Spacecraft fault‐tolerant control using adaptive non‐singular fast terminal sliding mode

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

“…Therefore, the issue of actuator saturation has been a hot topic. Most of the existing literature studies deal with saturation constraints by replacing the standard saturation function sat( u ) with sat( u ) = χ ( u ) ⋅ u (see References , and ) or sat( u ) = ϑ + u (see References and ). These two methods simplify the controllers design at the cost of singularity because given that , the unknown constant γ δ in 0 < γ δ ≤ min( χ i ( u i )) ≤ 1 and its estimation in the controllers probably do not exist, and the saturation approximation error ϑ i → ∞ when u i → ∞.…”

“…The external disturbances vector d , which originates from gravitation, magnetic forces, solar radiation, aerodynamic drags, and so on, is usually unknown. With all these factors considered, the function N (Ω, q ) is nonlinear and uncertain.Remark The prerequisite for dealing with inertial uncertainties and external disturbances in most of the existing achievements is to satisfy some assumptions, for example, the inertial matrix is regarded as known in References , the upper bound of external disturbances is deemed as known in References , the external disturbances and perturbed inertial matrix are assumed to be differentiable in References and , the specific functional relationships between the angular velocity and the lumped unknown nonlinear function should be met as in References , , and so on. We admit that these assumptions have facilitated the controllers design, yet some limitations cannot be ignored, such as the following: (1) the upper bounds of the external disturbances and unknown inertial matrix cannot be easily obtained due to the complexity of the practical spacecraft system, and even if obtained occasionally, they are usually conservative estimates; and (2) some assumptions about specific functional relationships are rigorous because the given expressions are difficult to satisfy or controversial because some variables are treated as constants.…”

“…The main contributions are summarized as follows. This is the first attempt to combine the FNTSM technique and fuzzy logic system (FLS) to achieve the finite‐time attitude tracking for a rigid spacecraft subject to unknown inertial parameters, external disturbances, completely failed actuators failures, and saturation constraints. A smooth function with stronger saturation approximation ability is presented to deal with the actuator saturation constraints, which is quite different from many literature studies such as References , , , and so on. The attitude‐tracking scheme is more practical and less demanding because the requirement of a prior knowledge of uncertainties in most of the existing achievements (see References , , , to name a few) is removed. Unlike the common fault handling method in References , and , a less conservative approach for tackling actuator failures and saturations is provided through analyzing the uncertain control input amongst different cases. …”

Continuous robust fault‐tolerant control and vibration suppression for flexible spacecraft without angular velocity

“…In the work of Xu et al, the FTC approach based on terminal sliding‐mode method was presented for finite‐time attitude stabilization of satellite, which also resolved the potential singularity problem of traditional terminal SMC designs. Han et al proposed an adaptive nonsingular terminal slid ing mode fault‐tolerant controller for the spacecraft with actuator faults, external disturbances, and model uncertainties, which was able to ensure the finite‐time convergence. The SMC introduced above contains two phases: the reaching phase and sliding phase, while the conventional SMC can only be robust on the sliding phase .…”

Fault Tolerant Control Using Fractional-order Terminal Sliding Mode Control for Robotic Manipulators

“…In fact, various adaptive schemes have been proposed to design FTC for a number of robotic applications to compensate actuator faults [10,17]. Moreover, with NFTSMC scheme, adaptive control has been proposed for spacecraft attitude tracking in the presence of actuator faults, actuator saturations, disturbances and inertia uncertainties [7].…”