Variable structure backstepping control via a hierarchical manifold set for graceful ground vehicle path following

Graceful motion in vehicle steering is an important issue. Generally, this problem can be solved by controller design or planning a path in a real time. However, it may need the system to carry on more computing effort or make a compromise between the tracking accuracy and motion smoothness. In this paper, a multi-tiered model based steering control strategy is proposed for considering vehicle kinematics and dynamics simultaneously. In this strategy, the kinematic controller applies motion trajectory generation as basis to produce a set of hierarchal manifolds that gradually converge tracking errors by providing softer yaw rate commands. To minimize steady-state error caused by path curvature discontinuity, an integrator is embedded to these manifolds. A robust output feedback dynamic controller is designed to reject modeling errors and disturbances caused by side slip estimation from a robust observer. Steering rate is applied as the control input by considering steering actuator capabilities to replace traditional steering angle commands. Simulations and experiments validate control performance with a full-size passenger vehicle.