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UBC Theses and Dissertations

Hierarchical task decomposition and execution for robot manipulation task using a wrist force sensor Kotzev, Shmuel


The research developed force-motion strategies and subsequent force and position control algorithms, using a PUMA 560 robot arm and its original controller. A task decomposition methodology has been developed that enables a mechanical assembly task to be subdivided into a series of executable subtasks. By applying this methodology to the assembly of a hydraulic gear pump, a library of special purpose, task oriented, subtask programs were created. Most of these programs, though derived for a pump assembly task, are applicable (when used with appropriate parameters) to other assembly tasks. Most of the algorithms require force/torque sensory information that is supplied by a JR³ wrist force sensor. The force control algorithms use that data and system compliance in order to produce new position instructions that are transferred to the controller of the arm. The logic of the control law and system behaviour when contacting the environment, were checked, using the dynamics and compliance of a simplified structure of a robotic arm and its wrist sensor. A demonstration of the pump assembly task, using the arm, force sensor, controller and the derived library algorithms is an integral part of the thesis.

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