Design of a Compliant Robotic End-Effector Tool for Normal Contact Estimation

The use of industrial robots for machining operations such as polishing is gaining popularity these days. However, maintaining constant normal contact on unknown geometrical surfaces still remains a challenge. In order to cope with the issue, this research has developed a unique compliant robotic end-effector that can measure the depth and angles deviation of the robot from the normal complex surfaces in real-time without any prior geometric model of the workpiece. The indigenously developed compliant robotic end-effector is made up of three main components: a novel three-axis force/torque sensor, a compliant contact pin, and a data acquisition (DAQ) board. Initially, the three-axis force/torque sensor has been validated with both simulation and testing. The advantage of being able to take measurements in real-time is provided by the DAQ's automatic weight compensation feature. Additionally, the pose correction algorithm receives the estimated contact force as feedback during robot surface tracking in order to assess depth and angles and determine the proper distance and perpendicular relationship between the surface and the end-effector. The proposed scheme is then evaluated using a six-axis industrial robot. The experimental results show that the maximum average depth and angle errors are 0.13 mm and 0.64 degrees, respectively. The developed system has achieved significant improvement in contact-based robot surface measuring.