Author : Mohammed Chessab Mahdi and Abdal-Razak Shehab

In this paper the design of attitude determination and control subsystem of KufaSat Nanosatellite is presented. A three axis magnetometer, six single axis sun sensors, three axis gyroscope and GPS receiver are used as the sensors for attitude determination. TRIAD, algorithm are used for determining attitude estimate from two vector measurements This estimate is then passed to extended Kalman Filter, along with the gyroscope measurements, to obtain a finer attitude. The attitude controller is designed to achieve desired attitude with an accuracy of 5 degrees in nadir pointing using three orthogonal magnetic coils. Two attitude control modes has been considered , detumbling mode and stabilization mode , B-Dot control algorithm is used in detumbling mode while quaternion feedback regulator algorithm is used in stabilization mode. Performance of the control system is verified through closed loop simulations involving models of satellite kinematics and dynamics, space environment, sensors, control law and actuators. Simulations and results of both detumbling mode, and stabilization mode are presented. The simulations show that the satellite will detumble in 60 minutes after separation from the launcher and the stabilization mode controller able to point the satellite with a maximum error of 5 degrees.

Keywords: Attitude Determination, Attitude Control, Quaternion, B-dot algorithm, Nanosatellite, KufaSat

Article published in International Journal of Current  Engineering  and Technology, Vol.4,No.4 (Aug- 2014)