Kinematics analysis and elevation control of a bi-directional VSAT antenna

Lim, Dao Yan
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Mechanical Engineering
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The VSAT antenna is used for information exchange, which in order to do so it needs to align with the satellite in space. The pre-existing controller lacked the capability to control the antenna elevation motion, which leads to persistent steady state pointing error and occasional high amplitude oscillations. Extended motion testing of the antenna resulted in a few mechanical defects. This thesis explored and demonstrated multiple implementations of the classical controller and resolved the aforementioned problems. Specifically, the implementations are independent PI control, PI control with trajectory generation, PI control with Notch filter and trajectory generation, and PID control with second-order low-pass filter and trajectory generation. The antenna system with the controllers are demonstrated to be closed-loop stable through extensive root-locus analysis. Ultimately, the PI control with trajectory generation demonstrated the most desirable outcome. The systematic approach to analyzing the kinematics of the antenna as well as the system modelling of the dynamics of the antenna are also presented. The kinematics analysis verified that the antenna linkage is kinematically stable within the operating range. The system modelling suggested that the lumped antenna mass may be neglected.

Classical control, Dynamics modelling, Elevation control, Notch filter, Trajectory generation, VSAT