Description:
This thesis presents a dynamic analysis and a control system for a flexible space
manipulator, the Deployable Robotic Manipulator or DRM, which has a
deployable/retractable link. The link extends (or retracts) from the containing slewing
link of the manipulator to change the DRM's length and hence its workspace. This
makes the system dynamics time varying and therefore any control strategy has to adapt
to this fact. The aim of the control system developed is to slew the manipulator through
a predetermined angle given a maximum angular acceleration, to reduce flexural
vibrations of the manipulator and to have a certain degree of robustness, all of this while
carrying a payload and while the length of the manipulator is changing. The control
system consists of a slewing motor that rotates the manipulator using the open-loop
assumed torque method and two reaction wheel actuators, one at the base and one at the
tip of the manipulator, which are driven by a closed-loop damping control law. Two
closed-loop control laws are developed, a linear control law and a Lyapunov based
control law. The linear control law is based on collocated output feedback. The
Lyapunov control law is developed for each of the actuators using Lyapunov stability
theory to produce vibration control that can achieve the objectives stated above for
different payloads, while the manipulator is rotating and deploying or retracting. The
response of the system is investigated by computer simulation for two-dimensional
vibrations of the deployable manipulator. Both the linear and Lyapunov based feedback
control laws are found to eliminate vibrations for a range of payloads, and to increase the
robustness of the slewing mechanism to deal with uncertain payload characteristics.