| Supported by the national creation fund of technology &science middle-small enterprises-"the research and develop vehicle electric power steering (EPS) system based on redundant and fault-tolerant control (05C26115101374), and of Sichuan province science &technology research fund-"the research and develop vehicle electric power steering (EPS) system (03GG008-001) ", this paper researches the column-type power-aided EPS. Combining modern control theory, modern design method and computer simulation technology, the research mainly focuses upon the system total design project of the column-type power-aided EPS, and the analysis of key technologies and methods of EPS system, such as the theory model and dynamic performance of control process, the control strategy, the robust fault-tolerant control principal and method, the approach and method to improve steering follow performance, and the analysis of method of steering return-to-middle control and so on. The achievements and highlights of this research are as follows:(1)System total design project of the column-type power-aided EPS is given and the system total structure design is performed by used of three-dimension CAD technology, based on the function requirement analysis of the EPS. The system total performance parameters is decided by analyzing the configuration and the framework form of the EPS. The paper details the main technology fields have some relationship to EPS. It also deeply analyzes the key technology problems of EPS and gives the method to solve these problems.(2)By analyzing of the configuration parts of EPS such as the force-aided motor, the torque sensor, the gear-rack transmit shaft and steering wheel, the EPS dynamics calculous model is founded and transformed to the state space model at first. Then, the dynamic performance of this original model is simulated and discussed in details with the given parameter. A conclusion is formed that the EPS dynamic performance under un-controlled state is frangible to inherent uncertainty as well as environment disturbance. And then, a state feedback control strategy based on pole arrangement method is given. The main idea is that the EPS system is stabilized by its poles are arranged as well as its unknown state signals are deduced by used of the state observer or state estimater. Finally, both the EPS system power-aided performance and its road feeling performance are discussed when the EPS is controlled to meet some system performance restriction.(3)Based on the discussion of the steering road feeling of EPS under the state feedback control, a estimate method to steering road feeling of EPS is given at first which defines that the steering road feeling can be represented by the ratio of the steering wheel reverse torque (T_h) and the steering resistance torque(T_l)when the T_l is in the action and the steering wheel is fixed. Then, by forming the state equation which gives the T_l as its input and the T_h as its output, the following change characteristic of the steering wheel reverse torque T_h is researched when the steering resistance torque T_l changes its value. Finally, the steering road feeling of EPS is achieved.(4) By analyzing of the factors restricting the improvement of the steering following performance of EPS, a view that the steering angle following performance is the main factor to influence the steering following performance of EPS is pointed. Then, a PID parameter fuzzy self-adjustment control arithmetic is given which combines the linear PID control and the fuzzy control to form the fuzzy PID control arithmetic. This control arithmetic can change the PID parameter during the dynamic process in order to improve the steering angle following speed, and as a result, to improve the steering following ability of EPS.(5)The paper gives the concept of the active return-to-middle control. A state space model of the system return-to-middle is formed and a PD control arithmetic based on the full state feedback is given. A simulation to the given control arithmetic justifies that this arithmetic can improve the steering return-to-middle performance and return stability.(6)Using the fault-tolerant control principal and method, a concept is given and testified of function redundancy fault-tolerant control in the sense of observability (detectability). This concept is specially pointed to sensor failure. Base on that concept, a concept of the degree of the sensor importance in the sense of observability is given and its calculate formula is also given. By analyzing the simulation result, this method can effectively help to confirm the quantity of the EPS sensors. In fact, this method can also help confirm general system sensor quantity.(7) Oriented at uncertainty attribute of actual EPS system, a control strategy and controller design method is discussed in the light of modern robust fault-tolerant control theory. Aiming to sensor failure, the variable control strategies such as the robust fault-tolerant control based on the state feedback, the robust fault-tolerant control based on the Riccati equation, the robust fault-tolerant control based on the state observer are discussed, and by using the Lyapunov stability theory and Lyapunov equation, a integrality robust fault-tolerant control rule for sensor failure is given under the condition of the EPS has some degree of the linear uncertainty of parameter fluctuation. Then, the sufficient conditions of realizing integrality robust fault-tolerant control and its design method and steps are given. Finally, a simulation of the robust fault-tolerant controller realization is given.(8)The Fault-tolerant technology to the design of EPS controller is applied. In this controller, there are two 8086 CPUs which function as Dual systems, one 8086 is the main CPU and the other is the online backup one. Both CPU work in the task level at the same time. This paper mainly discusses the dual-system fault-tolerant system's some key technologies such as comparison, synchronization, exchange, and fault diagnosis.
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