Path Following Control of Bi-steerable Cars: a Lyapunov-based Approach

Path following control is important in order to realize autonomous driving of robotic vehicles. The need to move automated cars in cluttered environments, as well as parking in tight places, often leads to following complex reference paths with small radius of curvature, which can be implemented successfully by vehicles with increased manoeuvrability, such as the four-wheel steering (4WS) cars. This paper proposes a feedback path control law for a bi-steerable car (4WS vehicle where the steering angle of the rear wheels is a function of the steering angle of the front one). First, kinematic model of the car in error coordinates expressed in a moving reference frame, which is partially linked to the vehicle is derived. The control law is constructed using Lyapunov-based control design techniques, yielding asymptotic stability of the closed-loop system in error coordinates. Simulation results illustrate the effectiveness of the proposed controller.