Adaptive Fault-tolerant Control Approach Research Articles

Fixed-time nonsingular adaptive attitude control of spacecraft subject to actuator faults

In this article, a fixed-time adaptive fault-tolerant control approach is presented for the attitude tracking of rigid spacecraft subject to inertia uncertainties, external disturbances, and actuator faults. The designed controller is developed as a combination of the fixed-time integral sliding mode control and parametric adaptation technique. The fixed-time integral sliding mode controller has no singularity problem naturally by constructing a novel integral sliding mode surface based on the bi-limit homogeneous method. Moreover, the parametric adaptation technique is incorporated to estimate the total uncertainty indirectly. Benefiting from this development, the designed controller is smooth with no obvious chattering phenomenon and does not require any information on the upper bound of the total uncertainty. The attitude and angular velocity tracking errors under the designed controller can regulate to the minor fields about zero in fixed time. A remarkable feature of the designed controller is that it is not only robust against inertia uncertainties and external disturbances, but also insensitive to multiple types of actuator faults. Finally, simulation results show the effectiveness and merits of the presented control approach.

Adaptive dynamic surface output feedback control for a class of quadrotor aircraft with actuator faults

PurposeThe purpose of this study is to propose an adaptive fault-tolerant control approach based on output feedback for a class of quadrotor unmanned aerial vehicles system. In the event of a controlled actuator failure, a stable flying of the aircraft can be achieved by selecting an appropriate sliding mode surface.Design/methodology/approachAiming at the actuator failure of quadrotor aircraft during flight in the controllable range, a dynamic surface sliding mode passive fault-tolerant controller based on output feedback is designed based on the strong robustness of sliding mode method. Due to the unknown nonlinearity dynamics and parameter uncertainties in the system, a nonlinear observer is used to estimate them online.FindingsThe stability of the suggested algorithm is established using appropriate Lyapunov functions, and the performance of the proposed control approach is demonstrated using hardware-in-the-loop simulation.Originality/valueAn error performance function is introduced into the controller to ensure the convergence speed and accuracy of errors are within the predetermined range. By using the norm estimation method, there is only one parameter that needs to be updated in each step of the control process, which considerably minimizes the calculation burden. Finally, the validity of the proposed control scheme is verified on the hardware-in-the-loop simulation, and the results show that the proposed control method has achieved the desired results.

Prescribed performance adaptive fault tolerant control approach for nonlinear large‐scale systems with time delay interconnection and dead zone input

AbstractIn this study, a prescribed performance adaptive fault tolerant tracking control scheme is presented for a class of nonlinear large‐scale systems with time delay interconnection, dead zone input, and actuator fault. The radial basis function neural networks are used to approximate unknown nonlinear functions. Different from the barrier Lyapunov functions used to achieve the symmetrical prescribed performance, a new error transformation is introduced in this study to achieve the desired asymmetrical prescribed performance. In addition, Nussbaum function is introduced to solve the difficulties caused by dead zone input and actuator fault. Based on the appropriate Lyapunov–Krasovskii functions, the effect of time delay interconnection could be compensated. By using backstepping procedures, an adaptive fault tolerant tracking control approach is developed for the considered large‐scale systems, and the stability of the closed‐loop systems is analyzed by Lyapunov theory. Meanwhile, the prescribed performance of the tracking error could be guaranteed. Finally, the effectiveness of the proposed control approach is illustrated by two simulation examples.

Event-Triggered Robust Adaptive Sliding Mode Fault-Tolerant Control For Nonlinear Systems

In this article, a novel two-channel event-triggered adaptive fault-tolerant control approach is designed to handle the degree freedom nonlinear system with disturbances. The main purpose of this article is to maintain the output tracking ability while reducing the transmission burden. The objective is realized by designing a novel adaptive sliding mode controller integrated with the event trigger mechanism. Concretely, the state, actuator fault, and lumped disturbance information are obtained by designing a composite observer, in which the disturbance upper bound is not needed. Then, the obtained information is utilized to design the controller. In the proposed method, the lumped disturbance and nonlinear estimated values are contained in the sliding mode manifold to enhance the robustness. Additionally, an adaptive parameter is also integrated into the controller to compensate for the disturbance. Furthermore, a specific event-triggered controller is proposed to keep the tracking ability and to reduce the transmission load of the fault system. The no Zeno phenomenon performance is analyzed and, finally, the applications to a suspension system and a two-tank system are given to show the fault tolerance ability of the proposed method.

Distributed adaptive fault-tolerant control approach to cooperative output regulation for linear multi-agent systems

In this paper, the cooperative output regulation problem for linear multi-agent systems with actuator faults is considered. It is assumed that the actuator faults are outage faults and loss-of-effectiveness faults. First, a distributed finite-time observer is designed to estimate the state of the exosystem. Based on the state of the finite-time observer, a distributed adaptive fault-tolerant controller is designed. Then, it is shown that the cooperative output regulation problem can be solved with the proposed fault-tolerant controller. Compared with the existing cooperative output regulation results, a novel lemma is introduced to guarantee the solvability of the regulator equations under actuator faults, and the developed controller is effective to compensate the actuator faults. Finally, a simulation example is presented to show the validity of the proposed method.

A fault tolerant tracking control for a quadrotor UAV subject to simultaneous actuator faults and exogenous disturbances

ABSTRACTAn observer-based robust adaptive Fault Tolerant Control approach is proposed in this paper to tackle the problem of trajectory tracking for a quadrotor unmanned aerial vehicle (UAV) suffering simultaneous actuator faults, exogenous disturbances and actuator saturation limits. An adaptive fuzzy state observer is proposed to estimate the immeasurable states by using fuzzy logic systems to approximate the unknown nonlinear functions of the uncertain system model. Based on the estimates of the fuzzy observer, an Integral Terminal Sliding Mode Controller that guarantees finite time convergence of the states to a small neighbourhood of zero, even under impaired conditions, is developed. Stability analysis was carried over using the Lyapunov method. The proposed approach was implemented to a quadrotor UAV and its performance was assessed under nominal conditions, and by subjecting the quadrotor to disturbances, simultaneously occurring actuator faults and input saturation limits. Excellent tracking performance and robustness even under worst-case scenarios are among the positive features of the proposed approach.

Adaptive Fault-Tolerant Control of Wind Turbines With Guaranteed Transient Performance Considering Active Power Control of Wind Farms

As high-order nonlinear large-scale systems, wind farms composed of multiple wind turbines (WTs) need to adopt active power control (APC) to track the power set points, rather than the maximum power points. In this paper, the proportional distribution strategy is utilized to specify the power set point according to the available output power of each WT based on the ultra-short-term wind speed prediction. Then, we convert the APC problem into the rotor speed tracking control problem, and a robust adaptive fault-tolerant control approach based on the barrier Lyapunov function is developed to track the desired power signal of each WT with guaranteed transient performance and robustness to actuator faults. The effectiveness and the merit of the proposed approach are validated by applying it to the APC of a wind farm.

Robust adaptive sliding-mode fault-tolerant control with L 2 -gain performance for flexible spacecraft using redundant reaction wheels

A robust adaptive fault-tolerant control approach for attitude tracking of flexible spacecraft is proposed for use in situations when there are reaction wheels/actuator failures, external disturbances and time-varying inertia-parameter uncertainties. More specifically, a robust controller based on sliding-mode control scheme is first designed to ensure that the equilibrium point in the closed-loop system is uniform ultimate bounded stability, incorporating constraints on actuator failures, whose failure time instants, patterns and values are unknown, as motivated from a practical spacecraft control application. Then, this controller is redesigned such that an assumption on a bound required of the unknown and time-varying inertia matrix is released by using online estimation for this bound. The prescribed robust performance is also evaluated by L2-gain less than a given small level for the penalty output signal. Complete stability and performance analysis are presented, and illustrative simulation results of an application to flexible spacecraft show that the high precise attitudes control and vibration suppression are successfully achieved using various scenarios of control effect failures.

Adaptive backstepping fault-tolerant control for flexible spacecraft with unknown bounded disturbances and actuator failures

In this paper, a robust adaptive fault-tolerant control approach to attitude tracking of flexible spacecraft is proposed for use in situations when there are reaction wheel/actuator failures, persistent bounded disturbances and unknown inertia parameter uncertainties. The controller is designed based on an adaptive backstepping sliding mode control scheme, and a sufficient condition under which this control law can render the system semi-globally input-to-state stable is also provided such that the closed-loop system is robust with respect to any disturbance within a quantifiable restriction on the amplitude, as well as the set of initial conditions, if the control gains are designed appropriately. Moreover, in the design, the control law does not need a fault detection and isolation mechanism even if the failure time instants, patterns and values on actuator failures are also unknown for the designers, as motivated from a practical spacecraft control application. In addition to detailed derivations of the new controller design and a rigorous sketch of all the associated stability and attitude error convergence proofs, illustrative simulation results of an application to flexible spacecraft show that high precise attitude control and vibration suppression are successfully achieved using various scenarios of controlling effective failures.