Failure-tolerant control for small agile satellites using single-gimbal control moment gyros and magnetic torquers

Abstract

This paper focuses on the attitude control problem of small agile satellites using single-gimbal control moment gyros (CMG) and magnetic torquers (MTQ). CMGs are regarded as effective torque generators for agile satellites because of their torque amplification capability. However, they are vulnerable to failure due to their complex inner mechanism. In this paper, different failure cases of CMGs are analyzed. A flexible failure-tolerant control strategy is developed by automatically redistributing the required control torque among the operating CMGs and MTQs, with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures. The performances of maneuvers about different directions under different failure cases are also discussed and examined. Numerical simulations demonstrate that the proposed strategy maintains certain agility in the cases of one or two CMGs failing. Moreover, a survival strategy with only one CMG left is also verified. Both sun-pointing stabilization and earth-pointing stabilization can be achieved in this case, which fulfill some basic mission requirements.

Finite‐time attitude‐tracking control for rigid spacecraft with actuator failures and saturation constraints

“…The reliability of a spacecraft system mainly depends on its fault tolerability. Among existing fault‐tolerant schemes, actuator failures are particularly emphasized (see References , , , , to name a few) and various techniques are developed to design the fault‐tolerant controllers for spacecraft systems such that the degradation caused by actuator failures can be compensated. In this work, the attitude‐tracking control of spacecraft with actuator fault is further studied.…”

“…(9) and (10), and suppose Assumptions 1-4 are satisfied. Given the control laws (46), (47), the FNTSM manifold S i converges into the region |S i | ≤ Δ S (48) in finite time T reach , then the tracking errors e i (t) and Ω ei (t), respectively, converge into regions |e i (t)| ≤ Δ e (49) and…”

“…In this section, simulations experiments are conducted to verify the effectiveness of the proposed controllers (46) and (80) by considering two cases of actuator failures mentioned in Section 3. To further demonstrate the control performances, comparisons with existing achievements are carried out.…”

“…The performance of controller (46) is depicted in Figures 4-8. As can be seen in Figures 4 and 5, the attitude tracking and angular velocity tracking are achieved, respectively, and the tracking errors converge into small regions around origin in finite time.…”

“…The actuator distribution matrix D and actuator faults scenario Γ = diag{Γ 1 , Γ 2 , Γ 3 , Γ 4 , Γ 5 , Γ 6 } remain the same as Equation (96) To make an relatively fair comparison, the initial condition is selected to be the same as that in Reference 33, that is, (20,26,26), control parameters of controller (54) in Reference 33 remain the same as those in section 5.2 of Reference 33, that is, = 0.1, k 0 = 20, k 1 = 2, k 2 = 0.2, = 0.5, 1 = 1, 2 = 0.6, = 0.001, r 1 = 3, and r 2 = 5. Except for K 1 = 2I 3 , K 2 = 0.2I 3 , and = diag (43,48,46), control parameters of controller (80) remain the same as those in Table 2. Control performance comparisons between controller (80) and controller (54) in Reference 33 are shown in Figures 20-22.…”