FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A SYSTEM FOR TESTING OFF-ROAD VEHICLE AND METHOD THEREOF


2. APPLICANT
MAHINDRA & MAHINDRA LTD.
1, GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001.
AN INDIAN COMPANY.

The following specification describes the invention.

Field of the Invention
The present invention relates to a system and method for testing off-road vehicle such as tractor. The invention further relates to a device / means to provide/ develop negative pull during draw bar testing of tractor and method thereof.
Background of the Invention
In testing of off-road vehicles such as tractor, measurement of power at wheels and fuel consumption measurement is of paramount importance. The fuel consumption needs to be estimated at varying realistic operating conditions with respect to time. The tractor is mounted with implements that utilize drawbar, Power Take Off (PTO) and hydraulic power available on a tractor. The power consuming devices mounted on a tractor are drawbar, PTO and hydraulic system for implements. The fuel consumption of the tractor depends on power consumed by each of these and a combination under varying operating conditions in field. Typically, depending on soil topography and usage conditions power requirement varies continuously. This results in a dynamic change of the engine operating point. Therefore field performance test is necessary to know drawbar power and fuel consumption of tractor with different implements. But due to heterogeneity of soil and climate, number of tests is required. Further there is no repeatability of data as field operating conditions keep changing over a period of time from season to season. This makes it difficult for designers to take any concrete action based on field results.
To test the tractor, conventional practice is to operate the tractor in field using matching implements and monitor it over a period of time say 1500 to 2000 hours. However this is a laborious process and cannot be adopted under the demanding market conditions. Further there is lack of repeatability and the test results obtained are acceptable for that point of comparison only and cannot be used as a data base. To overcome these problems drawbar power simulation method is used. Following are the field operating conditions that need to be simulated and monitored are:

Varying drawbar Load at wheel
Varying PTO Load at PTO output shaft
Varying Hydraulics Load due to Tractor hydraulics or CE equipment At
Hydraulics Pump
Power steering Pump loading due to Steering load based on front Reaction
Wheel slip as a function of Drawbar load.
Engine Over running in down slope haulage
Statutory testing
In this method, the tractor pulls the load car on the height adjustable linkage drawbar. The load car tires transfer the pull through eddy current dynamometer. The dynamometer produces required braking torque that is controlled by signal from a load cell between the test tractor and load car for High (Horse Power) HP tractors, for low HP tractors load car engine will give the required Push/Pull to simulate the effective pull. Generally, a hydro static device to compensate for the inertia pull of the truck is utilized that enables to start from zero pull reading.
Japanese Patent JP01010917 discloses wagon device loaded onto tractor to eliminate the necessity of insertion and removal of a pin, by connecting the first support table having a stand to one end of a dump driving unit, mounting the rear end side of the first support table vertically movable on the tractor car body side so as to freely fix and release the first and second support tables.
United States Patent 3667291 discloses tractor pull load measuring device having an elongated frame supported at its rear end by ground engaging wheels and having a slid below the frame pivotally connected thereto forwardfy of the wheels. The skid is adapted to engage the ground along its length during use or be raised above the ground for transport by a tongue being connected to the skid and the frame being pivoted upwardly about an axis through the wheels thereby lifting the rear of the skid. A ballast trolley is moveable from over the wheels on the frame to the front end as the wheels turn thereby increasing the drag due to the load being transferred to the skid engaging the ground. Measuring indicia along the frame is provided to indicate the pulling ability of the vehicle being tested in terms of how far the ballast trolley is moved forwardly

United states patent 4173352 discloses combination articulated tractor and tow car. it discloses an articulated tractor with two engines in tandem, particularly an agricultural tractor having a three-point lifting device, a unit having a selectively positioned drawbar adapted to turn about an upright shaft carried between parallel supporting plates is detachably fastened to the lifting device
United States Patent 7337054 discloses systems and methods for controlling slip of a ground engaging traction device. The system includes slip calculator to transmit an actual slip signal.
However the systems mentioned in the prior art suffer from following drawbacks:
Lack of dual loading mechanism on the same load car to test higher and
lower power capacity tractors wherein drawbar load on the test tractor is
applied by dynamometer and / or load car engine itself. Need of power
absorbing devices or use of separate load car to test lower power capacity
tractors.
Lack of facility of auto steering with load compensation leading to
undesirable change in the loading during turns due to change in the angle
between tractor and the load car. Further effective drop in load on turn due
to the acting components of load on turn leading to danger of tractor
moving outwards from the track
Use of additional hydro static device to compensate for the inertia pull of
the load car to enable to take readings from zero pull / load
Lack of facility to measure instantaneous slip of the tractor wheel and use
of the same to control drawbar load on test tractor at a set slip
Lack of provision to use weight of the load car itself as a load
inability to simulate and test tractor for PTO operated implements for field
loading conditions using a single valve in the hydraulic circuit of the tractor
Lack of facility to test the tractor with load car on Mud track in place of
concrete to maintain same friction (u) as that of soil
need of using electronic cards for PID and logic controls
Inability to simulate loading on engine due to hydraulics loading, need of

additional proportional valve that is controlled through PID

Need of separate mechanism to maintain true rolling of fifth wheel
Need of separate control modules for hydraulic, electrical and other various
input parameters
Lack of facility to monitor or control individual wheel slip on continuous
basis
There is unfulfilled need in the market place to develop a load obviating the problems listed above to ensure testing of tractor near practical farming conditions.
Summary of the Invention
Main object of the invention is to provide a system and method for testing off-road vehicle such as tractor.
Yet another object of the invention is to provide a device / means to develop negative pull on the off-road vehicle such as tractor during draw bar testing and method thereof.
Yet another object of the invention is to provide a coupling device / linkage assembly between tractor to be tested and load car.
Yet another object of the invention is to provide a control system to configure tractor to be tested, load car and load measuring means.
Yet another object of the invention is to eliminate problems of undesirable change in loading on turns while testing the tractor.
Yet another object of the invention is to provide a control system with a common control model for various parameters to facilitate standardization of the control system and interfaces to reduce complexity
Yet another object of the invention is to control the load car engine so as to maintain zero / nullify relative speed between the load car and the tractor.

Yet another object of the invention is to use engine of the load car itself to simulate downhill conditions by providing push to the tractor under test.
Yet another object of the invention is to eliminate need of power absorbing devices or use of separate load car to test lower power capacity tractors.
Yet another object of the invention is to obviate the problems associated with Hydro static device to compensate for the inertia pull of the load car to enable to start from zero pull reading.
Yet another object of the invention is to use dead weight of the load car itself as a load instead of dynamometer for lower power capacity tractors.
Yet another object of the invention is to simulate drawbar pull by loading load car through its engine in case of dead weight of the load car being higher than required pull necessary for the lower power capacity tractor
Yet another object of the invention is to measure instantaneous slip of the tractor wheel and use of the same to control drawbar load on test tractor at a set slip.
Yet another object of the invention is to enable to take readings from zero pull / load without using additional hydro static device.
Yet another object of the invention is to enable tractor testing on mud track using load car.
Thus in accordance, one aspect of the invention provides a system comprising a coupling device (height adjustable linkage drawbar means) to couple the load car to the tractor, a load car, wheel slip measuring device, electronic proportional control pressure limiting valve adapted to be mounted on the tractor hydraulic circuit and a control system configured between the said coupling device, tractor to be tested and the load car
wherein the said coupling device / height adjustable linkage assembly / height adjustable linkage drawbar comprises of

a base plate / mounting means, at least two hinged brackets distanced apart vertically at the end of the said plate and hingably connected / fitted to the said base plate, at least two hinge pins operably inserted in the said hinges, at least two link base- brackets that are operably connected to the said hinge pins and thereby to the said hinged brackets, a substantially flat front plate mounted / attached to the said link base-brackets, first steering bracket attached to the said base plate in connection with the second steering bracket that is attached / fixed to the said front plate adapted to fit front rail/s, a lead screw adapted to be fitted vertically in the said front plate, a sliding bracket engaged in the said lead screw and connected to the one of the ends of turn buckle, a bottom bracket one of the ends of which is adapted to be connected to the said sliding bracket and other end to a load cell that is adapted to be connected to an assembly of guide bar and toe fork provided with a linear guide so as to ensure that only pull/push and not side load component is sensed by the load cell;
wherein
the said load car comprises of eddy current dynamometer used as loading device comprising of isolator, temperature controller for dynamometer temperature monitoring, thyristor circuit, load amplifier, speed amplifier, airconditiontng means, control system, power system that includes engine and transmission, generator, rear toe, eddy current brake, planetary gear box, chain box, radiator, fuel tank, compressor, wheel speed sensor, tyre cooling blower, balance weight box and water tank;
wherein the tractor pulls the load car on the said height adjustable linkage drawbar so as that the load car tires transfer the pull through eddy current dynamometer wherein the dynamometer produces required braking torque that is controlled by signal from the said load cell for higher power capacity tractors wherein for )ower power capacity tractors, the said load car engine is used to provide required push/pull to simulate the effective pull

wherein
the control system that comprises of a data processing means, data storage means and display means operates in control modes such as drawbar pull control, slip control, hydraulic control with drawbar pull control and hydraulic control
wherein
in drawbar pull control mode set point is fixed as the drawbar pull to be required and process variable is the actual drawbar pull sensed from loadcell wherein process output of the control system is fed to push-pull control system; if push mode is activated then control demand is given to throttle controller to control engine speed wherein if pull mode is activated then control demand is given to eddy current dynamometer controller
wherein
in slip control mode wherein all four wheel slip is calculated with respect to reference slip followed by averaging rear and front wheel slip that becomes process variable of the slip control system wherein process variable is averaged rear wheel slip and process set point is set slip wherein output of the slip control system is given to push-pull control system
wherein
in hydraulic control with drawbar pull control mode hydraulic and drawbar pull control loops execute simultaneously wherein hydraulic control loop having pressure is process variable and set point is the set pressure and its process output is given to proportional valve
wherein
in hydraulic control mode test tractor pump pressure is controlled to give the same pressure curve as experienced by tractor in actual field operating condition with various implements.

wherein
wheel slip measurement device comprises of a 2500 PPR encoders adapted to be fitted on the load car and tractor to be tested, data acquisition and processing means wherein the slip measurement device operates in steps of: measuring load car speed by measuring its front wheel speed using the said encoder, calculation of linear speed of the loadcar for the tire radius or alternatively by measuring the number of pulses for a given distance covered ; measuring the tractor wheel speed using the said encoder, calculating linear speed of the tractor for the tire radius or alternatively by measuring the number of pulses for a given distance covered; measuring speed for each of the drive wheel with no load condition & with load condition, calculation of the tractor wheel slip as a function of wheel speed with no load and wheel speed with load wherein the instantaneous slip is calculated by measuring the distance travelled by rear wheels of test tractor with respect to distance travelled by reference wheel of the load car at each instant of time, calculation of instantaneous slip as a function of wheel speed with no load and wheel speed with load and using the said instantaneous slip as process variable to slip control loop.
In another aspect of the invention the control system operates to control dynamometer speed in steps of:
defining / calculating a ratio of voltage supplied to the said thyrister card and maximum speed of rotor of the dynamometer wherein the said ratio is used to generate control voltage for desired rotor speed change, defining / calculating a ratio of the voltage supplied to the said thyrister card and maximum load of the dynamometer and use the same to generate control voltage for desired change in the load
In yet another aspect of the invention main invention the same basic control model controls servo electric, servo hydraulic types of controls to facilitate standardization of the control system that leads to reduction in complexity wherein measuring parameters include drawbar pull through dynamometer, hydraulic

system pressure through the said electronic proportional control pressure limiting valve, tractor speed , fuel consumption, wheel slip, ground speed.
In yet another aspect of the invention a track cleaning means is adapted to be fitted on the load car so as to maintain constant coefficient of friction between the wheels of loadcar, tractor and the test track.
In yet another aspect of the invention dynamometer cooling system is based on natural convection of air wherein cooling air is circulated / routed around the said dynamometer without using external blowing means.
Description of the Invention
Definitions:
Load: In the context of load car, it is represented in terms of pull measured in kg; In the context of Engine Control it is represented in terms Torque measured in kg-m
Features and advantages of the invention will become apparent in the following detailed description and the preferred embodirnents with reference to the accompanying drawings.
Figure 1 Schematic of coupling device (Sheet 1)
Figure 2 Load car system and power flow (Sheet 2)
Figure 3 Block diagram of the dynamometer control (Sheet 3)
Figure 1 depicts the height adjustable coupling device that is in the form of height adjustable linkage that comprises of a base plate / mounting means 1. At least two hinged brackets 2 distanced apart vertically at the end of the said plate and hingably connected / fitted to the said base plate at the locations 50 and 51 wherein corresponding two hinge pins 52 and 53 are operably inserted in the said hinges as shown in the Figure. Two link base- brackets indicated as 4 are operably connected to the said hinge pin 52 and 53 assembly respectively and

thereby to the said hinged brackets 2. The pins allow swinging movement of the brackets that facilitates appropriate turning of the test tractor without variation in loading while negotiating a turn on the test track. A substantially flat front plate 5 is mounted / fixed to the base of the said link base-brackets 4 wherein the said front plate is adapted to mount rail/s 6. First steering bracket 16 is attached / fixed to the said base plate 1 and is operably connected to the second steering bracket 18 that is attached / fixed to the said front plate 4. A lead screw 15 is adapted to be fitted vertically in the said front plate 4. A sliding bracket 14 is engaged in the said lead screw and is connected to the one of the ends of turn buckle 13. One of the ends of a bottom bracket 7 is adapted to be connected to the said sliding bracket 14 and the other end to a load cell 8. The load cell is adapted to be connected to an assembly of guide bar 26 and toe fork 11 provided with a linear guide so as to ensure that only pull/push in linear direction but not side load component is sensed by the load cell. In one of the embodiments the remote display at test tractor is connected to the dual VGA card. User can view only indicators and test related messages on the display which is mounted on the test tractor, and the indicators on the display are flexible. Any analog channel and digital channel and calculate channel can be shifted to remote display.
The schematic of the load car is depicted in Figure 2. It comprises of eddy current dynamometer 4 that is coupled to the gear box 3 using flexible couplings 60. It further comprises of (not shown in the Figure) an isolator, temperature controller for dynamometer temperature monitoring, thyristor circuit, load amplifier, speed amplifier, airconditioning means, control system, power system that includes engine and transmission, generator, rear toe, eddy current brake, planetary gear box, chain box, radiator, fuel tank, compressor, wheel speed sensor, tyre cooling blower, balance weight box and water tank.
There is an option of two power flow paths as shown in the Figure 2 indicated by black (solid lines) and blue lines (dashed line).
The first power flow path uses engine of the load car. In this case the traction on rear wheel 5 is controlled by load car engine 1. The rear wheels 5 are connected

to transfer gear box 6 via the propeller shaft 8 .The Transfer gear box has two output paths. In the first path as indicated by bold line, it is connected to the engine 1 of the load car through a six speed transmission 2 and propeller shaft 7. Thus the first power flow is in the following sequence:
Rear wheels Axle to differential 5
Propeller shaft 8
Transfer box 6
Propeller Shaft 7
Load Car Transmission 2
Engine 1
The Engine is controlled by two methods wherein in the first method consists of using foot throttle pedal at driver end. The second method includes close loop operation with the help of computer wherein throttle position is controlled based on speed and drawbar pull requirement of load car. Operation of the throttle facilitates to develop negative puli on the off-road vehicle such as tractor to be tested during draw bar testing. The control system controls the engine throttle controller based on the feedback received from load cell on front tow so as to maintain zero relative speed between the load car and the tractor by nullifying the load on the load cell through speed compensation. This aspect of the invention obviates problems of undesirable change in loading on turns while testing the tractor. The engine throttle controller is used to give a push to the tractor as well so as to simulate downhill conditions by providing push to the tractor under test. Since it is possible to govern and regulate speed of the load car with the aid of selection of gear and engine throttle condition it is possible to achieve a wide range of speed and drawbar conditions to test lower power capacity tractors. The judicious utilisation of a throttle controller obviates the need to use a separate mechanism such as a hydrostatic device to compensate for the inertia pull of the load car to enable to start from zero pull reading.
The second power flow path uses dynamometer wherein the traction on rear wheel 5 is controlled by eddy current dynamometer 4. The rear wheels 5 are

connected to transfer gear box 6 via the propeller shaft 8. In the power flow path indicated by dashed lines, the transfer box is connected to the eddy current dynamometer 4. A coaxial gear box 3 is used to step up the speed at dynamometer end. The second power flow is in the following sequence:
Rear wheels 5
Axle to differential
Propeller shaft 8
Transfer box 6
Speed amplification Gear Box 3
Eddy current Dynamometer 4
In operation the tractor to be tested pulls the load car on the said height adjustable linkage drawbar so as that the load car tires transfer the pull through eddy current dynamometer as described by power flow path two wherein the dynamometer produces required braking torque that is controlled by signal from the said load cell for higher power capacity tractors wherein for lower power capacity tractors, the said load car engine is used to provide required push/pull to simulate the effective pull as described in the power flow path one.
The wheel slip measurement device comprises of a. 2500 PPR encoders adapted to be fitted on the load car and tractor to be tested, data acquisition and processing means wherein the slip measurement device operates in steps of:
measuring load car speed by measuring its front wheel speed using the
said encoder
calculation of linear speed of the load car for the tire radius or alternatively
by measuring the number of pulses for a given distance covered
measuring the tractor wheel speed using the said encoder
calculating linear speed of the tractor for the, tire radius or alternatively by
measuring the number of pulses for a given distance covered;
measuring speed for each of the drive wheel with no load condition & with
load condition
calculation of the tractor wheel slip as a function of wheel speed with no
load and wheel speed with load wherein the instantaneous slip is

calculated by measuring the distance travelled by rear wheels of test tractor

with respect to distance travelled by reference wheel of the load car at each instant of time
calculation of instantaneous slip as a function of wheel speed with no load and wheel speed with load and using the said instantaneous slip as process variable to slip control loop.
The control system comprises of a data processing means, data storage means and display means. The control system uses a generic control model that controls servo electric, servo hydraulic types of controls to facilitate standardization of the control system that leads to reduction in complexity wherein measuring parameters include drawbar pull through dynamometer, hydraulic system pressure through the said electronic proportional control pressure limiting valve, tractor speed, fuel consumption, wheel slip, ground speed.
The control system operates in control modes such as drawbar pull control, slip control, hydraulic control with drawbar pull control, hydraulic control with slip control wherein in drawbar pull control mode set point is fixed as the drawbar pull to be required and process variable is the actual drawbar pull sensed from load cell wherein process output of the control system is fed to push-pull control system; if push mode is activated then control demand is given to throttle controller to control engine speed wherein if pull mode is activated then control demand is given to eddy current dynamometer controller.
The control system operates to control and measure slip wherein in slip control mode wheel (driving) slip is calculated from distance travelled by each wheel with respect to distance travelled by reference wheel of the [oadcar. Similarly all four wheel slips are calculated followed by averaging rear and front wheel slip that becomes process variable of the slip control system wherein process variable is averaged rear wheel slip and process set point is set slip wherein output of the slip control system is given to push-pull control system.
The control system operates in hydraulic control with drawbar pull control mode hydraulic and drawbar pull control loops execute simultaneously wherein hydraulic control loop having pressure is process variable and set point is the set pressure

and its process output is given to proportional valvs. In hydraulic control with slip control mode hydraulic and slip control loops executes simultaneously wherein both slip control and hydraulic control loops operate as mentioned above.
Figure 3 depicts block diagram of the dynamometer control wherein eddy current dynamometer 100 that is configured with the thyristor card 101, temperature and pressure sensor 102, load feedback sensor 103, The isolator 104 is further configured with the said thyristor card 101. The soft controller 105 is configured with the said isolator 104, sensors 102 and further with the feedback sensor 103. The said controller 105 comprises of the first summing amplifier 106 that is provided with a converter 108 and proportional integral and derivative controls K|, Kp and KD wherein the rate of signal is defined and further supplied to the second summing amplifier 107 that converts the signal into voltage signal again. The load signal 110 is fed to the said controller 105.
is used as loading device. It consists of isolator, temperature controller for dynamometer temperature monitoring, thyristor circuit, load amplifier, speed amplifier. A separate control system is provided for speed and torque control.
The control system operates to control dynamometer speed in steps of:
defining / calculating a ratio of voltage supplied to the said thyristor card and maximum speed of rotor of the dynamometer wherein the said ratio is used to generate control voltage for desired rotor speed change, defining / calculating a ratio of the voltage supplied to the said thyristor card and maximum load of the dynamometer and use the same to generate control voltage for desired change in the load,
Defining / calculating a ratio of maximum speed to maximum torque (load) wherein this ratio is used to generate torque load based on speed demand and vice versa wherein the same (speed and load) is converted into control voltage signal

In yet another embodiment, throttle controller, slip controller, servo hydraulic controller are processed in accordance with the aforementioned steps wherein the controf parameters include sfip, pressure, throttfe position, speed and load.
In one of the embodiments a track cleaning means is adapted to be fitted on the load car so as to maintain constant coefficient of friction between the wheels of loadcar, tractor and the test track.
In yet another embodiment dynamometer cooling system is based on natural convection of air wherein cooling air is circulated / routed around the said dynamometer without using external blowing means.
16/16
Thus it is evident from the present invention that the judicious combination of the said height adjustable coupling device in the form of the linkages wherein load cell is disposed on the said coupling device such that only pull / push is exerted on the load cell and not the side load component resulting in overcoming problems of undesirable variation in load while negotiating a turn and the configuration of the load car engine throttle control with the control system so as to maintain zero relative speed between the load car and the tractor to be tested facilitates effective utilisation of the dead weight of the load car itself resulting in flexibility of testing lower power capacity tractors as well and obviating the use of hydro static device and facilitating testing of tractor near practical farming conditions.