Analogous to a vacuum boosted system, Electro-Hydraulic Braking System (EHB) is free from engine vacuum and supplies a braking force proportional to driver input. The independence of engine vacuum makes it especially suitable to be used in electric vehicles (EVs) and hybrid electric vehicles (HEVs). As a key component of EHB, master cylinder is driven by the pump rather than the vacuum booster. Even if the pump fails, the cylinder can also build proper pressure. Meanwhile, in order to maintain the pedal feeling, a pedal stroke simulator is applied in the system.
In this paper, aiming at decreasing the size and cost of master cylinder and providing an ideal pedal feeling without compromise of performance, a new integrated master cylinder of EHB system is designed including two parts: master cylinder and pedal stroke simulator. The key components of the integrated master cylinder are motor pump, solenoid valves and composite springs. A model of the EHB and other key components of the brake system are established in AMEsim-MATLAB/SIMULINK. AMEsim is responsible for hydraulic part while SIMULINK for control part. Some parameters of the components are discussed to research their effects on system performance. In addition, to verify the system availability, the PWM method is adopted to regulate the fluid pressure in the pressure following control. Finally, braking performance is tested under three modes through the match of EHB model and vehicle model in CarSim. The simulation result demonstrates that the EHB system not only can satisfy the demands of braking system, but also conform to ideal stroke-force curve.