the use of angular speed sensors, as does any application where orientation is significant. Some of the aforesaid applications are now briefly discussed.

First, with low accuracy acceleration sensing, say better than +/- 0.5 g, acceleration measurements of over 0.5 g after a period of rest may be used to trigger events, such as sounding an alarm unless a correct password is entered. Again, a radio communications device may be advised that movement is taking place and more frequent beaconing is required. A machine tool may be powered up on movement. A device may be made to react to tapping by the user. A pending appointment reminder may be re-activated when moved unless cancelled by a sharp tap. The touching together of two devices can be deduced by the measurement of simultaneous sharp accelerations on each. Yet again, a potentially dangerous machine tool may be shut down if the user makes a sudden movement or falls. Also, with low accuracy measurement of velocity, a device carried by the user may determine if the user is walking, running or driving. With low accuracy measurement of position, a supplementary aid to portable location devices is made possible, or a device may be informed if it is in an unusable position, e.g. upside down, and can be powered down.

Second, with medium accuracy of acceleration sensing, say better than +/- 0.1 g, basic information on position and orientation can be computed. For example, acceleration measurements can determine the angle of a device relative to the vertical in order to orientate and scale a displayed image. Again, orientation measurement may be used for radio control of a steering wheel or throttle. Shaking gestures may be used to erase, turn pages etc. in a display device. Detection of a deliberate jog may be used promptly to silence an alarm. Sustained lack of acceleration may indicate free fall and trigger a defensive response. Again, correlated accelerations may indicate that two devices are joined or being carried together. Medium accuracy velocity measurements or tilting gestures may control movement of a cursor or viewpoint . Third, with measurement of acceleration of better than +/ O.Olg, the acceleration measurements can be employed directly to measure orientation as part of a user interface to computer applications. Again, vibrations can be analysed, for example to detect operation and predict wear. High accuracy velocity measurements enable the use of accurate gestures to give commands, and gestures can be employed to point at printers, bins and the like. High accuracy velocity measurements also make it possible to pick up sound. With high accuracy position measurements, a portable device can be kept informed of its position in a building and/or inform the user where to go or of the surroundings . Precision measurements can be made, even through walls. Again, the position measurements can be employed to determine a virtual reality viewpoint, turning a display into a window on a virtual world.

As previously mentioned, the use of accelerometers to measure the direction of gravity gives two degrees of orientation information, but cannot detect rotations about the gravity vector Vg. A magnetic sensor such as the KVH C100 compass engine allows measurement of the local magnetic field vector Vm. Knowledge of the sensor orientation relative to Vg and Vm is sufficient to determine the full three-axis orientation of the sensors. Thus a means for recalibrating angular rate sensors is provided, or for some applications such as pointing devices, the magnetic sensor replaces the angular rate sensor.

In all these possible applications, the nature of the device cr equipment to which the invention is being applied will be readily apparent. In all instances, the invention provides a portable device or equipment incorporating a computerised controller with a sense of movement, which is utilised by the controller in application of its program to the device or equipment.

An embodiment of the invention will now be described by way of example and with reference to the following drawings in which: Figure 1 is a schematic view of a device equipped with a computerised controller,

Figure 2 is a schematic representation of a controlling circuit for use in accordance with the invention and

Figure 3 is a diagram of signals from an accelerometer representing different accelerations .

Description of a preferred embodiment

Figure 1 is a schematic view of a movable device 10 with a sensing means 12 for motion sensing, in this case acceleration sensing, in accordance with the invention.

The sensing means 12 is connected to a video tile 14 such that signals can be sent to and received from the video tile 14. The video tile 14 is connected to a computer network 16 which is able to receive and send signals to the video tile 14.

Movement of the device 10 produces acceleration which is sensed by the sensing means 12. A signal representing the acceleration is sent to the video tile 14 for processing by an internal circuit means such as that shown in Figure 2. The internal circuit means processes the signal so as to produce a graph of acceleration against time together with a display of the device tilt to the horizontal for display on a liquid crystal display (LCD) screen 18 incorporated into the video tile 14.

Figure 2 is a schematic representation of the individual controlling elements present in Figure 1. The sensing means 12 further comprises an accelerometer 20, a Field Programmable Logic Array (FPGA) device 22 and a sensor processor 24.

The accelerometer 20 may typically be a lOOOL-010 device manufactured by Silicon designs Inc, while the FPGA device 22 is preferably a Xilinx XC4006 chip and the sensor processor 24 is typically a transputer such as aa Inmos IMS T222 chip.

The signals sent between the elements of the sensing means 12 are represented by the letters A,B,C.

On movement of the device 10 a current proportional to the acceleration is produced by the accelerometer 20. This is converted to a digital data signal by means of a pulse generator. Signal A comprises a digital clock signal from the FPGA device 22 to the accelerometer 20 and the data signal generated by the accelerometer in response to movement of the device 10. These signals are shown in Figure 3.

The digital clock signal, conveniently of 250kHz, shown in the first line in Figure 3, is supplied continuously to the accelerometer 20. The data signal returned by the accelerometer is a continuous sequence of pulses whose average frequency represents the acceleration of the device 10. Zero acceleration, for example free fall or when the sensitive axis of the sensor is perpendicular to gravity, is represented by a signal of roughly 50% pulses, as shown by the third pulse sequence in Figure 3. The pulses are synchronous with the clock signal supplied from the FPGA device 22. As the acceleration varies the data signal varies in width and period, as shown by the second, fourth and fifth pulse sequences in Figure 3.

The FPGA device 22 receives data signals from up to six sensor channels to give sufficient degrees of freedom for the location velocity and acceleration determination required for the device 10. The FPGA device 22 counts the number of pulses on each channel continuously. The FPGA device 22 has an extra internal channel that counts at maximum rate. The count on this channel is a reference level for the six external channels. For example, if the internal count increases by 256 clock pulses and 128 pulses are seen in the data signal from the accelerometer 20 then the device 10 is at Og, while 64 pulses represent -lg and 192 pulses represent lg. The FPGA device 22 is addressed by the sensor processor, or transputer, 24 by signal B. This interface signal consists of a transputer clock signal, 16 bit address and data buses, interrupt request and acknowledge lines, memory enable and byte strobes.

When addressed by the transputer 24, the FPGA device 22 takes a snapshot of all accelerometer data signals. Typically the transputer is run at a sampling rate of 20kHz. The transputer 24 determines how the sensor parameter has changed between the sampling points. Counting over a long sampling interval enables greater accuracy to be achieved. The counts can be accumulated in the transputer 24 over longer periods to obtain higher accuracy measurements, while simultaneously detecting high frequency changes such as sharp taps at high sampling rates.

The transputer 24 is calibrated by signals sent from the network 16 via the video tile 14. This low frequency fine calibration adjusts for temperature variation and other system drifts.

The signal C from the transputer 24 communicates with the video tile 14 via an Inmos link. This allows the processes in the transputer 24 to be loaded, controlled and communicated with via the video tile 14 and in turn controlled by the computer network 16. The use of a network 16 is not essential. Calibration information is sent from the network 16 via the video tile 14 to the transputer 24 and blocks of binary counter samples are sent from the transputer 24 to the video tile 14 at lOMbits per second.

Alternatively the link between the transputer 24 and the video tile 14 may be a remote link such as provided by electromagnetic signals.

The elements associated with the video tile 14 control interpretation of the sampled data received from the transputer 24 and allow communication between the network 16 and the sensing means 12 .

Referring to Figure 2, the video tile 14 comprises a link adaptor 26 connected to an FPGA device 28. The FPGA device 28, which is typically a Xilinx XC4005H chip, acts as a central processor communicating with the network 16, a video random access memory VRAM framestore 30, a further FPGA device 32 and optionally a pen digitiser 34.

The link adaptor 26 is typically a Inmos IMS C011 chip and allows the transputer 24 to communicate with the other elements on the video tile 14 via a bus interface to the FPGA 28 device.

The VRAM framestore 30 may consist of several Micron MT42C8256 chips and possesses a parallel port connected to the FPGA device 28 and a serial port for sending signals to the second FPGA device 32. This further FPGA device 32 is typically a Xilinx XC4003A chip and the pen digitiser 34 may be a Wacom EB-A263 device.

The FPGA devices 22,28,32 are programmable devices wherein the hardware on the device is configured by loading suitable software. The use of an interactive network 16 thus allows easy alteration of ■ the configured hardware without the need for complex soldering operations. The response characteristics of the different elements are thus easily variable with respect to data accumulation and display.

The FPGA device 28 communicates with the network 16 via a network processor 36 such as Advanced Rise Machines ARM610 and a network interface 38 such as an Olivetti Research Laboratories ATMos which connects to the network 16. An interactive display with the computer network 16 can thus be provided on the LCD screen with interaction via the pen digitiser 34. However, interaction with the network 16 is not essential to the working of the invention. The first FPGA device 28 allows an image sent from the network 16 to be transferred one line at a time to the second FPGA 32 device. An image is sent to the VRAM framestore 30 from the network processor 36 via the FPGA device 28. The FPGA device 28 breaks the bus connection between the network processor 36 and the VRAM frame store 30 to prepare a line of the image for transmission from the VRAM serial port. Only one line is sent from the serial port of the framestore 30 to the second FPGA device 32 at any one time.

The second FPGA device 32 sends the signals to the LCD screen 18, typically a Sharp LQ9D011, for image display. It provides dithering to enhance the number of displayable colours on the LCD screen 18.

On movement of the device 10, the acceleration is sensed and processed by the system to create a display representing the acceleration versus time. Additionally, the angle of tilt of the device about the vertical, or sensitive axis of the accelerometer 20, can be determined by calibration of the sensing means 12 to the extreme values of acceleration i.e. +lg and -lg as seen at the vertically upright and vertically inverted positions.

The graph provides a real time display and detects small scale disturbances to the device, such as taps. If the device ιε tapped small spikes will be seen on the graph with the spike direction dependent on the direction of the tap.

The pen digitiser 34 is used to provide a function menu within the video tile 14 connected to the accelerometer 20.

The sensing means 12 may be attached to the video tile 14 to measure movement. Attachment of the sensing means 12 directly to the video tile 14 allows for advantages such as a display that is always in the correct sense for the viewer, such that when tilt movement is sensed the display is altered to ensure that the image presented remains the correct way up and is scaled correctly for the viewer.

Claims

1. Portable means which is moved or movable to assist the user equipped with a computerised controller, wherein said portable means also incorporates a motion sensor in communication with the controller.

2. Portable means as claimed in claim 1, having a sufficient number of sensors to detect motion in one, two or in three coordinate directions.

3. Portable means as claimed in claim 1 or claim 2, having one or more motion sensors each producing an analogue signal proportional to the motion parameter being sensed.

4. Portable means as claimed in claim 1 or claim 2 or claim 3, wherein at least one motion sensor comprises an accelerometer.

5. Portable means as claimed in any of claims 1 to 4, wherein at least one motion sensor comprises a piezo-electric vibrating gyroscope.

6. Portable means according to claim 3 or any claim appendant thereto, wherein means are provided for repetitively integrating the or each analogue signal over a selected time interval in order to produce a signal in the form of a stream of pulses, and the pulse stream is sampled and counted to obtain a signal representative of the sensed motion.

7. Portable means as claim in claim 6, wherein the sampling rate is sufficiently high to achieve a chosen level of accuracy of measurement .

8. Portable means as claimed in claim 6 or claim 7, wherein sampling and counting is performed by a programmable data processing means.

9. Portable means as claimed in claim 8, wherein the programmable data processing means is also employed for calibration, and to compensate for cross-channel sensitivities.

10. Portable means as claimed in claim 9, wherein the data processing means is programmed with an algorithm for auto- calibration.

11. Portable means as claimed in claim 8 or claim 9 or claim 10, wherein the data processing means is designed to be capable of sampling six channels simultaneously.

12. Portable means as claimed in any of claims 8 to 11 wherein the programmable data processing means is a programmable logic array.

13. Portable means as claimed in any of claims 1 to 12, having a silicon micromachined accelerometer for linear acceleration measurement.

14. Portable means as claimed in any of claims 1 to 13, having a magnetic field sensor to detect the local magnetic field vector.

15. Portable means as claimed in any of claims 1 to 14, comprising a single chip incorporating the one or more sensors and signal processing circuitry, and having an interface for circuit cooperation with the computerised controller.

16. Portable means as claimed in any of claims 1 to 15, providing a signal output to a video tile.

17. Portable means as claimed in claim 16, in which the video tile is remote from the portable means, which transmits an electromagnetic signal carrying the measurement signal for

RECTIFIED SHEET (RULE 91) reception by the video tile.

18. Portable means as claimed in claim 16, wherein the video tile incorporates a display device and is integrated with the portable means.