Contact detection using dither in force sensorless motion control

Abstract

Demand for using robots in unstructured environments has been increasing. When operating robots in unstructured environments, the robots often come into contact with objects intentionally or unintentionally. Since it is necessary to make contact with an object 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. A real-time force sensorless contact detection method based on applying dither and timefrequency analysis is proposed. Since the influence of dither on acceleration is attenuated when contact occurs, the proposed method judges the state of contact by monitoring the decrease in the dither frequency component of acceleration. The validity of the proposed method was shown by the improvement in contact detection performance verified through experiments.

Virtual-bilateral-type force control for stable and quick contact motion

“…For example, the force control performance becomes very low when the contact object moves dynamically. Some methods are implemented a kind of contact detection methods in the system to change the controller structure of gain value in order to solve this issue [14], [15]. But this section does not treat any system switching approaches.…”

LMI-based position command design of table systems considering compensation for impact force and interference

“…Therefore, force sensorless control approaches have been developed. In generally, a disturbance observer is utilized for force estimation [4], [5], [6], [7]. However, an estimation-delay of the disturbance observer due to a low pass filter may cause performance deterioration.…”