Singularity-Free Low-Complexity Fault-Tolerant Prescribed Performance Control for Spacecraft Attitude Stabilization

This paper is concerned with the problem of fault-tolerant prescribed performance attitude stabilization for spacecraft under model uncertainties and actuator failures. In most of the existing control designs for spacecraft described by the unit quaternion, the possible singularity issue of the virtual control coefficient matrix is neglected such that the controllability of the attitude subsystem cannot be warranted throughout. On the other hand, the related works depend on complex algorithms of approximation, estimation or diagnosis to deal with unknown system dynamics. In this paper, a singularity-free low-complexity fault-tolerant prescribed performance control (PPC) strategy is put forward. To exclude the singularity issue, an initialization principle of the performance envelope is devised. On this basis, a static PPC law is developed, without parameter identification, function approximation, disturbance estimation, failure detection, failure isolation, failure estimation. In place of the classical Lyapunov stability theory, a unified performance analysis framework based on proof by contradiction and the barrier Lyapunov function is constructed. It not only turns out attitude stabilization with the preassigned settling time and accuracy whenever the actuator failures happen, but also discloses the intrinsic robustness of the control system versus actuator failures and model uncertainties. A comparative study on a rigid spacecraft is performed to demonstrate the validity and advantage of our approach. Note to Practitioners—Attitude stabilization is a fundamental element for the spacecraft to accomplish various important missions. A mainstream method to model the spacecraft attitude is the unit quaternion. In this way, the control distribution matrix of the attitude subsystem becomes singular under certain attitude, which causes the loss of controllability. This problem is neglected by the majority of the existing attitude stabilization methods. On the other side, the harsh space environment with high-intensity radiation, extremely low temperature and dust and fine particles gives rise to actuator failures in the spacecraft control system. Whilst the existing fault-tolerant control methods are capable of accommodating the actuator failures ultimately, the control performance during the post-failure transient stage is inevitably degraded. This problem is solved by the fault-tolerant prescribed performance control method, whereas the control algorithm shows a high complexity due to the dependence of function approximation or parameter identification. Motivated by the above observation, this paper presents a singularity-free low-complexity fault-tolerant prescribed performance control approach for the spacecraft with unknown dynamics and actuator failure. It achieves fast accurate attitude stabilization even in the faulty case.