Note: Descriptions are shown in the official language in which they were submitted.
CA 02238624 1998-OS-20
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
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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 is addressed with the
present
invention 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.
SL>IViMARY OF TIC 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.
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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
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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.
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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
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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;
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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.
In another embodiment of the present invention there is provided a
method of simulating road conditions for a vehicle having at least one drive
wheel on either side thereof, which method comprises the steps of:
(a) providing first and second roller dynamometer assemblies, and a
control means for controlling at least one of them;
(b) positioning a drive wheel of one side of the vehicle on the first roller
dynamometer assembly and a drive wheel of the other side of the vehicle on the
second roller dynamometer assembly;
(c) driving the first and second roller dynamometer assemblies with the
drive wheels against resistance provided by the assemblies; characterised by
the
step o~
(d) simulating a curved driving condition by controlling at least one of the
first and second dynamometer assemblies so that the resistance applied to the
or
each drive wheel on one side of the vehicle is different to the resistance
applied
to the or each drive wheel on the other side of the vehicle.
It is preferable the above embodiment further comprises the step of
controlling both the first and second roller dynamometer assemblies to provide
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the respective resistances, simulating straight-line driving conditions during
a vehicle test by
substantially equalising the resistances applied by the first and second
roller dynamometer
assemblies, measuring wheel speeds of the drive wheels, inputting signals
representative
thereof into the control means, comparing the signals and increasing or
decreasing the
resistance applied by the or each roller dynamometer assembly to the or each
drive wheel to
simulate the curved or straight-line driving condition, and measuring the
total power output
of the vehicle with an algorithm that calculates total power absorbed by the
first and second
roller dynamometer assemblies, calculated as a function of the mass of the
vehicle, the speed
and acceleration of each roller of the first and second roller dynamometer
assemblies, and a
value associated with the vehicle aerodynamic and. frictional losses within
the dynamometer.
Preferably, the roller dynamometer assemblies are without a mechanical link,
a link between the roller dynamometer assemblies being in the form of an
electronic
link provided by the control means.
It is also preferable there is further comprising the step of permitting
during
testing at least one of the first and second roller dynamometer assemblies to
move
laterally relative to the ordinary direction of travel of the vehicle, and
permitting both
the first and second roller dynamometer assemblies to move laterally relative
to the
vehicle.
Desirably, the vehicle is a front wheel drive or a rear wheel drive vehicle.
It is further desirable there further comprises the step of providing further
roller dynamometer assemblies according to the number of drive wheels of the
vehicle
to be tested, and performing an emissions test on the vehicle during
simulation of road
conditions.
Preferably, the vehicle is selected from the group consisting of a four-wheel
drive, a truck or a bus.
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In another embodiment of the present invention there is provided an apparatus
for simulating road conditions for a vehicle having at least one drive wheel
on either
side thereof, which apparatus comprises first and second roller dynamometer
assemblies mechanically independent of the other, and a control means for
controlling
at least one of them, the arrangement being such that, in use, a drive wheel
of one side
of the vehicle is positioned on the first roller dynamometer assembly and a
drive
wheel of the other side of the vehicle is positioned on the second roller
dynamometer
assembly whereby the drive wheels can drive the first and second roller
dynamometer
assemblies against resistance provided thereby; characterised in that the
control means
comprise means for providing simulation of a curved driving condition by
controlling
at least one of the first and second dynamometer assemblies so that the
resistance
applied to the or each drive wheel on one side of the vehicle is different to
the
resistance applied to the or each drive wheel on the other side of the
vehicle.
It is desirable that in use the means for providing simulation of curved
driving
conditions controls; the resistance applied by both the first and second
roller
dynamometer assemblies, the control means comprises means for simulating
straight-
line driving conditions during a vehicle test by substantially equalising the
resistances
applied by the first and second roller dynamometer assemblies, and the roller
dynamometer assemblies are in communication with the control means, the
controller
in use receiving wheel speed and torque information from the roller
dynamometer
assemblies, the control means comprising processing means for comparing the
drive
wheel speeds and torque control means for controlling the resistance applied
to at
least one of the drive wheels to simulate the curved or straight-line driving
condition.
Preferably, the control means comprises total power absorption calculation
means for measuring the total power output of the vehicle based on the total
power
absorbed by the first and second roller dynamometer assemblies, calculated as
a
function of the mass of the vehicle, the speed and acceleration of each roller
of the
first and second roller dynamometer assemblies, and a value
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associated with the vehicle aerodynamic and frictional losses within the
dynamometer, the roller dynamometer assemblies are not mechanically linked, a
link between the roller dynamometer assemblies being in the form of an
electronic link provided by the control means, that in use at least one of the
first
and second roller dynamometer assemblies is independently moveable during
testing over a ground surface relative to the other assembly and in a
direction
lateral to the ordinary direction of travel of the vehicle, the or each roller
dynamometer assembly comprises roller means facilitating the independent
lateral movement, and the roller means comprises an array of linear bearings.
It is further desirable that in use both the first and second roller
dynamometer assemblies are independently moveable, the first and second roller
dynamometer assemblies each comprise a roller having an elongate generally
cylindrical body having opposed ends and a middle region, the body having a
generally hour-glass shape whereby the middle region has a narrowed waist
relative to the opposed ends of the body for supporting a drive wheel of the
vehicle at the waist, the cylindrical body comprises an upwardly stepped
portion
at each of the opposed ends having a diameter greater than the diameter of the
roller immediately adjacent the upwardly stepped portion, and the upwardly
stepped portion comprises a flywheel.
Preferably, there further comprises a rotary mount for mounting at least
one dynamometer on a carriage of the roller dynamometer assemblies for limited
rotational movement thereto, the rotary mount comprises first and second
concentric members engaged to the carriage and the dynamometer respectively
for rotation relative to each other, the first member comprises a disc and the
second member comprises disc-engaging means, the disc-engaging means
comprises a trunnion bearing array, and the roller dynamometer comprises a
carriage frame supporting a dynamometer having roller speed and wheel torque
sensing means mating with the roller that, in use, is engaged with a drive
wheel
of the vehicle.
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In the above embodiment, it is further preferable that 'the apparatus be
adapted
to simulate road conditions for a front wheel drive or a rear wheel drive
vehicle, the
number of roller dynamometer assemblies based on the number of drive wheels of
a
vehicle to be tested with the apparatus, and the number is suitable to test a
vehicle
selected from the group consisting of a four-wheel drive, a truck or a bus.
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.
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g
Similar numerals in the drawings denote similar elements.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1, 2 and 2(a), 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 Figures 2 and 2(a))
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.
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 journalled 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.
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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
CA 02238624 1998-OS-20
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
10 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
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11
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
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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
13
defined in the claims.
