Attitude control of a 3-axis stabilized satellite using adaptive control algorithm

In designing the attitude determination and control system (ADCS) of a satellite, the system cannot be modeled as a dimensionless point object. A practical object has physical size and thus rotates as well as translates. Such bodies are termed rigid bodies. Its dynamics is characterized by six degrees of freedom. Three degrees of freedom represent the motion of the center of mass. The other three degrees address the rotational motion of the object. The 6-DoF must be dynamically controlled. Traditionally, attitude determination involved using both rate gyros and star trackers. Rate gyros are prone to mechanical failure. Hence it is proposed to study the feasibility of replacing rate gyros with star sensors for attitude determination. A Kalman filter provides an optimal means to estimate the state of the system. Results show that the rates can be estimated to within 10/sup -7/ rad/s which is as good as from a gyroscope.