Design of passive magnetic attitude control system of Swayam

This paper includes the thorough design of Attitude Control System (ACS) of the Swayam - a 1U satellite with a scientific mission being demonstration of Passive Magnetic ACS, developed completely by the students of the College of Engineering, Pune (COEP). The payload of Swayam being store and forward messaging service, it is necessary to devise a control system that can provide favorable orientation for communication. The perturbing effects of external and internal torques are counteracted by the Swayam’s Passive Attitude Control System (ACS) which consists of hard and soft magnetic dipoles. The main advantages of the Passive Magnetic ACS are that it is flexible, simple and consumes zero power. The permanent magnet is placed parallel to the dipole antenna which aligns it along the Earth’s magnetic field thereby achieving favorable configuration for communication. The hysteresis rods are responsible for damping the rotational motion of the satellite along the two axes perpendicular to the antenna. The modeling and simulation of system plays a crucial role in sizing of the magnetic components of the ACS, number of hysteresis rods and their placement inside the satellite. The internal and mutual demagnetization effect of the hysteresis rods is also considered in their sizing and placements. A complete study and characterization of the magnetic properties of the materials including their temperature stability is performed. The Residual magnetic moment is measured and is considered in simulating the performance of the final ACS design using mathematical models. On-Board stabilization detection is implemented on the satellite using MEMS gyroscope which detects the stabilization of the satellite by measuring real-time angular velocities of the satellite. The challenges faced during design were low volume constraints, modelling of the hysteresis rods magnetization and testing and verification of the magnetic parameters of rods. The numerical simulations considering the final design predicts a stabilization time around 15 days with angle less than 10 degrees between antenna and Earth’s magnetic field.