Dynamically driven a Helmholtz cage for ground testing of attitude determination and control system (ADCS) of nanosatellites

Abstract

ADCS is one of the subsystems of nanosatellites that goes through ground testing before launching. By emulating magnetic fields experienced by nanosatellites in their orbits is modelled by a Helmholtz cage made of three pairs of orthogonally connected Helmholtz coils. The magnetic field in a certain orbit was modeled by implementing algorithms using the World Magnetic Model (WMM) in MATLAB (2018b). Using MATLAB Aerospace Toolbox, implemented algorithm acquired the orbit’s magnetic field as components in 3-axes which could be assigned to the three sets of coils in the Helmholtz cage. One of its three coils was selected and supplied a current through an Arduino-based driver. The resulting magnetic field at the center of the coil was measured by Honeywell’s HMR2300 magnetometer by increasing pulse width. Using this data, a relationship between pulse width and the created magnetic field was obtained. For modelling the orbital magnetic field inside the cage, the magnetic field experienced by a Nanosatellite in its orbit was calculated using the implemented algorithm by taking a Two-Line Element (TLE) dataset. The pulse widths related to the magnetic field values in one particular axis throughout one period of the Nanosatellite were calculated using the derived relationship and the related current variation was applied to the corresponding coil. The magnetic field created by the coil was measured and plotted. The plotted expected magnetic field variation and the experimentally implemented magnetic field variation are fairly similar and within the range of the Earth Magnetic Field. While the theoretical variation was smooth, the experimental variation had discontinuities.