Fault-tolerant Control Performance Research Articles

Dissipativity-Based Integrated Fault Estimation and Fault Tolerant Control for IT2 Polynomial Fuzzy Systems With Sensor and Actuator Faults

The integrated fault estimation and fault-tolerant control scheme is developed in this paper for a series of interval type-2 polynomial fuzzy systems with both sensor faults and actuator faults, where the bi-directional influence between fault estimation unit and fault-tolerant control unit is investigated. Considering the existence of sensor faults, unmeasurable premise variables are investigated for more general situations and Class III state/fault estimation observers are established for the final fault estimation and fault-tolerant control purposes. To increase design flexibility and reduce physical implementation complexity, the proposed method allows the observer and original system to share asynchronous membership functions and a different number of fuzzy rules. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(\mathcal{Q,S,R}) \,-\, \alpha$</tex-math></inline-formula> dissipative performance index is also introduced to fulfill a wider vary of perfor-mance requirements. Membership-function-dependent stability constraints are given in the format of bi-linear polynomial matrix inequalities to obtain less conservative results, which are computed by a two-step path-following method. Superiority and validity are demonstrated by an inverted pendulum example in terms of estimation errors, fault-tolerant control performance and control inputs.

A Novel Framework of Cooperative Design: Bringing Active Fault Diagnosis Into Fault-Tolerant Control.

Fault-tolerant control (FTC) may conceal fault symptoms, thereby increasing the difficulty of fault diagnosis (FD). In this article, a novel framework for the cooperative design of active FD and FTC is proposed to optimize FD performance while maintaining fault-tolerance performance. The proposed framework consists of four steps: 1) controller design; 2) residual generation; 3) performance evaluation; and 4) gain tuning. First, a controller with undetermined gains is constructed, and a fault detection observer is designed to generate residuals that can indicate the fault. Then, the performance of fault detection is evaluated. Finally, suboptimal controller gains are obtained by solving an optimization problem. Within the framework of the collaborative design, the occurring faults can be detected faster and more accurately, and the performance of FTC can be guaranteed at the same time. A simulation study is provided to demonstrate the effectiveness of the developed framework.

Event-Triggered Fault-Tolerant Control for Nonlinear Networked Control Systems

This paper addresses the communication congestion and actuator fault in a nonlinear networked control system. A weighted average event-triggered mechanism adopted the weighted average of data packets is proposed to alleviate the communication congestion and save the network communication resources. Meanwhile, based on the system state estimation and fault estimation obtained by a state-fault observer, a fault-tolerant controller is designed to compensate and reduce the influence of fault and nonlinear factors in the networked control systems. The stability of the closed-loop system is proved by the Lyapunov–Kroasovskii theory, and the gains of the observer and controller are obtained by linear matrix inequalities. The feasibility of the proposed scheme is verified by the networked motor control system. The proposed weighted average event-triggered fault-tolerant control scheme can reduce the data transmission without affecting system performance. Meanwhile, it not only has fault-tolerant control performance but also reduces the influence of nonlinear factors on the system output.

Performance Comparison of Fault-Tolerant Control for Triple Redundant 3 × 3-Phase Motors Driven by Mono-Inverter

In this article, the fault-tolerant control (FTC) strategy based on current redistribution is compared for three types of triple redundant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 3$ </tex-math></inline-formula> -phase motor: surface-mounted permanent magnet synchronous motor (SPMSM), synchronous reluctance motor (SynRM), and permanent magnet-assisted synchronous reluctance motor (PMa-SynRM), under a single-phase open-circuit fault. The output torque of SPMSM and SynRM is produced by permanent magnet (PM) torque and reluctance torque, respectively. Nevertheless, for PMa-SynRM, it is necessary to determine the distribution ratio of PM torque and reluctance torque in the proposed FTC strategy. By comparing the FTC performance of motors, the conclusions are as follows: 1) torque ripple of the SPMSM can be completely suppressed; 2) torque ripple minimization for the SynRM and PMa-SynRM can be realized; and 3) optimal solution obtained in SynRM can also be applied to the PMa-SynRM when the load is heavy. In addition, to reduce the complexity and improve the reliability of the control system, a mono-inverter-driven triple-paralleled control system is constructed in healthy and postfault operations. The comparison results of the FTC strategy for three types of motor are obtained by simulation. And the experimental results based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\,\times \,3$ </tex-math></inline-formula> -phase PMa-SynRM are accomplished to verify the feasibility of the theory.

Sensor Fault-Tolerant Control of Microgrid Using Robust Sliding-Mode Observer.

This work investigates sensor fault diagnostics and fault-tolerant control for a voltage source converter based microgrid (model) using a sliding-mode observer. It aims to provide a diagnosis of multiple faults (i.e., magnitude, phase, and harmonics) occurring simultaneously or individually in current/potential transformers. A modified algorithm based on convex optimization is used to determine the gains of the sliding-mode observer, which utilizes the feasibility optimization or trace minimization of a Ricatti equation-based modification of H-Infinity () constrained linear matrix inequalities. The fault and disturbance estimation method is modified and improved with some corrections in previous works. The stability and finite-time reachability of the observers are also presented for the considered faulty and perturbed microgrid system. A proportional-integral (PI) based control is utilized for the conventional regulations required for frequency and voltage sags occurring in a microgrid. However, the same control block features fault-tolerant control (FTC) functionality. It is attained by incorporating a sliding-mode observer to reconstruct the faults of sensors (transformers), which are fed to the control block after correction. Simulation-based analysis is performed by presenting the results of state/output estimation, state/output estimation errors, fault reconstruction, estimated disturbances, and fault-tolerant control performance. Simulations are performed for sinusoidal, constant, linearly increasing, intermittent, sawtooth, and random sort of often occurring sensor faults. However, this paper includes results for the sinusoidal nature voltage/current sensor (transformer) fault and a linearly increasing type of fault, whereas the remaining results are part of the supplementary data file. The comparison analysis is performed in terms of observer gains being estimated by previously used techniques as compared to the proposed modified approach. It also includes the comparison of the voltage-frequency control implemented with and without the incorporation of the used observer based fault estimation and corrections, in the control block. The faults here are considered for voltage/current sensor transformers, but the approach works for a wide range of sensors.

Reverse-Order Multi-Objective Evolution Algorithm for Multi-Objective Observer-Based Fault-Tolerant Control of T-S Fuzzy Systems

In this study, a multi-objective $H_{2}/H_{\infty }$ observer-based fault-tolerant control (FTC) design with reverse-order multi-objective evolution algorithm (MOEA) is proposed to deal with the FTC problem of Takagi-Sugeno (T-S) fuzzy systems. To achieve the optimal robust FTC design for the T-S fuzzy systems under the sensor and actuator faults, as well as external disturbance and measurement noise, the multi-objective $H_{2} /H_{\infty }$ observer-based FTC scheme is proposed to efficiently estimate the system state and the fault signals based on a proposed smoothed fault signal model. Then, multi-objective $H_{2}/H_{\infty }$ FTC performance can be achieved by an estimated state and fault signal feedback scheme to efficiently compensate the effect of fault signals and attenuate the effect of external disturbance. By using the proposed indirect method, the multi-objective $H_{2}/H_{\infty }$ observer-based FTC design problem is transformed into linear matrix inequalities (LMIs)-constrained multi-objective optimization problem (MOP). Besides, to overcome the difficulties in searching large fuzzy parameters of observer-based FTC design for solving the LMIs-constrained MOP, a reverse-order MOEA is proposed to overcome the bottleneck to efficiently solve the MOP for multi-objective $H_{2}/H_{\infty }$ observer-based FTC of T-S fuzzy system by searching feasible objective vectors in the objective space instead of searching fuzzy design parameters in the parametric space. Two practical examples are considered for the performance validation with (i) $H_{2}/H_{\infty }$ observer-based FTC design for the missile guidance system with the actuator and sensor fault signals due to the sudden cheating side-step maneuvering and the hostile jamming interference and (ii) $H_{2}/H_{\infty }$ observer-based FTC design for inverted pendulum system which effected by the constant actuator fault.

Optimizing the fault diagnosis and fault-tolerant control of selective catalytic reduction hydrothermal aging using the Unscented Kalman Filter observer

The performance of the selective catalytic reduction (SCR) system has been confirmed to be distinctly affected by hydrothermal aging fault. In this paper, an observer based on the Unscented-Kalman-Filter (UKF) algorithm theory is designed to identify the states of hydrothermal aging so that the aging SCR can be more accurately and efficiently diagnosed and fault-tolerant controlled. Furthermore, a model reference adaptive controller (MRAC) based on the theory of Lyapunov is constructed to enhance the fault-tolerant control performance of SCR Simulation, on the basis of the diagnosis information of UKF observer. The simulations and comparisons are performed to verify the performance of aging diagnosis and fault-tolerant control. The corresponding results show that the UKF observer has better estimation accuracy and respond speed for SCR aging, simultaneously, the fault-tolerant control performance of SCR aging is also better.

Sensor Fault Tolerant Control for Aircraft Engines Using Sliding Mode Observer

This paper investigated the problem of fault estimation and fault-tolerant control (FTC) against sensor faults for aircraft engines. By applying a second order sliding mode observer (SOSMO) to the engine on-board model, estimations of the system states and sensor faults could be obtained simultaneously, and the result of state estimation was unaffected when using the reduced-order sliding mode system. This result gave rise to the idea to use the estimated states instead of physical sensor signal in the engine close-loop feedback control. Unlike those using passive FTC concepts, the tradeoff between control performance and robustness was inherently unnecessary. Meanwhile, compared to active FTC approaches, because any classical state/output feedback method can be directly applied to the proposed scheme without any controller reconfiguration, extra undesired dynamic responses caused by parameter reconfiguring were avoided. In this paper, the proposed FTC scheme was tested on the nonlinear model of a civil aircraft turbofan engine, and numerical simulation results showed satisfactory sensor FTC performance.

Hybrid approach to design Takagi–Sugeno observer‐based FTC for non‐linear systems affected by simultaneous time varying actuator and sensor faults

This study uses a novel approach, integrating fault estimation and fault decoupling methods, in designing a new Takagi–Sugeno multiple integral unknown input observer (TSMIUIO)-based fault tolerant control (FTC) system. The motivation is to tackle the challenges underlined in designing observer-based FTC for non-linear systems affected by simultaneous time-varying actuator and sensor faults, exogenous input, and sensor noise. In such systems, the FTC design challenges are the constraints imposed by the structure of input/output matrices, the need of extending the order of the observer to estimate simultaneous faults, the bi-directional interaction caused by the state and faults’ estimation errors, and the unpredictable time behaviour of fault signals. These challenges motivate the proposal of TSMIUIO to (i) ensure acceptable FTC performance, irrespective of the time behaviour of sensor fault; (ii) relax the complexity of TSMIUIO by avoiding the use of extended state approach for estimating simultaneous faults; and (iii) eliminate the BDI in the estimated signals that feed the controller. The effectiveness of the proposed method is illustrated using a single-link flexible joint robot and translational oscillator with an eccentric rotational proof mass actuator benchmark.

Stochastic Model Predictive Fault Tolerant Control Based on Conditional Value at Risk for Wind Energy Conversion System

Wind energy has been drawing considerable attention in recent years. However, due to the random nature of wind and high failure rate of wind energy conversion systems (WECSs), how to implement fault-tolerant WECS control is becoming a significant issue. This paper addresses the fault-tolerant control problem of a WECS with a probable actuator fault. A new stochastic model predictive control (SMPC) fault-tolerant controller with the Conditional Value at Risk (CVaR) objective function is proposed in this paper. First, the Markov jump linear model is used to describe the WECS dynamics, which are affected by many stochastic factors, like the wind. The Markov jump linear model can precisely model the random WECS properties. Second, the scenario-based SMPC is used as the controller to address the control problem of the WECS. With this controller, all the possible realizations of the disturbance in prediction horizon are enumerated by scenario trees so that an uncertain SMPC problem can be transformed into a deterministic model predictive control (MPC) problem. Finally, the CVaR object function is adopted to improve the fault-tolerant control performance of the SMPC controller. CVaR can provide a balance between the performance and random failure risks of the system. The Min-Max performance index is introduced to compare the fault-tolerant control performance with the proposed controller. The comparison results show that the proposed method has better fault-tolerant control performance.

Self-triggered fault estimation and fault tolerant control for networked control systems

A framework of self-triggered fault diagnosis (FD) and fault tolerant control (FTC) for networked control systems (NCSs) is presented in this paper. The self-triggered scheduler is implemented in a smart sensor node. By means of uncertain polytopic theory, we first design a fault diagnosis observer, which has a similar structure with Kalman filter, to simultaneously estimate the fault and state using the self-triggered nonuniform sampled outputs. Then, based on the obtained fault and state information, an active fault tolerant controller with a state-estimate-dependent self-triggered scheduler is provided. We prove that the closed-loop faulty system is input-to-state stable (ISS) under the proposed self-triggered sampling mechanism. Finally, simulation results are provided to verify that the proposed self-triggered FD and FTC scheme can significantly reduce the sampling cost while preserving the desired fault estimation and FTC performance.

A Speed Sensor Fault-Tolerant Control of the CPPM Machine for Electric Vehicle

A speed sensor fault-tolerant control (FTC) strategy for electric vehicle is proposed in electric vehicles using a consequent-pole permanent-magnet (CPPM) machine. In order to obtain good FTC performance at low speed region, a HF voltage injection method is proposed to detect the rotor position from the magnetic saliency. This magnetic saliency of a CPPM machine is analysed by the finite-element analysis (FEA), and the high-frequency (HF) impedances are measured to confirm the saliency. At high speed range, the extended-electromotive force (EMF) method is applied when the failure of the speed sensor is detected. The speed sensor FTC strategy is verified effective by experimental results on a 25kW CPPM machine at different operating conditions. The reliability is enhanced and smooth transition to the fault-tolerant operation is realized. DOI: http://dx.doi.org/10.5755/j01.eee.20.7.5087

Study on Fault-Tolerant Technique Based on Knowledge Modules of Hydraulic Fault Theory

Fluid power transmission and control, fuzzy control and related fault-tolerant control technology, which have been widely used, as the core of control and power transmission. At the same time the hydraulic system is developing to be large-scale and complicated, which makes the high reliability and safety more and more important. There is no doubt that the researches conducted in the hydraulic system of fault tolerant control field will create significant value in application. This article summarizes the Knowledge Modules of Hydraulic Fault (KMHF), which is the necessary premise to carry out researches on the fault-tolerant techniques based on Knowledge Modules of Hydraulic Fault. On this basis, this article takes the pressure-flow compound control module as an example, introduces the principle design, analyzes the static and dynamic of their pressure /flow control unit. Especially, the paper employs the simulation tools-AMESim, to conduct simulation calculation and analysis of the pressure perception control module which is based on Knowledge Modules of Hydraulic Fault. Besides, this paper has carried out experiments on the automatic hydraulic drill platform to research the test fault-tolerant control performance of the pressure perception control module. The simulation and test results show that the new fluid fault-tolerant technique based on Knowledge Modules of Hydraulic Fault proposed in this article practically improves the reliability and safety of the hydraulic system, and has great value for application.

Fault diagnosis and fault-tolerant control for sampled-data attitude control systems: an indirect approach

This article proposes an indirect approach for fault diagnosis and fault-tolerant control in the satellite attitude control system with sampled-data measurements. The proposed method is based on a discrete-time approximation model of the continuous attitude dynamics. By considering the fault term as an auxiliary state vector, an augmented plant is constructed. Then an observer is designed to simultaneously estimate the system state vector and the fault term. Specifically, the observer design problem is reformulated as a set of linear matrix inequalities and can be conveniently solved by standard linear matrix inequality tools. The fault-tolerant controller is easily derived using the fault diagnosis result and the H∞ index is adopted to analyze the fault-tolerant control performance. Finally, numerical simulation results are given to demonstrate the effectiveness of the proposed method.

Fault-Tolerant Control Performance Comparison of Three- and Five-Phase PMSG for Marine Current Turbine Applications

This paper deals with the use of permanent magnet multiphase generators in marine current turbines with the aim to highlight their fault-tolerance. In this context, the performances and the fault-tolerant capabilities of a five-phase permanent magnet synchronous generator are evaluated within a marine current turbine and compared to a classical three-phase generator. For both topologies, a robust nonlinear control strategy is adopted. The adopted control consists of an adaptive control approach that combines three strategies: a maximum power point tracking (MPPT), an optimal fault-adaptive reference current generation, and high-order sliding modes. Simulations are carried-out using a Matlab/Simulink-based marine current turbine simulator to analyze the generator performances during open-circuit faults. Conclusions are then derived regarding multiphase generators' key features for marine applications.

Fault Tolerant Control for a Second Order LPV System using Adaptive Control Methods

A Fault Tolerant Control (FTC) reconfigurable structure for a second order nonlinear process is developed. This structure is based on a Model Reference Adaptive Control (MRAC) with a H∞Gain Scheduling controller designed using an Linear Parameter- Varying (LPV) system: MRAC-H∞GS-LPV. The MRAC-H∞GS-LPV was compared with a structure named MRAC-LPV that is based on an MRAC design using an LPV system. A coupled-tank system is used as testbed in which different types of faults (abrupt-additive fault, gradual-additive fault and multiplicative fault) with different magnitudes and different operating points were tested. Results showed that the use of an H∞GS controller in combination with an MRAC improves the FTC performance because fault accommodation is faster. In addition, the structures based on Lyapunov theory were able to deal more efficiently with the faults and the changes in the operating points of the nonlinear model of the system.

Fault estimation and fault-tolerant control for descriptor systems via proportional, multiple-integral and derivative observer design

We present a proportional, multiple-integral and derivative (PMID) observer technique that can simultaneously estimate system states, fault signals and the finite times derivatives of the faults for a descriptor system with input and measurement faults. Furthermore for a descriptor system with input and measurement faults and unknown disturbances (including modelling errors), a robust PMID observer is designed to simultaneously estimate system states, fault signals, the derivatives of the faults, and attenuate disturbances successfully. Fault-tolerant design is another important issue in this study. By using the obtained estimates of states and faults, and linear matrix inequality technique, a fault-tolerant control scheme is addressed, which ensures the closed-loop plant to be internally proper stable with prescribed H∞ performance index even as unbounded faults occur. Finally, a numerical example is given to illustrate the design procedures, and simulations show satisfactory tracking and fault-tolerant control performance.