Optimal Design of Passive Link Systems and Sensor Fusion for Precise Position Measurement of Robot End-Effector

Many industrial robots utilize feedback control to perform precise tasks such as welding. The trajectory tracking performance of feedback control critically depends on the accuracy of sensor information, which often suffers from link deflection and homing error of the joint displacement sensors. To address these problems, this paper introduces lightweight and highly rigid passive link systems (PL) for acquiring measurement information with reduced deflection effects. To optimally integrate these redundant measurements, a sensor fusion method is developed, based on the resolution ellipsoid, to achieve precise estimation of the end-effector position. An optimal design methodology for the PL is also proposed, and the effectiveness of both proposals is validated experimentally. Moreover, to address biases observed in the experimental data relative to the true values, we propose a bias removal method based on Recursive Least Squares (RLS). We demonstrate through experimental data that this method enables precise position measurement of the end-effector.