Active damping control of hybrid stepping motor

It is well known that microstepping reduces the resonance behavior of a stepping motor since the rotor moves in a sequence of very small steps. However, the under-damped nature of the motor does not change. In this paper, a control scheme to reduce the resonance of a hybrid stepping motor is proposed. The motor currents are controlled in a frame synchronously rotating with the excitation frequency. The d-axis current provides the torque to oppose the external load, and the q-axis current provides the transient torque to damp the motor. The motor velocity is estimated via an observer that tracks the angle of the motor back EMF voltage. Both simulation and experimental results have shown that the proposed control scheme is very effective to damp out the resonance of micro-stepping controlled motors.