Model-based telerobotic control with virtual fixtures for satellite servicing tasks

Our goal is to develop new methods for telerobotic on-orbit servicing of spacecraft under ground-based supervisory control of human operators to perform tasks in the presence of uncertainty and telemetry time delay of several seconds. We propose a new delay tolerant control methodology, using virtual fixtures, hybrid position/force control, task frame formalism, and environment modeling, that is robust to modeling and registration errors. The task model is represented by graphical primitives and virtual fixtures on the teleoperation master and by a hybrid position/force controller on the slave robot. The virtual fixtures guide the operator through a model-based simulation of the task, and the goal of the slave controller is to reproduce this action (after a few seconds of delay) or, if measurements are not consistent with the models, to stop motion and alert the operator. This approach is suitable for tasks in unstructured environments, such as servicing of existing on-orbit spacecraft that were not designed for servicing. We introduce the overall control concept, its main components, and an example application in which the remote slave robot cuts the tape that secures a flap of multi-layer insulation over the access panel of a satellite mockup.