Fault Tolerant Attitude Control for Small Satellites Using Single Gimbal Control Moment Gyros and Magnetic Torquers

Abstract

A fault tolerant control scheme is proposed for the attitude stabilization of a small satellite using single gimbal control moment gyros (SGCMGs) and magnetic torquers (MTQs). The dynamic model of a rigid spacecraft using SGCMGs and MTQs is established, and the faults of SGCMGs are modeled as additive and multiplicative unknown dynamics. By designing a well-tuned linear extended state observer (LESO), the dynamic uncertainties, external disturbances, and the unknown faults of SGCMGs are estimated accurately and compensated actively in real time without knowing the exact spacecraft model. Then, based on the singular value decomposition (SVD) theory, the command torque is decomposed and distributed to SGCMGs and MTQs, respectively; therefore SGCMGs only need to output the torque component orthogonal to the singular direction when encountering singularity, ensuring the controllability of SGCMGs. Through comparison with a conventional proportional-derivative (PD) control method, the numerical simulations demonstrate that this scheme can tolerate potential SGCMGs faults and resolve the singularity problem, maintaining the desirable stability and performance of the satellite.