The Hybrid Attitude Control System for the Geosynchronous Satellite

Abstract

The hybrid attitude control system for a geosynchronous satellite has been developed. The hybrid attitude control system which is a 3-axis stabilized attitude control system combines the best features of the conventional zero-momentum and bias-momentum control system. The system employs an earth sensor to get the roll and pitch attitude information, and a CSSA (Coarse Sun Sensor Assembly) on a solar array paddle for the yaw attitude information. When the yaw information is not measurable on account of kinematic yaw measurement singularity of the sun sensor, the system takes a yaw attitude observer which depends on the Euler equation of the satellite attitude motion. During this periods, the yaw attitude control becomes relatively a open loop so that the observer uses the pitch momentum of the satellite as a gyroscopic stiffness to estimate the yaw attitude error by the earth sensor outputs. The present paper shows a design method of the hybrid control system to determine the optimum combinations of the observer parameters. With this method, we can also determine sensor requirements and predict the performance of the control system. These results are validated by the computer simulations. The paper concludes that the hybrid control system provides new capability to the attitude control system design for the geosynchronous satellite.