Design Of Electric Power Steering Controller Based On Permanent Magnet Synchronous Motor

Compared with other steering systems such as EHPS,the electric power steering system(EPS)has energy-saving,environmental-friendly,and easy to install and adjust advantages.Therefore,it has been widely used.At present,most domestic EPS products use brushed DC motor as the power-assisted motor,although the control method is simple,it makes the system operation inefficient and has limited applications in the automotive field.Permanent magnet synchronous motor(PMSM)have the characteristics of large power density,high efficiency,etc.The use of EPS as a servo motor has become a development direction.This dissertation studied the electric power steering system based on PMSM.EPS system servo motor run in the constant torque region,designed a i_d=0 vector control method,completed the basic power-assist function of the EPS system.Aiming at the heavy steering problem of EPS system,a negative i_d compensation flux-weakening control method was designed.It mainly completes the following research contents:For the closed-loop i_d=0 vector control of the traditional EPS system,the current is obtained by three-resistor or two-resistor sampling reconstruction,and there is a problem of poor control accuracy,designed a single-resistor current sampling reconstruction method.For the current in the low modulation ratio region and the transition region,the current cannot be reconstructed,and the"double switching PWM"method is used to solve the problem.This method achieves current sampling by inserting different minimum sampling pulses and zero pulses in each phase of the PWM.Through the bench test,it is verified that this method can solve the problem of reconstructing the current sampling in the special region,and realized current sampling and phase current reconstruction in the whole region.For the problem that the driver feels heavy when turning the steering wheel rapidly during the driving of the vehicle,a flux-weakening control method based on negative i_d compensation method is designed.The electric power steering based on PMSM,the speed of the motor can be increased by the field-weakening control,so that the assisting motor can provide an appropriate assist torque at a higher speed.Through the steering bench experiment,it is verified that the flux-weakening control method can effectively increase the motor speed by 1200 r/min,reduce the control torque by 1.1 N.m,and give the driver a good feel during quick steering.The design of the final hardware module and software module was completed,integrated an electric power steering controller based on PMSM,and the developed EPS controller was used for the real vehicle experiment with the LieBao CS10 vehicle.The experimental results show that the EPS controller can realize the basic power-assist function of the system when the vehicle is running under good working conditions,and has good assist follow-up performance,and has the function of assisting with speed.