회생제동 협조제어 시스템용 전자제어 부스터 설계 및 제어

Abstract

Recently, the automotive industry’s development direction and the major issues are represented by safety, eco-friendly and IT convergence technologies. Generally, these technologies can be implemented through the advanced electrification of the current systems. The need to reduce fuel consumption and exhaust emissions has derived Brake-by-Wire systems as new brake systems for Hybrid Electric Vehicles and Electric Vehicles. As a kind of BBW systems, electric booster systems have been actively developed for the last five years. These systems can provide precise pressure control and quiet operating characteristics by electrically controlling the motor position and torque to boost the master cylinder pressure. To realize all these potential benefits of the electric booster system, robust feedback control is required to deal with disturbance such as varying mechanical and hydraulic loads of electric booster components. Furthermore, feedback control should be used for higher performance as well due to the use of more sophisticated actuators and the availability of sensors. This thesis focuses on two typical subjects associated with the development of electric booster systems: system design and robust control. First, the architecture of the electric booster systems for regenerative braking cooperation is investigated which includes the communication with ESC and information of sensors such as pedal travel sensor, current and rotational angle sensors of the motor and pressure sensor of the master cylinder. System redundancy is also considered in case of failure of pedal travel sensor signals through the private CAN connection between the electric booster and the ESC. The hardware of electric booster systems is typically composed of an electric motor and a driving mechanism with rotary-to-rectilinear to control the master cylinder pressure. For feedback control, the sensors of electric booster systems are composed of a rotational angle position sensor, current sensors of the motor and pressure sensor to monitor the controlled hydraulic pressure. Based on the fundamental study on the structure and the analysis of electric circuit, the control algorithm of PMSM is designed with flux weakening control to extend the speed range of PMSM drive for rapid brake response. Secondly, an approximated linear time invariant model of electric booster system is derived for designing robust controllers. As a beginning step, an effective origin setting algorithm is developed using the FIR-filter type differentiator to ensure the pressure release function of the master cylinder at the initial position. With the derived electric booster model and origin setting algorithm, two robust controllers are designed based on the Lyapunov analysis to guarantee robust control performance and stability. Because a conventional sliding mode controller has a serious drawback chattering, a filtered sliding mode controller is proposed with a low-pass filter instead of an integrator. Due to the low-pass filter, the proposed controller has more controller design parameters and filtering ability. The intensified filtering ability may degrade tracking performance of the high frequency reference signal, and, thus, a disturbance observer is included in the filtered sliding mode controller. This technique effectively intensifies the controller performance. The performance of the proposed controller is evaluated by numerical, hardware simulations and a real vehicle experiments. Finally, availability in regenerative braking control is also shown in the real vehicle experiments.