Research On The Fault Diagnosis And Fault Tolerant Control Of The Electric Power Steering System

The developing process of steering system has experienced several phase from the simple Mechanical Steering System, Mechanical-Hydraulic Steering System to Electric-Hydraulic Steering System, till the Electric Power Steering System (EPS) with lower energy consumption and higher performance. The EPS is applied more and more widely in the automobile industry, which is led by its advantages over the traditional hydraulic power steering systems in safety, environmental protection, engine efficiency, flexibility of installation, and easiness on the adjustment. In recent years, EPS got lots of successful applications in some foreign countries, while the domestic products are still in the developing phase. It is a hot topic and owns a promising future.In this paper, the characteristics of EPS, operational principles, and structures are discussed and the current domestic and abroad research situation is addressed; by analysis of dynamic, kinematics and load characteristics of EPS, a mathematic model of mechanical steering and EPS is established by using Newton law and the related physical principles and the impact of the mechanical parameters on the system characteristics is addressed; the stability of EPS is analyzed; the stability of EPS is analyzed; the assist characteristics is analyzed theoretically and the determination of feature parameters for the straight-line assist are discussed.EPS is non-linear and multi-input and output system, sensor fault makes it difficult to keep the satisfying performance. Therefore, in order to guarantee the system performance, the closed-loop system must have robustness. Based on the studies of mathematic modeling and the assist characteristics, the control algorithm of sensor fault is addressed in terms of steering operation, in which the key research includes Integrity Control of Passive Fault Tolerant Control Algorithm. At last, the Fault Control Algorithm is analyzed by emulator.In order to realize Fault Diagnosis function of EPS system, an EPS based on ARM chip with Fault Diagnosis function is designed. The system hardware includes the D.C. motor drive circuit, the data display circuit, the sensor interface circuit, the alarm and the relay drive circuit. The system software takes the CodeWarriorIDE debugging environment as the platform. The result of experiment indicates the performance of system.