Robust vibration suppression control using system identification of minor control-loop system

In vibration suppression control with a wide bandwidth for resonant plant, it is a requisite to identify such plant with high accuracy. However, the more complicated the plant, the more difficult its system identification becomes. In this paper, the authors propose to identify a modified plant with a minor control loop (MCL), fedback with just an output, instead of identifying an original plant itself. As to the design of the MCL, the original plant is modified to have an optimal damping factor. To identify the modified plant, the autoregressive exogenous (ARX) model and least squares method are applied. Through this system identification, the authors can derive an exact uncertainty between the nominal and identified parameters. Therefore, a robust vibration suppression control system, which has a wide bandwidth, can be systematically designed. The effectiveness of the proposed design method for a servomotor-fed two-mass resonant system is demonstrated through simulations and experiments.