Fault tolerant control for 4-wheel drive in-wheel motor electric vehicle

Abstract

The increased use of fossil fuels due to increased vehicle ownership and increased population has accelerated environmental pollution and global warming. In order to solve this problem, eco-friendly vehicles have been developed. Within eco-friendly vehicles, micro electric vehicles are designed to reduce vehicle mass while maintaining a good level of mobility. Interior space utilization is very important in micro electric vehicles so in-wheel motors have been implemented in order to optimize passenger cabin space. Electric vehicles, especially those with in-wheel motors can experience different types of fault than conventional vehicles. For vehicles that have independent 4-wheel drive and in-wheel motors, a motor fault can occur. In this case, the vehicle can continue to drive but the faulty motor generates a drag force and the vehicle could lose stability. This can cause an accident with nearby vehicles or vehicles on the other lane. A collision can be avoided with the use of fault tolerant control. Fault tolerant control is characterized by being able to operate the vehicle continuously under a fault, possibly at a reduced level of performance rather than failing completely. In this thesis, a fault tolerant control method is presented by constructing an algorithm that distributes torque to three wheels to prevent vehicle drift out on one motor fault condition. In order to verify the presented algorithms, a simulation was conducted; Matlab/Simulink® was used to implement the algorithms and CarSim® was used to confirm vehicle behavior. The simulation results under straight acceleration and constant straight acceleration driving conditions confirm that a vehicle with the proposed algorithm could accurately follow the desired path within a minimum error range, and thus prove that the proposed fault tolerant control algorithms can improve the safety of electric vehicles with in-wheel motors.