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Variable Geometry Truss Manipulator

Technology Category: Robotic Design / Advanced Control Systems

Description: The Variable Geometry Truss (VGT) manipulator was developed to reduce the deflection for a manipulator designed to reach 16 feet from its base and lift a 2150 lb payload. Using the Double Octahedral Variable Geometry Truss concept pioneered by NASA Langley Research Center, a concept was developed by PNNL, and NASA completed the detail design and fabrication. PNNL staff developed the control systems that were implemented on the actual robot. The VGT that was developed performed well in the high payload task, and was able to position a 1000 lb. load anywhere it its workspace with only 1/8th inch of deflection. A comparable traditional manipulator was also developed, and its deflection was approximately 2 inches under the same loading conditions.

The VGT gets its strength from the parallel manipulator structure, which means that each component of the robot caries only a portion of the overall load. In a traditional robot, each joint in the manipulator has to carry the whole load, and therefore the deflection in each joint is added to the previous joints, making the overall deflection much more. In a parallel manipulator, the deflections of each joint are less, since they share the load with all other joints in the robot.

Point of Contact: Joseph C Tucker (509) 375-2881