Observer-based Fault-tolerant Control Research Articles

Observer-based fault-tolerant control design for a class of sampled-data nonlinear systems with bounded disturbances

Observer-based fault-tolerant control design for a class of sampled-data nonlinear systems with bounded disturbances

Fault-Tolerant Control of Stochastic High-Order Fully Actuated Systems.

In recent years, high-order fully actuated (HOFA) systems, founded by Prof. GR Duan, have recorded rapid progress for deterministic systems. However, the control issue of stochastic fully actuated systems is still an open problem. This study develops a novel stochastic HOFA system model that complements the existing HOFA methodology. Notably, stochastic signals can be considered in the proposed model, different from the case in the deterministic model. By adopting a high-order operator, equivalent control and stabilization control laws are realized to guarantee the global asymptotic stability in probability of the closed-loop system. For the system with sensor gain faults, an observer-based fault-tolerant control law is designed. Finally, the simulation results validate the effectiveness of the proposed control schemes.

DFIG in Wind Energy Applications with High Order Sliding Mode Observer-based Fault-Tolerant Control Scheme using Sea Gull Optimization

This paper describes a new method for maximizing power extraction from a wind energy conversion system (WECS) by using a doubly fed induction generator (DFIG) that operates below nominal wind speed. To maximize the collected power of a wind turbine (WTG) exposed to actuator failure, a fault-tolerant high-order sliding mode observer (HOSMO) and Seagull Optimization Algorithm with a model predictive controller (MPC) technique is proposed. Evaluate both the real state and the sensor error simultaneously using a higher-order sliding-mode observer. Active fault tolerant controllers are designed to regulate wind turbine rotor speed and power in the presence of actuator defects and uncertainty. With the growing interest in employing wind turbines (WTGs) as the primary generators of electrical energy, fault tolerance has been seen as essential to improving efficiency and reliability. This research focuses on optimal fault-tolerant pitch control, which is used to modify the pitch angle of wind turbine blades in the event of sensor, actuator, and system failures. A Seagull Optimization Algorithm (SOA) is proposed to tune controller parameters to improve the performance of WT. The proposed method has achieved 92% of power tracking performance when compared to existing method.

Observer-based fault-tolerant fixed-time attitude tracking control for rigid spacecraft without angular velocity measurement

This paper investigates the problem of adaptive nonsingular fast terminal sliding mode fixed-time tracking control method for rigid spacecraft without angular velocity measurement. First, a novel fixed-time extended state observer is proposed to obtain accurate estimates of both unmeasurable angular velocities and integrated disturbance. Then, based on this sufficient qualification, an adaptive fast nonsingular terminal sliding mode controller is designed to make the state of the following spacecraft track a target spacecraft even when the tracking system has an actuator fault. Adaptive technology is introduced to compensate for the effect of observation error on the controller. Using the Lyapunov function and fixed-time property, it is proved that the control scheme can ensure that the attitude tracking error converges to the neighborhood of the origin in a fixed time and is independent of the initial conditions. Finally, numerical simulation examples are carried out to evaluate the effectiveness of the proposed fixed-time method.

High order sliding mode observer-based fault-tolerant control scheme for DFIG in wind energy applications with model predictive controller

This research presents a novel fault-tolerant predictive power control method for a Doubly-fed induction generator (DFIG) used in wind turbine control systems. Due to the proposed control mechanism, the system can continue to function effectively despite open-circuit or short-circuit faults in the insulated-gate bipolar transistors (IGBTs) of the MPC controller. Depending on the type of problem and its location, the tolerant IGBT overcomes power oscillations and limits the power converter's potential switching states. By monitoring the optimal generator speed, wind turbine control systems strive to maximize power output. For wind turbines operating in the partial-load area, a fault-tolerant model predictive control strategy is recommended in order to achieve control goals despite disturbances, uncertainties, sensor, and actuator difficulties. A high order sliding mode observer (HOSMO) is used to evaluate both the actual states and sensor-faults at the same time. A high order sliding mode (HOSM) control strategy based on the MPC controller is used to regulate the speed of wind turbines in order to harness the wind's maximum power.

Active Adaptive Observer-Based Fault-Tolerant Control Strategy for a Class of T–S Fuzzy Systems With Unmeasurable Premise Variables

This paper addresses the problem of fault-tolerant output tracking control for a class of Takagi-Sugeno (T-S) fuzzy systems with unmeasurable premise variables subject to additive and multiplicative actuator faults and external disturbances. In nominal conditions, utilizing a quadratic Lyapunov function and non-parallel distributed compensation (non-PDC) technique, the suggested strategy delivers linear matrix inequality (LMI)-based constraints. Simultaneously design of the proportional-integral (PI)-like state feedback controller and fuzzy anti-windup compensator is achieved with the aim of output tracking. In the faulty case, by considering the nominal system as a reference model, a direct adaptive projection-based approach is developed using the T-S fuzzy modeling and control techniques to supply the adaptive fault-tolerant controller components. An enhanced proportional-integral (PI) state/fault observer with unmeasurable premise variables is introduced only to provide the estimation of states to be used in the proposed controller. The overall closed-loop system ensures the uniformly ultimately bounded (u.u.b) solutions for error dynamics. Two examples, subsuming an inverted pendulum and a chaotic power system, have been used to present the merits and efficiency of the suggested approach persuasively.

Design of structured [formula omitted] flight controllers: Passive fault-tolerant versus observer-based structures

This article presents the structured H∞ design and validation of two types of flight controller architectures: a passive fault-tolerant controller for the longitudinal motion and an active observer-based fault-tolerant controller for the lateral-directional motion. In the first, the controller follows the conventional Stability/Control Augmentation System (SCAS) structure, and its gains are obtained in continuous-time with the hinfstruct command by considering a set of elevator Loss-Of-Efficiency (LOE) faults. For the second, the conventional Luenberger observer-based controller structure is used, and the design aims to monitor the health of the aileron and rudder actuators in addition to provide active tolerance against LOE faults. Two different discrete-time designs are obtained for the latter, one focused on control performance optimization (using also the hinfstruct command), and the other on simultaneous control and observer performance optimization (using the systune command and under a slightly relaxed control performance constraint). For the two types of architectures, unmodeled dynamics are represented by uncertain bounded time delays modeled as pure delays or first-order Padé approximations. The resulting controllers are implemented on-board JAXA’s research airplane MuPAL-α, and not only is their practicality demonstrated but also control performance is validated via Aircraft-In-the-Loop (AIL) testing under gust-free and realistic gusty conditions. This demonstration is at a Technological Readiness Level (TRL) of 7–8, resulting in a high-level of confidence in the validity of the proposed flight control structures.

Switched-type unknown input observer-based fault-tolerant control for cyber-physical systems in the presence of denial of service attack

The problem of security control for cyber-physical systems (CPSs) is gradually becoming a popular research topic. In the presence of the denial-of-service (DoS) attack, this paper investigates the switched-type unknown input observer-based fault-tolerant control problem for multi-channel CPSs. Firstly, based on the sampling mechanism, a switched-type unknown input observer (SUIO) which can discard the outdated information is designed to obtain state/fault estimations, and converting the estimation error system stability analysis under DoS attack into that under SUIO. Then, to compensate the effect of actuator fault, an SUIO-based fault-tolerant controller is designed. And the input-to-state stability of the CPSs is analyzed. In comparison with the existing UIO studies, this paper considers the case of DoS attack affecting the transmission channel, and the impact of DoS attack on estimation effect can be effectively reduced by introducing the switching mechanism. Finally, based on the simulation results of the given experiments, the effectiveness of the proposed method is illustrated.

Low-Power Fault-Tolerant Control for Nonideal High-Order Fully Actuated Systems

This article presents a novel observer-based fault-tolerant controller framework for a class of nonideal time-varying high-order fully actuated systems (HOFASs). The HOFAS theory is an emerging nonlinear dynamical system theory, which can yield global stability. In order to improve the ability of HOFAS theory to handle parameter uncertainties, actuator faults, and measurement noises, a nonlinear extended state observer and low-power fully actuated controller framework is established in this article. Particularly, the linear framework conforms to the generalized separation principle and highlights the advantages of HOFAS parametric design. Moreover, the work takes into account fault tolerance and noise suppression in engineering applications, reducing the dependence of HOFAS theory on model accuracy. The uniformly bounded stability and noise suppression performance are also proved theoretically and illustrated experimentally.

Descriptor sliding mode observer based fault tolerant control for nuclear power plant with actuator and sensor faults

In sophisticated and complex system such as nuclear power plant, fault estimation and fault tolerant control always play an important role in maintaining the system stability and assuring satisfactory and safe operation. Thus, in this work a fault estimation and fault tolerant control scheme based on sliding mode theory is proposed for a pressurized water reactor type nuclear power plant considering simultaneous actuator and sensor faults. First, using descriptor sliding mode observer approach, an accurate estimation of the system states and sensor fault vector have been obtained simultaneously. Then, based on the estimated information, an integral type sliding mode control scheme is proposed to stabilize the resulting faulty system. With the help of Lyapunov stability theory, reachabilities of the proposed sliding mode surfaces are shown in both the state estimation space and the error estimation space, simultaneously. Finally, the efficacy of the proposed control scheme is shown by applying it to a nuclear power plant.

A sliding mode observer-based robust fault-tolerant control allocation for descriptor systems

The problem of designing an observer-based fault-tolerant control allocation mechanism for a multi-input multi-output (MIMO) uncertain descriptor system (DS) subjected to actuator faults/failures and external uncertainties is discussed in this paper. The proposed approach guarantees system performance and closed-loop stability using the integral sliding mode control (ISMC) and a fixed control allocation (CA) strategy. A robust sliding mode observer (SMO) is designed to estimate the states of the DS in a realistic setting. The sliding surface is constructed with the estimated states, following the ISMC principle. To meet the admissibility conditions of DS, a multivariable super-twisting sliding mode control (STSMC) algorithm is designed. The CA technique reallocates the control effort to the remaining healthy actuators on the occurrence of any fault/failure. Lyapunov-based stability is established for the closed-loop system with the controller–observer pair. Finally, the proposed design is validated by evaluating various actuator fault/failure situations.

Adaptive fuzzy observer based non-quadratic control for nonlinear system subject to actuator faults and saturation

This paper provides a new non-quadratic stabilization conditions based on adaptive fuzzy observer for a class of Takagi-Sugeno (T-S) fuzzy systems subject to external disturbances and both actuator faults and saturation. Firstly, an observer based fault tolerant control (FTC) is proposed, not only to estimate both system states and actuator faults but also to compensate for the actuator faults and to stabilize the faulty system with input constraints. The saturation effect is transformed into dead-zone nonlinearity and the generalized sector bound condition is used to estimate the attraction domain. To less the conservatism of the quadratic Lyapunov technique, a proper integral structure based on the non-quadratic function is investigated. The H∞ criteria is considered and the robust stabilization conditions of the faulty closed-loop system are expressed as a linear matrix inequalities (LMIs) optimization problem. Finally, the robustness and the advantages of the proposed approach are demonstrated through a mixed CSTR and a numerical example.

Observer-based fault tolerant control design for periodic piecewise time-varying systems: a fault estimation approach

ABSTRACT This study tackles the fault estimation issue for a continuous-time periodic piecewise time-varying systems (PPTVSs) with delays, fault signal and external disturbances. In particular, the PPTVSs are conjured up by segmenting the fundamental period of the periodic system into a finite number of subintervals. Moreover, fault estimator is designed in line with periodic piecewise observer systems to estimate the immeasurable states of the PPTVSs and the fault signal, simultaneously. Subsequently, in accordance with the estimated values of the fault signal and state dynamics, a fault-tolerant controller is devised. Moreover, by utilising Lyapunov stability theory and matrix polynomial lemma, sufficient criteria are procured in context of linear matrix inequalities to affirm the uniform boundedness of the undertaken system and error system. Further, relying on the acquired constraints, the precise configuration of the fault-tolerant control and observer gain matrices are proffered. Eventually, by offering two illustrative examples including mass-spring-damper system, the utility and potential of presented theoretical insights are validated.

Interval observer-based fault-tolerant control for discrete-time switched linear system

Interval observer-based fault-tolerant control for discrete-time switched linear system

Learning Observer-Based Sensor Fault-Tolerant Control of Distributed Generation in an Islanded Microgrid for Bus Voltage Stability Enhancement.

In order to improve robust operating performance and enhance bus voltage stability, a learning observer-based fault-tolerant control strategy is proposed for the distributed generation in islanded microgrid with sensor faults and uncertain disturbances. Firstly, the output feedback control theory and the linear matrix inequality method are used to design closed-loop controller for the voltage source inverter of distributed generation; secondly, a fault-tolerant model and control structure of the distributed generation in an islanded microgrid with sensor faults is analyzed. By employing the fault output signal conversion filter and proportional derivative type learning observer, the online estimation and real-time compensation of the sensor fault signal are realized. Thirdly, the system synthesis of output feedback control and fault-tolerant control is completed. Finally, the multi-scenario sensor fault scheme simulation experiment verifies that the proposed control strategy has strong sensor fault tolerance and adaptability.

A novel learning observer-based fault-tolerant attitude control for rigid spacecraft

This paper investigates a learning observer-based fault-tolerant control strategy for a rigid spacecraft attitude system with external disturbance, parameter uncertainty and actuator faults. An adaptive learning observer design approach, which does not require the upper bound information of generalized perturbation, is proposed to estimate the attitude angular velocities and reconstruct actuator faults accurately and quickly. On this basis, a fault tolerant attitude tracking control scheme is developed for spacecraft attitude stabilization by combining the estimation value and backstepping control technique. The stability of the faulty attitude system under the designed fault-tolerant control method is analyzed using Lyapunov framework. Finally, simulations are given to show the effectiveness of the proposed method.

Adaptive Fuzzy Observer Control for Half-Car Active Suspension Systems with Prescribed Performance and Actuator Fault

In this paper, an adaptive fuzzy observer-based fault-tolerant controller is designed for a half-car active suspension system under the presence of uncertain parameters, unknown masses of passengers, and actuator failures. To improve the control performance, fuzzy logic systems (FLSs) are employed to approximate the unknown functions caused by uncertain dynamics of the suspension system. Then, an adaptive control design is developed to compensate for the effects of a non-ideal actuator. To improve passenger comfort, both vertical and angular motions are guaranteed simultaneously under the predefined boundaries by the prescribed performance function (PPF) method. Besides, the objectives of handling stability and driving safety are also considered to enhance the suspension performance. The system stability is proved according to the Lyapunov theory. Finally, the effectiveness of the developed approach is evaluated by comparative simulation examples on the half-car model. The simulation results show that the proposed control can improve the suspension performance as the RMS acceleration value is decreased by 68.1%.

Observer-based fault-tolerant control for non-infinitely observable descriptor systems with unknown time-varying state and input delays

This paper presents a fault-tolerant control (FTC) scheme for a class of non-infinitely observable descriptor systems (NIODS) that is affected by unknown time-varying state and input delays. The NIODS is first transformed into a form facilitating the manipulation of design freedom inherent in its structure. Some of the system states are then treated as unknown inputs to form an infinitely observable reduced-order system. A sliding mode observer (SMO) is applied to estimate the states and faults based on measurable signals. Next, a memoryless controller is designed using these estimates. Design conditions for the SMO and controller are derived in the form of linear matrix inequalities. In the case where the state and input delays are different, the FTC scheme is designed to limit the effect of the mismatch in delays on the output. In the case of equivalent state and input delays, the FTC scheme is designed so that the system output asymptotically converges to zero. A simulated example is lastly performed to verify the scheme’s effectiveness.

Adaptive neural network decentralized fault-tolerant control for nonlinear interconnected fractional-order systems

This paper studies the neural network (NN) decentralized observer-based fault-tolerant control (FTC) design problem on the nonlinear interconnected fractional-order systems. The considered fractional-order systems have the non strict-feedback form and are subject to immeasurable states and intermittent actuator faults. Neural networks (NN) are employed to identify the unknown dynamics, and a NN decentralized observer is formulated to estimate unknown states. By constructing appropriate Lyapunov functions and using the backstepping dynamic surface control (DSC) technique, a NN observer-based decentralized FTC method is developed. It is proved that the developed NN decentralized FTC scheme can guarantee that the controlled interconnected fractional-order system is stable and the track errors can be made smaller. Finally, a practical simulated example is provided to check the validity of the NN decentralized FTC algorithm.

Integrated fault estimation and tolerant control for discrete-time switched affine systems with mixed switching laws

This study is concerned with the issues of simultaneous actuator fault estimation and the design of observer-based fault-tolerant control for a class of discrete-time switched affine systems subject to a mixed switching scheme. A mixed switching law, which is composed of constant dwell-time and state-dependent switching logic, is introduced to avoid the chattering phenomenon of augmented error switched affine system, and a discretized Lyapunov function approach is used to ensure the asymptotic stability of error systems. Then, the simultaneous fault estimation and tolerant control based state observer are studied and the corresponding design problem is transformed into resolving a multi-objective optimization for augmented error systems with H∞ performance index. Moreover, the gains of fault estimator and tolerant controller are explicitly calculated via resolving the conditions of linear matrix inequalities. Finally, a practical application of DC motor/Buck–Boost converter is illustrated to verify the effectiveness and practicability of the developed approach.