US3333463A - Mileage accumulation dynamometer - Google Patents

Description

4 Sheets-5heet 1` R- HOLLINGHURST MILEAGE ACCUMULATION DYNAMOMETER Aug. l, 1967 Filed June 26. 1964 4 Sheets-Sheet 2 Filed June 2G, 1964 w|llrl++||| NSGQ Aug- 1, 1967 R. HOLLINGHURST 3,333,4.63

MI LEAGE ACCUMULAT I ON DYNAMOMETER Filed June 26, 1964 4 Sheets-Sheet 5 Aug. l, 1967 Filed June 26, 1964 `R. HOLLINGHURST MILEAGE AGCUMULTION DYNAMOMETER 4v sheets-snaai 4 United States LPatent O 3,333,463 MELEAGE ACCUMULATION DYNAMOMETER Ralph Hoilinghnrst, Glassboro, NJ., assignor to Mobil Oil Corporation, New York, N.Y., a corporation of New York Filed June 26, 1964, Ser. No. 378,395 Claims priority, application Great Britain, June 27, 1963, 25,526/63 12 Claims. (Cl. 73-117) The present invention concerns a method and apparatus for running the engine and associated power train in a motor vehicle in the same manner as in normal road operation, while maintaining the body of the vehicle stationary, so as to accumulate effective road mileage without the necessity of using the road.

Various petroleum products used in motor vehicles as fuels and lubricants, and other materials, must be tested with respect to their performance, under conditions as` closely similar as possible to those which occur in normal use. Difficulties occur in carrying out tests in motor vehicles under actual road conditions, due for instance to unpredictable traiiic conditions and variations in the perfomance of the driver.

To avoid these disadvantages it has already been proposed to operate motor vehicles for extended periods on a chassis dynamometer apparatus in which engine mileage may be accumulated under pre-arranged conditions of speed and load while the vehicle remains captive. We refer to such apparatus herein as a mileage accumulator dynamometer. It has also been proposed to operate such a dynamometer apparatus in response to a coded set of signals according to a program previously compiled or recorded. According to one know proposal, such a program is previously obtained in actual road use of a motor vehicle which serves as a master for subsequent tests.

Mileage accumulation dynamometers and their uses are described for instance in Automobile Engineer, April 1958, pages 142 to 145, and August 1958, pages 297 to 302, in United Kingdom patent specication No. 882,380 and in United States patent specification No. 3,050,994. The present invention is applicable in the employment of mileage accumulation dynamometers quite broadly and there is no need to describe these in particular detail herein.

A typical mileage accumulation dynamometer installation comprises a solid foundation, for instance of concrete, incorporating a well or pit in which the dynamometer itself is mounted. The lwell is covered by a deck on which the vehicle may stand, the deck being cut away so that the wheels of the vehicle which transmit the drive to the road can be arranged to ride on one or more traction rolls, these rolls being mounted on a common axle which transmits the wheel power through gearing and shafts to the machinery which simulates highway load conditions, which comprise windage, inertia, rolling friction and gradient (and braking). Anchoring points are provided so that the automobile or other motor vehicle may be secured against movement along the ground.

The traction rolls generally drive a centrifugal fan (or the latter may be wholly or partly powered separately) `the purpose of which is to provide, through suitable ducting adjusted to fit the size of the vehicle or more particularly its radiator, cooling air at the front of the vehicle and past its underbodyprepresenting the cooling effect of air on the road. The fan may also provide a resistance to be overcome by the engine, equivalent to the effective wind resistance of the motor vehicle. This is necessary because the air impinging on the stationary vehicle produces no drag on the vehicle engine under test. It is found in practice that the resistance set up by the 3,333,463 Patented Aug. 1, 1967 fan can be arranged to vary in approximately the same manner as the road wind resistance, as a function of the cube of the speed. If desired, and in any case when the fan is powered separately, appropriate alternative facilities for absorbing a matching amount of power from the traction rolls, must be made.

Some form of adjustable load is provided as an added drag on the traction rolls to represent the inertia due to the weight of the motor vehicle, i.e. the resistance to acceleration. This load generally takes the form of a series of selected flywheel weights proportional to the car weight and mounted to rotate on the dynamometer shaft, but other means, eg. electrical, may be utilized to provide the necessary degree of inertia. In the event that the inherent inertia of the system exceeds that of the vehicle under test, motor assistance may be used to reduce the effective inertia.

Vehicle rolling friction is approximated by the inherent frictional drag of the system.

Braking is applied to the traction rolls by means of the dynamometer brake in which an electric eld is applied to absorb energy derived from the rolls. The brake can be adjusted to enable (l) deceleration corresponding to the use of the car brakes, which are, of course, not in a position to perform their function normally, and (2) load application corresponding to the extra power needed on a gradient. For a given weight of car, the correct power absorption at a given speed to obtain any desired gradient may be computed. The most convenient dynamometer possesses a linear speed/power characteristic at a given excitation or'setting, when the simulated gradient obtained becomes independent of speed.

The dynamometer is normally equipped with roll locking friction brakes for use while mounting a vehicle for test, with emergency jacks in case of tire failure, and with other ancillary devices such as means for measuring the variation of any desired engine variable such as temperature, manifold vacuum, and the like, and means for controlling ambient atmospheric conditions.

Mileage accumulation dynamometers are designed to accommodate the whole range of vehicle sizes, weights and speeds, with suitable adaptation and proportioning of those components of the system which carry, produce or absorb loads. Such numerical adaptation forms no part of the present invention which is applicable quite generally. Several mileage accumulation dynamometers are preferably mounted together within the command of a common control point.

In one particular known system, the throttle position and braking load are varied according to a program predetermined by magnetic recording on a tape during a master test in a motor vehicle on the road. The throttle opening during consequent dynamometer tests must then be appropriately proportioned for each individual car put under test, to take into account the differences between the characteristics of the throttle and throttle linkage of each vehicle. This involves standardization at one particular road speed and is subject to error at other speeds.

According to further known apparatus the speed and throttle values are both predetermined according to a road program and a brake signal is used as compensating factor to obtain the correct desired speed for the given throttle position.

Variables such as throttle movements, wheel speed and braking actions, may be recorded on magnetic tape during an actual road run, or arbitrarily, by obtaining a voltage dependent on the variable by known means, e.g. with the aid of a potentiometer, and converting the voltage in an oscillator to a frequency modulated signal suited to recording. Such recorded signals may be used to control the appropriate elements of a chassis dynamometer by separating them from each other first if necessary in a discriminator and then converting them back to voltage signals for actuating dynamometer controls on playback. Such use of magnetic tape recordings is known to those skilled in the art and is not described herein in detail. It offers lamong its advantages the availability of a continuous control signal representing continuous road behaviour, capable of frequent cyclic repetition with a high degree of reproducibility, and a convenient way of storing a variety of predetermined programs. One tape output can be -used to control more than one mileage accumulation dynamometer.

It is the primary object of the present invention to provide a mileage accumulation dynamometer in which a predetermined wheel speed is obtained reproducibly under given conditions of load, among widely different test vehicles, without the need for compensatory throttle proportioning from vehicle to vehicle.

It is also an object of the invention to provide a dynamometer in which a predetermined wheel speed is obtained under given conditions of load according to a prearranged program, without the need for a master programming run on the road.

It is a further object of the invention to obtain typical and consistent simulation of engine behaviour in test runs on a mileage accumulation dynamometer whether from an arbitrary or from a prerecorded program.

It is a yet further object of the invention to provide a mileage accumulation system in which the wheel speed and Ibraking load are each specified according to a predetermined program and the throttle is adjusted automatically as the specified speed is approached so as to procure test conditions more closely similar than hithertoV adopted, to those found on the road.

The invention is based on the principle of specifying a predetermined speed under given load conditions and controlling the throttle in response to the speed attained.

According to the present invention a method of mileage accumulation on a chassis dynamometer comprises obtaining a predetermined wheel speed on the dynamometer under predetermined conditions of load by actuating the engine throttle automatically in response to actual wheel speed achieved. Y

According to the invention, therefore, a mileage accumulation dynamometer comprises one or more traction rolls adapted to be driven by the engine of a motor vehicle under test through the road wheel or wheels thereof, control means for determining a selected wheel speed in the rolls, means for applying a predetermined braking load, and control means for adjusting the engine throttle in accordance with actual wheel speed attained.

The control mean for wheel speed, load and initial throttle opening are preferably pre-set to vary according to a prepared test program. This program may be obtained by setting up timed automatic switch gear lor from a master tape recording produced on the road, of signals representing road speed and gradient or braking load. If desired, the gradient or braking signal may be applied manually on the tape, to obviate the use of a torquemeter.

The purpose 'of the throttle control means is to alter the throttle opening in response to the actual wheel speed attained in such a way as to bring that speed to the predetermined value desired, i.e. in dependence upon the difference between desired and realised speeds. The throttle control means is thus analogous to actuation by the driver on the road and is moreover capable of procuring the desired speeds without the assistance of corrective braking or other interferencewith the desired predetermined load conditions. The dynamometer system according to error signal is developed between the output of a tachometer driven by the traction rolls, and a reference voltage representing required wheel speed, the error signal then being utilized to adjust the throttle position in relation to the desired wheel speed and subject to feedback cor- .rections to avoid overshoot.

The invention makes possible the use of one or several test programs chosen at will on a wide variety 'of motor vehicles having unequal throttle characteristics, from a continuous tape recording of speed and load only, or even without a master trip or any trial and error experimentation (except to establish windage and friction characteristics). There is no need for throttle proportioning adjustment since the throttle is automatically adjusted according to need in obtaining the specified speed, once the throttle actuating means has been accommodated to the span of the throttle opening mechanism of the vehicle, e.g. the pedal.

Any given program may be applied to a wide range of vehicles after me-re adjustment of the inertial load in the dynamometer. It is moreover not necessary to determine the time occupied by acceleration or deceleration under various conditions, when preparing or recording the program, since the system reproduces actual road condi.

tions of itself.

Constant repetition of the same program is possible and a single operator can attend to the testing of several vehicles at once if more than one apparatus according to the invention is provided. The apparatus may be readily controlled manually, fully automatically by timed switchgear or from tape, and it may be stopped at any point in the program and Vre-set o-r allowed to Iproceed.

Tape operation offers the particular advantage of continuous reproduction of -road circumstances and behaviour as they occur, as opposed to the stepwise program of timed switchgear. Arbitrary program set up on tirned switchgear may be used to produce a taped continuous program by recording speed and gradient in a vehicle on the dynamometer of the invention.

Other engine variables of particular interest, such as temperature 'or manifold vacuum, may also be employed as controlling factors in a mileage accumulation dynamometer according to the invention by suitable modification of the controls, if desired also affecting the throttle.

Timed switch-gear for the provision of a manually compiled program of control signals for the dynamometer of the present invention for simulating events o-f real or` imagined road performance, may for instance take the following form, described by way of illustration.

For each event in a desired sequence of up to, say, 36 events, a set of controls is provided in a unit for the four functions: initial throttle opening, time, road wheel speed, and gradient. A uniselector enables the individual sets of controls to be brought in to operation in sequence and provides for cyclic repetition of the whole sequence, which may be shortened to fewer events by setting some of the individual time controls at zero.

For each event, the respective set of controls includes a timer, based on a ramp generator giving linear time controlover an interval of 5 minutes. A potentiometer is used to select a desired period from 10 seconds to 5 minutes in this interval, after which period a signal is passed to an additional timer giving up to l1 successive intervals of 5 minutes laccording to the setting of a 12- position switch, so that a total time for each event of from 10 seconds to 'one hour may be selected. At the end of each event, the uniselector is moved on to the next event and the next unit with a similar set of'controls.

Eachset of controls includes a rotary potentiometer switch tapping off a voltage for maximum throttle opening, as hereinafter explained in more detail, representing throttle shut to throttle fully open, in increments of one-tenth fully open. Setting this switch permits initial acceleration of the engine. Each set of controls includes at least one rotary potentiometer switch tapping olf a voltage representing desired road wheel speed, and calibrated as required according to maximum speed and increments of speed desired. Each set of controls may also include a further rotary switch tapping oi a voltage representing gradient, which is used to regulate field excitation in the dynamometer proportional to the required gradient effect, up to a maximum representing full braking, at, say, 150 HP.

The voltages representing throttle maximum setting, desired road wheel speed and gradient, are fed to the chassis dynamometer apparatus for instance as described below with reference to the accompanying drawings.

The electronic gear referred to in this description may be obtained, for instance, from Albert Mann Engineering Ltd., of Basildon, Essex, England.

The invention will now be more fully described, by way of illustration and without thereby limiting its scope, with reference to the accompanying drawings, in which:

v FIGURE 1 represents in schematic form the general L layout of a mileage accumulation dynamometer according to the invention;

FIGURE 2 represents also in schematic form the circuit for throttle control indicated generally in FIGURE l;

FIGURE 3 represents in graphic form the performance of two cars on a mileage accumulation dynamometer (A) of the prior art and (B) according to the invention.

The dynamometer shown in FIGURE 1 may, as to its physical layout and principal mechanical features, take any of the forms known to the art and is therefore not illustrated herein from a mechanical aspect, but in relation to the controls associated therewith and the manner of using them.

The dynamometer shown in FIGURE l is fed according to circumstances with operating signals as hereinbefore indicated, derived from timed switchgear (Auto), lfrom pre-recorded tape (Tape) or from manual setting of controls (Manual). These signals are fed in by lines 1, 2 and 3 respectively of an electrical control .panel 4. According to the disposition of the controls on this selection panel 4, the signals are passed forward as follows. AU Maximum Throttle signal voltage is passed along line 5, and a Required Road Speed signal voltage along line 6, to a throttle control circuit shown generally at 7 and more yfully described in relation to FIGURE 2. A Required Gradient signal voltage is passed along line 18 to a potentiometer 19 referred to as a car weight vernier, whereby the voltage is adjusted in accordance with car weight to allow for its effect in relation to gradient, and then passed in line 20 to the gradient/.brake control circuit shown at 16.

' The( throttle control circuit also receives a Road Speed signal representing actual speed attained, from line 17, and a reference voltage referred to as Comparator Balance Voltage from line 8. The throttle control actuates the throttle of the motor vehicle engine 10 through a mechanical linkage 9.

The engine 10 drives the road wheels of the vehicle through the usual power train, shown as a mechanical drive 11, these road wheels being mounted in driving relationshp on the traction rolls 12 of a dynamometer. The main dynamometer shaft 13, transmits the road wheel rotation to several components of the system. Shaft 13 conveys energy to the fan 21 for blowing cooling air 22 at the engine 10 and rotates a number of selected iiywheel weights shown generally at 15, to provide inertia corresponding to that of the vehicle. These weights provide increments of 100 to 200 pounds weight, for instance, in order to simulate vehicle inertia to within 50 pounds (less than the variation in fuel load of common vehicles), and are detachably mounted on the shaft. A tachometer 14 delivers the Road Speed signal already referred to, according to the revolutions of the shaft 13 which drives it. The shaft 13 also passes through the gradient appliance, provided for instance by one or more direct ycurrent generators feeding a resistive load, and shown generally at 16. The gradient effect, i.e. the drag on the shaft 13, is controlled with the aid of field excitation control through line 20,v the excitation voltage being supplied in line 32. Feedback may be applied fromy the tachometer generator to linearise the gradient effect with speed. The controlling signal voltage is modified by a factor according to vehicle weight, to take into account the fact that the effect of gradient is a -function of vehicle weight.

Braking is brought about by applying maximum gradient signal and minimum throttle signal, whereby constant deceleration takes place until at about l5 miles per hour a friction 'brake may be applied to stop the rolls.

Turning now to FIGURE 2, wherein parts common to FIGURE l are indicated by the same reference numerals, the Maximum Throttle voltage in line 5 is seen to be the anode voltage of a thermlionic valve 24 in a cathode follower circuit. The maximum cathode signal is thus determined by the Maximum Throttle signal. The Required Road Speed signal in line 6 is accepted by a summing circuit shown at 23, where it is compared with the Road Speed signal from line 17, to produce a resultant error signal in known manner in line 25 which is applied to the lgrid of the valve 24. Current ow in valve 24 thus depends on the difference between desired and achieved road wheel speed and this difference thus determines the signal in the cathode line 26, subject to the overriding effect of the anode voltage xed by the Maximum Throttle setting. The line 26 feeds a comparator circuit 27 Where the signal in line 26 is compared with a comparator balance voltage originating in line 8 Ifrom a stabilized source.

If the signal in line 26 is greater or less than the Icomparator balance voltage as supplied in line 29, a resultant signal passes to the servo actuation unit 31 to open or close the throttle respectively. The servo unit includes the necessary amplifiers to provide power for actuating the servo motor in response to the relatively small signals operating the circuit. 'Ihe servo motor operates the throttle |by means of a simple arm device, indicated at 9, incorporating a span adjustment whereby the full movement of the arm may be matched with the -full movement of the throttle linkage. The arm is generally attached to the accelerator pedal of the vehicle.

The servo motor also actuates a potentiometer 28 in operating the throttle, whereby the comparator balance voltage is modified. Ihe purpose of this modification is to provide negative feedback so that throttle opening is restrained or stopped as required road speed is approached, lest the actual road speed should overshoot the mark, and to prevent hunting.

The engine under test, and elements 10 to 14 of FIG- URE l, are also represented on FIGURE 2 for complete understanding of the circuit. It will be appreciated that the throttle maximum control overrides the speed control until the opening required in the throttle for the set speed is less than that already set by the throttle maximum control.

In the operation of the mileage accumulation dynamometer, the motor vehicle engine is started manually after the vehicle has been secured to the test deck, and the Maximum Throttle control is set so as to allow for the initial acceleration of the engine as the dynamometer takes over from the manual operator. Let us suppose that the maximum throttle setting is 9.9, representing nine tenths of maximum opening. As soon as there is an input in the Required Road Speed line 6, i.e. according to the setting of the source controls, whether tape, auto, or manual as described hereinabove, there will be an error signal in line 2S. This error will be large, and will bring about servo actuation of the throttle to nine-tenths fully open, according to the limitation set by the anode voltage of valve 24. At the same time, the potentiometer 28 moves, and the resultant negative feedback ensures proper throttle setting without hunting and also begins to restrain the throttle opening as the actual road speed rises.

The desired road speed varies, ofcourse, with time, as on the road, and the feedback arrangement permits the apparatus to simulate true driver behaviour in this respect, without chatter or hunting effects, by bringing back the throttle pedal after an initial excessive opening but before desired speed is actually attained. This control is applicable to any vehicle, irrespective of throttle characteristics, subject only to span adjustment. The throttle opening can be arranged to reduce `at a moment when the actual speed is within a certain fraction of the desired value, e.g. Subject to the Maximum Throttle setting, if the throttle is insufficiently open, the servo will open it further, and the desired road speed program is accurately followed by the actual speed, without application of un-predetermined braking and without any direct throttle program.

FIGURES 3A and 3B illustrate by comparison the advantages to be gained according to the present invention, by reference to the performance of two cars designated A and B. FIGURE 3A relates to the performance of cars A and B on a prior art .dynamometer, while FIGURE 3B lrelates to cars A and B running on a dynamometer according to the invention. The car performances are described in respect of so-called events but it will be appreciated that these may represent the stepwise sequences initiated by timed switchgear, or parts of a taped program considered stepwise for clarity. Six events have been considered, as indicated at the top of each iigure, timed according to the time scale of minutes along the horizontal axes of the iigures. The same events apply to both figures.

In the upper part of each figure, the vertical scale represents percentage gradient applied, while the lower portions represent road speed attained in miles per hour.

FIGURE 3A relates to a dynamometer system in which speed and throttle position are initially speciiied by the program, and an error signal is applied to the gradient/ brake to correct the speed obtained by applying load. Such a program is primarily designed to suit a particular car A; to apply it to another car B, the throttle opening must be standardised e.g. by iinding the opening ratio at 45 miles per hour for level road speed by experiment on the road, and then adjusting every throttle opening specihed for car B in the same ratio, by means of a special span adjustment for throttle proportioning. This ratio is, however, not in fact constant with speed, so that consequent errors are generated. In these iigures, car B is supposed to have approximately half the power available in car A. This comparison depends on the degree of throttle opening, and the consequent ditferences in car behaviour are shown shaded (and magnied for clarity).

In FIGURE 3A the events are as follows:

Event 1.- Program: 4 minutes at 45 m.p.h.

Car A requires 0.3 throttle (the throttle openings are shown on the figures against the identifying letters of the cars beside the relevant performance curves, in tenths of full opening) but car B requires 0.6 as determined in the abovedescribed experiment.

Event 2.-Program: 6 minutes at 80 m.p.h. `Car A requires 0.45-throttle to reach 80 m.p.h.` in about 3 minutes and hold .that speed. Car B on the other hand, given twice that amount of throttle opening according to the determined ratio, calls for the application of braking load as shown at I to restrain acceleration at 80 m.p.h.

Event 3.-Pr0gram: 10 seconds at 35 m.p.h.

Car A and car B both have throttles fully closed as brake excitation is applied and may decelerate together, but an error develops in Event 4. The brake application is denoted'by II.

Event 4.-Progntzm: 3 minutes at 35 m.p.h. Car A levels oit at 35 m.p.h. under 0.18 throttle, but with the calculated throttle of 0.36, car B runs at a lower speed, giving an error shown at V. Y

Car A uses 0.5 throttle, but the corresponding use of 1.0 (full) throttle in car B is too high, and corrective. braking or gradient of 10% is needed to keep the speed to 20 m.p.h. This gradient difference is shown at III.

Event 6.--Pr0grarm 6 minutelr at 35 m.p.h. (nio gradient) Car A continues at 0.5 throttle, accelerating to 35 m.p.h. as level ground is reached. Car B on the other hand, given a calculated full throttle again (see Event 5) needs brake application to keep the speed down to 35 m.p.h. Moreover, the time required to do this must 'be found by trial. As soon as this point (x) on the time scale is reached, a fresh command is given to car A of 0.18 throttle at 35 m.p.h."-

However, this will cause a speed error, as at 35 m.p.h. 0.36 is too low for car B. The brake error is shown at IV and the speed error at VI.

In FIGURE 3B the events are the same as far as intended program is concerned, and both cars are the same. Similar adjustments are made to match the inertia of the cars by attaching weights to the rolls mechanism and lto match the windage and friction characteristics of the cars by adjusting the fan loading. The weight compensation controls are set so that a given brake or gradient signal is proportioned according to the weight of each car. In this case, however, the throttle is controlled according to the present invention. The cars now behave as follows.

Event 1.-Prog1-am: 4 minutes wat 45 m.p.h.

The throttle is initially set at 1.0 with gradient at zero. Both cars run too fast with full throttle and the system cancels the maximum throttle and returns car A throttle to 0.3, car B throttle to 0.6, correct for 45 m.p.h. (see FIGURE 3B).

Event 2.-Program: 6 minutes at 80 m.p.h.

Initial throttle setting is 0.9 and both cars accelerate. As car A approaches m.p.h. the system reduces car AV throttle to 0.45, and car B throttle is reduced a little later to 0.8. Throttle reductions occur at or about point C in the diagram. Both cars are thereby held at 80 m.p.h. without brake signal alterations.

Event 3.--Progr:zm: 10 lseconds at 35 m.p.h.

Brake application with closed throttles brings both cars to 35 m.p.h., decelerating together due to the weight proportioning device.

Event 4.-Pr0gram: 3 minutes at 35 m.p.h.

The initial throttle setting is raised to 1.0 with zero braking and the system reduces car A throttle to 0.18, and car B throttle to 0.4, in response to the fact that the de-y sired speed is the same as the speed attained already. No speed error occurs with car B.

Event 5.-Pr0gram: 6 minutes at Z0 m.p.h. up 71/2% gradient Event 6.-Program: 6 minutes at 35 m.p.h.

Initial throttle is again 1.0, with zero gradient signal. Both cars accelerate until they approach the desired speed until in the neighbourhood of point Cthe system returns the throttles to the same ultimate settings `as in Event 4.

It will be seen from the foregoing description that throughout 'a varied series of events which are typical of actual road conditions the throttle is subject to a control which is derived from the engine speed and is a function to the difference between that speed and the desired speed.

What I claim is:

1. In an apparatus 'for operating several throttle actuated stationary vehicles having wheel systems mounted on traction rolls of a chassis dynamometer, the improvement which comprises means to generate a rst signal representative of Ia predetermined wheel speed, means to generate second signals representative of the actual wheel speed of each vehicle, means to generate error signals representative of the difference between said first and second signals, means to automatically and continuously apply said error signals to control the respective throttle of each vehicle, means to generate a third signal representative of a predetermined gradient load, means to generate further signals by modifying said third signal by respective factors equal to the weight of each of said vehicles and means to apply said further signals to control the respective resistive loads on the traction rolls of said chassis dynamometer for each of said vehicles.

2. In a method for operating a throttle-actuated stationary vehicle having a wheel system mounted on the traction rolls of a chassis dynamometer, the improvement which comprises generating a first signal representative of a predetermined wheel speed,

generating a second signal representative of the 'actual wheel speed of said vehicle,

comparing said signals and generating an error signal responsive to said first and second signals,

generating a third signal representative of throttle position,

generating a second error signal responsive to said third signal and said first error signal, and

applying said second error signal to control the movement of said throttle.

3. In the method of claim 2, the improvement wherein said third signal reduces the throttle opening when said first error signal is within a predetermined range.

4. In the method of claim 2, wherein several of said first error signals are generated to operate respective vehicles veach mounted on traction rolls of a chassis dynamometer, the improvement which comprises -generating a fourth signal representative of a predetermined gradient load,

generating fifth signals by modifying said fourth signal by respective factors equal to the weight of each of said vehicles to control the respective resistive loads on the traction rolls of the chassis dynamometer for each of said vehicles.

5. In the method of claim 2, the improvement which comprises generating a signal representative of a predetermined gradient load on said vehicle and applying said latter signal to control the resistive load n the traction` rolls of said chassis dynamometer.

6. In the method of claim 2, wherein a fan is adapted to cool said vehicle, the improvement which comprises operatively conveying energy from said dynamometer traction rolls to drive said fan.

7. In a method for operating a throttle-actuated stationary vehicle having a wheel system mounted on the traction rolls of a chassis dynamometer, the improvement which comprises generating a rst signal representative of a predetermined wheel speed,

generating a second signal representative of the actual wheel speed of said vehicle,

comparing said signals and generating an error signal representative of the difference between said signals, generating a third signal representative of a predetermined maXimum-limit throttle position,

generating a fourth signal responsive to said third signal and said error signal,

generating a comparator balance signal representative of throttle position,

generating a difference signal representative of the difference between said fourth signal and said comparator balance signal, and

applying said difference signal to control the movement of said throttle.

8. In an apparatus having la throttle-actuated stationary vehicle with a wheel system mounted on the traction rolls ofa chassis dynamometer, the improvement which comprises means to generate a rst signal representative of a predetermined wheel speed,

means to generate `a second signal representative of the actual wheel speed of said vehicle,

means to generate an error signal representative of the difference between said first and second signals,

means to generate a third signal representative of a predetermined maximum limit throttle position, and means responsive to said error signal and said third signal to generate a fourth signal, and

means to apply said fourth signal to control the position of said throttle.

9. In an apparatus having a throttle-actuated stationary vehicle with a wheel system mounted on the traction rolls of a chassis dynamometer, the improvement which comprises means to generate a first signal representative of a predetermined wheel speed,

means to generate a second signal representative of the actual wheel speed of said vehicle,

means to generate an error signal representative of the difference between said first and second signals, means to generate a comparator balance signal representative of throttle position,

means to generate a difference signal representative of the difference between said error signal and said comparator balance signal, and

means to apply said difference signal to control the movement of said throttle.

I0. In the apparatus of claim 9, the improvement which comprises means to generate a signal representative of a predetermined gradient load on said vehicle, and means to apply said latter signal to control the resistive load on the traction rolls of said chassis dynamometer.

11. In the apparatus of claim 9, the improvement wherein said means to generate said comparator balance signal is adapted to lreduce the throttle opening when said error signal is within a predetermined range.

12. In the apparatus of claim 9 wherein a fan is adapted to cool said vehicle, the improvement which comprises means to operatively convey energy from said dynamometer traction rolls to drive said fan.

References Cited UNITED STATES PATENTS 2,248,938 7/1941 Bennett 73l17 2,883,975 4/1959 Spetner 12?:102 3,016,739 1/1962 Ionach et al 73-116 3,050,994 8/1962 Heigl et al 73-118 X 3,099,154 7/1963 Vanderbilt 73-116 OTHER REFERENCES Obert, E. G., Internal Combustion Engines, 2nd edition, 1959, International Textbook Co., Scranton, Pennsylvania, page 48.

RICHARD C. QUEISSER, Primary Examiner.

J. W. MYRACLE, Assistant Examiner.

Claims (1)

1. IN AN APPARATUS FOR OPERATING SEVERAL THROTTLE ACTUATED STATIONARY VEHICLES HAVING WHEEL SYSTEMS MOUNTED ON TRACTION ROLLS OF A CHASSIS DYNAMOMETER, THE IMPROVEMENT WHICH COMPRISES MEANS TO GENERATE A FIRST SIGNAL REPRESENTATIVE OF A PREDETERMINED WHEEL SPEED, MEANS TO GENERATE SECOND SIGNALS REPRESENTATIVE OF THE ACTUAL WHEEL SPEED OF EACH VEHICLE, MEANS TO GENERATE ERROR SIGNALS REPRESENTATIVE OF THE DIFFERENCE BETWEEN SAID FIRST AND SECOND SIGNALS, MEANS TO AUTOMATICALLY AND CONTINUOUSLY APPLY SAID ERROR SIGNALS TO CONTROL THE RESPECTIVE THROTTLE

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