Design of simulation package for passive attitude control system of Swayam

Swayam, a 1-U Pico Satellite completely developed by the students of College of Engineering, Pune, is aimed at demonstrating a Passive Magnetic Attitude Control System (PMACS). The utility of the Satellite is point to point messaging and telemetry. Pointing accuracy for communication is achieved by aligning the satellite’s antenna along the Earth’s magnetic field using an on-board permanent magnet placed parallel to the antenna. The excessive angular rates are damped by the soft magnetic hysteresis rods placed perpendicular to the permanent magnet. The modeling and simulation of the system plays a crucial role in sizing of the magnetic components of the ACS, their placement, and analysis and prediction of attitude behavior of the satellite after launch. This paper describes the indigenously developed in-orbit simulation design for Attitude Control System of Swayam. The attitude control system simulation, considering the appropriate space conditions, determines the in-orbit angular dynamics of the satellite and checks the feasibility of communication with various ground stations. The simulation incorporates standard models such as SGP4 (Simplified General Perturbation) model for orbit and IGRF11 (International Geomagnetic Reference Field) model for the Earth’s magnetic field. The major challenges involves the modelling and simulation of the hysteresis behavior of soft magnetic materials to predict attitude accurately. The complexities involved in using history based model, Generalized Preisach, with iterative numerical technique, Runge-Kutta, are dealt with in order to obtain a stable and accurate solution. The simulation is completely developed in the C and is very flexible to make changes. The output of the simulation includes time required for the stabilization of the satellite after launch, residual angle, angular velocity of satellite at every instance of time and feasibility of communication of satellite with a particular ground station. The results of the attitude of the satellite and communication feasibility for number of orbits of the satellite are also presented in the paper.