Sensors and Sensor Networks: Indoor Global Positioning System (GPS) Sensor Application to Actuator Metrology and Automated Manufacturing Workcell Calibration

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This research uses newly available "indoor GPS" (iGPS) technology togenerate an accurate robotic reference model from a parametricdescription (dimensions, compliance, etc.) of its "as-built" components(actuators, links, etc.). The new metrology system uses infraredtransmitters and has sufficient accuracy to parametrically describe evenhigh precision systems. Completing the initial model requires theconstruction of a 2 meter cube high-precision sensor network. Once theparameters are known, they can be used to populate a developed modelallowing manipulator accuracy resolution previously attainable only atlaboriously taught locations. This development then allows for theconstruction of open architecture manufacturing cells (1, 3, and 10meter cubes). The iGPS and reference model will be used to "calibrateas assembled" (i.e. on demand) and maintain the cell preventing accuracydrift due to repair, upgrade, aging, temperature, etc. The benefits of modular robots are clear. Such systems allow flexiblemanufacturing, rapid repair, and upgrade, but these benefits have yet tobe realized. A significant barrier is the presence of error between thetool (actual) frame and goal (ideal) frame. While the repeatability(returning to a taught point) of a typical robot can be 0.005", itsaccuracy (commanded to a new point) may not be better than 0.1" due toconfiguration, load, model error, etc. Currently, teaching a roboticdevice is a time-consuming process required after repair, upgrade, andprocess change. But the accuracy is not sufficient to perform therequired high-precision operations without teaching. This fact trumpsother modular technology benefits. But the use of iGPS technology intandem with actuator metrology could lead to accuracy levels close torepeatability and remove this technological barrier.