UBC Theses and Dissertations

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UBC Theses and Dissertations

Dynamics and control of flexible spacecraft : a case study Muneer, Khan Mohd


The First Milestone Configuration (FMC) of the proposed Space Station Freedom is considered for investigating the dynamics and control aspects of a space based orbiting flexible structure. The system dynamics is governed by an extremely lengthy (even in the matrix form), highly nonlinear, nonautonomous and coupled set of equations amenable only to a numerical solution. Two distinctly different discretization procedures, using the system modes and the component modes, are applied to the design as well as the Lagrange orientations of the FMC. The system is found to be inherently unstable suggesting the need for control. To this end two control techniques are employed: the classical Linear Quadratic Regulator (LQR) is applied to the linearized set of governing equations of motion; and the Feedback Linearisation Technique (FLT) for the complete nonlinear set. The amount of information obtained through a planned parametric study of the system dynamics and control is indeed enormous. The results clearly show that under critical combinations of parameters the system can become unstable. However, both the LQR and FLT procedures, together with the on board Control Momentum Gyros (CMG's), can restore the system to the equilibrium state. To gain better insight into the physics of the system behaviour, the uncontrolled as well as the controlled responses of the FMC are animated on an IRIS graphics workstation. The thesis ends with a few recommendations for future study.

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