Controller Development Of Electric Power Steering System Based On Permanent Magnet Synchronous Motor

With the rapid development of China’s automobile industry, the advantages are widelyrecognized that the electric power steering system is more energy-saving andenvironmentally friendly, and could improve handling and stability of the full vehiclerelative to hydraulic power steering system. At present，foreign-funded enterprises and jointventures are in a monopoly position with more than90%market share of electric powersteering system in china. Local enterprises hold only less than10%market share, equipmentfor domestic small vehicles. Due to the existence of brush and commutator, electric powersteering system with brush DC motor is the short life and difficult to maintain. Therefore,internationally, the permanent magnet synchronous motor is becoming the mainstream of themotor used in electric power steering system. Because of electronic industry developmentlag, development of the electric power steering system by domestic local enterprises is stillbased on brush DC motor, and development of electric power steering system based onpermanent magnet synchronous motor becomes a bottleneck. The research on electric powersteering system based on permanent magnet synchronous motor has great significance inbreaking foreign monopoly of technology and market.This paper develop electric power steering system controller based on permanentmagnet synchronous motor. The concrete work as follows:(1) The research on control strategy of permanent magnet synchronous motor andcontrol strategy of electric power steering systemDifferent from the motor speed and position servo system, the electric power steeringsystem adopts torque-feedback control with follow-up speed and angle, which has highrequest in torque response and fluctuation. After analysis, to achieve such a request, first, thispaper describes the model of permanent magnet synchronous motor and carries outcoordinate transformation, realizing decoupling control. By above methods, this paperconstructs control strategy that currents of excitation direction equal zero. Second, six-wayswitch signal is outputed using space vector pulse width modulation to reach thefundamental permanent magnet synchronous motor control. At last, flux weakening controlstrategy is seted up. In electric power steering system control strategy, basic assist controladopts multi-point polyline control strategy. Assist Characteristic curve is smooth, simple,easy to debug. Besides, this paper analyzes the influences which motor compensation control Aand torque differential control have on dynamic response of steering system.(2) Controller hardware design of electric power steering systemIn this paper, the overall system hardware architecture is designed in which master chipTMS320F2812as the core, after requirements analysis of controller hardware design ofelectric power steering system. Through the rational selection of the chips and rationaldesign of the electric circuits in accordance with the principles of hardware design, minimumcircuit, drive circuit, external signal acquisition circuit and CAN communication circuit arecompleted. The electric power steering electronic control system has the characteristics oflow-voltage and high-current, this paper gives plenty of consideration in the ability towithstand high current and dissipate heat. In addition, fault detection, circuit protection andelectromagnetic compatibility are taken into account, which improve the reliability on thebasis of the achievement of controller hardware function.(3) Controller software design of electric power steering systemThis paper in accordance with the functional requirements of the electric power steeringsystem and the interrupt mechanism of the master chip designs software architecture of thesystem, including the initial program, the loop program, the electric power steering andmotor control interrupt program, the torque and angle signal decoding interrupt program.Then according to the principles of software design and the characteristics of master chip,this paper designs the motor position signal decoding program, torque and angle signaldecoding program, the AD signal acquisition program, the PWM signal generation program,the motor speed calculation program and CAN communication program. And softwaredesign requires clear level, definite relationship and independent module in order to modifyand debug software easily.(4) The bench test of electric power steering system controllerThe bench test of electric power steering system controller includes the bench test ofpermanent magnet synchronous motor and the bench test of the electric power steeringsystem. The bench test verifies the effectiveness of motor control strategy and electric powersteering control strategy and the effectiveness of all functional modules of the controllerhardware and software.