Application of Kitamori's Method to Stage Positioning Control Using Open Loop Transfer Function

The precise positioning stage is ordinary mounted on the vibration isolated table. For its stage, PID compensator is commonly implemented in the control loop and its parameter tuning is carried out through trial and error in the production field. This tuning easily introduces the tradeoff between the command and disturbance responses. Then, we have previously proposed the tuning formulas based on Kitamori's method. However, this calculating process was quite complex. In order to simplify the calculating process, this paper proposes that Kitamori's method should be applied using the open loop transfer function instead of the closed loop one. Firstly, the open loop transfer function of Kitamori's model is derived and the control strategy is clarified through the open loop frequency response. Secondary, the gain and phase margins are derived from Kitamori's open loop model. Finally, the denominator series expression is easily calculated by using the open loop transfer function and the same PID parameters that are derived from the closed transfer function can be quickly calculated.