Evaluation of Beam Load Cell Use for Base Reaction Force Collision Detection on Industrial Robots

Abstract

This thesis evaluates the ability of four beam load cells placed under the base of an industrial robot to accurately estimate robot link parameters and detect collision. This setup can be a cheaper option than using six-degree-of-freedom sensors, and is easier to implement than other detection methods. The beam load cells are placed under the base of robotic manipulators, and the reactions at the base of the robot due to its motion can be monitored to detect collision and estimate link parameters. The tradeoff to using only four load cells is a more limited ability to sense the reaction forces and moments.

The results of this research show that the method of using beam load cells, despite the limited ability to measure base reactions, was able to reduce parameter estimation error from 1,475 to 432Nm, or in terms of percentage from 28% to 8%. Furthermore, this method is capable of detecting collisions; however, the accuracy of parameter estimation and collision detection is limited by sensor noise and large amplitude vibrations in the tested robot system.