Passivity-Based Gain Independent Control for Transparent Sensing of Remote Environment

Teleoperated robots are traditionally used for extended human sensing and manipulation of remote environment. Though controllers have already been proposed in the literature to achieve stability and transparency in the system, their implementation becomes limited because of the complexities in tuning the gains. The objective of this paper is to propose novel controllers, which ensure the system stability and transparency irrespective of the controller gains. The proposed controllers are also shown to accommodate varying time-delays, during which the stability and transparency usually conflict each other. The non-linear tool of passivity analysis is used to demonstrate that the proposed controllers achieve the desired objectives. In addition to the proposed controllers, a torque based sensing is utilized to enhance the transparent sensing of the remote environment, which readily facilitates disturbance rejection for the proposed controllers. Therefore, the proposed methodology (combination of both the controller and sensing method) helps the user in accurately sensing the remote environment and concurrently maintaining global asymptotic stability for any arbitrary choice of controller gains. Experiments carried on a five-bar teleoperation system demonstrate global asymptotic stability and transparent sensing even under time varying delays, and with a much wider range of feedback gains.