Active Damping Control Of Hybrid Stepper Motor Based On IHF-PLL~3rd

Hybrid stepper motors have the advantages of simple structure,high reliability and high positioning accuracy,which are widely used in fields such as aerospace,medical equipment,household appliances,automated production lines and other fields.Hybrid stepper motors usually use open-loop control,but with the continuous development of modern technology,higher requirements for motor control accuracy and dynamic response have been put forward.The hybrid stepper motor has a small damping factor due to its own special mechanical mechanism,which often results in excessive oscillation and even lost steps during actual operation.In order to improve the control quality of the hybrid stepper motor,this thesis proposes an active damping control method.The structure,operating principle and space vector PWM control of the two-phase hybrid stepper motor are analyzed firstly in this thesis.Secondly,the mathematical model of the stepper motor in the stationary coordinate system is derived,then the stationary coordinate system is transformed into a coordinate system that keeps synchronous rotation with the stator current by using the Park transform,the mathematical model of the motor in the synchronous coordinate system is established.In addition,the current controller is designed based on the synchronous coordinates,and the simulation analysis is carried out for the static and synchronous coordinates current controllers respectively.The simulation results show that when the current is stepped input,there will be steady-state error in the current response of the static coordinate current controller,and the error is proportional to the motor speed,while there is no steady-state error in the synchronous current controller,therefore,this thesis uses the synchronous current controller as the current inner loop of the active damping control.Then,an active damping closed-loop control method is proposed to improve the control quality of the stepper motor with respect to the oscillations and lost steps caused by the small damping factor of the hybrid stepper motor.The method is based on the motor model in the synchronous rotating coordinate system,and the current _di is controlled at a constant rated current,and the error between the stator current speed and the actual motor speed and the stator current position and the actual rotor position is used to adjust the q-axis current to generate the instantaneous torque to suppress the oscillation phenomenon.Thirdly,in order to realize the closed loop of speed to increase the motor damping,a rotor information observation method combining the third-order phase locked loop(PLL~3rd)and integral harmonic filter(IHF)is proposed.In which,PLL~3rd can eliminate the steady-state error and improve the dynamic performance of motor speed observation,while IHF can effectively filter out the higher harmonic components in the back electromotive force before it enters the PLL~3rd.Finally,it is proved through experiments that the active damping control of hybrid stepper motor based on IHF-PLL~3rd method can effectively solve the drawback of under-damping of the hybrid stepper motor and effectively suppress the oscillation phenomenon during the actual operation of the motor to make the motor operate smoothly.