Traction Control System And Method

Abstract

A method for providing traction control on a wheeled vehicle involves receiving a speed reference signal. A variance in wheel size between a first and at least one other wheel of the vehicle is determined. Lastly, a drive control signal operable to control power to each of the first and at least one other wheel is output, the drive control signal being based on the speed reference signal and determined variance in wheel size and operable to provide that a tractive force exerted by each of the wheels on a corresponding surface during traction and/or braking is substantially similar.

1 - 24 . (canceled) 
     
     
         25 . A predictive traction control system for a wheeled electric vehicle comprising a plurality of independently controlled wheels, the system comprising:
 a receiver that receives a speed reference signal for the vehicle;   a determination module that determines a variance in wheel size between a reference wheel and at least one target wheel, based on angular velocity measurements taken for the reference wheel and the at least one target wheel; and   a control module that utilizes the speed reference signal and the determined wheel size variance to generate a pulse width modulated drive control signal for each wheel to balance tractive forces exerted by the wheel on a corresponding surface during traction and/or braking.   
     
     
         26 . The traction control system as claimed in  claim 25 , wherein the electric vehicle comprises a plurality of individual drive motors each coupled drivingly to one wheel, and
 wherein the pulse width modulated drive control signal for each wheel is used to control the drive motor for the wheel to apply a rotational force to the respective wheel in accordance with the drive control signal.   
     
     
         27 . A traction control system as claimed in  claim 26 , further comprising a communication module configured to transmit each drive control signal to the individual drive motor coupled to each wheel. 
     
     
         28 . A traction control system as claimed in  claim 27 , wherein the rotational force applied to each of the wheels is different if the variance in wheel size is above a set threshold. 
     
     
         29 . A traction control system as claimed in  claim 26 , wherein the individual drive motors are powered by one or more AC traction inverter circuits. 
     
     
         30 . A traction control system as claimed in  claim 25 , further comprising an angular velocity measurement module that determines an angular velocity of each target wheel relative to the reference wheel, the relative angular velocity for each wheel being processed to determine the wheel size variance. 
     
     
         31 . A traction control system as claimed in  claim 30 , wherein the relative angular velocity for each target wheel is determined by comparing a measured angular velocity of the target wheel against a measured angular velocity of the reference wheel. 
     
     
         32 . A traction control system as claimed in  claim 31 , wherein the angular velocity measurements are taken when the vehicle is travelling at a substantially constant speed. 
     
     
         33 . A traction control system as claimed in  claim 25 , wherein the reference wheel is used for determining a wheel size variance for each wheel of the vehicle. 
     
     
         34 . A traction control system as claimed in  claim 33 , wherein the axle of the reference wheel is a trailing axle of the vehicle. 
     
     
         35 . A traction control system as claimed in  claim 25 , further comprising a driver control module operable to generate the speed reference signal based on a user throttle input. 
     
     
         36 . A traction control system as claimed in  claim 25 , further comprising a surface condition determination module operable to determine the condition of the surface that the vehicle is travelling on, the surface condition also being utilized to generate the pulse width modulated drive control signal. 
     
     
         37 . A wheeled electric vehicle comprising:
 a plurality of independently controlled wheels;   a plurality of individual drive motors each coupled drivingly to one wheel;   a power source configured to provide electric power to each individual drive motor; and   a fraction control system as claimed in  claim 25 .   
     
     
         38 . The vehicle as claimed in  claim 37 , wherein the power source comprises an internal combustion engine and converter for output of electrical power. 
     
     
         39 . The vehicle as claimed in  claim 37 , wherein the power source is a DC power supply. 
     
     
         40 . A method for providing traction control on a wheeled vehicle comprising a plurality of wheels, the method comprising the steps of:
 receiving a speed reference signal for the vehicle;   determining a variance in wheel size between a reference wheel and one or more target wheels of the vehicle based on angular velocity measurements taken for the respective wheels;   generating a pulse width modulated drive control signal for each one of the one or more target wheels to balance the tractive forces exerted by each wheel on a corresponding surface during traction and/or braking, the drive control signal being generated from the speed reference signal and determined variance in wheel size.   
     
     
         41 . A method as claimed in  claim 40 , further comprising the steps of:
 transmitting the drive control signal for each target wheel to an individual drive motor coupled to the target wheel; and   controlling the individual drive motors in accordance with the received drive control signal to apply a rotational force to the respective wheel.   
     
     
         42 . A method as claimed in  claim 41 , wherein the rotational force applied to each wheel is different if the variance in wheel size is above a set threshold. 
     
     
         43 . A method as claimed in  claim 40 , wherein determining variance in wheel size comprises calculating a differential angularly velocity for each target wheel relative to the reference wheel and determining the variance in wheel size from the calculated differential angular velocity. 
     
     
         44 . A method as claimed in  claim 43 , wherein the differential angular velocity is calculated from measured angular velocity for each wheel of the vehicle. 
     
     
         45 . A method as claimed in  claim 44 , wherein the angular velocity measurements for each wheel are taken when the vehicle is travelling at a substantially constant speed. 
     
     
         46 . A method as claimed in  claim 45 , wherein a resolver measures the angular velocities of each wheel. 
     
     
         47 . A method as claimed in  claim 43 , wherein the reference wheel size is derived from the averaged sizes of trailing wheels. 
     
     
         48 . A method as claimed in  claim 40 , further comprising the step of determining a surface condition, the surface condition also being utilized to generate the drive control signal. 
     
     
         49 . A traction control method comprising:
 obtaining a speed reference for a wheeled vehicle;   measuring the angular velocity of a plurality of vehicle wheels, including a designated reference wheel, while the vehicle is travelling at a substantially constant speed;   determining a wheel size reference for each of the plurality of wheels from the measured angular velocity of the respective wheels, the wheel size reference for an individual wheel representing a size difference between the wheel and the designated reference wheel; and   modulating a drive control signal for each one of the plurality of wheels to balance the tractive force exerted by the respective wheels, each drive control signal being generated from the vehicle speed reference and the wheel size reference for a corresponding wheel.   
     
     
         50 . The method as claimed in  claim 49  further comprising determining a differential angular velocity for each one of the plurality of wheels, the differential angular velocity for each wheel representing the angular velocity of the wheel relative to the reference wheel. 
     
     
         51 . The method as claimed in  claim 49  further comprising modulating the width of pulses generated in a pulse width modulation (PWM) drive control signal for each one of the wheels to alter the tractive force exerted by the wheel. 
     
     
         52 . The method as claimed in  claim 49  further comprising comparing the wheel size reference for each one of the plurality of wheels to a threshold wheel size variance, and moderating the drive control signal for wheels with a wheel size reference that exceed the threshold wheel size variance.