Research On Coordination Control Strategy Of EPS And TCS For 4WD Vehicle

With the development of automotive electronic control theory and technology, a lot of electronic control systems, including electric power steering System(EPS) and traction control system(TCS), are widely used in automobile. EPS meets the vehicle performance requirements of steering portability at low vehilcle speed, handling stability at high vehicle speed, returnability and so on; TCS improves vehicle acceleration performance through controlling driving wheels’ slip rate. In this paper, in order to improve vehicle stability, safety and acceleration performance during turning, a four-wheel drive SUV is used to research on coordination control strategy of EPS and TCS.Firstly, all mathematical models of major components in vehicle system were established after analyzing the principle and technology of 4WD, EPS and TCS. These models include EPS model, engine model, inter-axle torque distributor model, powertrain model, tire model, brake model, whole vehicle model and some auxiliary calculation modules. Afterwards, all the mathematical models were transformed into block diagrams in Matlab/Simulink, which provided an off-line simulation platform for the research on control stragety. The control stragety of EPS includes power assisted control, returnability control and damping control; throttle percentage control, driving wheel braking control and inter-axle torque distribution control are applied in the stragety of TCS. After establishing sub controllers of EPS and TCS, the control strageties of subsystems are tested under different driving cycles through off-line simulation in Matlab/Simulink.Secondly, the coupling relationship between EPS and TCS has been clarified in this paper, the necessity of coordination control between EPS and TCS has been described as well. A hierarchical coordination control method is adopted without changing the sub controllers of EPS and TCS, and the upper coordination control stragety has been researched and designed in order to improve automobile comprehensive performance. Based on the four-wheel drive vehicle model and sub controllers of EPS and TCS, the off-line simulation was conducted in Matlab/Simulink with the purpose to verify the effectiveness of the upper coordination control stragety under three different kinds of driving cycles.Finally, based on the off-line model with coordination control stragety, d SPACE system and some crucial hardwares which include electronic throttle, position sensor and so on, a hardware-in-the-loop real-time simulation platform of coordination control has been built. The effectiveness of coordination control stragety between EPS and TCS has been tested further through the real-time and dynamic simulation experiment.