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UBC Theses and Dissertations

Design, construction and operation of a variable geometry manipulator Chu, Mark Sin Tian


This thesis focuses on design, dynamical simulation, operation and performance evaluation of a variable geometry manipulator used in space as well as ground based operations. The system is composed of a mobile base supporting two modules connected in a chain topology. Each module consists of two links: one free to slew while the other is permitted to deploy. The governing equations of motion for the planar dynamics of the manipulator system are obtained using the Lagrangian procedure. A Fortran computer program is written for the dynamical simulation of the system. The accuracy of the formulation and the validity of the computer simulation code are verified through energy conservation tests. An extensive parametric study follows which provides better appreciation of the complex interactions between the system variables, initial disturbances, manipulator maneuvers, as well as the revolute joints and pay load flexibility. It also identifies critical combinations of system parameters and maneuvers which may lead to an unacceptable response. Results indicate that the coupling effects together with the flexibility at the revolute joints have significant impact on the manipulator's performance. Obviously, this will affect the desired trajectory tracking by the end-effector, suggesting a need for a suitable control algorithm. This is achieved through the classical Proportional-Integral-Derivative (PID) control strategy. The design, construction and integration of a prototype manipulator system, which progressed concurrently with the numerical simulation phase are also described in detail. Finally, the numerically predicted results are compared with the prototype performance. The remarkable agreement tends to substantiate integrity of the prototype design and effective implementation of the controller. The study lays a sound foundation for further exploration of this class of novel manipulators.

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