On-line lubricant health monitoring in robot actuators

In this work a method is proposed to detect the changes in the quality of the lubricant in gear transmissions of robotic joints. The proposed method applies a fault detection approach to determine the lubricant consistency modifications. The residual signal is generated using only joint position, joint velocity and environmental temperature measurements. The residual generator is based on a dynamic friction model that describes the relation among the viscous friction term, temperature and the lubricant consistency. To estimate the viscous term of the friction, an observer was designed based on the dynamic model of the robot. Simulation results are presented to illustrate the applicability of the proposed modeling and health-monitoring methods.