Design And Control Of The Distributed Electro-hydraulic Braking System

In order to meet the increasingly strict requirements on energy saving, emission reduction and safe driving, electrification and intelligence have become technology trends of today’s automotive technology. The traditional hydraulic braking system of passenger vehicle can no longer meet the new requirements from these technology trends due to its structure and working pricinple, as a result, new braking systems are proposed. The Distributed Electro-hydraulic Braking system(DEHB for short) meets the new requirements, providing advangates such as flexible and accurate control, high safety and low cost, thus has a good application prospect. In order to contribute to energy saving, emission reduction and safe driving, and also to facilitate the application of DEHB, ‘Design and control of the Distributed Electro-hydraulic Braking system’ is choosen as the thesis topic.The prototype of the system as well as its research environment is the basis for the research on DEHB. A prototype of the DEHB actuator and its Electronic Control Unit was designed. A research environment was developed, including a numerical simulation environment, a hardware-in-the-loop test bed and a vehicle experiment platform. These work forms the foundation for the research on DEHB.Based on the research basis developed, research on the actuator pressure control was carried out. A gain-scheduling pressure control approach that takes the target pressure and the control mode as scheduling variables was proposed. The effectiveness of the approach was verified through lots of experiments, including step response, sawtooth response, sine wave response, normal braking, pump braking, ABS, AYC, etc. Experiment results show that the control performance is satisfactory, which forms the foundation for research on vehicle control.Safety is a key concern for the brake-by-wire system. Fault tolerant control(FTC) is a major approach that guarantees fail-safe of DEHB. Research on the FTC of DEHB was carried out. The FTC problem was divided into different regions according to the desired deceleration. A design method of the FTC was proposed, which aims to optimize the comprehensive control performance of FTC and the driver’s correction. A design concept, named ‘Implicit Hardware Redundancy’(or IHR for short) was proposed, providing a FTC performance that is comparable to braking performance when the system is normal.Slip control is a basic technology for new braking systems such as DEHB to improve brake control as well as driving safety. The traditional rule-based ABS does not contain a module that determines the optimal slip. To ensure that the slip control type of ABS of DEHB makes full use of the tyre-road friction, a searching algorithm for the optimal slip of ABS was proposed. The asymptotic convergence of the target slip calculated by the algorithm to the optimal slip was proved using the Lyapunov theory. Together with a gain-scheduling slip controller developed, the effectiveness of the searching algorithm was verified through simulations on uniform roads with low friction, medium friction and high friction, as well as on roads whose friction changes from low to high and from high to low. Comparing with the conventional rule-based ABS, the pressure modulation amplitude and the wheel speed fluctuation can be significantly reduced, improving control performance of ABS.