抄録
Variable speed drive systems of the 3-phase HB-type stepping motors are widely used because of their low speed and high torque property, inexpensiveness, robustness, low power loss, etc.. Open-loop speed/position control is applied to these motors because they have simpler construction and require no speed sensor for synchronous type motor. However, the motors are salient-pole machines, and periodical torque ripple such as cogging torque is produced due to saliency of the motors when they rotate. It causes mechanical vibration and acoustic noise.
In this paper, authors propose a repetitive control using acceleration sensor to reduce the vibration of the 3-phase HB-type stepping motor with cogging torque ripple. A mechanical system, where the acceleration sensor is attached to the motor or load frame to detect the vibration due to the torque ripple of the motor, is constructed. Because the vibration varies periodically due to the cogging torque, the repetitive control is effective for reduction of the vibration. The online Fourier Transformer (FT) is applied to the vibration signal detected by the acceleration sensor before inputted to the repetitive controller. All higher and lower order harmonics of the vibration will be cut off by the Fourier Transformer except a particular frequency component such as fundamental one, second order one, etc. of the vibration signal and therefore the stability of the control system is improved. Approximate analysis is performed to study the stability of the repetitive control system. Effectiveness of the proposed method is confirmed by the experimental results.
