An optimal anti-lock braking control strategy using nonlinear variable voltage charging scheme for an electric-wheel vehicle is developed with aim of improving energy recovery efficiency on the premise of vehicle safety under the critical braking situation. A variable voltage charging control scheme is proposed with its operational principles to obtain maximum energy recovery as well as to balance the energy differences of each battery cell during the anti-lock braking. Given the nonlinearity of in-wheel motor, the nonlinear variable voltage charging control law is obtained on the basis of parameters fitting via experimental data. An ideal regenerative braking torque calculated by the nonlinear variable voltage charging control law is set as one of the disturbance vectors and an optimal sliding mode-anti-lock braking control strategy is developed to provide optimal hydraulic pressure for anti-lock braking system. In this manner, the torque allocation process is omitted by using a compensation control of the hydraulic braking torque. Simulation results corroborate the effectiveness of the proposed optimal anti-lock braking control strategy with higher energy recovery efficiency.

This paper explores a coordinated control strategy of anti-lock braking system (ABS) for in-wheel motors (IWMs) 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 (BMS) to change charging voltage by choosing the number of battery in series to substitute 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 real-time regulate the regenerative braking torque. Simulation results under different braking road scenarios demonstrate that the proposed ABS control strategy can not only achieve an outstanding response for tracking ideal slip ratio, but also an efficient braking energy recovery efficiency.

The objective of this paper is to propose a modified optimal sliding mode control method for the hydraulic anti-lock braking system of a vehicle to achieve both robustness and optimal control performance. The longitudinal dynamic model of a vehicle, tyre model and hydraulic anti-lock braking system model are established, and the weakness of the common optimal sliding mode control method in designing the anti-lock braking system controller is analysed synthetically. The analyses form the basis for tracking an ideal slip ratio. A new modified optimal sliding mode controller is proposed to regulate the hydraulic anti-lock braking system for a better braking performance and robustness: the optimal sliding mode manifold function includes several virtual damping elements and infinitely small-sized items to meet the working conditions of the current optimal sliding mode control method. The control results of the proposed controller are compared with those of the common sliding mode controller. Simulation results under various road conditions demonstrate that the modified optimal sliding mode controller not only has strong robustness against uncertainties in the road adhesion coefficient but also achieves better control performance of the slip ratio.

To simultaneously track the ideal slip rate and realize ideal energy recovery efficiency under different complex road conditions, an electro-hydraulic compound anti-lock braking system based on interval type-2 fuzzy logic control strategy and its corresponding braking torque allocation strategy have been developed for electric vehicles. The proposed interval type-2 fuzzy logic controller aims to calculate the ideal total braking torque by four steps, namely, fuzzification, fuzzy inference, type reduction, and defuzzification. The slip rate error and the change rate of slip rate error are utilized as inputs in the fuzzification, and then, the membership degree interval of fuzzy variables determined by the upper and lower membership functions is used to calculate the activation degree interval of different fuzzy rules in the fuzzy inference process, which enhances the anti-interference ability to external uncertainties and internal uncertainties. The braking torque allocation strategy is proposed to maintain the maximum energy recovery efficiency on the premise of safe braking. The software of MATLAB/Simulink is applied to simulate the process of anti-lock braking control under two complex road conditions. Simulation results corroborate the proposed interval type-2 fuzzy logic anti-lock braking control system can not only obtain better slip rate control effect and outstanding robustness but also achieve ideal regenerative braking energy recovery efficiency under both joint-μ and split-μ road surfaces.