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The electric power steering system (Electric Power Steering EPS ) is a new type of power steering system , compared with the traditional power steering systems , it has the advantages of simple structure, light weight , small size , energy saving and environmental protection , installation and maintenance easy . The EPS system uses the motor directly to the power steering boost the size is determined by the assist characteristic curve , and then through the electronic control unit to calculate and control in real time according to the car's driving conditions provide reasonable power steering , making the car at low speeds when the steering light , steering with good handling and stability at high speeds . The EPS system has become the focus of power steering technology research . The paper first discusses the advantages of the electric power steering system , the research status at home and abroad , structure, composition, working principle and classification . Detailed analysis of the selection of the various components of the electric power steering system . In the brief introduction assist characteristic curve type and select the program on the basis of calculation to determine the the assist characteristic curve used by home and abroad References . Secondly, the control chip selection Freescale company MC9S12DG128 of microcontroller design a hardware circuit of the electronic control unit of the electric power steering system , including the power supply circuit, a torque signal processing circuit , the vehicle speed signal processing circuit , the motor drive circuit , the electromagnetic clutch circuit , the current sensor signal processing circuit. Simple motor structure , working principle and PID control , establishment of a mathematical model of the motor . Finally , MATLAB / Simulink electric power steering system simulation model and digital PID current control method is applied to the motor control model , based on the current form of help features , to achieve a target current PID closed-loop control . Simulation results show that the EPS control system a good boost performance , traceability and stability , and portability to meet the low speed and high speed handling and stability .
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