Passenger Car Active Braking System: model and experimental validation (Part I)

The paper proposes a method to characterize the dynamic behavior of a normal production hydraulic brake system through experiments on a hardware-in-the-loop (HIL) test bench for both modeling (Part I) and control (Part II) tasks. The activity is relative to analyze, model and control ABS/ESC digital valves, aiming at obtaining reference tracking and disturbance-rejection performance similar to that achievable when using pressure proportional valves. The first part of this two-part study is focused on the development of a mathematical model which emulates the pressure dynamics inside brake caliper when inlet valve, outlet valve and motor-pump are controlled by a digital or PWM signal. The model takes into account some inherent non-linearities of these systems, e.g. the variation of fluid bulk modulus with pressure while inlet and outlet valves together with the relay box are modeled as second order systems with variable gains. The HIL test rig is used for both parameters identification and model validation, which will be used for control strategy development presented in the second part of this research activity. Index Terms ABS test bench, brake hydraulic systems, dynamic system modeling, valve dynamics.