The Development of a Hardware-in-the-Loop Attitude Determination and Control Simulator for IlliniSat-2

The University of Illinois’ IlliniSat-2 CubeSat bus achieves 3-axis attitude control via a series of magnetic torque coils and attitude determination via Kalman filtered magnetometer data and a crude Sun vector measurement. This robust new attitude determination and control system (ADCS) requires extensive pre-flight simulation and testing. A hardware-in-the-loop ADCS simulator for IlliniSat-2, known as CubeSim, has been established for this purpose. The simulator retrieves magnetic field data from a satellite simulation in STK and subjects a physical IlliniSat-2 bus to the same magnetic field in real-time via a large triaxial Helmholtz coil, the HC3. The bus, fixed within the HC3, determines its attitude from the generated magnetic field. From here, the bus attempts control maneuvers with its torque coils; the control signals are intercepted and used to forward propagate the simulated attitude and angular velocity, which are fed back into STK. This system allows for testing and calibration of the ADCS of an assembled IlliniSat-2 bus prior to launch. The design process for the HC3 and related hardware, the development of the simulation software, and the associated calibration processes are discussed here.