Satellite attitude control using magnetic torquers and reaction wheels

In the last decades, access to space has become more affordable thanks to the introduction of CubeSat nanosatellites. Before launching a satellite into space, a dynamic simulator, such as an air bearing testbed, can be used to test its attitude control subsystems Hardware-In-The-Loop and to perform on-ground verifications. The goal of such a testbed is to be able to reproduce as faithfully as possible the space conditions. Mockups that represent nanosatellites by including all the features a spacecraft has, such as sensors and actuators, can be used as well. Magnetorquers and reaction/momentum wheels are usually used as main actuators because of their reduced dimensions. These actuators can be tested in such facilities to prevent in-orbit failures. The following thesis work is divided into two main parts. In the first one, using a MATLAB/Simulink, software is realized to simulate the attitude and orbit dynamic of a spacecraft equipped with reaction wheels and magnetic actuators, considering the major external disturbances on a LEO orbit. The simulator is used to study the case in which one of the 3 reaction wheels fails and how the spacecraft could recover the attitude with the use of 3 orthogonal magnetorquers. The desaturation phase of the wheel, using the magnetorquers, has been studied as well. An automatic control law for both tasks has been studied and implemented in the simulator, showing good results. In the second part of the thesis, the testbed in the CIRI Aerospace Laboratory and a 1U CubeSat mockup have been employed to test the studied control laws in the case of three magnetorquers and a momentum wheel. Prior to testing, the balancing process needed to reduce the disturbance torque was performed. Afterward, more tests on the detumbling phase were performed, changing the direction of the magnetic field, and test on the attitude control of the testbed was conducted, showing good results as well.