High-accuracy robotic metrology for precise industrial manipulation tasks

The majority of industrial production processes can be divided into a series of object manipulation and handling tasks that can be adapted for robots. Through significant advances in compliant grasping, sensing and actuation technologies, robots are now capable of carrying out human-like flexible and dexterous object manipulation tasks. During operation, robots are required to position objects within tolerances specified for every operation in an industrial process. The ability of a robot to meet these tolerances is the critical deciding factor that determines where the robot can be integrated and how proficient the robot can carry out high-precision tasks. Therefore, improving the positioning accuracy of robots can lead to new avenues for their integration into production industries. Given that tolerances in manufacturing processes are in the order of tens of micrometres or less, robots should guarantee high positioning accuracy when manipulating objects. The direct method of ensuring high accuracy is by introducing an additional measurement system(s) that can improve the inherent joint-angle-based robot position determination. In this paper, we present a High-Accuracy Robotic Pose Measurement (HARPM) system based on coordinate measurements from a multi-camera vision system. We also discuss the integration of measurements obtained by absolute distance interferometry and how the interferometric measurements can complement the vision system measurements. The performance of the HARPM system is evaluated using a laser interferometer to investigate robotic positions along a trajectory. The performance results show that the HARPM system can improve the positioning accuracy of robots from hundreds to a few tens of micrometres.