The CubeSTAR satellite is a student satellite project at the University of Oslo. The main mission is to measure the turbulence in the electron plasma using a novel Multi Needle Langmuir Probe system developed at the University of Oslo. In order to get correct measurements, it’s important that the probes are located in the front of the satellite in the orbit velocity direction.
In this thesis, the attitude control problem of the CubeSTAR nano-satellite is the main topic. The satellite will use three electromagnetic coils as actuators, mounted on each axis. These coils can generate a magnetic moment, and together with the Earth’s geomagnetic field, create a torque able to change the attitude of the spacecraft. The problem with using magnetic coils is that the magnetorquers only work in the direction perpendicular to the geomagnetic field, and there will always exist one axis that is not controllable. However, because the geomagnetic field is approximately periodic, the spacecraft becomes controllable over one orbit.
The spacecraft dynamics and the environmental models are derived and analyzed, and the design of the magnetic coils are presented. An adaptive PD-like controller and the LQR optimal control problem are presented and investigated for magnetic stabilization of the spacecraft, in addition to the B-dot detumbling control law. Simulations of the different controllers shows the performance when realistic disturbances are added to the system, and a recommendation based on these results are presented.
The attitude determination and control system will be implemented on a FPGA on-board the satellite. Implementation of the attitude control is achieved by using the DSP-builder software by Altera. The source code is compiled to HDL, and downloaded onto the FPGA. The performance of the FPGA is shown through hardware in-the-loop simulations.