Development of a new sensorless control algorithm for stepper motors to enhance speed stability and dynamics

A novel control method to reduce oscillations for three-phase stepper motors and to improve dynamics using a speed control with feed forward technique is proposed. The new concept uses a transformation of the model to allow a linear design of the observer and control, reducing so the real time calculations. Furthermore the stability of the nonlinear process is guaranteed with the optimal choice of the currents. The proposed algorithm has been successfully implemented in a control unit and the reached benefits could be verified in a positioning axis of an electro-discharge machining device. The results show that with the new method a more stable trajectory tracking and higher accelerations could be reached. Furthermore, the measurements show that higher speeds and better robustness in respect to step losses can be reached.