Abstract
Traditional friction braking torque and motor braking torque can be used in braking for electric vehicles (EVs). A sliding mode controller (SMC) based on the exponential reaching law for the anti-lock braking system (ABS) is developed to maintain the optimal slip value. Parameter optimizing is applied to the reaching law by fuzzy logic control (FLC). A regenerative braking algorithm, in which the motor torque is taken full advantage of, is adopted to distribute the braking force between the motor braking and the hydraulic braking. Simulations were carried out with Matlab/Simulink. By comparing with a conventional Bang-bang ABS controller, braking stability and passenger comfort is improved with the proposed SMC controller, and the chatting phenomenon is reduced effectively with the parameter optimizing by FLC. With the increasing proportion of the motor braking torque, the tracking of the slip ratio is more rapid and accurate. Furthermore, the braking distance is shortened and the conversion energy is enhanced.
Highlights
The anti-lock braking system (ABS) is the most important active safety system for road vehicles.The ABS can greatly improve the safety of a vehicle in extreme circumstances since the ABS can maximize the longitudinal tire-road friction while keeping large lateral forces that ensure vehicle drive-ability [1]
The conventional friction braking system must be retained and works together with the regenerative braking system since the regenerative braking torque is limited by many factors, such as the motor speed, the state of charge (SOC)
When the brake is applied, the brake control unit calculates the required braking torque on the front and rear wheels according to the brake pedal stroke, and estimates the available motor braking torque according to vehicle velocity, battery SOC and other information
Summary
The anti-lock braking system (ABS) is the most important active safety system for road vehicles. The contribution of the paper includes three aspects: (a) a sliding-mode methodology based on exponential reaching law has been adopted to design the ABS controller; (b) FLC is applied to optimize the parameter of the exponential reaching law; and (c) a distribution algorithm that the motor torque is taken full advantage is adopted to distribute the braking torque between the motor and the hydraulic braking system. The comparisons of performance of ABS with a Bang-bang controller and the proposed SMC controller, with and without the optimizing parameter, and the distribution of braking force using different actuator, are carried out with Matlab/Simulink
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