Fault Tolerant Sliding Mode Predictive Control for Uncertain Steer-by-Wire System

The Steer-by-Wire (SbW) system is an electronically controlled steering system that is able to improve steering capability without mechanical links between the steering wheel and the front wheels. However, failure of the SbW system actuator may lead to steering performance degradation and result in instability. In this paper, a fault tolerant sliding mode predictive control (SMPC) strategy for an SbW system is proposed. The sliding mode control is applied to improve the robustness of the model predictive control (MPC) in the presence of modeling uncertainties and disturbances, while the MPC is applied to enhance the fault tolerant capability of the steering control processes. The chaos particle swarm optimization (CPSO) algorithm is introduced to optimize the MPC and a two-stage Kalman filter is introduced to simultaneously provide fault information and state estimation. The performance of the proposed approach is validated through computer simulation. The results demonstrate that the proposed SMPC-CPSO controller is more robust and provides better tracking performance in the presence of model uncertainties, disturbance, and actuator faults than SCMP-PSOs (heterogeneous comprehensive learning particle swarm optimization, evolutionary particle swarm optimizer, etc), SMPC-differential evolution, MPC, SMPC, and MPC-PSO.

I. Introduction

The Steer-by-Wire (SbW) system is considered to be the most significant innovation among X-by-Wire technologies that will revolutionize the automotive industry. An SbW system composed of electronic control units, steering assist motors, and sensors that can replace the conventional mechanical steering column linkages in a car. The benefits offered by SbW systems include improved steering performance and handling characteristics with reduced power consumption. Currently, SbW technology has been successfully commercialized in the field of automotive industry such as Nissans Infiniti Q50, General Motors’ Hy-wire, Danfosss OEMs, Delphi Corporation’s Quadra-steer car, and Lecomble & Schmitts electro-hydraulic steering system. All of these systems deploy a number of backup systems including a conventional mechanical steering linkage to protect the steering system against faults. These provisions significantly increase the complexity and development costs of SbW systems, and undermine the original design objectives. Hence, there are still significant gaps in SbW technology and further research is required the address them. Of these, ensuring reliability and fault-tolerance capability are the most critical [1].