Abstract Direct yaw moment control can maintain the vehicle stability in critical situation. For four-wheel independently driven (4WD) electric vehicle with in-wheel motors (IWMs), direct yaw moment control (DYC) can be easily achieved. A fairly accurate calculation of the required yaw moment can improve vehicle stability. A novel sliding mode control (SMC) technique is employed for the motion control so as to track the desired vehicle motion, which is it for different working circumstances compared to the well-used traditional DYC. Through the weighted least square algorithm, the lower controller is used to determine the torque properly allocated to each wheel according to the desired yaw moment. Several actuator constraints are considered in the control strategy. In addition, a nonlinear tire model is utilized to improve the accuracy of tire lateral force estimation. Then, simulations are carried out and the values of vehicle states are compared. The simulation results show that the control system proposed can effectively improve the handling stability of the vehicle. Introduction Due to the pressure of energy crisis and environment protection, the various forms of electric vehicle have become the focus of research in current automotive industry. Among the different layout of the electric powertrains, the 4WD electric vehicle with in-wheel motors (IWMs) has become a more promising one [ 1] This configuration in fact allows redesign of inner spaces of the vehicle and presents, as an embedded feature, the possibility of independently distributed braking and driving torques on the wheels in order to generate a yaw moment to improve vehicle handling. Besides layout advantages, the 4WD electric vehicle also offers interesting opportunities for the design of active control systems, in particular as far as lateral dynamics control is concerned [ 2].To generate the yaw moment, many strategies are applied. Brake based systems (e.g. ESP) apply differential braking to the four wheels and the yaw moment is generated [ 3-4]. However the braking reduces the velocity of the vehicle, thus the driving ability, one of the three basic functions (the others are parking and turning) of the vehicle is lost. Besides, an obvious sense of involvement occurs while Electronic Stability Program (ESP) operates, and it may disturb the driver [5]. Then, some carmakers focus on the torque vectoring control (VTC),which makes vehicle dynamic control from the torque and the slip ratio of each wheel to the traction distribution of all wheels [6,7,8]. Compared with the traditional ESP, VTC can balance the utilization of friction between every wheel and the ground, which improve the vehicle stability. Unfortunately, the limitation of the active differential on the torque vectoring makes VTC behavior no good in extreme conditions. 4WD electric vehicle introduces a new realization to the vehicle dynamic control with the improvement on the direct yaw moment control (DYC), based on the fact that the four IWMs can be driven completely independently and the traction distribution can be achieved by any ratio in the driving ability. A precise yaw moment can shorten the control process, make perfect use of the IWMs’ fast response time and maintain the robustness of the whole system in critical conditions. According to available research literature [ 9-10], the control architecture for the stability control system is often hierarchical, of which the upper controller is to calculate the desired value of yaw moment to ensure yaw stability control, and the lower controller utilizes the wheel rotational dynamics and controls the torque distribution to provide the desired yaw moment. For the vehicle dynamics control system, yaw rate and sideslip angle are chosen as the control variables usually, and the number of operating motors is four. Therefore, there is a redundancy control for the stability control of four-wheel-motored electric ve