Sensorless control strategy of stepper motor based on super-twisting sliding mode observer

The open-loop control of the stepper motor is simple, but it has low positioning accuracy, large torque pulsation, and low energy efficiency. While the closed-loop magnetic field oriented control has high positioning accuracy, small torque pulsation, and high energy efficiency, but has problems such as complex structure and large amount of calculation. This paper proposes a hybrid control strategy using subdivision control and sensorless control based on sliding mode observer (SMO) for low speed and high speed respectively. Super-twisting SMO is designed observe back electromotive force (back-EMF) and sensorless speed closed-loop control is implemented. Compared with the traditional first-order SMO, the super-twisting SMO improves the estimation accuracy and stability of the rotor position and speed, weakens the system chattering, and improves the system robustness and dynamic response capability. Finally, an experimental platform on the basis of a 2-phase hybrid stepper motor was built to verify the effectiveness and reliability of the control strategy.