Fault Compensation Research Articles

Integral Non-Singular Terminal Sliding Mode Consensus Control for Multi-Agent Systems with Disturbance and Actuator Faults Based on Finite-Time Observer.

This paper studies the consensus fault-tolerant control problem of a class of second-order leader–follower multi-agent systems with unknown disturbance and actuator faults, and proposes an integral non-singular terminal sliding mode control algorithm based on a finite-time observer. First, a finite-time disturbance observer was designed based on a combination of high-order sliding mode and dual layers adaptive rules to realize fast estimation and compensation of disturbance and faults. Then, a sliding surface with additional integral links was designed based on the conventional sliding surface, and an integral non-singular terminal sliding mode controller is proposed to realize the robust consensus in finite time and accurately diminish the chattering phenomena. Finally, a numerical example and simulation verify the effectiveness.

Integrated State/Fault Estimation and Fault-Tolerant Control Design for Switched T–S Fuzzy Systems With Sensor and Actuator Faults

This article proposes an integrated design approach addressing the state/fault estimation (SFE) and fault-tolerant control (FTC) issues for switched T–S fuzzy systems with sensor and actuator faults and external disturbances. A switched fuzzy observer is developed to simultaneously estimate the system states and the sensor and actuator faults from measurement outputs affected by sensor faults. Based on this observer, a switched fuzzy FTC is designed to stabilize the closed-loop system and compensate for the effects of different considered faults, taking into account the presence of external disturbances. The mutual coupling between the estimation unit (SFE) and the control unit (FTC) supports the integrated design of these two units instead of the separated one. However, the separated design is the most adopted in the literature because the integrated design leads to complex stability conditions in the form of bilinear matrix inequalities. This work focuses on the integrated design considering the different interactions between the observer and the controller and thus ensuring good performance in terms of estimation, control, robustness, and fault compensation. For this purpose, a two-step integrated design strategy and a single-step integrated design strategy are proposed to formalize the integrated SFE and FTC design as linear matrix inequalities instead of bilinear ones. These strategies are based on the mode-dependent average dwell time concept, the piecewise Lyapunov function technique, and the robust <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> approach. The applicability and efficiency of the developed results are illustrated by studying a numerical example and a single-link robotic manipulator.

Consensus Control of Multi-Agent Systems Using Fault-Estimation-in-the-Loop: Dynamic Event-Triggered Case

The paper develops a novel framework of consensus control with fault-estimation-in-the-loop for multi-agent systems (MASs) in the presence of faults. A dynamic event-triggered protocol (DETP) by adding an auxiliary variable is utilized to improve the utilization of communication resources. First, a novel estimator with a noise bias is put forward to estimate the existed fault and then a consensus controller with fault compensation (FC) is adopted to realize the demand of reliability and safety of addressed MASs. Subsequently, a novel consensus control framework with fault-estimation-in-the-loop is developed to achieve the predetermined consensus performance with the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l_{2}-l_{\infty}$</tex> constraint by employing the variance analysis and the Lyapunov stability approaches. Furthermore, the desired estimator and controller gains are obtained in light of the solution to an algebraic matrix equation and a linear matrix inequality in a recursive way, respectively. Finally, a simulation result is employed to verify the usefulness of the proposed design framework.

Nonsingular fractional-order integral fast-terminal sliding mode control for underactuated shipboard cranes

Lack of actuators creates many challenges in controlling underactuated systems. Additional difficulty arises when underactuated systems are subject to actuator faults, parametric uncertainties, and disturbances. We develop an adaptive robust controller for such systems by combining various advanced techniques with many benefits. The core of the controller, which is based on nonsingular integral fast-terminal sliding mode, ensures high robustness and quick finite-time convergence, reduces chattering, and prevents singularity. Fault-tolerant control provides good fault compensation. Fractional derivatives make the control structure flexible because fractional orders are adjustable gains. Self-tuning control creates an adaption mechanism that endows the system an intelligent behavior. Two layers of the sliding mode that contain fractional derivative, terminal power, and definite integral ensure terminal Mittag–Leffer stability. We test the proposed approach on an underactuated floating crane through a simulation and an experiment. A comparison with other methods shows the superiority of our approach.

Non-droop-control-based cascaded superconducting magnetic energy storage/battery hybrid energy storage system

Existing parallel-structured superconducting magnetic energy storage (SMES)/battery hybrid energy storage systems (HESSs) expose shortcomings, including transient switching instability, weak ability of continuous fault compensation, etc. Under continuous faults and long-term power fluctuations, SMES part in existing SMES/battery HESSs will run out its energy and fail to quickly respond to subsequent disturbances. This paper proposes a new cascaded topology of SMES/battery HESS. It remains the superiorities of conventional HESS schemes from aspects of fast response (~5 ms) and large energy capacity. Moreover, it avoids the use of droop control and then resolves the transient dynamic problem between the switchover of the battery and SMES. In the cascaded HESS, both the energy storages simultaneously activate when power variation is detected, where the SMES is just for compensating the initial power insufficiency before the full-power start of the battery. The stored energy in SMES can be sustainably utilized and available for multiple repeated power compensations. A simulation is established to discuss the performance of the HESS as an uninterruptable power source with comparisons of the other three cases in aspects of response time, energy capacity, and capital cost. Finally, a scaled-down experiment is tested, and performance comparisons are discussed to verify the technical advancement of cascaded HESS.

Open-circuit faults diagnosis and Fault-Tolerant Control scheme based on Sliding-Mode Observer for DFIG back-to-back converters: Wind turbine applications

One of the most common types of wind turbines is the Doubly-Fed Induction Generator with a back-to-back converter. The Insulated Gate Bipolar Transistor switch’s open-circuit fault rate compared to the fault total rate in the wind turbine is noteworthy. The converter Insulated Gate Bipolar Transistor open-circuit causes a drawback in output current and as a result, the production performance of the turbine is reduced. In this article, a new method is presented for multiple Insulated Gate Bipolar Transistor open-circuit faults for open-circuit faults diagnosis. After the fault occurs, to maintain the performance of the turbine, fault compensation is performed based on the new Fault-Tolerant Control scheme. The proposed method is inexpensive, and for fault detection and location determining no need for additional sensors and hardware. This method uses residual output based on the Sliding Mode Observer with SAT function to detect faulty phase and overcome chattering Doubly-Fed Induction Generator converter. To residual evaluate and reduce the false alarm rate against changes in operating points and transient currents, the adaptive threshold is used. For efficient control of active or reactive power and dc-link voltage, a six-leg converter control based on Simplified Space Pulse Width Modulation is replaced by a five-leg converter based on Space Vector Modulation. Several experimental results using hardware in the loop Doubly-Fed Induction Generator test setup with a back-to-back converter are presented. It is shown the fault diagnostic algorithm is effective and robust against false alarms for both rotor and stator-side converters. The experimental result presents that the Fault Tolerant Control scheme can make power switch fault easily managed by the hardware reconfiguration and new control strategy adjusting.

Real-Time Diagnosis and Fault-Tolerant Control of a Sensor Single Fault Based on a Data-Driven Feedforward-Feedback Control System

Fault diagnosis is studied based on the system type, which facilitates the realization of the engineering configuration and improves the diagnosis efficiency. The fault-tolerant control method is unified based on the concept of fault compensation. According to the dynamic characteristics of the system, the method takes the boundary value of no-fault signal fluctuation as the basis for fault detection, then takes the changing intensity of the solenoid valve control signal after the fault occurs as the fault location basis. Finally, it takes the difference or ratio of the signals before and after the fault occurs as the fault estimation. For the basis of fault separation, the integral value of the fitting equation between the fault signal and time is used as the Eigenvalue of fault type separation to comprehend fault separation. A program is written in C++ and combined with MATLAB/S-Fun function to realize fault tolerance. At the same time, the dynamic model calibration and real-time fault diagnosis, and fault-tolerant control process of sensor fault diagnosis are provided, which makes it suitable for general engineering feedforward-feedback systems and has a certain suppression effect on noise. The simulation results verify that the method is not only viable and it is exact.

Performance-improved finite-time fault-tolerant control for linear uncertain systems with intermittent faults: an overshoot suppression strategy

This paper presents a novel prespecified finite-time and overshoot-restrained fault-tolerant tracking control scheme to compensate the intermittent faults in linear uncertain systems. Starting from the system tracking error dynamics model, we design a speed excitation function to improve the response speed of the control. A finite-time performance index function is established in the zero-sum game framework for the fault-free optimal control policy. Based on Lyapunov stability theory, a fault compensation oriented fault estimation and diagnosis method is proposed to ensure the uniformly ultimately bounded stability of tracking errors. It is noteworthy that the proposed speeding fault-tolerant control can accelerate the trajectory tracking, narrow the upper bound of tracking errors and restrain the overshoot. Numerical and practical experiments fully illustrate the effectiveness of the proposed strategy.

Intelligent Discrete Sliding Mode Predictive Fault-Tolerant Control Method for Multi-Delay Quad-Rotor UAV System Based on DIECOA

This paper introduces a novel intelligent sliding mode predictive fault-tolerant control method based on the Dynamic Information Exchange Coyote Optimization Algorithm (DIECOA), which is applied to a quad-rotor UAV system with multi-delay and sensor fault. First, the system nonlinearity and sensor fault are dealt with by means of interpolation transformation and system state expansion, and an equivalent system is obtained. Second, the quasi-integral sliding mode surface is used to construct the prediction model so that the initial state of the system is located on the sliding mode surface, and the global robustness is guaranteed. Third, this paper introduces an improved fault and disturbance compensation term, which effectively weakens the adverse effect of time delays and enhances the FTC performance of the system. Fourth, the Dynamic Information Exchange (DIE) strategy is designed to further improve the coyote individual replacement mechanism and speeds up the solution and convergence speed of the method in this paper. Finally, the simulation is carried out on the fault-tolerant simulation platform of the quad-rotor Unmanned Aerial Vehicle (UAV), and the results show the rationality of the method.

Composite neural learning event-triggered control for dynamic positioning vehicles with the fault compensation mechanism

This paper focus on the novel composite neural learning event-triggered control for dynamic positioning vehicles with the fault compensation mechanism. In the proposed algorithm, the system uncertainties are tackled with by incorporating the dynamic surface control (DSC) and the robust neural damping techniques. Besides, the serial–parallel estimation model (SPEM) is developed to produce the prediction errors, which could be employed to derive the corresponding composite adaptive law. And the unknown actuator faults and gain uncertainties are effectively compensated for merits of the composite intelligent learning method. Furthermore, the idea of relative threshold strategy is utilized to construct the event-triggered mechanism. The event-triggered input could reduce the communication burden in the channel from controller to actuators. Through the direct Lyapunov theory, the parameters setting can be derived to guarantee the semi-global uniformly ultimately bounded (SGUUB) stability of all error signals in the closed-loop system. Finally, the effectiveness of the proposed algorithm is validated through the simulation experiments.

Power Regulation and Fault Diagnostics of a Three-Pond Run-of-River Hydropower Plant

Hydropower generation is one of the most prominent renewable sources of power. Run-of-river hydropower is like traditional hydropower but has significantly less environmental impact. Faults in industrial processes are a cause for large amounts of losses in monetary value and off times in industrial processes and consumer utilities. It is more efficient for the system to identify the occurring faults and, if possible, to have the processes running without interruption with the occurrence of a fault. This work uses a model previously proposed—the three-pond hydraulic run-of-river system and integrates it with a turbine and regulated power generation. After integration of the hydraulic system with the turbine and power generation, we then design a diagnostic system for commonly occurring faults within the system. Mathematical models of the faults are formulated and residues are calculated. Fault detection and identification is achieved by analyzing the residues and then a fault-tolerant control is proposed. The Fault Diagnostic Module can correctly detect the faults present and offers sufficient fault compensation to make the system run nearly normally in the event of fault occurrence. With the emergence of distributed power generation smart grids and renewable energy, this fault diagnostic is able to reliably offer uninterrupted power to the grid and thus to consumers.

Adaptive Sliding Mode Fault Compensation for Sensor Faults of Variable Structure Hypersonic Vehicle.

This paper investigates the sensor fault detection and fault-tolerant control (FTC) technology of a variable-structure hypersonic flight vehicle (HFV). First, an HFV nonlinear system considering sensor compound faults, disturbance, and the variable structure parameter is established, which is divided into the attitude angle outer and angular rate inner loops. Then a nonlinear fault integrated detector is proposed to detect the moment of fault occurrence and provide the residual to design the sliding mode equations. Furthermore, the sliding mode method combined with the virtual adaptive controller constitutes the outer loop FTC scheme, and the adaptive dynamic surface combined with the disturbance estimation constitutes the inner loop robust controller; these controllers finally realize the direct compensation of the compound sensor faults under the disturbance condition. This scheme does not require fault isolation and diagnosis observer loops; it only uses a variable structure FTC with a direct estimation algorithm and integrated residual to complete the self-repairing stable flight of variable-structure HFV, which exhibits a high reliability and quick response. Lyapunov theory proved the stability of the system, and numerical simulation proved the effectiveness of the FTC scheme.

Robust ADP-Based Sliding-Mode Fault-Tolerant Control for Nonlinear Systems with Application to Spacecraft

This paper considers a novel fault-tolerant control (FTC) scheme for a category of cascade nonlinear systems with mismatched uncertainties and unknown actuator faults. The robust adaptive dynamic programming (RADP) is used to design a novel optimal sliding surface (SS) off-line, which renders the corresponding sliding-mode dynamics able to obtain robustness of stability to mismatched uncertainties. Subsequently, a simple sliding-mode control (SMC) with the adaptive fault compensation is developed to guarantee reachability of the sliding mode. Then, it is proven that the weight errors of neural networks (NN) of RADP and the closed-loop system are stable based on Lyapunov stability theory. In the simulation section, this proposed scheme is used to deal with the attitude FTC of a spacecraft, and simulation results verify the effectiveness of the proposed novel control scheme.

Unscented-Kalman-filter-based single-phase adaptive reclosing of shunt-compensated extra-high-voltage transmission lines

This paper proposes a novel two-stage adaptive reclosing mechanism for shunt-compensated extra-high-voltage transmission lines. In the first stage, secondary arc extinction peak-based criterion (SAEPC) is established to monitor the precise instant of secondary arc extinction. The approach depends on the magnitude of the faulty phase voltage and the estimated weighted lower-order harmonics. The harmonics root mean square factor (HRF) is presented in the second stage for fault classification, i.e., temporary or permanent. The proposed scheme not only identifies the quenching instant regardless of fault location, compensation level, and arc extinction speed but also determines the nature of the fault. Simulation studies demonstrate the effectiveness and reliability of the proposed scheme and its ability to mitigate the limitations of existing single-criterion harmonics-based reclosing techniques.

Fault tolerant consensus control of multi-agent systems under dynamic event-triggered mechanisms

In this paper, the fault-tolerant consensus control (FTCC) problem is studied for multi-agent systems (MASs) with the dynamic event-triggered mechanism (DETM). To ease the communication burden, DETM governed by an additional internal dynamical variable is introduced. A novel fault-tolerant controller is presented to mitigate system performance degradation caused by failures, where a simple fault compensator is constructed through a protocol-based observer. Then, some sufficient conditions are established to examine the bounded consensus while optimizing the predetermined quadratic cost criterion. In addition, the explicit expression of the desired controller is also parameterized through orthogonal decomposition. Finally, two simulation results are made for the sake of verifying the effectiveness of the developed FTCC scheme, the fault compensation test as well as the quadratic cost one.

Adaptive bipartite output consensus of nonlinear fractional-order multi-agent systems

A distributed control approach is proposed for a class of fractional-order multi-agent systems with unknown nonlinearities under signed bipartite digraphs. Unlike the existing results, the follower's dynamics are studied with strict-feedback fractional-order form as well as a general class of actuator faults with unknown magnitude, pattern and occurrence time is studied. To provide a simple and efficient control strategy, first a novel command fractional-order filter based on the backstepping design is proposed such that the difficulty of calculation of the fractional derivative order of the virtual control laws is removed, as well as improving the bipartite output consensus accuracy. Then, to cope with dynamic's uncertainties, the proposed method is integrated with adaptive neural approximator and minimal learning parameter scheme which reduces communication loads. Besides, a distributed fault compensation protocol based upon the proposed command fractional-order filter and relative output information of neighbours' agents is extended to ensure bipartite output consensus, without relying on any global information of the singed digraph as well as any explicit fault detection mechanism. Finally, it is guaranteed that all the error signals within the closed-loop network system are converged into adjustable compact sets around the origin. The simulation results verify the validity of the presented control approach.

Monte Carlo Analysis of Bayesian Optimization-based Pitch Controller with Pitch Fault Compensation for Offshore Wind Turbine

Offshore wind turbine (WT) rotors are subjected to asymmetrical loads, resulting in enhanced fatigue of the blade structures, which requires reliable load mitigation techniques (e.g. individual pitch control, IPC). The IPC-enhanced pitch motion increases the occurrence of pitch actuator faults. This phenomenon has accelerated the emergence of new research areas combining IPC with the fault tolerant control (FTC)-based fault compensation. The research considering the IPC and pitch system-related FTC is referred to as a fault-tolerant IPC “co-design” scheme. However, it is important to enhance the robustness of this scheme by careful design of the IPC system. The robustness is tuned using a Bayesian optimization-based Proportional-Integral PI control. The Bayesian optimization algorithm is adopted to search for optimal controller coefficients by evaluating the Gaussian process model between the designed objective function and the coefficients. The pitch actuator faults are estimated and compensated by the robust unknown input observer UIO-based FTC strategy. The robustness and effectiveness of this “co-design” scheme are verified using the 5MW NREL FAST WT with Monte Carlo simulations.

Sensor Fault Tolerant Control for Hybrid Systems With Sinusoidal Disturbance

This paper aims to design of an active fault-tolerant control AFTC of switched systems in the presence of sensor fault and periodic disturbances. AFTC requires sensor fault estimation. Thus, a data-based projection approach is proposed based on performance measures that allow fault estimation without relying on mathematical models and fault assumptions. A new switching control strategy is proposed for fault compensation and recovering the desired performances. These techniques integrate a bank of controllers, corresponding to a set of partial models to design a set of switching control laws, compensating for the fault effect and attenuating the disturbance. A new linear matrix inequality based on Lyapunov stability analysis is proposed to compute control gains. This technique allows finding the optimal values of the control gains matrices, which ensure both sensor fault compensation and disturbance attenuation. A comparative study of the proposed strategy with existing work is carried out to show the effectiveness of the designed fault-tolerant control.

Universal System for Detection and Compensation of Current Sensor Faults in Three-Phase Power Electronic Systems

Abstract The article discusses the universal current sensor fault detection and compensation mechanism, which can be applied in three-phase power electronics (PE) symmetrical system. The mechanism is based on the assumption that a symmetrical system can be described using different components in the stationary reference frame. The solution given in article as a Cri-base detector was tested in electrical drives with induction motors (IMs) and permanent magnet synchronous motors (PMSMs). This study also proves that the same algorithm can work stable in active rectifier systems. Such an application of this detector has not been previously reported in the literature. The article describes the detection of various types of faults in different phases. The fault-tolerant voltage-oriented control (FTVOC) of an active rectifier is compared with previously described solutions for IMs and PMSMs. By analysing in various types of systems, the work proves the universality of the detector based on Cri markers.

Current Sensor Fault Reconstruction and Compensation of an AC-Voltage Sensorless Controlled Single Phase Grid Connected Converter using PI-Observers

Current Sensor Fault Reconstruction and Compensation of an AC-Voltage Sensorless Controlled Single Phase Grid Connected Converter using PI-Observers