Development of the Control Logic of Electronically Controlled Hydraulic Brake System for Hybrid Vehicle

The control logic of electronically controlled hydraulic brake system for hybrid vehicle is introduced in this paper. The hybrid brake system consists of the electronically controlled hydraulic brake system, electric motor and vacuum management system. The electronically controlled hydraulic brake system is developed and named as Advanced ESC system. This system has 14 linear valves, a motor, and multi-pumps. These linear valves are tested to find the dynamic characteristics, which is the relation between hydraulic force, magnetic force and spring force. By using this force relation, valve is controlled to be open or closed state. The multi-pumps are adapted to improve NVH and hydraulic pressure rise rates. After the regenerative brake torque of electric motor is studied, the control flow chart of this brake system is determined. During vehicle stop, the regenerative brake torque of electric motor gradually increases and then reaches to max torque to regenerate. Near to vehicle stop speed, the regenerative brake torque is rapidly decreases to control the engine. So the hydraulic pressure must be controlled to be on the decrease, hold and increase state, which makes brake system meet the needs of driver’s brake feelings. The valves and motor can be controlled by feedforward and feedback controller. The feedforward controller gains are obtained by using the characteristic of each component. On the basis of these kinds of knowledge, the control algorithm for electrically controlled hydraulic brake system is developed according as the change of regenerative brake torque of electric motor. The performance of cooperation control between electric motor and electrically controlled hydraulic brake system is tested using hybrid electric vehicle.