Adaptive Nonsingular Fixed-Time Attitude Stabilization of Uncertain Spacecraft

Fixed‐time attitude tracking control for spacecraft based on adding power integrator technique

“…For the purpose of comparison, the proposed controllers are compared with the NTSMC by Chen et al Then two cases are considered. In the first case, the proposed fixed‐time controller (FTC) in (5) and the proposed AFTC in (8) are compared with the NTSMC with no external disturbances and thruster faults.…”

“…It means states q e and ω e can converge to a certain residual set D 1 in a fixed time T 2 . D 1 and T 2 , which are independent of initial values of q e or ω e , are related to the control parameters , and will be given in the proof of this theorem . Proof See Appendix B. Remark The sign function sign(·) is explicitly introduced in some adaptive attitude controllers and some finite‐time controllers, which results in the chattering problem inevitably. Although a saturation function or a boundary layer can be applied to weaken the effect of chattering in the practical engineering, its proof of finite‐time stability is difficult.…”

“…It has been utilized to design attitude controller for spacecraft. Based on NTSMC, Reference designs a fixed‐time controller for attitude stabilization. A fixed‐time attitude tracking controller is developed based on Sin‐FM in Reference .…”

“…As mentioned in the above paragraph, TSM methods have some weaknesses. Therefore, the bound of settling time in Reference may tend to infinity when states converge to zero; there exists an unknown period of time in the complete bound of settling time in Reference and the bound of settling time in References and may tend to infinity if states converge along with the asymptotic sliding mode surface. Although the fixed‐time control method in Reference has no singularity problem and it can give a complete bound of settling time, the exponent parameters are fixed and it is difficult to use this method to design a continuous attitude controller for spacecraft, even if disturbance is not taken into account.…”

“…In comparison with most of the finite‐time attitude controllers that are based on the conventional concept of finite‐time stability, such as the homogeneous attitude controllers, the terminal sliding mode attitude controllers, and the “AAPIC” attitude controllers, two novel attitude controllers are designed based on the concept of “fixed‐time stability,” which can be seen as a special case of finite‐time stability Compared with most of the existing fixed‐time attitude controllers that are designed based on the TSMC, such as those in References , the two proposed fixed‐time controllers are designed based on the AAPIC. In comparison with the research results related to finite‐time attitude control, such as those in , this study further considers the case where external disturbance and thruster faults exist. Moreover, compared with many discontinuous finite‐time controllers, the two proposed controllers are continuous. …”