چكيده به لاتين
In this thesis, for the controller design of a satellite with high-resolution imaging capabilities in the presence of under-actuated reaction wheels, we first discussed the fundamental principles of satellite control. This includes concepts such as: coordinate systems, satellite rotational dynamics and kinematics, environmental disturbances and next actuator dynamics, and control algorithms. The actuators used to control the attitude of the satellite are: reaction wheels and magnetic torquers, which have been a common choice for low-earth satellites. Reaction wheels are used for high-precision attitude maneuvers with large angles and high operational speeds. Additionally, magnetic torquers are used for maneuvers such as: detumbling, desaturating reaction wheels, and stabilizing the satellite's three axes. A control system design was implemented by linearizing the system's dynamic equations and applying it to the nonlinear dynamics. The control law used to meet the control objectives is PD control law implimented for both the magnetic controller and the reaction wheel torque controller, using Simulink/MATLAB software, it is done initially to control the satellite by three reaction wheels, then for when the reaction wheels are underactuated (which includes defects in the reaction wheel of the x axis, defects in the reaction wheel of the y axis, and defects in the reaction wheel of the z axis of the satellite body frame for cases where one wheel becomes defective, and then for defects of the wheels of the x and y axes, the wheels of the x and z axes and the wheels of the y and z axes, and finally the defects in the three reaction wheels) It is implemented with the help of magnetorquers. The control system designed by assigning a separate controller to each mode in the presence of environmental disturbance torques such as: gravity gradient, atmospheric drag, solar radiation and magnetic disturbance torque. The designed controller was able to meet the requirements of remote sensing imaging with high resolution in cases where one or two reaction wheels fail; except for the case where the fault occurs along the y-axis. For the case where three wheels were faulty, the control system was no longer able to meet the requirements of high-resolution imaging, and it was also shown that the controller is able to eliminate the effects caused by the multiplicative moment of inertia.