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Motion control of non-fixed base robotic manipulators

University of British Columbia

Robotic manipulators mounted on spacecraft experience a number of kinematic, dynamic, and control problems because the motion of the spacecraft is affected by the robot motion. Because of this dynamic coupling, robot motion required to produce a given robot end-effector position for a fixed base manipulator would not result in correct end-effector position for the same manipulator mounted on a spacecraft. In this thesis, the general three dimensional equations of motion are derived for an n link manipulator mounted on a non-fixed base object. Instead of performing a single inverse kinematic calculation at the beginning of a movement to determine the required joint setpoints, multiple inverse kinematic updates are done throughout a movement. The updating sequence is determined by an optimal inverse kinematic updating algorithm. This motion control algorithm is based on experimental simulation results performed in Matlab and a set of performance indices that are used as guidelines. Simple PD joint controllers are used for servoing the manipulator joints for a planar robot application. A joint trajectory generator utilizing velocity time scaling and quintic polynomials is developed. In addition to compensating for the base motion, it is shown that multiple updating requires less energy consumption than single inverse kinematic calculation based movements. Endpoint overcompensation and endpoint servoing are two techniques that enable any desired manipulator accuracy assuming kinematic and dynamic singuarities are not encountered. The derived motion control techniques incorporate the base motion without base motion control. Knowledge of the system dynamics is not required and the iterative inverse kinematics is performed online without model prediction.

Thesis/Dissertation

application/pdf

2009-03-11

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http://hdl.handle.net/2429/5918

Mechanical Engineering

University of British Columbia

UBCV

DSpace