| Wheels could be easily locked while emergent brake. Totally locked wheels could decrease the friction force between wheels and ground surface. If front wheels were locked, the drivers could not control the direction of vehicles; and if rear wheels were locked, side-slipping could easily occur. Anti-lock Braking System, known as ABS, could prevent vehicles from losing driving stability efficiently.Based on domestic and international research, considering the real-timing and control stability of ABS control algorithm and the characteristics of ESC system that it has a pressure sensor of brake master cylinder, the article presented a control algorithm, which used set PID parameters to control the vehicle brake. The PID parameters were set real-timely with logic threshold according to the driving status when braking. The algorithm doesn't only have the characteristics of quick response and simple arithmetic in logic threshold control, but also have the characteristics of stability and well-adaption in PID control. The algorithm also avoid the disadvantages of wide fluctuation and bad comfort ability with logic threshold controlling wheel brake force and complexity and slow response of parameters setting with simple PID control.A control network of brake system was built based on CAN protocol and the functions of the network were verified. ECU hardware-in-the-loop test bench based on CAN network was set up with two kinds of real-time system, on which hardware-in-the-loop experiments were made. Field test research of controller at typical conditions was accomplished. The article provided important references for ABS control system development.Based on the above theory, the article discussed the following issues:First, to establish vehicle dynamics model. The model of 15 DOFs was adopted in the article to develop ABS system, which include 6 DOFs of vehicle body in three directions(3 translational and 3 rotational), 3 DOFs in front axles(jumping DOF of left and right wheels and DOF of steering) and 2 DOFs in rear axles(jumping DOF of left and right wheels). For ABS, chassis control is largely associated with tyre force control. They are both based on the research of tyre force characteristics, so fairly mature tyre model based on Pacejka'96 magic formula was adopted. In the mean time, engine module, power train module and brake system module were included, so a complete simulation model was achieved. The model could meet the requirements of simulation in different conditions such as linear acceleration, linear brake and steering brake. With the offline real-time simulating function of CANoe, the information gathered from real vehicle was put into the model to calibrate the precision of the model.Second, research on strategy of ABS control system. Combined control of logic threshold and PID was adopted. The control system determined whether to enter ABS control through logic threshold. The ground surface was recognized in the first circulation of logic threshold control, and then reasonable target value of slip rate was decided. Brake force was controlled with set PID parameters, taking advantage of the control precision of PID control. When the response of PID delayed and the angular deceleration of wheels exceeded the set logic threshold again, the logic threshold control took into effect again and again until the wheel does not tend to lock or the vehicle speed is lower than 3Km/h, then it quit controlling ABS.Third, research on network protocol of ABS control system. The application of CAN bus technology of control system in automotive field has grown wider these years. The network scheme of ABS control system was presented in the article. Through the analysis of CAN protocol and requirements and control functions, the protocols of the physical layer, data link layer and application layer of ABS control system network were established based on CAN protocol. The message quantity, the sending node of message, the receiving node of message and the combination of signals in message were specifically defined in network protocol. Offline simulation model was established with CANoe, which is a professional development and test tool of CAN network at system level from Vector. The communication function of offline simulation system proved to be valid and it can control the braking force, so the validity of protocol and the performance of the network were verified. The average load factor of network and delay rate of message sending could meet the real-time requirement.Fourth, hardware-in-the-loop test bench development based on CAN network. Hardware-in-the-loop test bench could strengthen the safety of experiment, shorten development time and save development cost, and it has become an important and essential section in the development of control system. Fully considering the simulation degree of test bench and real vehicle, the article established a hardware-in-the-loop test bench based on CAN network with real-time system to ensure the communication between control system and vehicle in the way of real vehicle. The test bench was used on self-developed ABS controller to test the function and performance of the controller. It has played an important role in the earlier stage of controller development and avoided potential injury to testing personnel brought by failure of controller.Last, research on real vehicle experiment of ABS control system. After tests on hardware-in-the-loop test bench, the controller was installed on real vehicle to be adjusted. Relative tests were made on high adhesive road in summer and low adhesive road in winter. The tests proved that the strategy of combined logic threshold and PID has achieved desired target, and could meet the requirement of brake on high and low adhesive road. Compared with the former ABS control system, the strategy is quicker in response and more stable. The article lays the foundation for domestic research on ABS control system.
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