Study On Control Algorithm Of Traction Control System For Light Off-Road Vehicle On Sand

With the development of automobile industry, more and more demands to vehicle safety capability are taken into account. Traction control system are widely equipped in all kinds of vehicles. It can prevent the driven wheels from slip during auto accelerates especially when auto starts, accelerates or cornering, which can improve vehicle stability, handling and acceleration.TCS is a new active safety control system which was developed in the middle of 80's, which gets the optimum longitudinal traction by controlling vehicle driving slip ratio. It is based on the principle that maintaining the driving slip ratio value round the optimum slip ratio so that traction can not only be fully used but also the lateral stable potentiality is guaranteed.In this dissertation, a model for the interaction of driven rigid wheel and sand is presented. The controller for engine throttle opening and threshold control algorithm for brake are designed. On the basis of the scheme of acceleration dynamic simulation models, an off-line simulation platform is established and off-line simulation research on control algorithm of traction control system is made.In details,four subjects are studied as follows:1. Model for the interaction of driven rigid wheel and sandWith the J.Y.Wong's"pressure-sinkage"and"shear-displacement"equations, a model for the interaction of driven rigid wheel and sand is presented in this dissertation. The tractive performance of driven rigid wheel on sand can be predicted more accurately by takeing account of the effect of distribution of stress beneath the tyre. At the same time, a simplified method is set up to replace the above complicated model, not only ensuring the precision of the result, but also making the caculation easier and quicker.2. Traction control system simulation modelAn part-time 4WD vehicle TCS control simulation modle is established, this simulation model including driver's attention model, vehicle acceleration dynamic model, and TCS control logic model. The vehicle acceleration dynamic modle is made up of the engine model, the brake model, the driveline model, the tire model, the whole vehicle model, and other assistant models to simulate the acceleration process of vehicle on sand; The TCS control logic model contains the engine's throttle control modle and the brake control model.According to the above works, an off-line simulation platform based on Matlab/Simulink is accomplished.3. Control strategy and control algorithms of TCS on sandThe control target of TCS control on sand is established, for vehicle accelerating on sand, the traction control system should firstly ensure the trafficability of the vehicle firstly, and make the net thrust of sand as large as possible to accelerate the vehicle. The controller for engine throttle opening using PI algorithms and for brake using threshold control algorithm are designed.4. Simulation for control algorithms of traction control systemTo validate the effect of control algorithm of traction control system put forward in this thesis, a simulation study is made on sand and simulation results indicate that the control algorithm can prevent excess spin of driven wheel effectively and improve traction.