TRANSFER FUNCTION-BASED MICROSATELLITE ATTITUDE CONTROL MODEL
The oversimplification of existing transfer function models used in literature results in inadequate characterisation of microsatellite Attitude Control System, hence the need to develop a transfer function-based Systems dynamics model that adequately characterise the system. The first step in the development of an Attitude Control System for a satellite is the modelling of its dynamics. The modelling is usually carried out using the state-space approach due to the nonlinear nature of satellite Attitude Control Systems dynamics. The mathematical expressions of the satellite structure dynamic accelerating torque about its three axes were presented in this study. The actuator model was based on the dynamic model of the Brushless DC motor under the wheel loading. A linear amplifier with a first-order transfer function model was proposed to reduce the effects of sudden changes in motor speed. Proportional – Integral – Derivative controller was also proposed in this study. The responses of the subsystems and overall system to unit step function were simulated. The simulation results show that the uncompensated system was open-loop unstable, while it was closed-loop stable with rise time and settling time of 2.21s and 3.98s, respectively for all the three axes. The corresponding values of Percentage Overshoot and steady error are both zero.
Authors : Ajiboye, A. T., Opadiji, J. F. and Popoola, J. O.
Category : Open Access Volume (Issue) : 7(1) Date Uploaded : 1st July 2021
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4th May 2019
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