For Fault Tolerant Control Research Articles

Reliable [formula omitted] fuzzy control for fault-tolerant actuator failures of active suspension system

A new methodology for fault tolerant control (FTC) is proposed to compensate actuator failures using Takagi–Sugeno systems. This makes possible to design the controller that represents actuator failures using a scaling factor by solving a family of linear matrix inequalities (LMIs). The resulting control system guarantees asymptotic stability, compensates the effect of actuator faults and ensures certain an H∞ performance level. This methodology is applied to the active suspension systems that motivated this research, where in the context of active suspension (AS) systems, the guaranteed performance correspond to ride comfort in the presence of road disturbances. Thus, a controller is developed for a quarter-car model with active suspension. The simulated results illustrate the effectiveness of the proposed approach.

Decoupled Design of Fault-Tolerant Control for Dual-Three-Phase IPMSM With Improved Memory Efficiency and Reduced Current RMS

Fault tolerance is critical to real-time control of the dual-three-phase interior permanent magnet synchronous machine (IPMSM). This article proposes an efficient decoupled design for fault-tolerant control (FTC) of dual-three-phase IPMSMs to improve the average torque and minimize the current root mean square (rms) for torque ripple and loss reduction under the open-phase fault. Specifically, the FTC design is divided into two subtasks to derive the FTC strategy with a simplified design, in which the two subtasks are the fundamental current design and the harmonic current design. The optimal current solution to FTC is derived in a memory- and computation-efficient way. The proposed solution can achieve better transient performance and reduce the current rms for FTC, which is critical to practical applications with dynamic changing loads. In comparison with existing methods, the proposed FTC can effectively reduce the request of memory and computation resources from the drive system. Extensive experiments and comparisons are conducted to evaluate the proposed FTC on a laboratory dual-three-phase IPMSM.

Fuzzy-based metaheuristic algorithm for optimization of fuzzy controller: fault-tolerant control application

PurposeFuzzy-based metaheuristic algorithm is used to optimize the fuzzy controllers for the nonlinear level control system subject to uncertainty specially in the main actuator that has lost effectiveness (LOE). To optimize the fuzzy controller, type-1 harmonic search (HS) and interval type-2 (HS) will be used.Design/methodology/approachThe type-1 and type-2 fuzzy-based HS algorithms are designed for optimization of fuzzy controllers for Fault-Tolerant Control (FTC) applications, and this research proposes a fuzzy-based HS metaheuristic method. The performance of a fuzzy logic-based HS algorithm applied to a nonlinear two-tank level control process with a main actuator that has lost effectiveness (LOE) and also the same controller will be tested on DC motor angular position control with and without noise.FindingsThe key contribution of this work is the discovery of the best approach for generating an optimal vector of values for the fuzzy controller's membership function optimization. This is done in order to improve the controller's performance, bringing the process value of the two-tank level control process closer to the target process value (set point). It is worth noting that the type-1 fuzzy controller that has been optimized is an interval type-2 fuzzy system, which can handle more uncertainty than a type-1 fuzzy system.Originality/valueThe type-1 and type-2 fuzzy-based HS algorithms are designed for optimization of fuzzy controllers for FTC applications, and this research proposes a fuzzy-based HS metaheuristic method. The performance of a fuzzy logic-based HS algorithm applied to a nonlinear two-tank level control process with a main actuator that has LOE will be tested on DC motor angular position control with noise. Two nonlinear uncertain processes are used to demonstrate the effectiveness of the proposed control scheme.

Fuzzy-enhanced robust fault-tolerant control of IFOC motor with matched and mismatched disturbances

<p style='text-indent:20px;'>This paper focuses on the dynamical analysis of the permanent magnet asynchronous motor with the aim of subsequently designing effective robust control laws for the indirect field-oriented control (IFOC) devices. We first perform some tasks which demonstrate the existence of chaos phenomenon in the IFOC using relevant indicators such as phase portraits, bifurcations diagrams and Lyapunov exponents. Chaotic signature and some striking transitions are revealed such as period-doubling, torus, period-adding and chaos when an accessible parameter of the IFOC motor is changed. More interestingly, a certain range of the parameter space corresponds to the transient chaos. This behavior was not reported previously and can be considered as an enriching contribution. Secondly, due to the great interest to reduce the upper bound of uncertainties and interference, conventional sliding mode control (SMC) has been abundantly investigated for fault-tolerant control (FTC) systems. However, this approach presents several drawbacks in terms of overshoot, less robustness, transient state error, large chattering and speed of convergence that limit its use for industrial applications. For these reasons, the integral sliding mode control (ISMC) and the fuzzy sliding mode control (FISMC) are proposed to keep the IFOC motor in the regular operation zone. The optimal feedback gains and a sufficient condition are proposed for the stability of the overall IFOC system is drawn based on the linear quadratic regulator (LQR) method. To highlight the effectiveness and applicability of the proposed control scheme, numerical simulation results are presented. This analysis allows us a great knowledge of engineers for interpreting the operation of the IFOC motor. To highlight the effectiveness and the applicability of the proposed control scheme, numerical simulations results are presented and clearly demonstrated the feasibility of these techniques.</p>

Fuzzy Logic Based Metaheuristic Algorithm for Optimization of Type-1 Fuzzy Controller: Fault-Tolerant Control for Nonlinear System with Actuator Fault

This research offers a fuzzy-based harmonic search (HS) metaheuristic technique for optimizing type-1 fuzzy controller for Fault-Tolerant Control (FTC) for nonlinear level control application subject to two uncertainties (i.e. actuator fault and external process disturbances), using type-1 and interval type-2 fuzzy-based HS algorithms. The effectiveness of a fuzzy logic-based adaptive HS algorithm in a nonlinear two-tank level control process with the primary actuator has dwindled (LOE). The work key contribution is the discovery of the best technique for constructing an optimal vector of values for the fuzzy controller’s membership functions (MFs) optimization. This is made to improve dynamic response by bringing the process value of the two-tank level control process close to the target process value (set-point). It’s worth noting that the type-1 fuzzy controller’s optimized MFs use an interval type-2 fuzzy system for parameter adaptation of the HS algorithm, which can handle greater uncertainty than a type-1 fuzzy system. In this case, the limiting MFs of interval type-2 fuzzy sets are type-1 fuzzy sets, which defne the footprint of uncertainty (FOU). Simulation results show that FHSO using an interval type-2 fuzzy system outperforms FHSO using a type-1 fuzzy system in the optimal design of a type-1 fuzzy controller.

A novel direct field‐oriented control strategy for fault‐tolerant control of induction machine drives based on EKF

AbstractThis article presents a novel Direct Field‐Oriented Control (DFOC) strategy for Fault‐Tolerant Control (FTC) of wye‐connected 3‐Phase Induction Machine (3‐PIM) drives under the stator winding open‐phase failure. In the proposed control strategy, instead of flux measurement, an Extended Kalman Filter (EKF) for flux estimation is used. The introduced controller with minor modifications can be used during normal and stator winding open‐phase failure conditions. With the proposed DFOC system, the speed and torque pulsations that normally happen during the open‐phase failure can be reduced. The performances of the proposed EKF‐based DFOC strategy and the conventional control strategy for a faulted machine using simulations and experiments under different operation conditions are compared. Simulation and experimental results demonstrated an important improvement in speed and torque pulsations through this type of fault. Results also confirmed the superiority of the proposed EKF‐based DFOC scheme over the conventional control scheme to balance the faulted machine phase currents.

Frequency domain $ H_{\infty} $ control design for active suspension systems

<p style='text-indent:20px;'>A methodology for fault-tolerant-control(FTC) is proposed that compensates actuator failures in active suspension systems (ASS). This methodology is based on a Frequency Domain approach that represents failures using a scale factor to optimize the ASS and improve ride comfort. The controller design is carried out using off-the-shelf tools based on linear matrix inequalities (LMIs), guaranteeing asymptotic stability, compensating the effect of actuator faults, and ensuring certain <inline-formula><tex-math id="M1">\begin{document}$ H_{\infty} $\end{document}</tex-math></inline-formula> performance. In the context of ASS, the performance guarantees correspond to ride comfort in the presence of road disturbances. To validate the approach, controllers are developed and tested in simulation for a quarter-car model: the results illustrate the effectiveness of the proposed approach.</p>

Passivation blocks for fault tolerant control of nonlinear systems

This paper describes a novel passivity/dissipativity based approach for fault tolerant control (FTC) of nonlinear systems by means of fault hiding, i.e., by inserting reconfiguration blocks (RBs) between the plant and controller to mitigate the fault effects. The proposed approach is used to design a new kind of RB, called passivation block (PB), which is generically employed for sensor and actuator faults and achieves simultaneously series, feedback and feedfoward passivation of the controller during a fault occurrence. Based on the dissipativity theory, new conditions are obtained to design a dynamic PB (DPB) which requires minimum information on the system model. In particular, the proposed DPB can be systematically obtained by combining the LMI-based conditions based on the knowledge about the passivity indices. Numerical simulations are carried out and indicate that the PBs are able to stabilize an example of a faulty nonlinear system.

A Modified FOC Strategy With Optimal Rotor Flux for FTC of Star-Connected TPIMDs Against Single-Phase Open Fault

In this research, a modified field-oriented control (MFOC) strategy with optimal rotor flux for fault-tolerant control (FTC) of star-connected three-phase induction machine drives (TPIMDs) against single-phase open fault (SPOF) is proposed. First, an FTC scheme based on using an unbalanced transformation matrix (TM) for stator current components in order to control the TPIMD during SPOF is presented. Then, the model of the losses based on the extended mathematical model of the machine in the rotational reference frame is calculated. The minimum losses of the drive system are determined by the calculation of optimal flux at any operating condition. The optimal flux is then used as the reference flux in the presented FTC system. The introduced strategy with some changes can be used during normal and SPOF conditions. Simulation and experimental results are given to confirm this new FTC approach. It will be shown that the introduced method gives good results both in normal and SPOF operations.

Performance-Guaranteed Fault-Tolerant Control for Uncertain Nonlinear Systems via Learning-Based Switching Scheme.

This article is concerned with the challenge of guaranteeing output constraints for fault-tolerant control (FTC) of a class of unknown multi-input single-output (MISO) nonlinear systems in the presence of actuator faults. Most industrial systems are equipped with redundant actuators and a fault detection-isolation mechanism for accommodating unexpected actuator faults. To simplify the system design and reduce the risk of false alarm or missed detection brought by the detection unit, a learning-based switching function scheme is proposed to automatically activate different sets of actuators in a rotational manner without human intervention. By this means, no explicit fault detection mechanism is needed. An additional step has been made to guarantee that the system output remains in user-defined time-varying asymmetric output constraints all the time during the occurrence of failures by utilizing error transformation techniques. The stability of the transformed system can equivalently deliver the result that the original system output stays in the required bounds. Hence, system crash or further catastrophic outcomes can be avoided. A neural network is integrated to embody the adaptive FTC design for dealing with unknown system dynamics. The dynamic surface control (DSC) technique is also invoked to decrease complexity. Furthermore, the stability analysis is carried out by the standard Lyapunov approach to guarantee that all the signals of the closed-loop system are semiglobally uniformly ultimately bounded. Finally, the simulation results are provided to verify the effectiveness of the proposed scheme.

An adaptive approach for the fault tolerant control of a nonlinear system

In this paper hybridisation between two optimisation methods such as modified bacterial foraging optimisation algorithm (MBFOA) and adaptive neuro fuzzy inference system (ANFIS) is presented for determining the optimal proportional-integral (PI) controller parameters, for fault tolerant control (FTC) in an wind energy conversion system (WECS). Initially, detection and diagnosis of fault is performed by the ANFIS. The wind turbine actual output performance and the estimated output values are given as an input to the ANFIS. The residuals, which are the outputs of ANFIS is used for deciding, whether the signal is a fault signal or a non-fault signal, which utilises the knowledge-based computation technique. By using the step size modified bacterial foraging optimisation algorithm-based FTC, the gain parameters are optimised based on the occurrence of fault. Then the proposed hybrid fault tolerant control model is implemented in the MATLAB/SIMULINK platform and the effectiveness is analysed by comparing with the other techniques. The comparison results demonstrate the superiority of the proposed approach and confirm its potential in controlling the fault in a WECS.

A Review on Recent Development of Spacecraft Attitude Fault Tolerant Control System

Motivated by several accidents, attitude control of a spacecraft subject to faults/failures has gained considerable attention in a wider range of aerospace engineering and academic communities. This paper is concerned with industrial practices and theoretical approaches for fault tolerant control (FTC) and fault detection and diagnosis (FDD) in spacecraft attitude control system. An overview on recent development of spacecraft attitude FTC system design is presented. The basis of a FTC system is introduced. The existing engineering FTC techniques and theoretical methodologies, including their advantages and disadvantages, are discussed. Moreover, closely associated with the reliability-relevant issues, recent progress in attitude FTC design strategies is reviewed. A brief review of some open problems in the general area of spacecraft attitude control design subject to components faults/failures is further concluded.

Robust Fault-Tolerant Control for a Class of Second-Order Nonlinear Systems Using an Adaptive Third-Order Sliding Mode Control

Due to the robustness against the uncertainties, conventional sliding mode control (SMC) has been extensively developed for fault-tolerant control (FTC) system. However, the FTCs based on conventional SMC provide several disadvantages such as large transient state error, less robustness, and large chattering, that limit its application for real application. In order to enhance the performance, a novel adaptive third-order SMC, which combines a novel third-order sliding mode surface, a continuous strategy and an adaptation law, is proposed. Compared with other innovation approaches, the proposed controller has an excellent capability to tackle several types of actuator faults with an enhancing on robustness, precision, chattering reduction, and time of convergence. The proposed method is then applied for an attitude control of a spacecraft and the results demonstrate the superior performance.

Robust Quasi–LPV Model Reference FTC of a Quadrotor Uav Subject to Actuator Faults

Abstract A solution for fault tolerant control (FTC) of a quadrotor unmanned aerial vehicle (UAV) is proposed. It relies on model reference-based control, where a reference model generates the desired trajectory. Depending on the type of reference model used for generating the reference trajectory, and on the assumptions about the availability and uncertainty of fault estimation, different error models are obtained. These error models are suitable for passive FTC, active FTC and hybrid FTC, the latter being able to merge the benefits of active and passive FTC while reducing their respective drawbacks. The controller is generated using results from the robust linear parameter varying (LPV) polytopic framework, where the vector of varying parameters is used to schedule between uncertain linear time invariant (LTI) systems. The design procedure relies on solving a set of linear matrix inequalities (LMIs) in order to achieve regional pole placement and H∞ norm bounding constraints. Simulation results are used to compare the different FTC strategies.

Simultaneous State and Parameter Estimation Based Actuator Fault Detection and Diagnosis for an Unmanned Helicopter

Abstract Simultaneous state and parameter estimation based actuator fault detection and diagnosis (FDD) for single-rotor unmanned helicopters (UHs) is investigated in this paper. A literature review of actuator FDD for UHs is given firstly. Based on actuator healthy coefficients (AHCs), which are introduced to represent actuator faults, a combined dynamic model is established with the augmented state containing both the flight state and AHCs. Then the actuator fault detection and diagnosis problem is transformed into a general nonlinear estimation one: given control inputs and the measured flight state contaminated by measurement noises, estimate both the flight state and AHCs recursively in each time-step, which is also known as the simultaneous state and parameter estimation problem. The estimated AHCs can further be used for fault tolerant control (FTC). Based on the existing widely used nonlinear estimation methods such as the unscented Kalman filter (UKF) and the extended set-membership filter (ESMF), three kinds of adaptive schemes (KF-UKF, MIT-UKF and MIT-ESMF) are proposed by our team to improve the actuator FDD performance. A comprehensive comparative study on these different estimation methods is given in detail to illustrate their advantages and disadvantages when applied to unmanned helicopter actuator FDD.

Wavelet-based prognosis for fault-tolerant control of induction motor with stator and speed sensor faults

This paper presents a wavelet-based prognosis technique for fault-tolerant control (FTC) of an induction motor (IM) drive. The wavelet is used for analysis in fault detection due to its good filtering characteristics, localized capability and superior de-noising. The fault-tolerant algorithm is applied to a 1-kW IM to maintain the performance of the machine at an acceptable level. The FTC algorithm has been implemented in a new topology to ensure the best performance recovery in case of open and short stator winding faults, as well as speed sensor faults. In the worst-case scenario of operation, a protection stage has been implemented to stop motor operation. Experimental results demonstrate the reliability and effectiveness of the technique for diagnosis and prognosis of stator and speed sensor faults. The Texas Instrument TMS 320F28335 is used for the real-time implementation of the proposed wavelet-based prognosis and the FTC of the IM drive under different fault situations.

Frequency-interval control reconfigurability for automated processes

Faults in automated systems will often result in undesired behavior and shut-down of the processes. The consequences of these could be damage to the plant, to personnel and resources, or even to the environment. In particular, in the case of natural disasters, faults are often inevitable. The objective of the methods for fault-tolerant control (FTC) is to prevent simple faults turning into severe failure. Therefore, FTC methods help to increase plant availability and to reduce the risk of safety hazards. However, these methods cannot be effective if sufficient redundancy does not exist in the system. A measure for control reconfigurability which reveals the level of redundancy in connection with feedback control is proposed in this paper. The proposed control reconfigurability measure is developed in particular for many applications in which one is interested in analysis and control within a frequency-interval. Compared to the other counterparts, the proposed measure encodes more information on the level of redundancy within the frequency-interval of interest. An illustrative example is given to show the computation of frequency-interval control reconfigurability and its relevance to redundant actuating capabilities in the models.

Bi-criteria optimal fault-tolerable control for SY-II remote operated vehicle

This paper proposed a bi-criteria weighting approach for fault tolerant control (FTC) of SY-II remote operated vehicle (ROV). This approach integrates the minimum kinetic energy (2-norm optimal) approach with the infinity-norm approach through a weighting coefficient, on the basis of SY-II ROV force allocation model. For the realization of fault tolerable control, this approach converts a quadratic programming problem into primaldual neural network. From the motion control simulations and experiments, bi-criteria optimization approach outperforms minimum kinetic energy optimization in FTC, SY-II ROV can realize 2-degree of freedom (DOF) horizontal fault tolerant control with one main thruster and any of horizontal ones. Therefore, this scheme is proved to be of superiority and computational efficiency, both the reliability and safety for ROV have been improved.

Youla Parameterization Based Adaptive Controller Design for Fault Tolerant Control

AbstractA new adaptive controller for fault tolerant control (FTC) is proposed in this paper. It is realized by adapting the reconfigurable fault parameterized matrix with the estimated fault. The proposed approach is applied in a linear reduced order aircraft model, and simulation results show the effectiveness.

New fault tolerant control strategies for nonlinear Takagi-Sugeno systems

New fault tolerant control strategies for nonlinear Takagi-Sugeno systemsNew methodologies for Fault Tolerant Control (FTC) are proposed in order to compensate actuator faults in nonlinear systems. These approaches are based on the representation of the nonlinear system by a Takagi-Sugeno model. Two control laws are proposed requiring simultaneous estimation of the system states and of the occurring actuator faults. The first approach concerns the stabilization problem in the presence of actuator faults. In the second, the system state is forced to track a reference trajectory even in faulty situation. The control performance depends on the estimation quality; indeed, it is important to accurately and rapidly estimate the states and the faults. This task is then performed with an Adaptive Fast State and Fault Observer (AFSFO) for the first case, and a Proportional-Integral Observer (PIO) in the second. Stability conditions are established with Lyapunov theory and expressed in a Linear Matrix Inequality (LMI) formulation to ease the design of FTC. Furthermore, relaxed stability conditions are given with the use of Polya's theorem. Some simulation examples are given in order to illustrate the proposed approaches.