A simulation framework for a reaction wheel based AOCS

The attitude control problem for geo-stationary satellites poses a challenge to a control system designer due to the tradeoff between limited number of actuation techniques available and the robustness of the system. The reaction wheels present an economical solution in terms of energy and also enable a smooth control technique as opposed to a chattering control exhibited by thruster techniques. By continuously exchanging momentum between the spacecraft body and reaction/momentum wheels a fine pointing control can be implemented. This work describes a simulation framework built for the design of an attitude control system for an indigenous communication satellite. It describes the modeling of the dynamics of the spacecraft structure carrying reaction wheels and its capacity for external disturbance rejection. The controller and the associated compensator algorithms are discussed in the context of pitch axis control. Finally an integrated model allowing 3-degrees of freedom to the spacecraft structure carrying three separate reaction wheels is implemented. The expected performance of the control system is demonstrated through a simulation showing a graphic reorientation of a multi-faced body in accordance with the attitude control command issued by the autopilot.