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SS316H steel

2013年9月4日 by admin

SS316H steel

Electric power steering system is a new type power steering system developed rapidly in recent years. This new system can solve the contradiction between handiness and sensitivity, and has many advantages such as energy saving, environmental protection and easy assemblity. Recently, electric power steering system is gradually replacing the hydraulic and electro-hydraulic power steering system, and becoming automotive technology research focus all over the world.The paper comes from the national 863 project, studying on the electric power steering system stability and current control algorithm to an A0 class car as an object, In this papSS316H er, EPS system steelmodeling, stability, optimal PID parameters, current control strategies and hardware and software development are discussed in detail. Paper is divided into seven chapters.Chapter I is an introduction. A brief introduction of electric power steering system principle, structure and classification was gived. The context of the history and development situation of electric power steering system stability and the current control algorithm were summed up. The main contents of this paper were pointed out.Chapter II is EPS system model establishment. This chapter established the EPS system model with MATLAB/Simulink. In the modeling process, PID feedback control was used. By analyzing the formation of ground-reaction force, the ground reaction force was modled as proportional to the rack displacement. The changes to the moSS316H steeltor electrical parameters, low pass filtering nature of current sensor and characteristics of EPS controller lag were taking into full account in modling process. Though the current sweep experiment, the current step experiment, and the steering wheel turning experiment of frequency domain and time domain methods, the model established was validated.Chapter III is the analysis of EPS stability. The basic concepts of system stability and common determination methods were reviewed. To analyze the EPS system stability, the method of using PID parameters stability regions was proposed. The influence of system stability was studied by drawing three-dimensional PID parameters stability space. And then, the influence of the PID parameters stability region when system parameters are changing was studied, and then the influence on the system stability was got.Chapter IV is the study on the optimal PID parameters with genetic algorithm. The stability, rapidity and accuracy of EPS system were analyzed. By taking into account of all the various performance requirements EPS, the method of using genetic algorithm to optimize PID parameters was proposed. On this basis, the influence of system parameters on the optimal performance and the optimal PID parameters along with the robustness of the system were studied, and the influence of parameters on the system performance were obtained.Chapter V is the study of the current control strSS316H steelategy and its robustness. By analyzing the influence of system parameters on system performance, a current control strategy is proposed which content selecting the curvilinear assistance, motor speed feedforward control, battery voltage compensation and the optimal PID parameters adaptive method. By using Monte-Carlo random sampling test method, the EPS system stability, current control effect and robustness were evaluated.Chapter VI describes the EPS software and hardware system development and the real vehicle validation. The development process of the motor testrig and EPS controller hardware were introduced by describing its composition and realization of each module. The EPS controller software was carried out using uC/OS-II embedded operating system. The motor back-EMF coefficient and the resistance which change with the electric current were measured, and then, a more accurate estimate of motor speed was achieved by varying motor parameters. And at last, the EPS system stability and the current control strategy were validated in a real vehicle.Chapter VII gives a summary of the paper and a research prospect in the future.Through simulation analysis and real vehicle validation for the electric power steering system stability and current control strategy, the main conclusions are as follows:(1) EPS system stability is more sensitive for these parameters than the others: motor resistance, back-EMF coefficient, assist gain and battery voltage.(2) The optimal performance and the optimal PID parameters are sensitive to motor resistance, back-EMF coefficient, assist gain a greater impact and the battery voltage, and insensitive to motor torque coefficient, motor inductance and the elasticity coefficient of the ground reaction force.(3) Current control performance and robustness of EPS can be improved by using curvilinear assistance, motor speed feedforward control, battery voltage compensation and the optimal PID parameters adaptive method.(4) Motor resistance and back-EMF coefficient change with the motor current, and a more accurate motor speed can be estimated using variable parameters.This paper has been innovative in the following areas:(1) The method of using PID parameters stability regions to analyze the EPS system stability was proposed. The influence on the system stability was got by studing the influence of the PID parameters stability region when system parameters are changing. The SS316H steel ethod of getting optimal PID parameters using genetic algorithm was proposed, and the optimal current control method and system robustness can be studied by analyzing the optimal performance and the optimal PID parameters.(2) The current control strategy which contents curvilinear assistance, motor speed feedforward control, battery voltage compensation and the optimal PID parameters adaptive method was proposed. Monte-Carlo random samplin SS316H g test method was proposed to verify the control strategy.(3) A more accurate motor speed estimate method using variable parameters was proposed, in which motor resistance and back-EMF coefficient change with the motor current SS316H steel