## 1 Introduction  
Autonomous vehicles can sense the road environment through the on-board sensor system, automatically plan the traffic route and then reach the target position [1]. As the major component of Intelligent Transportation System (ITS), autonomous vehicles have become the focus of research these years. One of the most fundamental issues related to autonomous cars is the path following problem, which serves as the basis for the design of control laws that enable a vehicle to follow the desired path with minimum error and behave with good stability against external disturbances [2; 3]. The past decades have witnessed many researches in trajectory tracking [4; 5; 6]. Many control structures have been proposed, which are mainly based on EPS (electronic power steering) [7], AFS (active steering system) [8], or SBW (steer by system) [9]. A model predictive controller (MPC) is presented for solving the path-tracking problem of terrestrial autonomous vehicles that can better match the target criteria. A new path tracking technique called \"vector pursuit\" is also proposed. It was shown that the new method could be more robust, resulting in more accurate path tracking. [PERSON] et al. pointed out the limitations of existing schemes that restrict their consideration to kinematic models and showed that it is possible to obtain an increase in performance through the use of approximate dynamical models that capture first-order effects [10; 11; 12]. Nevertheless, due to the structural limits on the front wheel steering vehicle, the control approaches in the aforementioned literature have been proposed to just stabilize the path-following errors, and little research addressed the vehicle stability. The 4 WS (Four wheel steering) vehicle has the structure with independents of both steering positions of the front and rear wheels, which is conducive to the control of vehicle stability [13]. In recent years, there have been many studies on the stability control and path tracking control of 4 WS vehicles. A model-based control for fast autonomous four-wheel mobile robots on soft soils is developed. This control strategy takes into account slip and skid effects to extend the mobility over planar granular [14]. In Reference [15], a nonlinear four-wheel steering (4 WS) autonomous Vehicles (AVs) path tracking systems using robust adaptive sliding mode controller is researched. An automatic path-tracking controller of a four-wheel steering (4 WS) vehicle based on the sliding mode control theory is proposed in Reference [16]. The controller has an advantage in that the front and rear wheel steering can be decoupled at the front and rear control points. In Reference [17], the path-following control problem for four-wheel independently actuated autonomous ground vehicles is investigated through integrated control of active front-wheel Steering and direct yaw-moment control. From the above literature, it can be seen that the 4 WS vehicle can solve the stability control problem well. However, as for 4 WS vehicle, due to the lateral and longitudinal coupling characteristics and nonlinear characteristics of vehicle dynamics, it is difficult to guarantee the accuracy of path tracking under the complex conditions of high speed or variable speed. The 4 WIS/4 WID electric vehicle is driven by in wheel motors and is designed with independent steering actuators. It enables higher flexibility in vehicle motion control by independently controlling the driving force and the rotation angle of each wheel, and has the advantages of environmentally friendliness, saving energy, and so on [18; 19; 20]. In recent years, the research on the trajectory tracking of 4 WIS/4 WID electric vehicles has attracted more and more attention. In Reference [21], the lateral displacement at the virtual points near front and rear axles as new state variables is used in the path tracking controller design. [PERSON] et al.