Electric machine vs mechanical brakes for traction control with real time extremum seeking control

Performance of an extremum seeking electric machine based antilock braking (ABS) scheme is compared to mechanical braking based ABS. The advantage of the fast time constant (torque response) of an electric machine in an ABS application is quantified. A vehicle initiating a braking maneuver at a starting speed of 125kmph is considered. The vehicle stopping distance is reduced by 30% compared to mechanical braking system based ABS. The improved real-time slip optimization (RT-ESSO) algorithm guarantees reaching optimal slip under varying road conditions without any high frequency switching/chattering of the actuator found in variable structure controls schemes. Dynamic behavior of the ABS systems under varying road conditions is discussed. A permanent magnet synchronous machine with cross axis decoupling is considered for the electric machine.