Suppressing operator-induced oscillations in manual control systems with movable bases

There are many manual control tasks in which the operator\´s action is fed back to the input device, usually a joystick, through the operator\´s body dynamics excited by the base motion. This can lead to instability and reduced performance. This paper proposes a novel approach to the cancellation of such "biodynamic feedthrough". A prototype single-degree-of-freedom task in which the operator uses a force-reflecting joystick to position his/her base is considered here. A model-based approach is used to formulate μ-synthesis-based controllers that coordinate the motions of the joystick and the base. The solution is obtained by D-K iterations. The resultant controllers are robustly stable with respect to variations in the arm/joystick and biodynamic feedthrough parameters. They also provide a desired level of performance based upon position tracking between the joystick and the base and admittance shaping of the joystick. Experimental studies demonstrate the effectiveness of the proposed methods in the suppression of feedthrough induced oscillations. The approach developed in this paper, with some modifications, can be generalized to teleoperation from movable bases.