Progress towards a Revolute-joint Robot for the Precision Positioning of Material Samples or an X-ray Detector

At the Advanced Photon Source (APS), the desire to combine sample handling, sample positioning or goniometer functionality into one piece of equipment has provided the impetus for the development of a precision six degree-of-freedom robot with approximately 2 μm dynamic positioning uncertainty. This specification is driven by the need for a positioning uncertainty that should be 10 to 20 percent of possible x-ray detector resolution. Six-degree-of-freedom robots with 20 μm static positioning uncertainty are presently used at the APS in sample-changing applications. A history of these existing APS robotic sample-handling systems will be presented, along with discussion concerning the theoretical, computational and experimental issues associated with the design of a sample or detector manipulator with high trajectory precision. A computational model being developed is intended to capture the unique dynamics associated with the robot harmonic drive gearboxes. Incorporation of an accurate harmonic drive model into a multibody model is a novel approach to completely capturing the robot dynamics. The dynamic representation of the multibody model allows it to be used as a design tool and incorporated into a control architecture for use in the next-generation multi-degree-of-freedom manipulators for use on synchrotron beamlines. The successful operation of a multi-degree-of-freedom sample manipulator will represent a new paradigm in x-ray experimental sample positioning.