Design and Position Control of a Novel Electric Brake Booster 2018-01-0812
The electric vehicles and the intelligent vehicles put forward to new requirements for the brake system, such as the vacuum-independent braking, automatic or active braking, and regenerative braking, which are the key link for the vehicle’s safety and economy. However, the traditional vacuum brake booster is no longer able to meet these requirements.
In this article, a novel integrated power-assisted actuator of brake system is proposed to satisfy the brake system requirements of the electric vehicles and intelligent vehicles. The electronic brake booster system is designed to achieve the function of boosting pedal force of driver, being independent on vacuum source, supplying autonomous or active braking. It is mainly composed of a permanent magnet synchronous motor (PMSM), a two-stage reduction transmission (gears and a ball screw), a servo body, and a reaction disk. The scheme design and power-assisted braking control are the key for the electronic actuator. We translate the control problem of force control to position tracking. The strong nonlinearity and the load-dependent friction make the position tracking control of the electro-mechanical brake booster more challenging. Then, a Karnopp friction model is used in this article, and its parameters are identified by the method of multiple linear regression. Consequently, a modified proportional-integral (PI) control architecture is presented with techniques of a cascaded three-closed-loop PI controller, friction compensation based on friction model, and gain scheduling. Finally, based on rapid control prototype environment, the bench tests covering multiple kinds of brake conditions are designed and implemented to verify the performance of the controller. Test results show that both the position tracking performance and response time of the electronic brake booster system perform well. The booster characteristics keep consistency with vacuum brake booster but have better stability.