On the other hand, one of the authors had pro- posed a simple and easily realizable technique for eliminating the transient vibration of a drum driving servo system . This system is a typical example of the geared mechanical system such that the stiffness of the geared stage is much higher than those of a shaft, a coupling, and a timing belt. The proposed technique is based on a model-based control. The control model is related to the velocity control loop, and it is composed of reduced-order electrical and mechanical parts by considering that the transient vibration which should be eliminated is mainly dominated by the first vibration mode of the geared mechanical system. This model calculates the rota- tional speed of the driven machine part, which is converted to the motor shaft. The difference between the calculated rotational speed of the driven machine part and the motor speed is calculated dynamically, and it is added to the velocity command to suppress __________ Manuscript received April 20, 2002; revised June 24, 2003; accepted July 21, 2003. Recommended by Editor Keum-shik Hong. Masahiko Itoh is with the Department of Mechanical Engineering, Miyagi National College of Technology, 48 Nodayama Shiote, Medeshima, Natori-shi, Miyagi 981- 1239, Japan (e-mail: [email protected]). Hiroshi Yoshikawa is with the Control Systems Division, Sanyo Denki Co., Ltd., 1-15-1 Kita-Otsuka, Toshima-ku, Tokyo 170-8451, Japan (e-mail: [email protected] sanyodenki.co.jp).