A robust controller for maximizing braking force despite of the parameter variation

Anti-lock braking system (ABS) in the passenger car is a safety device, which adds hydraulic system to the existing brake system to prevent wheel from locking, so we can obtain maximum braking force on driving. Each channel to control braking pressure in the hydraulic system consists of sol-flow type using solenoid valve and flow control valve or sol-sol type using two solenoid valve. In this paper, the channel is composed of one solenoid valve with high responsibility and 1/4 vehicle model is used. The parameters relative to braking force are friction coefficient between wheel and road surface and vehicle weight. On driving, it is impossible to directly measure friction coefficient and friction coefficient changes in some boundary in condition of the road surface. Also vehicle weight becomes different in terms of load. Consequently, robust controller is designed to maintain braking force at maximum even in the presence of parameter variation in some boundary.