Model-based thermal drift compensation for high-precision hexapod robot actuators

TL;DR

This paper presents a model-based method to predict and correct thermal drift in high-precision hexapod robot actuators, significantly improving accuracy by reducing thermal expansion effects.

Contribution

It introduces a novel theoretical and experimental approach to model and compensate thermal expansion in robot actuators, enhancing precision.

Findings

Over 80% reduction in thermally induced expansion

Model validated through high-precision interferometric measurements

Method applicable to entire robot or similar components

Abstract

Thermal expansion is a significant source of positioning error in high-precision hexapod robots (Gough-Stewart platforms). Any variation in the temperature of the hexapod's parts induces expansion, which alters their kinematic model and reduces the robot's accuracy and repeatability. These variations may arise from internal heat sources (such as motors, encoders, and electronics) or from environmental changes. In this study, a method is proposed to anticipate and therefore correct the thermal drift of one of the hexapod precision electro-mechanical actuators. This method is based on determining a model that links the expansion state of the actuator at any given moment to the temperature of some well-chosen points on its surface. This model was initially developed theoretically. Its coefficients were then adjusted experimentally on a specific test-bench, based on a rigorous measurement campaign of actuator expansion using a high-precision interferometric measurement system. Experimental validation demonstrates a reduction of thermally induced expansion by more than 80%. This paves the way for thermal drift correction across the entire robot or similar robotics parts.