Mechatronic model of oscillations in hybrid stepper motors

Hybrid stepper motors combine the features of permanent magnet and variable reluctance motors, which makes them an attractive solution for a variety of low-cost applications. Oscillations in the phase current and in the motor position may however arise between two consecutive steps. This paper develops a model of the system, whose linearization yields closed form analytical expressions of the parameters (natural frequency and damping coefficient) characterizing such oscillations. A detailed simulation model of the system, including discontinuous effects of PWM amplification, is developed as well and validated with experimental data. The accuracy of the expression found for the oscillation parameters is also validated.