Fault Estimation and Fault-Tolerant Steering Law for Single Gimbal Control Moment Gyro Systems

Single gimbal control moment gyros (SGCMGs) have been widely used on agile satellites to get a rapid retargeting capability. To enhance the reliability and safety of the SGCMG system, this paper addresses the fault estimation and fault-tolerant steering problem. The SGCMG is modeled as a two-loop system including a wheel speed control loop and a gimbal rate control loop, and a cascade multiplicative fault model of SGCMG is developed. Then, in view of the complexity of the gimbal fault, a local adaptive fault estimator is proposed to reconstruct the total time-varying fault effects for each SGCMG. Using the estimated fault effects, a fault-tolerant steering logic is further developed to not only allocate the commanded attitude control torque properly but also compensate the fault effects. To verify the proposed fault estimator and fault-tolerant steering logic, numerical simulations are carried out on a SGCMG-actuated spacecraft.