Research On Electric Power Steering Control System Of Permanent Magnet Synchronous Motor

In order to meet demand of the basic power steering for electric drive light commercial vehicles,the paper is combined with the current domestic electric power steering research status,it is taken as the research object for the IPMSM of low-voltage with variable inductances,the basic power assist strategy is studied for the speed and torque demand of the electric power steering system under different working conditions with motor control strategy,and in accordance with the specification of hardware functional safety and the method of automatic code generation,the electric power steering control system of a permanent magnet synchronous motor is developed,which can realize the basic power steering.The permanent magnet synchronous motor control system studied in this paper has certain engineering practical value,and meets demand of some functional safety and safety integrity level,which lays a foundation for the introduction of other functions of electric power steering system and the design of functional safety throughout the whole safety life cycle.The main work of this paper includes:First,the power-assisted control strategy uses a curve-assisted characteristic curve with high accuracy to meet basic power requirements.The motor control strategy focuses on the vector control and speed-up control of the unequal variable parameters of the assist motor's direct axis and quadrature axis inductances.Since the permanent magnet synchronous motor is a builtin variable inductance motor,the vector control strategy of the maximum torque per ampere is adopted in a low-speed constant torque phase,and provides the current inquiry tables that satisfies maximum torque per ampere control,the motor can achieve dynamic control and improve motor utilization efficiency.The flux weakening control strategy is adopted in the highspeed constant power zone to improve the speed utilization range,and meets the needs of the vehicle to avoid obstacles quickly,and the MATLAB/Simulink model is constructed for off-line simulation experiments,which verifies the feasibility of the maximum torque per ampere control and the flux weakening control method.When the motor is switched from the constant torque region to the constant power region,the conversion process is relatively stable and the phase current waveform is stable.Then according to the characteristics of the motor simulation experiment,the EPS controller is developed,including hardware and software.The hardware platform design includes the control module based on 32-bit MPC5643 L chip,the drive module based on MC33937 driver chip,the signal acquisition,the relevant modules of the power supply and communication functions.Some functional safety requirements are taken into account in hardware design process,and some protection functions can be realized by the hardware itself.The software writing part adopts automatic code generation and manual written in combination with S32 integrated development environment.This method can significantly improve the efficiency of software writing.It uses MPC5643 L math and motor control library and motor control application optimization tool in the MATLAB/Simulink graphical interface environment to configure the mode of input interface,output control port and system function,and the bottom driver model can be built with motor control algorithm,and then RTW with Embedded Coder is used to combine the bottom driver model with the application layer control strategy to generate C language code,and the code file is copied to the S32 integrated development environment for project creation and then cross-compiled,which can be written into the MCP5643 L controller to control motor in the target hardware.Finally,it carried out for the motor phase current experiment and the bench test.The phase current experiment shows that the motor can complete the work according to the expected condition and verify the effectiveness of the motor control strategy.The experimental results of the bench are in line with the experiment accuracy of the EPS assist characteristic,and the basic power assist goal can be completed,and the rationality of the EPS control system is verified.