Improving Performance Using Torque Vectoring on an Electric All-Wheel-Drive Formula SAE Race Car

Various forms of electronic stability, traction and launch control have existed for over two decades, improving safety, sports performance and off-road capabilities of vehicles. These technologies involve individual control of each wheel’s drive torque or braking force in response to the dynamics of the driving conditions and the driver’s intentions. With the exception of launch control, applications of these electronic handling-improvement systems are rarely seen on the Formula SAE platform. This is mostly due to the limitations of a combustion engine and conventional drivetrain; individual control of torque to each wheel requires additional mechanical systems adding unjustifiable weight and complexity for the resulting gains. However, an all-wheel-drive electric Formula SAE vehicle with four individual hub motors has the potential for experiments with torque vectoring via electronic means, with minimal additional mechanical systems. The University of Western Australia’s Renewable Energy Vehicle (REV) group has been designing such a vehicle for the 2013 Formula SAE competition in Melbourne. Processing driver inputs such as steering angle, throttle and brake position in addition to the actual dynamic state of the vehicle observed through wheel speeds, three axes of acceleration and angular velocities, a torque vectoring algorithm has been designed and implemented on an ARM Cortex M3 microcontroller and has achieved significant improvements in cornering performance.