Design and Implementation of Simple Field-Oriented Control for Permanent Magnet Stepper Motors Without DQ Transformation

In this paper, a simple field-oriented control (FOC) without direct quadrature (DQ) transformation is proposed for position tracking of permanent magnet stepper motors (PMSMs). Conventional FOC methods require DQ transformation to linearize the mechanical dynamics for PMSMs. In this paper, a proportional-integral-derivative controller with velocity feedforward is developed to obtain the torque modulation required to track the desired position. In addition, a new commutation scheme is proposed to generate the desired currents with the torque modulation; this commutation scheme is equivalent to the microstepping where the desired currents have time-varying amplitudes with π/2 electrical phase advance. The proposed controller method is in the form of an FOC even though DQ transformation is not used. The proposed commutation scheme likens the PMSM to a two-phase permanent magnet synchronous motor. Experimental results validate the effectiveness of the proposed method.