ABSTRACT The distributed driving electric vehicle, uses four in-wheel motors as distributed power sources is a typical over-actuated system. Thus, this kind of vehicle has better stability potential and fault tolerance than the conventional one. In this paper, the general structure of fault-tolerance control (FTC) system based on control allocation is analyzed. And a reconfigurable driving force allocation strategy is proposed to ensure the trajectory tracking and stability when some motors’ faults occur. Both the constraints of tire force and actuators are taken into consideration. With motors’ faults treated as the constraints of actuators, FTC is integrated. For validation, the proposed allocation strategy is simulated in co-simulation environment based on Carsim and Matlab/Simulink. INTRODUCTION Electric vehicle is considered as one of ideal solutions for energy crisis, air pollution and green house effect. The type of distributed drive electric vehicle studied in this paper can have four in-wheel motors as controllable actuators. Because of the quick response of in-wheel motors, a distributed drive electric vehicle can realize many advanced vehicle stability control systems more easily than conventional vehicles, such as ASR, DYC, ESP, etc. However, due to the significantly growing system complexity and number of actuators, fault probability on this kind of electric vehicles is naturally higher than conventional vehicles. This paper considers only the in-wheel motor faults of distributed drive electric vehicles. The in-wheel motor faults may be caused by mechanical failures, overheat of the motors, or faults associated with the motor drivers. When such a fault occurs, the faulty wheel may fail to provide the expected torque and thus jeopardize the vehicle motion control [ 1]. Therefore, it is necessary to enhance the fault tolerance ability of distributed driving electric vehicles. Several FTC strategies for electric vehicles have been suggested in the literatures [ 1], [2], [3]. Tracking performance of faulty vehicles is emphasized in their algorithms, while the constraints of tire-force saturation is not studied. Optimization method is commonly used in studies about FTC [ 4], [5], [6] to take the tire-force allocation into consideration. However, because of the presence of equality constraints set in algorithm, the optimization problem may have no solution when the vehicle is running in some extreme conditions, high-speed steering or lower tire-road friction coefficient for example. Chaotic outputs of control system may happen in such conditions and threaten driving safety of human-vehicle. In this paper, a reconfigurable driving force allocator with fault- tolerance capacity is proposed for distributed driving electric vehicles. Both the constraints of tire force and actuators have been taken into consideration. And a three-level allocation strategy with different performance functions and constraints is designed to guarantee the trajectory tracking and stability of the faulty vehicle at extreme conditions. The rest of this paper is organized as follows: The general structure of FTC system for distributed driving electric vehicles is introduced in part 2. The proposed allocation strategy is introduced in part 3. Simulation results based on Carsim and Matlab/Simulink are provided in part 4 followed by conclusive remarks. GENERAL STRUCTURE OF FTC SYSTEM It is known that a distributed driving electric vehicle is a typical over-actuated system. Control allocation which is widely used in motion control and fault-tolerance control for over-actuated systems, such as aircrafts and robots, can also be applied to the distributed drive electric vehicles well [ 7]. The idea of control allocation, as it is shown in Figure 1, offers the advantage of the modular design where the high-level motion controller can be designed without considering of detailed information about actuators. Therefore, the pr