A METHOD AND SYSTEM FOR IMPROVING VEHICLE HANDLING
FIELD OF INVENTION
[001] Embodiments of the current disclosure relates to vehicle handling system, more particularly related to Anti-lock braking system(ABS) and Traction control system.
BACKGROUND
[002] Present day vehicles are generally equipped with ABS and traction control systems. The types of ABS and traction control systems known in the art estimate the maximum value of torque that can be applied to the tire and limit the torque from the brakes and prime movers accordingly. Thereby limiting excess wheel slip.
[003] The said ABS and traction control systems are designed to operate the tires at a preset value of wheel slip. However the value of slip that generates peak tire forces are highly dependent upon the operating conditions such as the normal load on the tire, tire pressures, tire temperature, vehicle speed and so on. Also the factors evident in the prolonged use of tire such as wear and heat cycles also change the characteristics of the tire. The operation of the tire at a preset value of wheel slip which does not adapt to the changes in the operating conditions limit the true performance capabilities of the tire. Thereby increasing the stopping distance during braking and reducing vehicle acceleration capabilities.
[004] Thus, in order to overcome at least a few of the shortcomings of the current ABS and traction control systems, the present invention provides a method to improve the braking and acceleration capabilities of a vehicle.

BRIEF DESCRIPTION
[005] In accordance with the embodiments of the current invention, a method for estimating and updating the tire reference property for an ABS and traction control system is provided. The said ABS and traction control systems are operatively coupled to data set that stores the tire reference properties. Furthermore, the said ABS and a traction control system are operatively coupled to a feedback control loop that updates the said tire reference properties.
[006] Furthermore, the said feedback control loop comprises of a system that estimates the tire instantaneous states, tire forces and moments generated using a sensors and data acquisition system that is operatively coupled to the said feedback control system. Furthermore, the said system estimates the tire forces and moments by comparing the said instantaneous tire states with the said reference tire properties. Furthermore, the said estimated tire forces and moments estimated using the sensors and data acquisition system is compared with the forces and moments expected from the reference tire properties for a given instantaneous tire state. Furthermore, a control logic is applied to update the tire reference properties for any deviations in the expected behaviour of the tires.
[007] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.
BRIEF DESCRIPTION OF DRAWINGS

The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:
[008] FIG. 1 is a flowchart that depicts the functioning of Vehicle control system coupled with a system that estimates and updates the tire properties in accordance with an embodiment of the present disclosure;
[009] FIG. 2 depicts the process of estimation of instantaneous tire state, in accordance with the first embodiment of the present disclosure;
[010] FIG. 3a, is an exemplary embodiment depicting the process of estimation of camber/inclination angle of the wheel, in accordance with the first embodiment of the present disclosure;
[011] FIG. 3b is and exemplary embodiment depicting the process of estimation of slip angle and slip ratio of the wheels, in accordance to the first embodiment of the present disclosure;
[012] FIG. 4 depicts the process of estimation of instantaneous tire forces and moments, in accordance with the first embodiment of the present disclosure;
[013] FIG.5 depicts the process of updating the tire properties, in accordance with the first embodiment of the present disclosure.
[014] FIG 6a is an exemplary embodiment that shows the GPS data of a vehicle in a manoeuvring state similar to a skid-pad;
[015] FIG 6b, FIG 6c, FIG 6d, and FIG 6e are exemplary embodiments representing variation of speed, lateral acceleration, yaw-rate and turning radius respectively of the said vehicle, at the said manoeuvring state;

[016] FIG 6f and FIG 6g are exemplary embodiments representing the steering potentiometer reading and the steering angle respectively of the said vehicle, at the said manoeuvring state;
[017] FIG 6h and FIG 6i are exemplary embodiments representing the variation of left front and left rear tire slip angle respectively with time, for the said vehicle at the said manoeuvring state;
[018] FIG 6j and FIG 6k are exemplary embodiments depicting the variation of lateral force of the left front and left rear tires respectively with time, for the said vehicle at the said manoeuvring state;
[019] FIG 61 and FIG 6m are exemplary embodiments depicting the variation of the wheel camber of the front and the rear tires respectively due to roll with time, for the said vehicle at the said manoeuvring state; and
[020] FIG 6a to 6m are exemplary embodiments that depict the method of estimating the vehicle state and tire forces, in accordance with the first embodiment of the current description.
DETAILED DESCRIPTION
[021] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

[022] The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.
[023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
[024] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
[025] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise.
[026] The Embodiments of the current invention are related to handling system of a vehicle, more particularly related to ABS and Traction control system. Unlike the conventional method of operation of ABS and traction control system which

tends to operate the tire at a preset value of tire operating slip regardless of operating conditions, the embodiments of the current invention intend to operate the tires at their peak operational capabilities by updating the value of tire slip that provides the peak tire forces, by considering the influencing factors such as tire operating temperature, tire wear, road surface, tire pressure, and other such influencing factors. Thereby, making full use of the grip that is made available by the tires at a given operating state.
[027] The embodiments of the invention are applicable to all types of vehicles comprising of ABS or traction control system. The said vehicles are powered by any prime mover such as an IC engine or an electric motor. The torque output of the said prime mover is limited to the maximum value of tractive force that the tires can withstand at the corresponding value of slip ratio and other tire operating parameters such as slip angle, tire inflation pressure, and normal load, where the said tractive force is defined as the force exerted by the tires in the longitudinal direction which moves the tire footprint forward of the axle; as used herein, the slip ratio is defined as the ratio of difference in the vehicle speed and the tire speed to the vehicle speed. Further, the said slip angle is defined as the angle between plane of rotation of the wheel and the direction of heading of the tire on the road surface. Furthermore, the said normal load is the load on the tire in the direction normal to the road plane. Furthermore, the brake torque is also limited to the maximum value of braking force that the tire can withstand at the corresponding value of slip ratio and other tire operating parameters.
[028] FIG. 1 is a flowchart that depicts vehicle control system coupled with a system that estimates and updates the tire properties. 112 represents the tire properties that serve as a reference for the vehicle control systems. 112 represents the feedback loop of the vehicle control systems. 103 represents the Vehicle control

systems. 104 represents the actuators controlled by the vehicle control system. The functional components and aspects of the said Vehicle control system and the actuators are beyond the scope of this disclosure and are not discussed for the sake of brevity. 105 represents the collection of data into the data acquisition module with the help of sensors that assist the said vehicle control systems. Furthermore 105 includes sensors that are not limited to accelerometers, gyroscopes, Inertial measurement units, GPS, tire temperature measuring devices, steering sensors, tire pressure measuring devices, tire pressure monitoring system, and wheel speed sensors. Further 106 represents the process of estimating tire operating parameters including but not limited to slip angle, slip ratio, camber angle, tire pressure, tire temperature, wheel normal load, and wheel speed. The estimated value of tire parameters are compared with the reference value for a given manoeuvring condition so that the vehicle control unit can take necessary decisions, this is represented by 102. 107 represents the processing unit estimating the expected vehicle behaviour for the instantaneous tire state in 106, using reference tire data. The estimated instantaneous vehicle parameters in 107 are compared with the sensor data collected in 105, this is represented in 108. The deviation is estimated in 108 and if the deviation 109 is found to be significant, the tire forces and moments corresponding to the current operating state of the tire are estimated and the new values of tire force and moments are updated. This is depicted in 111. Hence, the reference tire data set 112 is updated every time a deviation is observed in the vehicle operating behaviour. The feedback module 101 gathers information from the reference tire database and conveys it to the vehicle control unit. The feedback module completes the close loop system that helps the vehicle control system by iteratively learning about the updated tire data base.

[029] FIG. 2 is a flowchart that briefly explains the process of estimating the instantaneous tire parameters. 201 represents Sensors and Data Acquisition module including but not limited to accelerometers, gyroscope, GPS, steering angle sensors, tire temperature sensors, tire pressure sensors/tire pressure monitoring system, and wheel speed sensors. Further, the said accelerometer and gyroscope provide data including but not limited to vehicle acceleration in 3 axes and rate of rotation about the 3 axes respectively. Furthermore, the said GPS gives positional data and its derivatives. Furthermore, the said steering angle sensor provides the position of the steering wheel. Furthermore, the tire pressure sensor or tire pressure monitoring system provides data about the tire pressure. The data obtained from the above mentioned sensors are used to estimate instantaneous vehicle states including but not limited to Roll/lean angle, pitch angle, vehicle yaw, wheel angle with vehicle longitudinal plane, velocity, linear and angular accelerations, yaw moments, and other such parameters that define the instantaneous state of the vehicle. This is depicted in 202. 203 depicts vehicle properties including but not limited to wheel base, track widths, camber gains due to steer, bump and roll, roll gradients, roll stiffness, pitching stiffness, mass and inertia of the vehicle and other such properties required to estimate the tire forces and moments. The vehicle instantaneous parameters from 202 and the properties of the vehicle from 203 are collectively used by the processing unit to estimate the instantaneous tire states including but not limited to wheel rpm/velocity, tire temp, slip angle, slip ratio, normal loads, and tire pressure. The estimated tire state is depicted in 204.
[030] FIG. 3a is an exemplary embodiment of the invention which depicts the process of estimating wheel camber. The data from the accelerometer and gyroscope 301, gives the rate of roll and the corresponding lateral acceleration of the vehicle. The data from 301 along with the vehicle properties such as roll

gradient from 203, are used to estimate the roll/lean angle of the vehicle, depending on whether the said vehicle is a two wheeled vehicle or a multi wheeled vehicle respectively. As used herein, the roll gradient is defined as the amount of body roll of the said vehicle per unit lateral acceleration expressed in g's. Furthermore, the said roll gradient has the units deg/g. This is depicted in 303. Further, the estimated roll/lean angle from 303 along with the vehicle property such as roll camber gain from 203, are used to estimate the camber angle of the wheel due to roll as depicted in 306. Wherein the said roll camber gain is defined as the camber angle developed by the wheel per degree of body roll. The said roll camber gain has the unit deg/deg.
[031] Furthermore, the said wheel develops camber due to steering. This is because of the geometry of the steering axis. Properties such as castor angle, castor offset, kingpin offset and kingpin inclination are primarily responsible for the developed camber angle due to steering. Wherein, the said castor angle is defined as the angle between the steering axis and the vertical when the vehicle is viewed from the side view. As used herein, the said castor offset is defined as the deviation of the steering axis from the wheel center in the side view. Furthermore, the said kingpin offset is defined as the deviation of the steering axis from the center of the wheel when viewed from the front view. Furthermore, the said kingpin inclination is defined as the inclination of the steering axis from the vertical when viewed from the front view. Further, the steering sensor 302 provides the position of the steering. The data from 302 along with the vehicle properties related to the steering geometry from 203 are used to estimate camber angle developed due to steering. This is depicted in 307.
[032] Camber angle is also developed due to the compliance in the assembly. The sum of compliance camber, camber due to bump and static camber is depicted in 308. Wherein the said camber due to bump is defined as the camber angle

developed by the wheel because of its vertical travel. The said bump camber is developed mainly because of the geometry of the steering system. Furthermore, the said static camber is the camber angle set on the said vehicle at static condition. The said static camber angle is set to negate the effects of roll camber developed due to body roll or bump camber developed due to wheel travel. The camber set on the said vehicle mainly depends on the kind of performance expected from the vehicle. The sum of camber angle developed due to body roll, steering, and compliance together yield the resultant camber developed by the wheel.
[033] FIG. 3b is an exemplary embodiment that depicts the procedure for estimating the slip angle and slip ratios of the wheel. The said slip angle is depended on factors such as the lateral acceleration of the vehicle, vehicle body slip angle, yaw-rate, distance of the Cg to the wheel axle, and steering angle. Wherein the said vehicle body slip angle is defined by the inverse tangent of the ratio of lateral vehicle velocity to the longitudinal velocity of the vehicle. The said body slip angle can also be defined as the angle made by the vehicle resultant velocity with the longitudinal velocity of the vehicle.
[034] The said slip angle and slip ratios can be estimated using the data from wheel speed sensors 310, accelerometer and gyroscope 301, GPS data 311, and steering sensor 302. The said data obtained from the said sensors are used to estimate the slip angle and the slip ratio by considering the said vehicle parameters 203. The said wheel rpm/velocity, tire temp, slip angle, slip ratio, normal loads, and tire pressure collectively represent the instantaneous tire states. These instantaneous properties determine the force and moments generated by the tire. The effects of each of the said parameters may not be mentioned here in detail.
[035] FIG. 3a and 3b collectively forms an exemplary embodiment depicting the method of estimating the tire instantaneous state using the on-board sensors

available. Further the said tire instantaneous states are estimated after the instantaneous vehicle states including but not limited to the roll angle, steering angle, wheel angle, wheel travel, pitch angle, and yaw-moment are estimated. Wherein the said roll angle is defined as the angular deflection of the vehicle about the longitudinal roll axis of the vehicle, wherein the said roll axis is defined as the axis about which the said roll occurs. Furthermore, the said wheel angle is the angle between the wheel and the longitudinal plane of the vehicle. Furthermore, the said wheel travel is defined as the vertical motion of the wheel. Furthermore, the pitch angle is defined as the angular deflection of the vehicle about the transverse axis perpendicular to the longitudinal plane of the vehicle. Furthermore the said yaw moment is defined as the moment created about the center of gravity of the vehicle and the said yaw moment is responsible for the turning and aligning effects of the vehicle.
[036] FIG. 4 depicts the process of estimating the tire forces and moments generated by the tires at the said tire instantaneous states. The sensor and data acquisition system 201 along with the vehicle properties are used to estimate the instantaneous vehicle states including but not limited to Roll/lean angle, pitch angle, vehicle yaw moment, wheel angle, velocity, linear acceleration, and angular accelerations. This is shown in 402. The vehicle state along with the vehicle inertial properties 403(comprising of vehicle inertia in x, y, z directions, their cross products and mass of the vehicle) are used by the processing unit to estimate the forces generated by the tires. The forces and moments thus estimated are represented by 404. The forces and moments generated by the tire can also be measured using wheel force transducers.
[037] FIG. 5 depicts the control logic and the process used to update the tire reference properties. The instantaneous tire states 204 corresponds to some forces

and moments estimated from the sensors and data acquisition system. This is represented by 502. The said instantaneous tire states corresponds to some value of forces and moments when referred to the reference tire data. The corresponding data obtained by referring to the reference tire data is represented by 503. The difference between 502 and 503 is estimated and is shown as 504. If the said difference is beyond the permissible level of deviation, the reference data is updated to the reference tire data set for the said instantaneous tire state. Thereby increasing the set of data points available in the reference data set and reducing the approximations involved.
[038] FIG. 6a is an exemplary embodiment that shows the GPS data of an exemplary vehicle in a manoeuvring condition that is similar to a skid-pad. The said GPS data is a trimmed data obtained from a long run of continuous testing.
[039] FIG. 6b is an exemplary embodiment depicting the longitudinal velocity of the said exemplary vehicle at the said manoeuvring condition. The fluctuation in the longitudinal velocity was done by the driver in order perform the said manoeuvre. The graph shows the variation of longitudinal speed versus time. Wherein the said longitudinal velocity is expressed in kmph.
[040] FIG. 6c is an exemplary embodiment that depicts the lateral acceleration of the said vehicle performing the said manoeuvre. Wherein the said lateral acceleration is expressed in g's. The resulting fluctuation in the lateral acceleration is due to the fluctuation in the vehicle speed and the turning radius.
[041] FIG. 6d is an exemplary embodiment that depicts the yaw rate of the said vehicle performing the said manoeuvre. Wherein the said yaw rate is defined as the rate of change of yaw angle and is expressed in deg/s. The graph shows the variation of yaw rate versus time. The said yaw rate can also be obtained by the

ratio of lateral acceleration to longitudinal velocity. Wherein the said lateral acceleration should be expressed in m/s2.
[042] FIG. 6e is an exemplary embodiment that depicts the variation of turning radius of the said exemplary vehicle at the said manoeuvring state. The graph shows the variation of turning radius expressed in meters versus time. The said variation in the turning radius can also be seen in FIG. 6a where the GPS data shows the path of the said exemplary vehicle.
[043] FIG. 6f is an exemplary embodiment that depicts the variation of steering potentiometer reading of the said exemplary vehicle at the said manoeuvring state. The said steering potentiometer reading is expressed in volts. The graph shows the variation of steering potentiometer reading with time.
[044] FIG. 6a till FIG. 6f are the data obtained from sensors and data acquisition obtained during vehicle testing.
[045] FIG. 6g is an exemplary embodiment that depicts the variation of steering wheel angle of the said exemplary vehicle at the said manoeuvring state. The said steering wheel angle is expressed in degrees. The steering wheel angle is obtained by multiplying the data from the steering sensor with the calibration constant. Wherein the said calibration constant is defined as the change in the steering wheel angle to the corresponding change in the potentiometer reading, expressed in deg/V. The graph shows the variation of steering wheel angle with time.
[046] FIG. 6h and FIG. 6i are exemplary embodiments that depict the variation of left front and left rear tire slip angle respectively of the said exemplary vehicle at the said manoeuvring state. The said slip angle is estimated by processing the data obtained from the sensors and data acquisition system using the vehicle

properties. The said slip angle is expressed in degrees. The graph shows the variation of slip angle with time.
[047] FIG. 6j and FIG. 6k are exemplary embodiments that depict the variation of left front and left rear tire lateral force respectively of the said exemplary vehicle at the said manoeuvring state. The said lateral force is estimated by processing the data obtained from the sensors and data acquisition system using the vehicle properties. The said lateral force is expressed in Newtons. The graph shows the variation of lateral force with time.
[050] FIG. 61 and FIG. 6m are exemplary embodiments that depict the variation of front and rear tire camber angle respectively of the said exemplary vehicle at the said manoeuvring state. Wherein the said camber angle is estimated using the process depicted in FIG. 3a. The said camber angle is expressed in degrees. The graph shows the variation of camber angle with time.
[051] Furthermore, the data shown in FIG. 6b till FIG. 6m are smoothened using known processes such as a Kalman filtering. The said kalman filter is also used to fill in the missing data points that occurs due to a loss in the GPS signal. The said Kalman filter takes inputs from the Inertial measuring unit to perform the said task.
[052] Various embodiments of the current disclosure, assists the said vehicle control system to operate the tires near its peak operating conditions, thereby making the system more efficient in their respective operating conditions. The factors evident in the prolonged use of tire such as wear and heat cycles, limit the true performance of the vehicle which are overcome by the current invention. Also, the updated data from the tire data set further provides necessary information about the tires and its behaviour at different operating conditions and the change in tire characteristics with prolonged use. Furthermore, the vehicle control unit

monitors the functioning of the vehicle, checks the response of the vehicle, compares it to the expected response, and learns from the deviation in the response by updating the reference properties. Hence, the vehicle control unit recursively learns about the vehicle, which helps it adapt to changes such as a change in tire, change in terrain conditions, wear in the components, change in operating temperature, etc. Furthermore, this data can be retrieved for further development of the said systems to improve their performance.
[053] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.
[054] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.

WE CLAIM:
1. A method for recursively educating a vehicle control unit for improved vehicle
handling, the method comprising:
sensing a plurality of parameters associated with a tire behaviour of at least one tire of the vehicle;
receiving the sensed data instantaneously;
comparing the received data with a pre-stored reference data for the corresponding plurality of parameters;
updating the reference data based on the result of the comparison, and
communicating the updated reference data to the vehicle control unit for recursive learning which facilitates improved vehicle handling.
2. The method as claimed in claim 1, wherein the plurality of parameters are
indicative of tire forces and moment at various operating states.
3. The method as claimed in claim 2, wherein the plurality of parameters comprise
wheel base, track width, camber gains due to steer, bump and roll, roll gradients,
roll stiffness, pitching stiffness, mass and inertia of the vehicle with or without
passengers, and other such properties required to estimate the tire forces and
moments
4. The method as claimed in claim 1, wherein the pre-stored reference data
associated with the tire comprises a consolidated reference data obtained during
tire testing, data collected from the vehicle at the instantaneous tire operating states,
data depicting the instantaneous tire operating state at the instantaneous vehicle
operating state and data depicting the tire forces and moments at tire operating
condition.

5. The method as claimed in claim 4, wherein the data obtained from tire testing facilities includes at least a lateral force, longitudinal force, normal load, slip angle, slip ratio, inclination/camber angle, tire pressure and rotational speeds.
6. The method as claimed in claim 4, further comprising of tire forces and moments data generated because of vehicle manoeuvring, wherein the said tire forces and moments are inclusive of the tire normal load, longitudinal force, lateral force, rolling resistance, overturning moment and aligning moments.
7. A system for recursively educating a vehicle control unit for improved vehicle handling, the system comprising:
one or more sensors mounted on the vehicle, wherein the sensors are configured for sensing a plurality of parameters associated with at least one tire of the vehicle;
a data acquisition module configured for receiving the sensed data from one or more sensors;
a database for storing reference data associated with plurality of parameters associated with at least one tire of the vehicle;
a processing unit configured for :
comparing the data received by the data acquisition module with the stored reference data; and
updating the stored reference data based on the results of comparison;
a feedback module configured for detecting a change in the stored reference data and communicating the updated reference data to the vehicle control unit for improved vehicle handling.

8. The system as claimed in claim 8, wherein the feedback module is configured to
iteratively learn the updated reference data prior to communicating with the vehicle
control unit.
9. The system as claimed in claim 8, wherein the processing unit is further
configured to estimate the tire moments and force at various operating states based
on the data received from the one or more sensors.
10. The system as claimed in claim 8, wherein the processing unit is further
configured to estimate a vehicle behaviour based on the stored and updated
reference data.