Collision avoidance techniques for tele-operated and autonomous manipulators in overlapping workspaces

This paper describes the integration of several techniques for cooperative control of both tele-operated and autonomous redundant manipulators with overlapping workspaces. Motivating this research is a tele-operated surgical manipulator(s) supported by autonomous robot(s) that insert/remove items from the surgical workspace. The dynamic and unpredictable location of obstacles in a small workspace requires a complete strategy to avoid collisions when completing critical tasks and minimizes the need for user (i.e. the surgeon) intervention to make path planning decisions or resolve impasse situations. Three techniques are integrated into the decision-making for the manipulators: an intelligent and intuitive EEF velocity scaling, coordinated null-space optimization across affected manipulators, and collision detection. Central to all three techniques is an estimated time- to-collision formulation that combines distances between objects with their higher order properties, thus only objects currently moving towards each other are included in the collision avoidance techniques. The use of multiple techniques derived from the terms of a single metric results in a computationally efficient strategy for tele-operated and autonomous manipulators sharing the same workspace.