Brake System Control for Hybrid Electric Vehicles Considering Temperature and Dynamic Characteristics

抄録

Regenerative braking converts from thermal energy to electric energy and stores the electric energy different from conventional frictional braking. The regenerative braking system is a key technology for electric and hybrid electric vehicles to increase fuel efficiency. This brake system generates frictional braking force by an electro-mechanical brake and regenerative braking force operated by an electric motor. However, there are several problems due to each different characteristic of frictional brake and regenerative brake. First, the friction coefficient is changed depending on temperature, so the sum of brake torques of two brake systems is not steady. Second, characteristic differences between two brake systems generate the unexpected deceleration at transient region when shifting both systems. These problems cause unstable vehicle motion and uncomfortable feeling to drivers. To solve these problems, the thermal model of frictional brake system is developed to predict the temperature variation of the system, and then frictional brake force is calculated more accurately. From the predictive frictional brake force, a compensation control algorithm is developed to maintain the requirement of total brake force. In addition, the concurrence control algorithm is proposed that the controller gain is modified considering the dynamic characteristic of frictional brake system. Finally, the cooperative control algorithm combined two algorithms are developed to improve the vehicle driving stability and ride comfort. The performance simulator for hybrid electric vehicle is developed to tune the parameters of brake systems in the lab by using MATLAB/Simulink. The various simulations and simple experiments are implemented in order to verify the proposed algorithms, and the improvement of vehicle driving stability is proved by using the developed algorithms.