Nonlinear wheel-slip dynamics of battery electric vehicle for anti-lock brake system control by traction motor

Anti-lock brake system control by traction motor requires optimal utilization of ground adhesion coefficient during regenerative braking, and it is essential to maintain the stability of battery electric vehicle throughout the process. Further, the wheel slip ratio control of brake-electric system differs from that of brake-hydraulic system due to the large difference in the response time of brake torque. Therefore, it is particularly challenging to prevent the lock of all traction wheels through torque control of the traction motor. While much of the research on brake-electric system has focused on optimizing the energy regeneration efficiency in the barke process, comparatively little is known about the stability control of battery electric vehicle. Here this article discusses a series of studies on the nonlinear dynamics of wheel slip and model predictive controller, and a torque demand control approach was designed based on both of these. That is, how a nonlinear model predictive controller could be used for anti-lock brake control of traction wheels. In order to find the optimum value of the wheel slip ratio, an ideal slip ratio curve illustrated by ground adhesion coefficient and wheel slip ratio was developed, which is used as an optimal target boundary of control algorithm. The developed approach has been downloaded into a vehicle control unit, and tested in real-world conditions using a battery electric vehicle to fully realize practical application of anti-lock brake system control by traction motor torque.