"Three Axis Satellite Attitude Control PD Control Approach for Magnetic Torquer"
Kapil Rathi1, Dr. J. Shanmugam2 , P.Natrajan3
1Division of Avionics
3ISRO Satellite Centre
Magnetic control is a favourable way to stabilize spacecraft. Often, the hardware is simple and lightweight, and does not degrade or change mass over time. A magnetic control system does have limitation. The Control, which is in the form of magnetic moment, can only be applied perpendicular to the local magnetic field. There is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field.
In this paper, control law is developed to stabilize the spacecraft on three axes. Spacecraft control is subjected to nonlinear and uncertainties. Non-linear robust control design H∞ control can be applied to achieve stability. The PD controller architecture is assumed for the spacecraft attitude control and concepts in nonlinear H∞ control can apply to obtain robustness properties.
This paper attempts to generalize non-linear H∞ control method by using storage function or Hamilton–Jacobi function which is the solution of the Hamilton-Jacobi Inequality, for the the stability and robustness of the attitude problem. A new controller structure which is suitable for attitude control is identified. The stability and accuracy of the closed-loop system is demonstrated in the presence of disturbances including gravity-gradient torques, drag torques, and solar radiation pressure torques.
Keywords: Three axis attitude control, magnetic control, H∞ control, PD controller, Hamilton-Jacobi Inequality, micro-satellite;
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