WO1999060363A1

WO1999060363A1 - Portable roller dynamometer and vehicle testing method

Info

Publication number: WO1999060363A1
Application number: PCT/CA1999/000457
Authority: WO
Inventors: Jacek L. Rostkowski; William Desmond Mcgonegal; Frederick J. Hendren; Roman Gorny
Original assignee: Her Majesty The Queen In Right Of Canada, Represented By The Minister Of The Environment
Priority date: 1998-05-20
Filing date: 1999-05-19
Publication date: 1999-11-25
Also published as: EP1080354A1; CN1188685C; AU3922599A; BR9911030A; JP2003513227A; CN1301340A; HK1038258A1; MXPA00011230A

Abstract

A roller dynamometer is provided, having at least one supporting carriage having a rotatable roller and a dynamometer linked to the roller for measuring torque output of a vehicle. The carriages are rollable on a substrate for positioning under a vehicle. In one aspect, multiple dynamometer and roller units are provided, for engagement with multiple vehicle wheels, with the units being linked electrically for common control by a control unit that simulates either straight line or curved driving conditions. In a further aspect, the dynamometer is supported on the carriage by a rotary mount. In a further aspect, the rollers have a generally hourglass shape to permit vehicle wheel self-centering.

Description

PORTABLE ROLLER DYNAMOMETER AND VEHICLE TESTING METHOD

FIELD OF THE INVENTION

The invention relates to a dynamometer and test method for simulating road conditions, for testing a vehicle having at least two drive wheels, and more particularly to a dynamometer having rollers for engagement with the vehicle wheels, and that is relatively compact, inexpensive and portable. Further, the invention relates to an apparatus and method permitting simulation of straight-line and curved driving conditions. The invention may also be adapted for use with a vehicle having a single drive wheel such as a motorcycle.

BACKGROUND OF THE INVENTION

Emissions testing and maintenance of vehicles is effective if vehicle road conditions may be effectively simulated. This is typically accomplished by means of a roller arrangement for contact with the drive wheels of the vehicle, with the rollers being operatively linked to a dynamometer for placing a controlled load on the rollers. The load quantum will be a function of the rotational speed of the rollers (i.e. the simulated vehicle speed), simulated and real frictional losses, and a polynomial equation representing wind resistance of the particular vehicle. The dynamometer simulates two aspects of vehicle performance, namely inertia and drag. Inertia in this case is governed by the weight of the vehicle and the equivalent of rotating masses of the vehicle, with the device thus simulating inertia based on this factor. Drag is simulated by the dynamometer applying a resistance to the rollers, governed by the actual wheel speed of the vehicle and the wind resistance factor. Inertial energy may be provided by means of a fly wheel as well as simulation by other means

Conventional roller testing stands for motor vehicles typically comprise one or more large rollers, with a single roller spanning the left and right vehicle wheels For example, the apparatus disclosed in US Patent 3,554,023 (Geul), US Patent 5,154,076 (Wilson et al) and US Patent 5,193,386 (Hesse, Jr et al), are all of this type It is also known to provide a testing assembly for use with a motorcycle that contacts the sole driven wheel of the vehicle (US Patent 5,429,004 - Cruickshank)

Conventionally dynamometer resistance is provided by a braking mechanism such as an electric motor, water brake, etc However, other resistance-generating means may be employed and the present invention is not limited to the use of any particular braking means

Conventional dynamometer-based testing devices are typically large, heavy and correspondingly expensive This results in part from the provision of a single roller for contact with left and right driven wheels of a vehicle, that is wide enough for use with substantially all conventional vehicles, resulting in a large and heavy roller arrangement This drawback may be addressed by providing a testing apparatus whereby the individual left and right vehicle drive wheels are each provided with their own roller arrangement, with each set of rollers being separately and independently linked to a corresponding dynamometer The individual dynamometer assemblies are thus not mechanically linked, but linked only electronically through a controller The individual dynamometers may be then placed in communication with a common control unit to equalize the simulated loads between the vehicle drive wheels This arrangement also permits for unequal loads and wheel speeds between the individual units, to simulate a vehicle driving around a curve SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved roller dynamometer and testing method for simulating road conditions for testing a vehicle.

A further object is to provide a roller dynamometer comprising multiple dynamometer assemblies not mechanically linked to each other for common rotational movement, each dynamometer assembly for contact with an individual vehicle wheel, with the effective width of the roller dynamometer being variable by changing the distance between the individual units.

A further object is to provide a roller dynamometer that may be used with any conventional vehicle, and which has the capacity to simulate either straight-line or curved driving conditions.

A further object is to provide a relatively lightweight and portable roller dynamometer that may be conveniently transported to a testing site.

In light of the above objects, the present invention comprises in one aspect a roller dynamometer assembly for simulating road conditions for a vehicle having at least two drive wheels, comprising: first and second dynamometer carriages; carriage support means associated with at least one and preferably both carriages for supporting one or both carriages and permitting the carriage to be moved relative to a substrate; first and second rollers not mechanically linked with each other rotatably mounted to respective carriages for supporting and rotatably contacting a corresponding vehicle wheel; first and second dynamometers (conveniently comprising electric motors) each having speed and torque sensing means and engaged to a corresponding roller for applying a load to said corresponding roller whereby road conditions are simulated on a vehicle engaged with said apparatus.

The carriage support means, which preferably comprise roller means such as an array of linear bearings, permit independent lateral (relative to the vehicle) movement of the carriages. This permits adjustment of the carriage spacing to accommodate different vehicles (permitting the use of relatively compact rollers) and roller self-centering on the vehicle wheels when the device is in use. The latter is particularly useful when the device simulates curved driving conditions.

The rollers may also have a stepped portion at each of the opposed ends to serve as a wheel stop and fly wheel.

The apparatus further conveniently incorporates a rotary mount for supporting and mounting each dynamometer to corresponding carriages for limited rotational movement relative to said carriage.

The rotary mount preferably comprises first and second concentric members, such as a disc and trunnion bearing arrangement, engaged to said dynamometer and carriage respectively for rotation relative to each other.

In one version, the dynamometers are in communication with a controller, the controller receiving wheel speed and torque information from each of the dynamometers. The controller includes processing means for comparing rotary speed differences between the first and second dynamometers and torque control means for controlling the torque applied by at least one and preferably both of the dynamometers to substantially equalize the respective rotary speeds of said rollers. The control means preferably directs a faster spinning dynamometer to apply a greater amount of power absorption to its corresponding roller, relative to the slower spinning dynamometer.

The controller may include total power absorption calculation means, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometers.

In one version, the torque control means further permits control of one or both dynamometers to apply a controlled unequal rotary speed of the respective rollers to simulate a curved driving condition.

In another aspect, the invention comprises a roller dynamometer vehicle testing assembly for simulating road conditions for a vehicle, comprising: at least one roller mounted to a frame for supporting and rotatably contacting a vehicle wheel; a dynamometer engaged to the roller for applying a load to the roller whereby road conditions are simulated on the vehicle engaged to the apparatus; a rotary mount for engaging and supporting dynamometer onto the frame for rotational movement relative to the frame, the rotary mount comprising first and second concentric members engaged to said dynamometer and carriage respectively.

The rotary mount is conveniently of the type characterized above. Further, the apparatus is conveniently provided with rollers for contact with the drive wheels of the test vehicle. In a further aspect, the invention comprises a roller dynamometer for simulating road conditions for a vehicle having at least two drive wheels, comprising first and second roller dynamometer assemblies for independent engagement with corresponding drive wheels, each roller dynamometer assembly comprising at least one roller engaged to a corresponding dynamometer, the first and second dynamometer assemblies for independent rotation of the respective rollers relative to each other and each having rotary speed and detection means and power absorption means, and a control unit for receiving rotary speed and torque information from said dynamometers and having a logic circuit for comparing and measuring any speed differences and controlling one and preferably both dynamometers in response to speed differences

The logic circuit controller controls the power absorption means of the first and second dynamometers to achieve either straight-line or curved driving simulation

The controller conveniently includes total power absorption calculation means, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometer

In a further aspect, the invention comprises a method for simulating road conditions for a vehicle, comprising the steps of providing first and second independent roller dynamometer assemblies each associated with torque and rotational speed sensors, the first and second assemblies being associated with a controller for receiving speed and torque information from each dynamometer assembly and independently controlling the resistance applied thereby; supporting at least two vehicle drive wheels on corresponding first and second roller dynamometer assemblies; driving the drive wheels with the test vehicle; independently measuring the speed and torque of the two drive wheels; independently controlling at least one and preferably both roller dynamometer assemblies to control the rotary speed thereof.

A further step may comprise measuring the total power output of the vehicle with an algorithm that calculates total dynamometer power absorption, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometer.

The rollers preferably comprise in any of the above devices and methods a generally hourglass configuration for self-centering of the vehicle wheels.

The present invention will now be described by way of detailed description and illustration of specific examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a plan view of one embodiment of the present invention; Figure 2 is a side elevational view of a portion of the apparatus as shown in Figure 1 ; Figure 2a is an end elevational view of Figure 1 ; Figure 3 is a plan view of an individual roller unit for use in accordance with the present invention; Figure 4 is a plan view of a further embodiment of a roller carriage; Figure 5 is a side view of Figure 4; Figure 6 is a perspective view of the apparatus in use; and Figure 7 is a block diagram showing the operation of the invention.

Similar numerals in the drawings denote similar elements.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figures 1 and 2, the apparatus 10 includes first and second identical carriages 24, one of which is illustrated herein. In use, the respective carriages are positioned under the left and right vehicle wheels when a vehicle is engaged for testing with the device. The carriages each support individual rollers, described below, for engagement with the vehicle wheels, and dynamometers mating with the rollers. The carriages are conveniently positioned on a smooth, level, hard surface 15. Each carriage may be moved laterally (relative to the vehicle) on the surface by roller means associated with each carriage, such as a linear bearing array 30 (shown in Figure 2) on the lower face of the carriages. The roller means further permit the carriages to roll laterally while bearing the vehicle, in order to accommodate the self-centering of the carriage rollers.

Turning to Figures 3-5, each carriage 24 comprises a generally rectangular carriage frame 32 composed of side frame members 34, end frame members 36, the whole being bisected by paired transverse frame members 40 and 42 to form first and second rectangular carriage portions 32a and 32b. The first carriage portion 32a supports the rollers, described below, and the second carriage portion 32b supports the dynamometer, described below. End and transverse frame members 36 and 40 of the first carriage portion 32a each support a pair of axle bushings 50 for rotatably supporting the rollers 54. Roller axles 56 associated with each of the rollers are rotatably joumalled within the axle bushings. The end and transverse members 36 and 42 of the second carriage portion 32b support dynamometer mounts 60, for rotatably mounting a dynamometer 46 to the carriage. The dynamometer and mounts will be described in greater detail below.

The first carriage portion 32a supports a pair of spaced-apart rollers 54 in parallel orientation for supporting and rotationally engaging a driven wheel of a vehicle.

In one version, one of the rollers 54 of the pair is engaged to a dynamometer. The other roller freewheels. Each carriage thus supports a single dynamometer, comprising a power absorption unit ("PAU") associated with a single vehicle drive wheel. It will be seen that with modification, the rollers can be sized to accommodate paired drive wheels of the type found in trucks and busses.

The dynamometer mounts 60 each comprise a disc 62 fixedly mounted to the carriage portion 32b for engagement with a corresponding end face 64 of the dynamometer 46. A circular array of bearing cartridges 66 are mounted to each end face of the dynamometer, and rotatably engage the fixed disc, which includes a recessed rim 68 which comprises a bearing race.

A strain gauge holder comprises first and second arms 70, 72 extending from the dynamometer and carriage member 32b respectively. A strain gauge 74 joins the respective arms and restricts rotation of the dynamometer relative to the carriage. The strain gauge comprises a transducer for converting torque between the dynamometer and the carriage into electrical current. In a further embodiment, shown in Figures 3 and 4, the carriages 24 each comprise frame members 80 forming a rectangular configuration for supporting the rollers. A dynamometer support member 82 comprising a generally plate-like member extends from a transverse frame member outwardly away from the centre of the apparatus. Each dynamometer support has an upwardly extending bushing 84 for rotatably engaging and supporting a dynamometer 86. Each roller 54 is releasably engaged to a corresponding dynamometer by means of a releasable coupling 90. A strain gauge, not shown, linking the dynamometer to the dynamometer support limits rotational movement of each dynamometer and permits accurate measurement of the rotational forces acting on the dynamometer.

Turning to the rollers 54, which are shown more particularly at Figure 5, each of the rollers includes an upwardly stepped portion 66 at each respective end, which serves both as a fly wheel and a wheel stop to minimize the risk of a vehicle wheel disengaging from the roller.

Each roller 54 has a generally hour-glass shape, and comprises a central axis, with the body of the roller diverging from generally the mid-point of the central axis at an angle of about 170° to about 179° 59' relative to the longitudinal axis of the roller.

It is found that this arrangement facilitates accurate positioning and enhances self-centering of a wheel on the roller without undue tire wear. Lateral movement of the rollers in response to the self-centering motion is accommodated by the rollable movement of the carriage on the substrate permitted by the linear bearings.

Figure 6 illustrates the disposition of the apparatus 10 under the front (drive) wheels of a vehicle 100 (shown in broken line). In the arrangement shown, the vehicle under test comprises a front-wheel drive vehicle. The apparatus may be readily adapted for use with motorcycles and other single- wheel drive vehicles, rear-wheel drive or four-wheel drive vehicles, or other drive arrangements, by means of adapting or re-positioning the units and/or providing additional units for mating with corresponding vehicle drive wheels.

Each dynamometer includes a rotational speed measurement means such as an internal optical position reader (referred to below), for measurement of the rotational position of the dynamometer shaft. The optical reader data is transmitted to the central controller described below, which calculates the rotational speed of the dynamometer and the corresponding roller.

The dynamometers are each linked to a central control unit 200, which will now be described by reference to Figure 7. The control unit permits the individual left and right dynamometers to apply a substantially exactly equal load to the corresponding wheels, to simulate straight-line driving conditions. Alternatively, a controlled unequal load may be applied to simulate the vehicle driving around a curve.

Electric signals from transducers 202 associated with strain gauges 74, indicative of the torque, may comprise amplitude or frequency variable signals. These signals, along with the signals from the optical position reader 204, are transmitted to the controller. The controller separately receives speed and torque information from each corresponding roller unit. In a straight-line driving simulation, all of the rollers should spin at the same speed. Since there is no mechanical link to transmit rotation movement between the roller units corresponding to the respective vehicle sides, a logical link is created by the controller to permit the controller to control the transducer to maintain identical speeds. The controller accordingly includes a comparator circuit 206 to assess any speed difference between the respective dynamometers. If any speed difference is detected, this information is transmitted to logic circuit 207, which in turn controls left and right motor control circuits 208 associated with each dynamometer, which in turn increase or decrease, as the case may be, the load applied by the respective dynamometer.

The logic circuit 207 may include software that applies a power splitting algorithm based on roll speed difference to control the respective dynamometers. The control algorithm calculates an appropriate control signal such that more of the absorbed power will be shifted to the faster spinning roll, with more load applied by the corresponding dynamometer, in order to slow it down. The dynamometer attached to the slower spinning roll will be required to absorb less power, permitting the corresponding roller to speed up. A vehicle power output logic circuit, which may be software-driven, will calculate the total power absorbed amongst all rolls, based on the following: a) the mass of the vehicle; b) the real time roll acceleration; c) the roll speed and roll load to be simulated, the latter based on known vehicle aerodynamic and friction loss factors; d) frictional losses within the dynamometer to be compensated for; and e) the force output of the vehicle.

A display 212 displays the simulated vehicle speed, turn radius and power output.

The examples given above identify an electric motor-type dynamometer; it will be seen that any suitable PAU may be used. It will be further seen that the apparatus and method have been described by reference to a vehicle having at least two drive wheels, aspects of the invention may be readily adapted for use with a vehicle having a single drive wheel, such as a motorcycle.

Although the present invention has been described by way of preferred version, it will be seen that numerous departures and variations may be made to the invention without departing from the spirit and scope of the invention as defined in the claims.

Claims

WE CLAIM:

1. A roller dynamometer vehicle testing assembly for simulating road conditions for a vehicle having at least two drive wheels, comprising: first and second roller carriages; carriage support means for supporting at least one of said first and second carriages on a substrate whereby said at least one carriage may be moved laterally relative to said vehicle on said substrate; each carriage rotatably supporting a roller for independently supporting and rotatably contacting a vehicle drive wheel; and each carriage supporting a dynamometer, each dynamometer having speed and torque sensing means and engaged to a corresponding roller for applying a load to said corresponding roller whereby road conditions are simulated on a vehicle engaged with said apparatus.

2. The apparatus as defined in claim 1 , wherein each said carriage has rotatably mounted thereto at least two spaced-apart rollers in parallel relationship for rotatably supporting and engaging a wheel.

3. The apparatus as defined in claim 1 , wherein said carriage support means comprises roller means.

4. The apparatus as defined in claim 3, wherein said roller means comprises an array of linear bearings mounted to each of said carriages.

5. The apparatus as defined in claim 1 , wherein each of said carriages includes carriage support means.

6. The apparatus as defined in claim 1 , wherein said rollers each comprise an elongate generally cylindrical body having opposed ends and a middle region, said body having a generally hour-glass shape whereby the middle region has a narrowed waist relative to the opposed ends of said body

7 The apparatus as defined in claim 1 , wherein said rollers each comprise a generally cylindrical body having opposed ends, and having an upwardly stepped portion at each of said opposed ends having a diameter whereby the diameter of said stepped portion is greater than the diameter of said roller immediately adjacent said portion

8 The apparatus as defined in claim 7, wherein said stepped portion comprises a fly wheel

9 The apparatus as defined in claim 1 wherein said dynamometers each comprise an electric motor

10 The apparatus as defined in claim 1 , further incorporating a rotary mount for mounting at least one of said dynamometers to a corresponding of said carriages for limited rotational movement relative to said carriage

11 The apparatus as defined in claim 10, wherein said rotary mount comprises first and second concentric members engaged to said dynamometer and carriage respectively for rotation relative to each other

12 The apparatus as defined in claim 11 , wherein said first member comprises a disc and said second member comprises disc engaging means

13 The apparatus as defined in claim 12, wherein said disc engaging means comprises a trunnion bearing array

14 The apparatus as defined in claim 1 wherein said dynamometers are in communication with a controller, said controller receiving wheel speed and torque information from each of said dynamometers, and having processing means for comparing rotary speed differences between said first and second dynamometers and torque control means for controlling the torque applied by at least one of said dynamometers to substantially equalize the respective rotary speeds of said rollers

15 The apparatus as defined in claim 14, wherein said torque control means control both of said dynamometers

16 The apparatus as defined in claim 14, wherein said control means directs a faster spinning dynamometer to apply a greater amount of power absorption to a faster spinning roll, relative to a slower spinning dynamometer

17 The apparatus as defined in claim 14, wherein said controller includes total power absorption calculation means, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometers

18 The apparatus as defined in claim 14, wherein said torque control means further permits control of said dynamometers to apply a controlled unequal rotary speed of the respective rollers to simulate a curved driving condition

19. A roller dynamometer vehicle testing assembly for simulating road conditions for a vehicle, comprising: at least one roller rotatably mounted to a frame for supporting and rotatably contacting a vehicle wheel; a dynamometer engaged to said at least one roller for applying a load to the roller whereby road conditions are simulated on the vehicle engaged to said apparatus; a rotary mount for engaging said dynamometer to said frame for rotational movement relative to said frame, said rotary mount comprising first and second concentric members engaged to said dynamometer and carriage respectively.

20. The apparatus as defined in claim 19, wherein said first member comprises a disc and said second member comprises disc engaging means.

21. The apparatus as defined in claim 20, wherein said disc engaging means comprises a trunnion bearing array.

22. The apparatus as defined in claim 19, wherein said at least one roller has a generally hourglass shape for self-centering of said vehicle wheel.

23. A roller dynamometer for simulating road conditions for a vehicle having at least two drive wheels, comprising: first and second roller dynamometer assemblies, each said roller dynamometer assembly comprising at least one roller for contact with a vehicle drive wheel and engaged to a corresponding dynamometer, said first and second dynamometer assemblies for independent rotation relative to each other and each having rotary speed and torque detection means and power absorption means; and a control unit for receiving rotary speed and torque information from said dynamometers and having a logic circuit for comparing and measuring any speed differences between said dynamometers and controlling at least one of said dynamometers in response to said speed differences.

24. The apparatus as defined in claim 23, wherein said logic circuit controller controls the power absorption means of said at least one dynamometer to achieve straight-line driving simulation.

25. The apparatus as defined in claim 23, wherein said logic circuit controller controls the power absorption means of said at least one dynamometer to achieve curved driving simulation.

26. The apparatus as defined in claim 23, wherein said dynamometer comprises an electric motor.

27. The apparatus as defined in claim 23, wherein said controller includes total power absorption calculation means, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometers.

28. The apparatus as defined in claim 23, wherein said control means controls both of said dynamometers.

29. A method for simulating road conditions for a vehicle, comprising the steps of: a) providing first and second roller dynamometer assemblies each having torque and rotational speed sensors, and a controller for receiving speed and torque information from each dynamometer assembly and independently controlling the resistance applied thereby, b) providing a test vehicle having at least two drive wheels, c) supporting said at least two drive wheels on corresponding first and second roller dynamometer assemblies, d) driving said at least two drive wheels with said test vehicle, e) independently measuring the speed and torque of said at least two drive wheels, and f) independently controlling with said controller at least one of said first and second roller dynamometer assemblies to control the rotary speed thereof

30 A method as defined in claim 29, comprising the further step of measuring the total power output of the vehicle with an algorithm that calculates total dynamometer power absorption, wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometer

31 A method as defined in claim 29, wherein the first and second dynamometer assemblies are controlled to simulate straight-line driving conditions

32 A method as defined in claim 29, wherein the first and second dynamometer assemblies are controlled to simulate curved driving conditions

33 A method as defined in claim 29, wherein both of said dynamometers are independently controlled by said controller AMENDED CLAIMS

[received by the International Bureau on 26 October 1999 (26.10.99); original claims 2, 3, 15-17, 24-26, 28 and 30-33 cancelled; original claims 1, 4-14, 18-23, 27 and 29 amended and renumbered as claims 1, 2-12, 13-18, 19 and 20 (5 pages)]

1. A roller dynamometer vehicle testing assembly for simulating road conditions for a vehicle having at least two drive wheels, of the type comprising first and second roller assemblies (54) for rotatably supporting right and left hand vehicle drive wheels, each roller assembly being associated with a dynamometer having roller speed and wheel torque sensing means, characterized by: first and second roller carhages(32) for independently supporting corresponding first and second roller assemblies, said first and second roller carriages each comprising an independent and separately transportable unit not mechanically connected to the other unit; carriage support means (30) for supporting at least one of said first and second carriages on a substrate independently of said other of said first and second carriages whereby said at least one carriage may be displaced on said substrate, in a direction which is lateral relative to the elongate axis of said vehicle, while bearing said vehicle; and each carriage supporting a dynamometer (46), each dynamometer engaged to a corresponding roller for applying a load to said corresponding roller whereby road conditions are simulated on a vehicle engaged with said apparatus.

2. The apparatus as defined in claim 1 , wherein said carriage support means (30) comprises an array of linear bearings mounted to each of said carriages and capable of permitting said carriage to be rolled laterally relative to the axis of said vehicle while bearing on a solid hard surface.

3. The apparatus as defined in claim 1 , wherein there is further provided second carriage support means (30) for supporting a second of said

AMENDED SHEET (ARTICLE 15) roller carriages for lateral movement on said substrate while bearing said vehicle.

4. The apparatus as defined in claim 1 , wherein said rollers (54) each comprise an elongate generally cylindrical body having opposed ends and a middle region, said body having a generally hour-glass shape whereby the middle region has a narrowed waist relative to the opposed ends of said body.

5. The apparatus as defined in claim 1 , wherein said rollers each comprise a generally cylindrical body having opposed ends, and having an upwardly stepped portion (67) at each of said opposed ends having a diameter whereby the diameter of said stepped portion is greater than the diameter of said roller immediately adjacent said portion.

6. The apparatus as defined in claim 5, wherein said stepped portion comprises a flywheel.

7. The apparatus as defined in claim 1 , further incorporating a rotary mount (60) for mounting at least one of said dynamometers for limited rotational movement relative to said carriage.

8. The apparatus as defined in claim 7, wherein said rotary mount comprises first and second concentric members (62,64) engaged to said carriage dynamometer respectively for rotation relative to each other.

9. The apparatus as defined in claim 8, wherein said first member (62) comprises a disc and said second member (64) comprises disc engaging means.

10. The apparatus as defined in claim 9, wherein said disc engaging means (64) comprises a trunnion bearing array.

11. The apparatus as defined in claim 1 , wherein said dynamometers are in communication with a controller (200), said controller receiving wheel speed and torque information from each of said dynamometers, and having processing means (206) for comparing rotary speed differences between said first and second dynamometers and torque control means (208) for controlling the torque applied by at least one of said dynamometers to substantially equalize the respective rotary speeds of said rollers.

12. The apparatus as defined in claim 11 , wherein said controller (200) includes total power absorption calculation means (207), wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometers.

13. The apparatus as defined in claim 11 , wherein said torque control means further permits control of said dynamometers to selectively apply a controlled equal or unequal rotary speed of the respective rollers to selectively simulate either a straight-line or a curved vehicle path.

14. A roller dynamometer vehicle testing assembly for simulating road conditions for a vehicle, of the type comprising; at least one roller (54) rotatably mounted to a frame for supporting and rotatably contacting a vehicle wheel;

AMENDED SHEET (ARTICLE 1 ?) a dynamometer (46) engaged to said at least one roller for applying a load to the roller whereby road conditions are simulated on the vehicle engaged to said apparatus; characterized by: a rotary mount (60) for engaging said dynamometer to said frame for rotational movement relative to said frame, said rotary mount comprising first and second concentric members (62,64) engaged to said carriage and dynamometer respectively.

15. The apparatus as defined in claim 14, wherein said first member (62) comprises a disc and said second member (64) comprises disc engaging means.

16. The apparatus as defined in claim 15, wherein said disc engaging means comprises a trunnion bearing array.

17. The apparatus as defined in claim 14, wherein said at least one roller has a generally hourglass shape for self-centering of one of said vehicle wheels on said roller.

18. A roller dynamometer for simulating road conditions for a vehicle having at least two drive wheels, of the type comprising: first and second roller dynamometer assemblies (10), each said roller dynamometer assembly comprising at least one roller (54) for contact with a vehicle drive wheel and engaged to a corresponding dynamometer (46), said first and second dynamometer assemblies (10) for independent rotation relative to each other and each having rotary speed and torque detection means (204,74,202) and power absorption means; characterized by: a control unit (200) for receiving rotary speed and torque information from said dynamometers and having a logic circuit (207) for comparing and measuring any speed differences between said dynamometers and controlling at least one of said dynamometers in response to said speed differences, characterized by said logic circuit controller provided with means to control the power absorption means of said at least one dynamometer to selectively simulate either a straight-line or a curved vehicle path.

19. The apparatus as defined in claim 18, wherein said controller includes total power absorption calculation means (207), wherein the total power absorbed amongst all dynamometers is calculated as a function of the mass of the vehicle, the speed and acceleration of each roller, and a value associated with the vehicle aerodynamic and frictional losses and frictional losses within the dynamometers.

20. A method for simulating road conditions for a vehicle, of the type comprising the steps of: a) providing first and second roller dynamometer assemblies (10) each having torque and rotational speed sensors (74,202,204), and a controller (200) for receiving speed and torque information from each dynamometer assembly and independently controlling the resistance applied thereby; b) providing a test vehicle having at least two drive wheels; c) supporting said at least two drive wheels on corresponding first and second roller dynamometer assemblies; d) driving said at least two drive wheels with said test vehicle; e) independently measuring the speed and torque of said at least two drive wheels; and f) independently controlling with said controller at least one of said first and second roller dynamometer assemblies to control the rotary speed thereof; characterized by: the first and second dynamometer assemblies being controlled to selectively simulate either a straight line or a curved vehicle path.

AMENDED SHEET (ARTICLE D