Design And Simulation Of A Three-Axis Stabilized Satellite And Kalman Filter Rate Estimator

Design requirements for a small satellite (NPSAT-1) Attitude Determination and Control Subsystem (ADCS) is a three-axis stabilized spacecraft which requires a control attitude of +/- 1.0 degrees and knowledge attitude of +/- 0.1 degree. Several design aspects are considered in development of attitude control systems for a small satellite, such as: spacecraft dynamics, space environment, disturbance torques, orbit type, and spacecraft complexity. The ideal spacecraft's attitude sensor is a rate gyroscope, which provides rate information to the attitude control system. In the case of NPSAT-1, due to budget constraints alternative sensors will be utilized, such as: a three-axis magnetometer, earth sensors, and a Global Positioning System (GPS). A small satellite designed to have a three-axis stabilized, biased momentum system, must have a robust control system and requires a momentum wheel to provide stiffness to maintain attitude, and magnetic torque rods on each axis. The current design of NPSAT-1 uses all of these sensors to provide rate information for damping and stability to the control system that requires a complicated attitude control design. The purpose of this attitude control design simulation is to investigate and propose a control law utilizing a single pitch momentum wheel and three magnetic torque rods. A further proposal is to utilize a constant speed momentum wheel to avoid momentum damping and over speed, replace the pitch control with magnetic torquers, and develop a Kalman filter estimator to provide all the required angular rates.