Abstract:
This thesis examines the problem of designing robust dynamic output feedback controllers for four-inwheel independently driven Electric Vehicles (EVs) using differential speed steering. The four-wheel independently driven Electric Vehicle (FWIDEV) is a nonlinear system. The nonlinear system is transformed into uncertain polytopic model and the TS fuzzy model. These models capture uncertainties and nonlinearities in the system and to solve these problems, two robust controller synthesis approach are proposed — first, the parameter-dependent Lyapunov function approach and second, the TS fuzzy Lyapunov function approach. Specifically, the robust controller aims are to ensure asymptotic stability and improved performance of the EVs despite variations in the road adhesion coefficient, longitudinal velocity and external disturbance. The aim also includes respecting the constraints on the control input and system output. The solutions to the problems are based on deriving sufficient conditions for such controllers to exist using linear matrix inequalities constraint approach. Those sufficient conditions are utilised in designing a robust dynamic output-feedback controller, a robust model predictive controller and robust dynamic TS fuzzy controller. Importantly, the design conditions guarantee the robust stability and performance of the EVs over a broader range of operating conditions. Also, the performances of the controller are compared to the controller design for a linear system under normal operating conditions. Finally, simulation results show the capabilities of the synthesised controllers using the FWIDEV nonlinear vehicle dynamics model that considers the effect of uncertain road conditions and varying longitudinal velocities. More so, the experimental results also validate the improved performance of the robust controller.