Low-impact dither-based contact detection in motion control

Demand for using robots in unstructured environments has been increasing. Since it is necessary to make contact with objects in order to execute complicated tasks, not only contact avoidance but also contact detection and stabilization of contact are required. This paper focuses on detecting contact during operation and applies the contact detection method using a dither signal to detect contact state at the moment of contact event. Methods for reducing influence of the dither on control or motion are then proposed considering the following two cases: application of the dither on an object is acceptable; and it is preferable to be avoided. A method of separating the dither element from the measured force using a ratio of inputs while applying the force including the dither to an object was proposed for the former case. A method of applying the dither in limited situation and stopping application in the contact state was proposed for the latter case. The validity of the proposed methods was verified by experiments on contact detection during teleoperation.