Research On Navigation Control Simulate Of Autonomous Vehicle With Electric Four-wheel Steering

Autonomous vehicles has important applications in various fields of nationaldefense and the economy, but as the supply of oil resources conflicts, as well as goodspeed regulation ability, excellent steering stability and high mobility requirements,using an electric four-wheel steering undoubtedly is an important direction for thedevelopment of autonomous vehicles. Navigation control is the foundation anddifficulties of autonomous vehicles, This paper is to research on navigation controlautonomous vehicle with electric four-wheel steering.Firstly, Establish a three degrees of freedom vehicle dynamics model, wh ichcontains lateral, yaw, roll. Provide constraints to the lateral acceleration and partangles of vehicles, which ensure the system can operate in a stable condition. Makethe relationship between front and rear wheels to meet the dynamic compensationcontrol, ensure the vehicle the centroid side-slip angle is zero. By comparing changesof the yaw angle-velocity and the centroid side-slip angle on different speeds,demonstrated the operational stability of four-wheel steering vehicle is superior to thefront wheel steering vehicle; Further by analyzing influence of the vehicle ridecomfort and stability with the roll angle-velocity and lateral angle-acceleration,demonstrates the necessity to consider the establishment of a three-dimensionalmodel including roll.Focuses on the designing of the sliding mode controller based on the previewerror. Obtain formulas of the lateral error and direction error at preview point toensure a good path tracking ability. Combined with the three-dimensional dynamicmodel, establish the state space model, which proved be controllable, observable andstabilizable. The state differential equation is divided into a reaching mode and asliding mode, for the sliding mode, determines the switching function based onquadratic optimal control; for the reaching mode, select the index reaching law to determine the function of the reaching law. To reduce buffeting furtherly, usingsaturation function instead of the sign function.Navigation control simulate using matlab, design an optimal controller based onthe above state space model. and through a circular path, the straight path, the pathvariable curvature of the track, demonstrated tracking speed of sliding modecontroller is slightly lower than the optimal controller, but the tracking accuracy androbustness on different speed is much better than the optimal controller.