2DOF Control-Based Fast and Precise Positioning for Vibratory Mechanism with Nonlinear Friction

The paper presents a practical compensator design approach for the fast-response and high-precision positioning using a two degrees-of-freedom (2DOF) controller. In the controller design for mechatronic positioning devices, effects of resonant vibration, nonlinear friction, and dead time components on the positioning performance are especially paid attention: a feedforward control based on the coprime factorization description successfully suppresses the mechanical vibrations and provides the fast response, where a disturbance observer compensates for effects of nonlinear friction on the positioning performance. The Smith method, on the other hand, is adopted to the designs of both the feedforward compensators and the disturbance observer, in order to compensate for the effects of the dead time. The proposed positioning controller has been verified by experiments using a prototype which simulates the vibratory mechanism with the nonlinear friction and the dead time components