INTRODUCTION The four-wheel independently driven and steered (4WID/4WIS) electric vehicle is a promising vehicle architecture due to its potential in emission and fuel consumption reduction [ 1]. A 4WID/4WIS electric vehicle utilizes four in-wheel motors and four steering motors to drive and steer the wheels independently, which has become an ideal platform to study the next-generation vehicle control. Such a actuation flexibility together with the in-wheel motors' fast and precise torque responses may enhance the existing vehicle control strategies, e.g., traction control system, direct yaw moment control, and other advanced vehicle stability control systems [ 2], [3], [4]. Owing to the significantly increased system complexity and number of actuators, the probability for fault taking place is higher. Therefore, the demands on reliability, safety, and fault tolerance for 4WID/4WIS electric vehicle are substantially elevated. Several fault-tolerant control strategies for ground vehicles have been previously suggested in the literature [ 5], [6], [7] and several fault-tolerant control methods for electric motors are proposed [ 8], [9], [10]. Some integrated control studies for 4WID/4WIS electric vehicle have been reviewed. For instance, Yang [11 ] puts forward a hierarchical integrated control strategy for 4WID/4WIS electric vehicle yaw stability which is integrated RBS DYC AFS/ARS ABS/TCS effectively. Zhu [12] considers a novel kind of vehicle-network architecture of the power system based on the 4WID/4WIS electric vehicle. However, most of these algorithms dealt with the problems associated with conventional vehicle architectures, it is thus necessary to design the control systems which are capable of detecting, identifying, and tolerating faults so as to improve the reliability and safety for the 4WID/4WIS electric vehicle. In this paper we propose a FTC approach for 4WID/4WIS electric vehicles based on EKF and SMC, as shown in Figure 1. The FD module estimates the in-wheel motor parameters so as to diagnose parameters variations caused by in-wheel motor fault by means of EKF algorithm. A motion controller based on SMC is able to compute the generalized forces/moments to follow the desired vehicle motion. By considering the tire adhesive limits, a reconfigurable control allocator optimally distributes the generalized forces/moments among healthy actuators. An actuator controller calculates the driving torques of the in-wheel motors and steering angles of the wheels. Figure 1. Schematic diagram of the proposed FTC architectureFault-Tolerant Control for 4WID/4WIS Electric Vehicle Based on EKF and SMC Chunshan Li, Guoying Chen, Changfu Zong, and Wenchao Liu ASCL, Jilin University ABSTRACT This paper presents a fault-tolerant control (FTC) algorithm for four-wheel independently driven and steered (4WID/4WIS) electric vehicle. The Extended Kalman Filter (EKF) algorithm is utilized in the fault detection (FD) module so as to estimate the in-wheel motor parameters, which could detect parameter variations caused by in-wheel motor fault. A motion controller based on sliding mode control (SMC) is able to compute the generalized forces/moments to follow the desired vehicle motion. By considering the tire adhesive limits, a reconfigurable control allocator optimally distributes the generalized forces/moments among healthy actuators so as to minimize the tire workloads once the actuator fault is detected. An actuator controller calculates the driving torques of the in-wheel motors and steering angles of the wheels in order to finally achieve the distributed tire forces. If one or more in-wheel motors lose efficacy, the FD module diagnoses the actuator failures first. Then the reconfigurable control allocator accommodates faulty in-wheel motors and reconfigures the control allocation law of the healthy motors to achieve the desired vehicle motion to the greatest extent. Experimental verification is made to show that the proposed F