In many studies, alternating current (AC) servo motors are used for the conventional investigation of acceleration control methods using a disturbance observer. A surface permanent magnet synchronous motor (SPMSM) is normally used with the servo motors. Both a low-velocity drive and a high-torque drive are necessary for smooth robotic motion control; however, the SPMSM is not always suitable for these driving conditions. A hybrid-type stepping motor (HBSTM) is more suitable for robotic motion control because, unlike an SPMSM, it has many pole pairs and is able to drive at a lower velocity without mechanical gears. Therefore, this paper proposes an acceleration control method for an HBSTM. However, the HBSTM has a high frequency periodic disturbance torque caused by the cogging torque, which is greater than that of the SPMSM. Moreover, the frequency of the torque ripple, which is caused by the offset and gain error of the current sensor, becomes higher than that of the SPMSM. In the proposed acceleration control system for an HBSTM, this torque ripple is not appropriately compensated for by the phase lag, which occurs in the low-pass filter (LPF) of the disturbance observer. Therefore, this paper proposes using a torque ripple compensator. A new fine acceleration control method considering the torque ripple for an HBSTM is realized by deploying the torque ripple compensator in the proposed acceleration control system for the HBSTM. This proposed system adequately suppresses the torque ripple and realizes smooth acceleration control.
2013 The Institute of Electrical Engineers of Japan