Abstract This paper presents an ideal force distribution control method for the electric vehicle, which is equipped with four independently in-wheel motors, in order to improve the lateral stability of the vehicle. According to the friction circle of tyre force, the ideal distribution control method can be obtained to make the front and rear wheels reach the adhesion limit at the same time in different conditions. Based on this, the force re-distributed control is applied to enhance the security of vehicle when the in-wheel motor is in the failure mode. The simulation result shows that: the force distributed method can not only improves the lateral stability of the vehicle but also enhances the vehicle safety. Introduction Compared with the traditional vehicles, the driving and braking force of four-wheel-drive electric vehicle can be distributed arbitrarily between front and rear axles and the distribution method is more flexible. In addition, different distribution methods have different impacts on the stability of the vehicle dynamics and energy-optimized. Therefore, it is very important to study the distribution methods of driving and braking force between front and rear axles. Nowadays there are a lot of exploration and research on the torque distribution between the front and rear axles [ 1, 2, 3]. Not to consider the issue of energy-optimized, from the perspective of dynamic stability study, “I” curve as the ideal force distribution in the straight line braking condition is widely used [4, 5], but the “I” curve is derived while the wheels didn't produce the lateral force. When the vehicle make turns or produce the tire lateral force, the “I” curve couldn't guarantee that the front and rear axles reach the adhesion limit at the same time, so it is not always effective in the whole vehicle driving conditions. In the literatures [ 6, 7, 8, 9], the driving and braking force dynamic optimization distribution was proposed, in which the optimization goal is to minimize the vehicle road adhesion utilization, and it can ensure that the total road adhesion utilization rate of four wheels is least and the better adhesion potential of the each wheel can also improve the stability of the vehicle. However, this method requires some vehicle information, such as tire lateral force, road adhesion coefficient, tire load, tire slip rate and so on. This method is susceptible to the measurement and estimation accuracy of the vehicle state and is difficult to be applied in the actual vehicle system. In this paper, considering the need of the vehicle lateral stability, according to the friction circle of tyre force, the ideal distribution ratio can be gained to make the front and rear wheels reach the adhesion limit at the same time when the vehicles operate in various different conditions. And it can improve the lateral stability of the vehicle as large as possible. With a simplified model of two-wheeled vehicles the ideal driving and braking force distribution method is obtained with the theoretical derivation and at last the force re-distributed control to improve the security of vehicle when the in-wheel motor is in the failure mode was presented. The simulation analysis results verified the effectiveness of the force distribution method. Simplified Vehicle Model Since the research is only about the driving and braking force distribution between the front and rear axles, and the two- wheel vehicle model is used as a simplified model for the analysis, considering the vehicle longitudinal and lateral movement, which is shown in the Fig. 1.A Study on Force Distribution Control for the Electric Vehicle with Four In-wheel motors2014-01-2379 Published 09/30/2014 Yang Li, JianWei Zhang, Konghui Guo, and Dongmei Wu Jilin Univ. CITATION: Li, Y., Zhang, J., Guo, K., and Wu, D., "A Study on Force Distribution Control for the Electric Vehicle with Four In-wheel motors," SAE Technical Paper 2014-01-2379, 2014, doi