Robust solenoid current control for EHB

This paper describes a method for the estimation of solenoid resistance. With the estimated solenoid resistance, PWM duty ratio can be compensated to achieve a robust solenoid current control. Because EHB is a wet type BBW(Brake By Wire), HU(Hydraulic Unit) performs not only ABS/TCS/ESP functions but also CBS(Conventional Brake System) function. To implement the CBS function, HU must be able to control the wheel pressure in a wide temperature range and for a long duration. During the development of EHB, it is found that a change in solenoid resistance is a major disturbance to both current control and pressure control. Developed method uses a model for solenoid current and an iterative method for calculating the solenoid resistance. Furthermore, the effect of measurement noise can be eliminated by averaging. The proposed method can economically estimate the solenoid resistance and make current control and pressure control very robust with respect to temperature change and noise.