Controller Reliability Assessment Model: A New Method for Reliability Assessment of Attitude Control Subsystem in Space Missions

Abstract

The objective of this research is to assess the reliability of the controller and attitude control subsystem (ACS) of a LEO satellite using the presented Controller Reliability Assessment Model (CRAM). CRAM is based on the Software in the Loop (SIL) simulation which leads to the construction of a database from ACS performance. Using data analysis techniques leads to a comprehensive understanding of the ACS’s controller functionality and determines the failure rate of the controller’s component. In addition, Reliability Block Diagram (RBD) is implemented to visualize the contribution of the controller and estimate the reliability of the controllers according to the evaluated failure rates and reliability mathematical model for three years of operating. CRAM defines the relatively most robust, and accurate controller with the fastest response and highest reliability. In the designed control system, solar radiation, gravity gradient, and aerodynamic effects are considered as external disturbances. The actuator's loss of effectiveness is considered as an internal disturbance. The Tetrahedron configuration of reaction wheels is modeled in which three reaction wheels serve as three-axis control, and one reaction wheel as a redundant actuator. In this research, controllers such as PD, H∞, and two different types of sliding mode controllers are considered.