Counteracting modeling errors for sensitive observer-based manipulator collision detection

Modeling errors are one of the elements responsible for deficiencies in sensorless collision detection of robotic systems. By providing a specific formulation of manipulator equations, this paper presents a time-variant threshold for observer residues in joint space of a manipulator in order to provide more accurate collision detection ability compared to constant thresholds. The time-variant threshold considers modeling errors in both robot's parameters and its friction forces. Simulation results using real-life collision forces and experiments on the Phantom Omni device are provided to validate the proposed scheme.