Varying Charge Voltage in the Steps Control Method of ABS for In-Wheel Motors Driven Electric Vehicles Based on an Improved LQG Scheme

This paper explores a coordinated control strategy of the anti-lock braking system (ABS) for in-wheel motors driven electric vehicles to recover more braking energy while satisfying the target of slip ratio control based on a newly varying charge voltage in steps control (VCVISC). The novel VCVISC method is proposed on the existing battery management system to change the charging voltage by choosing the number of batteries in the series to substitute for the converter. The reason that the conventional linear quadratic Gaussian (LQG) control employed in ABS control does not function is examined by theoretical derivation, and an improved LQG scheme is presented to calculate the real-time required braking torque by adding virtual damping and infinitely small terms in the Riccati equation. A distributing strategy of braking torque is presented to maximize the energy recovery, which is realized by using the VCVISC method to regulate the regenerative braking torque in real time. Simulation results under different braking road scenarios demonstrate that the proposed ABS control strategy can achieve not only an outstanding response for tracking ideal slip ratio, but also an efficient braking energy recovery efficiency.