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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 43601 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Salarieh, Hassan
- Abstract:
- In this work dynamic behavior of a two body TSS with main satellite as rigid body is studied and effects of tether elasticity and tension on the satellite dynamic are indicated in station keeping phase and circular orbit. Also a simplified modeling is introduced which could be used in nonlinear controller design. Lagrange and extended Lagrange method is used to derive equations of motion. It is shown that longitudinal vibration of tether has small effect on satellite attitude and angular velocity and because of high frequency it can be decoupled from satellite dynamic. In the simplified model, orbital motion is decoupled from equations of TSS and main satellite dynamic. Effect of decoupling on main satellite and tether is studied. Finally the simplified model is verified with exact model and growth of error is plotted.At control part, a new method for controlling tether libration is introduced. In this method, tether libration is reduced using attitude control of main satellite. It uses only typical actuators which are used for satellite attitude control and no more specific actuator for tether is not added. To prove applicability of new idea, at first controllability of linear system is investigated. After that a linear LQR controller is designed to regulate attitude motion and libration of system by controlling attitude of main satellite. The linear controller works at low amplitudes, but increasing tether libration amplitude, controller diverges. To solve problem, a nonlinear controller is designed using feedback linearization method to regulate tether libration. It works well in high amplitudes.
- Keywords:
- Decoupling ; Orbit Control System ; Feedback Linearization ; Linear Quadratic Requlator (LQR) ; Tethered Satellite System (TSS)
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محتواي پايان نامه
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