Accuracy Management for Robots Subjected to Process-Induced Loads

Multi-jointed robots are very well known in the art. They are important to many industries. While some robots are required for precision movements and repetition under minimal load (an extreme of which would be a computer... [ view full abstract ]

Multi-jointed robots are very well known in the art. They are important to many industries. While some robots are required for precision movements and repetition under minimal load (an extreme of which would be a computer controlled coordinate measuring machine (CMM) for which highest accuracies are desired, where the load displaced by the robot is minimized), and an opposite extreme is a robot that is designed to apply large forces, with little concern for accuracy (for example manipulating large molten metal vessels to deposit the melt into large molds in a foundry setting). The applications of present concern require both enough accuracy (relative to the resolution of control over joints of the robot) as well as the development by the robot of enough force (relative to joint torques and link stiffnesses) to make accurate motion control under load difficult: that is, applications of interest are those that subject a robot to solicitations (forces, torques, wrenches) that excite the robot compliances (link and joint) to the extent that the robot paths fall outside of tolerance, and needs to be managed. Such applications include friction stir welding (FSW), drilling, milling, trimming, and some mounting and assembly processes, inter alia.
In this presentation, the authors will present a new accuracy management technology for robots operating under load, including an innovative automated calibration technique having several advantages over existing calibration methods. Several industrialization projects where this technology has been a key enabler will finally be highlighted by the authors.