Bond graph model-based evaluation of a sliding mode controller for a combined regenerative and antilock braking system

Combined regenerative and antilock braking in electric/hybrid-electric vehicles provides higher safety in addition to an energy storing capability. Development of a control law for this type of braking system is a challenging task. The antilock braking system (ABS) uses a control strategy to maintain the wheel slip within a predefined range. A sliding mode controller (SMC) for ABS is developed to maintain the optimal slip value. The braking of the vehicle, performed by using both regenerative and antilock braking, is based on an algorithm that decides how to distribute the braking force between the regenerative braking and the antilock braking in emergency/panic braking situations as well as in normal city driving conditions. Detailed bond graph models of a quarter car and four-wheeled vehicles are used in this article to implement and test the control laws. It is found that with combined regenerative and antilock braking, the vehicle's safety increases (in terms of stopping distance and manoeuvrability) and some amount of kinetic energy can be recovered and stored in the regenerative battery pack. The passenger comfort is improved when a sliding mode ABS controller is used in place of a standard ABS controller for the mechanical braking part. Moreover, the influence of load transfer on the wheels during braking was evaluated on a four-wheeled vehicle model.