Study of Active Isolation System with Feedforward Control.

Active vibration control is important in protecting precision machines from microvibration. However conventional active vibration controllers have only feedback control loops, for example, PID and LQR, thus, it is difficult to completly suppress shock motions. When the control object is excited by shock motions such as X-Y stage movements, it shows instantaneous response because of feedback control delay. This paper suggests a practical method for active control using feedforward control together with conventional feedback control. The authors paid attention that the X-Y stages repeat the identical pattern movements. In this case, it is easy to obtain sample data of the disturbance response, and the feedforward signal is calculated easily and correctly using this sample data and the measured transfer functions. This method is verified experimentally by driving a DC servo -stage on an active isolation system. The data show that this feedforward control method yields good results for self-exciting-type precision machines.