Robust variable-scale bilateral control for micro teleoperation

This paper discusses variable-scale bilateral control for micro teleoperation. A method is proposed to synthesize robust variable-scale controllers that guarantee system stability and realize robust performance in contact with any arbitrary, but passive, operator and environment. The proposed method is based on the formulation as a robust output feedback constant scaled H-infinity problem. A variable scaled teleoperation system appears as a polytopic linear parameter-varying (LPV) plant, with an affine relation on the scale factors. Gain-scheduling is used to derive robust stable time-variant H-infinity controllers for online variable scaling. Improved controller performance is obtained through the introduction of an affine and scheduled-parameter-dependent weighting. The controller synthesis problem is formulated as a set of linear matrix inequalities (LMI's) augmented with a nonconvex rank condition. An efficient algorithm is constructed to synthesize a set of sub-optimal controllers over the parameter space. The validity of the proposed methods are confirmed experimentally.