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This article addresses a novel adaptive compensation strategy for a flexible manipulator in the presence of unmodeled system dynamics and an infinite number of time-varying actuator faults. Differing from the existing results, the unmodeled system dynamics are represented by a nonlinear time-varying delay function, which is tackled with the aid of neural network technique and Lyapunov–Krasovskii function. By introducing the projection technique and a piecewise Lyapunov function, a fault-tolerant control method is proposed, the uniformly ultimate boundedness of the closed-loop system is ensured, and the number of actuator faults is allowed to be infinite. Simulation and physical experiment results show that the manipulator can track the desired angle and the vibration can be suppressed effectively under the proposed scheme for the system with uncertainties and actuator faults. [ABSTRACT FROM AUTHOR]

Magnetic bearing is an important part of modern high-speed rotating machinery. The performance of power electronic converter highly determines the quality of magnetic bearing drive. In this article, a fault-tolerant converter with series-winding topology is introduced. Compared with the traditional topology, the current stress of phase leg is reduced while the utilization of dc voltage is guaranteed, and fault-tolerant operation can be realized in the case of open-circuit fault of the switching device. This article introduces the characteristics of the series-winding topology and the current control method. Open-circuit fault detection methods and countermeasures are also analyzed. Experimental results show the effectiveness of the proposed topology. Fault-tolerant experiments under static suspension and rotation of the rotor demonstrate the performance of the topology. This kind of series-winding topology provides a new scheme with good performance and high reliability for the design of magnetic bearing controllers. [ABSTRACT FROM AUTHOR]

Time delays, model uncertainties, faults, and disturbances are frequently the main causes of performance degradation and instability in industrial process control. This article presents a fault-tolerant robust model-predictive control design for processes that involve the above effects and process constraints. The uncertainties are modeled into a polytopic affine form based on variations in the system's parameters. A new model based on augmentation of the state variables and tracking error is used that provides increased degrees of freedom for the control design and guarantees tracking performance. A parameter-dependent Lyapunov–Krasovskii functional is used to design a state-feedback control that reduces the conservatism of the conventional approach and ensures robust stability and tracking performance of the closed-loop system. At each sampling instant, a control action is computed by solving an online constrained optimization problem that minimizes the upper bound of the “worst-case” performance index. Finally, the proposed framework is employed for the fault-tolerant control of a continuous stirred tank reactor to demonstrate its effectiveness in mitigating actuator faults and tracking the desired set point. [ABSTRACT FROM AUTHOR]

Fault-tolerant control is normally required to achieve continuous operation under postfault modes in some critical fields. Regarding the remedial strategy for open-end-winding permanent magnet synchronous machines (OW-PMSMs) in the case of open-phase fault, the typical way is to reconfigure the controller after the fault is detected. Different from those mainstream control strategies, which account for the postfault situations by reconfiguring controllers or modulators, the fault-tolerant predictive control strategy proposed in this article handles the asymmetry produced by open-phase fault in a different manner. By combining the predictive control strategy with an embedded vector-resonant control scheme, the proposed strategy can achieve effective regulation of OW-PMSMs in both pre- and postfault operations. Controller reconfiguration and switching between pre- and postfault control modes based on fault detections are thus avoided. Besides, with the rotor flux harmonics taken into account and benefiting from the proposed zero-sequence controller, the triple-frequency component in the zero-sequence current is successfully suppressed to reduce torque ripples while the fundamental-frequency component in the zero-sequence current is properly retained under postfault operations, which is required in order to obtain an uninterrupted rotating magnetic field after one phase is open circuited. Experimental validations are conducted to verify the effectiveness of the proposed strategy and its superiority over conventional voltage compensation methods. [ABSTRACT FROM AUTHOR]

This article presents a new fault-tolerant drive for a five-phase interior permanent magnet synchronous machine (IPMSM) to achieve the maximum torque per ampere (MTPA) operation under open-circuit faults. In the postfault space vector pulsewidth modulation strategy, the voltage vectors are reconstructed by the reduced-order transformation matrix, which is derived from the optimal reference fault-tolerant currents under single-phase and double-phase fault. The z subspace is particularly controlled to reduce the total harmonic distortions of current under single-phase fault, and the distributions of space voltage vectors are established to realize the fault-tolerant operation under double-phase fault. Meanwhile, the high-frequency signal is injected into the space vector under fault condition inherently to detect the MTPA points. Therefore, this method is parameter independent in the tracking of the MTPA point under postfault operation. Besides, the proposed method can effectively reduce the amplitudes of the fault-tolerant currents and improve the torque and efficiency performances compared with $i_{d}= 0$ fault-tolerant control. Finally, on an IPMSM prototype drive system, the effectiveness of the proposed method is verified by the experiment. [ABSTRACT FROM AUTHOR]

This article proposes a fault-tolerant control method for the battery-supercapacitor (SC) hybrid energy storage system (HESS) based on the cascaded multilevel converter during active dc-side failure (ADCF). When ADCF occurs, the magnitude of the output voltage will be seriously affected because of the decline of the dc-side voltage. Consequently, the system cannot operate normally. To tackle this problem, an auxiliary power loop, which uses the dual-frequency phase-shifted carrier pulsewidth modulation to transfer power between different energy storage units, is added into the HESS. The topology of the HESS and the principle of power transfer during failure operation are introduced. The requirement to the numbers of different types of cells: discharging, charging, and standby, is analyzed mathematically. The SC capacity and the control system designs are given. Finally, the simulation results obtained from MATLAB/Simulink as well as experiments based on a prototype are presented to verify the effectiveness of the HESS and the fault-tolerant control. [ABSTRACT FROM AUTHOR]

The relative pose control problem for spacecraft rendezvous and docking missions in the presence of control input constraints, actuator's partial failures, and unknown external disturbances is studied in this paper. A smoothly adaptive fault-tolerant constrained controller is developed based on the adaptive nonlinear state feedback method. Different from the traditional fault-tolerant saturated controllers, the proposed control approach explicitly accounts for the control input constraints with straightforward tuning parameters in controller. Meanwhile, the exact knowledge of the actuator failures is not required and uncertain failure information can be rejected. A smooth control signal containing simple saturation functions is designed, and the unknown bounded external disturbances can be rejected by the proposed method. The proposed controller can ensure ultimately, uniformly bounded stability of the closed-loop system, where relative pose and velocities converge to the small neighborhoods of zero. Numerical simulation results demonstrate the effectiveness of the proposed control approach. [ABSTRACT FROM AUTHOR]

This paper is devoted to attitude tracking control of fractionated spacecraft with wireless communication. We consider the practical case that the spacecraft suffers from uncertain inertia parameters, external disturbances, and even unknown and time-varying actuator faults. Within the framework of the backstepping method, a novel event-triggered adaptive fault-tolerant control scheme is proposed. In our design, an event-triggering mechanism is introduced to determine the time instants for communication, which successfully avoids continuous communication and Zeno phenomenon. Then, with the aid of a bound estimation approach and a smooth function, the impacts of the actuator faults, as well as the network-induced error, are effectively compensated for. Moreover, by employing the prescribed performance control technique, it is shown that the attitude tracking errors can converge to predefined arbitrarily small residual sets with prescribed convergence rate and maximum overshoot, no matter if there exist unknown actuator faults. Compared with conventional adaptive attitude control schemes, the proposed scheme significantly reduces the communication burden, while providing high reliability and stable, rapid, and accurate response for attitude maneuvers. Simulation results are presented to illustrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents a novel fault-tolerant method for active–neutral-point-clamped (ANPC) inverter using a modified carrier-based pulsewidth modulation. At a fault event, the ANPC inverter is divided into subinverters, and the modulating signal is modified to two modulating signals. The modified modulating signals are used to control the subinverters and allow continuous operation of the three-level ANPC inverter during faulty conditions even up to four open-switch faults per phase. This technique provides the fault-tolerant capability of the ANPC inverter without the need to add any additional phase legs or complex control strategies. Furthermore, the proposed technique ensures the voltage balancing of the dc-link capacitors. The performance of the proposed fault-tolerant technique is verified through simulation studies in MATLAB/Simulink under different faulty conditions. The feasibility of the proposed technique is also verified experimentally. [ABSTRACT FROM AUTHOR]

Active magnetic bearing is a core technology for high-speed rotational machines. Power electronics converter as the active magnetic bearing drive is the actuation unit and its topology highly impacts the performance of the bearing system. This paper introduces the progress of topology of active magnetic bearing drive. The initial topology of an H-bridge does not sufficiently utilize the power electronics devices. The topology with half-bridge and shared phase-leg has been proposed as the fundamental topology. In this paper, two approaches of novel magnetic bearing drive topology modification have been developed on the basis of the fundamental topology. In the first approach, central phase-leg for multiaxis magnetic bearing drive can be further shared and the power electronic devices can be globally optimized in the whole system. Further, a topology with current in the reverse direction can reduce the central phase-leg current rating and power losses. In the second approach, fault-tolerant magnetic bearing drive topology has been developed on the basis of the fundamental topology, too. It can ride-through the open-circuit fault of power electronics switch-in operation and keep levitation for the magnetic bearing. The series work of novel topologies can improve the performance of an active magnetic bearing system in application. [ABSTRACT FROM AUTHOR]

In this paper, the transient thermal response of a conventional double-layer switched-flux permanent-magnet machine is studied for both healthy and fault conditions such as inter-turn short-circuit. A highly optimized and accurate cosimulation model for different operating conditions is developed requiring low computation and time resources. The electromechanical models for both healthy and faulty operation are implemented in MATLAB/Simulink while the thermal model is implemented using three-dimensional (3-D) finite-element model (FEM) software. Both models are dynamically coupled to enable the influence of temperature rise on the electromagnetic performance and vice versa to be predicted. Operation under various conditions are investigated, and it is found that the temperature rise under fault conditions and high speed can lead to irreversible demagnetization of the permanent magnets. The superposition principle is used to accurately estimate the impact of short-circuit currents on the temperature rise. A series of dynamic tests are carried out to validate the transient thermal response prediction when operating during both the healthy and fault conditions. [ABSTRACT FROM AUTHOR]

In this paper, a short-circuit fault-tolerant operation control strategy of dual-winding permanent-magnet motor (DWPMM) under the four-quadrant condition for electrical flight surface actuator application is proposed and investigated. By the comparative analysis of the current fault-tolerant permanent-magnet motor drive system, it can be concluded that the DWPMM drive system is suitable for electrical flight surface actuator application. However, the current DWPMM drive system lacks the research on short-circuit fault-tolerant operation under the four-quadrant condition. Then, the electrical flight surface actuator system based on the DWPMM and short-circuit fault-tolerant operation control strategy under the four-quadrant condition is proposed and investigated. The experimental results show that the electrical flight surface actuator system based on the DWPMM can achieve the high performance of the four-quadrant fault-tolerant control with short-circuit fault under the four-quadrant operational condition. [ABSTRACT FROM AUTHOR]

This paper presents an average dwell-time method for fault-tolerant control of a class of uncertain switched linear time-delay systems and also designs an algorithm to determine the parameters pertaining to the dwell-time condition. Compared to the literature results, this paper features the following: 1) the proposed method is independent of switching polices if switchings are slow enough in the average sense; 2) the proposed control design guarantees exponential stabilization of this class of time-delay linear systems with actuator faults; and 3) this method treats all actuators in a unified manner without a need to identify which are faulty or healthy actuators. The proposed method is applied to the water pollution control problem, for the first time, to deal with different ratios of stream flow rates to effluent flow rates. [ABSTRACT FROM AUTHOR]

Recently, a few fault-tolerant control strategies have been proposed for T-type three-level inverters to improve the reliability of the inverter system. However, the neutral-point (NP) voltage oscillations suppression is never considered in the previous fault-tolerant control strategies. In order to suppress the NP voltage oscillations when open-circuit fault occurs to NP switches, this paper proposes two novel fault-tolerant control strategies named as improved two-level switching tolerant control and hybrid switching tolerant control (HS-TC). Both methods are implemented by adding an optimal time-offset to the three-phase turn-ontimes. The corresponding time-offset value of each method is simply calculated considering the phase current and dwell time of [O] state. Moreover, an NP voltage balancing algorithm to eliminate the dc deviation and a dc bias to further reduce the NP voltage oscillations are used in the HS-TC. The performance and comparison of the tolerant controls with respect to the NP voltage oscillations, current total harmonic distortion, and dynamic response are illustrated and analyzed through the simulation and experimental results. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is very attractive in a high-voltage dc (HVdc) transmission system due to its high modularity and scalability. It is also a promising candidate for medium-voltage applications. An MMC has many power devices that lead to a relatively low reliability based only on a direct failure rate calculation. The reliability of an MMC can be improved by redundant designs. Lots of redundant designs and strategies have been proposed in recent years, while their reliability improvements are hardly quantified in existing literature. In practice, reliability improvement with constraint costs is a challenge. In view of these, this paper proposes a reliability and cost assessment scheme for MMC redundant designs and strategies. Reliability and cost are quantified for comparison purposes. A medium-voltage application is used to demonstrate the reliability and cost assessment scheme. The reliability analysis is based on a combinatorial model and the Poisson process model. The cost analysis focuses on capital cost and power loss cost. The proposed reliability and cost analysis scheme provides a guideline for MMC redundant design and redundant strategy selection. [ABSTRACT FROM AUTHOR]

This paper introduces a novel fault-tolerant control for the maximum torque per ampere (MTPA) operation in five-phase interior permanent magnet synchronous machine (IPMSM), termed MTPA fault-tolerant control. The key of this fault-tolerant control is that the reluctance torque is considered and used by MTPA under open-circuit fault. Based on the decoupled model of five-phase IPMSM on synchronous frame and the computing method of d-axis and q-axis voltages under various open-circuit faults, the virtual signal injection control (VSIC) can be applied to realize the MTPA under the fault-tolerant operation by the postfault field-oriented control (FOC) and carrier-based PWM (CPWM). This method is parameter independent in tracking of the MTPA points under the fault-tolerant operation. Besides, it can effectively reduce the amplitude of the fundamental current and improve efficiency compared with traditional $i_{d} = {\text{0}}$ fault-tolerant control. Moreover, it is robust to current and voltage harmonics and machine torque disturbances under the postfault operation. The proposed method is verified by experiments under various postfault operating conditions on an IPMSM prototype drive system. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach for the control of a permanent magnet synchronous machine with a quadruple three-phase star-connected winding configuration after a short-circuit (SC) fault in one voltage source inverter. The approach includes an adaption of the closed-loop current control that allows operation of the faulty unit to proceed without the need to adapt the reference currents. This allows an operation of the faulty drive with increased postfault mean torque. Additionally, a strategy for postfault torque error compensation is proposed, which can be used to reduce the torque ripple while the load distribution is better balanced. Results are respectively compared to the case when applying a symmetric SC to the faulty unit, which is the conventional strategy in case of a transistor SC fault. The current limit of the drive is considered in all cases. The benefits of the approach are validated through experimental tests. [ABSTRACT FROM AUTHOR]

This paper investigates the open-circuit fault-tolerant current control for a five-phase fault-tolerant permanent-magnet (PM) machine used for electric vehicles. By relieving the common constraint of zero neutral point current in the existing fault-tolerant control strategies and reconfiguring the maximum round rotating magnetomotive force under different fault conditions, the new current sets, which enable the five-phase PM machine to output the maximum smooth torque, are obtained by the analytical method. Compared with the existing fault-tolerant control strategy, larger torque and lower torque ripple can be obtained with the proposed fault-tolerant control strategy, and the five-phase PM machine can safely operate with the loss of up to three phase windings. The proposed fault-tolerant control strategy is verified by both finite-element analysis and experimental results. The developed fault-tolerant current control strategy can be generalized into any multiphase PM machines. [ABSTRACT FROM AUTHOR]

The bidirectional ac/dc converter is widely used to realize the power conversion between ac and dc microgrid, but the faults of switch devices and unbalanced grid voltages may lead to the decline of power quality and affect normal operation of the converter. The four-switch three-phase (FSTP) fault-tolerant structure is reconstructed from a six-switch three-phase structure with switch device fault. In order to reduce harmonic currents and output power fluctuations under unbalanced grid voltages, finite states model predictive direct power control (MPDPC) with power compensation method is proposed for FSTP structure and predictive power model of the bidirectional FSTP ac/dc converter is established. The power compensation values are expressed by grid voltages and their quadrature signals that lagging 90 electrical degrees in the αβ stationary coordinate system. Compared with the conventional method, phase-locked loop, pulse width modulation, and complex positive-/negative-sequence extraction of grid voltage are not required. Ripples of active power or reactive power under unbalanced grid voltages are eliminated. The proposed fault-tolerant MPDPC with power compensation method ensures the continuous and reliable operation of the bidirectional ac/dc converter with high power quality. Simulation and experimental results are presented to validate the proposed control strategy under symmetrical unbalanced grid voltages with switch device faults. [ABSTRACT FROM PUBLISHER]

In this paper, novel remedial direct torque control (DTC) schemes are proposed for open-circuit faults in T-type neutral-point-clamping (T-NPC) three-level asymmetric six-phase permanent-magnet synchronous motor (PMSM) drives. First, a simplified space vector modulation (SVM) is designed and applied for DTC-controlled asymmetric six-phase drive, in such a way that both good current harmonic performance and fast dynamic response are available. Based on the SVM-DTC scheme, a remedial strategy is proposed for the open-circuit faults in phase windings. The key is to derive the relationship between the stator fluxes and the stator voltages of all phases under faulty condition. Then, a derived perturbation term is compensated for normal voltage references, and the fault-tolerant scheme is, thus, implemented without changing control structure of normal condition. The remedial DTC schemes are also studied and proposed for open-switch faults in T-NPC six-phase drives. The modulation methods are redesigned for the faults in half-bridge switches and NPC switches. The experiments are carried out on a laboratory prototype to verify the validity and performance of the proposed fault-tolerant control schemes. [ABSTRACT FROM PUBLISHER]

This paper introduces new schemes for detection, isolation, and compensation of speed and current sensor (CS) faults in field oriented induction motor (IM) drives. These schemes do not use any kind of machine model and motor parameters. This is a prominent feature of the proposed approaches, which only rely on main concepts of field-oriented control (FOC)-based IM drives. Moreover, the proposed fault detection and isolation (FDI) schemes can take partial sensor failures into account. These kinds of faults that might be caused by mechanical or electrical failures, or intentional sensor tampering, are difficult to be dealt with since embedded speed and current control loops react swiftly, and inherently try to camouflage partial sensor failures. CS faults result in imbalance current flow in the motor stator phases, and speed sensor fault repudiates the orthogonally alignment of field and torque current components in field oriented IM drives. These features are cornerstones of introduced FDI methodology. Furthermore, model and parameter free compensators are proposed to recover normal operation of the machine before fault incident. After in-depth analysis, extensive simulation and experimental tests validate the proposed schemes. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of finite-time sampled-data control for nonlinear flexible spacecraft described by Takagi–Sugeno (T–S) fuzzy model with stochastic actuator failures. Different from the existing literatures, T–S fuzzy approach is used to model the nonlinear behaviors of flexible spacecraft for its good approximation performance. A novel and general input model related to Markovian variables is developed to depict the stochastic actuator failures, which is capable of covering various faulty modes. With the aid of stochastic analysis and convex optimization techniques, a novel fault-tolerant fuzzy switching controller is designed to carry out the finite-time attitude stabilization for flexible spacecraft with the existence of stochastic failures and sampled-data inputs, and an optimal $H_\infty$ performance level is ensured simultaneously. Finally, a practical example with simulation results are provided to validate the effectiveness of the developed control strategy. [ABSTRACT FROM PUBLISHER]

The fault-tolerant capabilities are compared in this paper for the conventional double-layer switched-flux permanent-magnet machine and its single-layer counterparts, i.e., C-core, E-core, and modular. The comparison includes the interturn short-circuit and irreversible demagnetization faults. A combination of Simulink and finite element models is used in the study. Based on the predictions, it is found that the modular topology produces the lowest short-circuit current and also has the best demagnetization withstand capability while the conventional one produces the highest short-circuit current and has the worst demagnetization withstand capability. The frozen permeability method is employed to separate the flux produced by armature current and magnets, and the results showed that, besides the influence of short-circuit current, the available magnet volume and magnetic circuit configuration play an important role in the demagnetization process. It is also found that removing half of the magnets, such as using C-core, E-core, and modular topologies, generally improves the demagnetization withstand capability and also increases the torque per magnet volume. Measured results are also presented to validate the short-circuit current predictions and magnet demagnetization. [ABSTRACT FROM PUBLISHER]

This paper investigates the field-programmable gate array (FPGA) implementation of a fault-tolerant space vector-hysteresis current control (SV-HCC) for three-phase grid-connected converter. The proposed control ensures continuous operation despite of an open-circuit fault in one grid current measurement circuit (caused by defected cables, lines or connectors at the output of the current measurement circuit). It is based on hardware redundancy of current measurement circuits for fault detection and isolation. The faulty measured current is identified through the computation of residuals with well-defined thresholds. Thanks to the high computation capabilities of FPGAs, the implemented fault-tolerant SV-HCC is executed with a very high sampling frequency and very low execution time. As a consequence, the defined theoretical thresholds remain available for the experimental tests. Several experimental results, carried out on FPGA-based prototyping platform, are given in order to illustrate effectiveness and reliability of the proposed fault-tolerant SV-HCC. [ABSTRACT FROM AUTHOR]

In order to take advantage of conventional switched reluctance motors (SRMs), the SRM is integrated with the bearingless motor technology and then a reluctance type of bearingless motor is created, named as bearingless SRM (BSRMs). Not only electromagnetic torque but also the levitation forces should be controlled in BSRMs, which is different from SRMs. The levitation forces should always exist even when winding fault occurs. Therefore, the absent levitation forces that ought to be produced by the fault winding should then be compensated by other winding. This paper proposes the compensation strategy of levitation forces for BSRMs when one stator winding is short circuited. The short-circuit fault is investigated and the short-circuit current is expressed for the derivation of radial forces. Then, the winding compensation rule and the mathematical model of levitation forces are developed to facilitate the compensation control for the motor levitation. After that, the proposed compensation strategy is verified by simulation results in MATLAB/Simulink. Experimental results are also presented to demonstrate the performance. [ABSTRACT FROM PUBLISHER]

In this paper, a maximum-power-point-tracking controller for variable-speed wind turbines (VSWTs) is developed, which is shown to be able to account for modeling uncertainties, unexpected disturbances, subsystem failures, and actuation saturation simultaneously. A novel memory-based approach is used to predict wind speed that is used to generate desired rotor speed accordingly. It is shown that the proposed algorithm not only is robust against nonlinear aerodynamics and adaptive to unknown and time-varying inertia/damp/stiffness properties of VSWTs but also is able to accommodate actuator failures under torque constraints. The benefits of the proposed control method are analytically authenticated and demonstrated with Fatigue, Aerodynamics, Structures, and Turbulence code and Simulink. [ABSTRACT FROM PUBLISHER]

In this paper, a decentralized fault-tolerant control (FTC) system is proposed for near-space vehicle (NSV) attitude dynamics. First, NSV reentry attitude dyna mic models with an uncertainty, actuator failure models, and a control surface damage model are described. Next, a new local fault identification algorithm is proposed to iden tify different types of actuator faults, which is based on multiobserver techniques. The local fault identification is constituted by a fault detection observer, fault parameter identification observers, and a decision-making mechanism. Then, a global adaptive sliding-mode observer is used to design the command filter backstepping fault- tolerant controller. Our focus is on the accommodation for actuator faults, control surface damage, uncertainties, and the resulting disturbances of the NSV. Finally, simulation results are given to demonstrate the effectiveness and poten tial of the proposed FTC scheme. [ABSTRACT FROM PUBLISHER]

This paper addresses the problems of observer-based fault reconstruction and fault-tolerant control for Takagi–Sugeno fuzzy descriptor systems subject to time delays and external disturbances. A novel fuzzy descriptor learning observer is constructed to achieve simultaneous reconstruction of system states and actuator faults. Sufficient conditions for the existence of the proposed observer are explicitly provided. Utilizing the reconstructed fault information, a reconfigurable fuzzy fault-tolerant controller based on the separation property is designed to compensate for the impact of actuator faults on system performance by stabilizing the closed-loop system. In addition, the design of the fault reconstruction observer and the fault-tolerant controller is formulated in terms of linear matrix inequalities that can be conveniently solved using convex optimization techniques. Finally, simulation results on a truck–trailer system are presented to verify the effectiveness of the proposed approaches. [ABSTRACT FROM PUBLISHER]

This paper addresses real-time fault-tolerant control (FTC) of nonlinear systems by adopting the internal model control structure with embedded iterative computation. We first study the Runge–Kutta (RK) type methods for solving the nonlinear ordinary differential equations and derive the convergence conditions in the control-theoretic framework. Then, we propose an observer-like iterative solution to improve the convergence rate of the RK method by embedding the sensor signals into the iterative computation. Based on these results, real-time FTC is achieved and enhanced by employing the modified numerical algorithm in the iterative computation and estimation. This paper is mainly motivated by the increasing demands on the reliability of integrating the fast converging iterative solutions of differential equations into the embedded control systems. The effectiveness of the proposed schemes is demonstrated through the experimental and simulation results on three-tank systems. [ABSTRACT FROM PUBLISHER]

An intelligent complementary sliding-mode control (CSMC) (ICSMC) is proposed in this paper for the fault-tolerant control of a six-phase permanent-magnet synchronous motor (PMSM) drive system with open phases. First, the dynamics of the six-phase PMSM drive system with a lumped uncertainty is described in detail. Then, the fault detection and operating decision method is briefly introduced. Moreover, a CSMC is designed to stabilize the fault-tolerant control of the six-phase PMSM drive system. Furthermore, to improve the required control performance and to maintain the stability of the six-phase PMSM drive system under faulty condition, the ICSMC is developed. In this approach, a Takagi–Sugeno–Kang-type fuzzy neural network with asymmetric membership function (TSKFNN-AMF) estimator with accurate approximation capability is employed to estimate the lumped uncertainty. In addition, the adaptive learning algorithms for the online training of the TSKFNN-AMF are derived using the Lyapunov theorem to guarantee the closed-loop stability. Additionally, to enhance the control performance of the proposed intelligent fault-tolerant control, a 32-b floating-point digital signal processor, TMS320F28335, is adopted for the implementation of the proposed fault-tolerant control system. Finally, some experimental results are illustrated to demonstrate the validity of the proposed fault-tolerant control for the six-phase PMSM drive system via ICSMC. [ABSTRACT FROM PUBLISHER]

This paper deals with the problem of sensor-fault-tolerant control for linear parameter varying (LPV) systems. The LPV systems under consideration are subject to modeling uncertainties and depend on a set of parameters that are assumed to be bounded and available online. Three schemes are proposed to achieve sensor-fault-tolerant control. First, a low-order LPV observer is proposed to simultaneously estimate the unmeasured states and the sensor faults. Second, the estimated sensor faults are used to design a fault decision scheme to detect the sensor faults and to prevent false alarms caused by modeling uncertainties and/or measurement noise. Third, a fault-tolerant control scheme is designed by using the estimated states and the estimated sensor faults to compensate for the effects of sensor faults. To show the effectiveness of the proposed results, the developed schemes are applied to three practical examples consisting of a continuous stirred tank reactor, a single-link robotic arm, and a liquid level process. The simulation results for the first two examples and the experimental results for the liquid level process example indicate that the proposed schemes work well. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the fault diagnosis and fault-tolerant problem for a linear drive system subject to system noise. First, we propose a residual generator based on the Kalman filter, which can be used to detect if a failure occurs. Second, two Kalman filters are designed to diagnose the fault type. Third, when a fault is diagnosed, the fault-tolerant control is used to accommodate this failure. Finally, the proposed method is tested in a real linear drive system. [ABSTRACT FROM PUBLISHER]

In this paper, a new variable structure control law is proposed in order to obtain the shaft positioning of a symmetrical six-phase induction machine when phases are lost and when large variations of inertia occur. The algorithm based on a time-varying switching line guarantees the existence of a sliding mode since the beginning of the shaft motion. Indeed, the surface is first designed to pass through the initial representative point and, subsequently, to move toward a predetermined desired surface via shifting. With this algorithm, the induction machine behavior is exactly the same in healthy or in faulted modes when one or more stator phases are lost and whatever the mechanical shaft configuration is. The capacities of this control technique with a mechanical sensor have been tested in simulation and then validated experimentally on a specific setup. [ABSTRACT FROM PUBLISHER]

The increasing use of distributed power-generation systems, as with the case of wave-power-generation plants, requires a reliable fault-ride-through capability. The effects of grid fault include uncontrolled turbogenerator acceleration, dangerous rotor peak currents, and high reactive-power consumption so that the plant may contribute to the voltage dip. A simple solution is automatic disconnection from the grid, but this policy could lead to a massive power-network failure. This is why new Grid Codes oblige these systems to remain connected to the grid. In this paper, an oscillating-water-column-based wave-power-generation plant equipped with a doubly fed induction generator is modeled and controlled to overcome balanced grid faults. The improvement relies on the implementation of a control scheme that suitably coordinates the airflow control, the active crowbar, and the rotor- and grid-side converters to allow the plant to remain in service during grid fault, contributing to its attenuation by supplying reactive power to the network and complying with new Grid Code requirements. The simulated results show that it obtains a great reduction of the rotor currents, improving the transients and avoiding rotor acceleration. Similar results are obtained from the experimental implementation. [ABSTRACT FROM AUTHOR]

In this paper, a simple fault diagnosis scheme for brushless direct-current motor drives is proposed to maintain control performance under an open-circuit fault. The proposed scheme consists of a simple algorithm using the measured phase current information and detects open-circuit faults based on the operating characteristic of motors. It requires no additional sensors or electrical devices to detect open-circuit faults and can be embedded into the existing drive software as a subroutine without excessive computation effort. The feasibility of the proposed fault diagnosis algorithm is proven by simulation and experimental results. [ABSTRACT FROM AUTHOR]

Fault tolerance is gaining interest as a means to in- crease the reliability and availability of distributed energy systems. In this paper, a voltage-oriented doubly fed induction generator, which is often used in wind turbines, is examined. Furthermore, current, voltage, and position sensor fault detection, isolation, and reconfiguration are presented. Machine operation is not interrupted. A bank of observers provides residuals for fault detection and replacement signals for the reconfiguration. Control is temporarily switched from closed loop into open-loop to decouple the drive from faulty sensor readings. During a short period of open-loop operation, the fault is isolated using parity equations. Replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. There are no large transients in the current. Measurement results and stability analysis show good results. [ABSTRACT FROM AUTHOR]

This paper presents a fault detection method for open-circuit faults of a switching device in neutral-point-clamped inverter systems, which is based on the inherent characteristic of continuous pulsewidth modulation. The proposed method is achieved by measuring the pole voltage and its duration time. The pole voltage includes information of switching states in the inverter system but not affected by the load. Therefore, a fault condition of the inverter system itself can be diagnosed through analysis of pole voltage. Compared to conventional fault detection methods, the proposed fault detection method has faster detection capability that is within two sampling times and is much simpler to implement. Therefore, the use of the proposed method could minimize harmful effects such as imbalance of dc-link voltage and overstress on other switching devices. The validity of the proposed fault detection method is verified through experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an optimal control technique for $n$-phase permanent-magnet (PM) machines under various open circuit faults is presented. Under the fault conditions, the currents in the healthy phases are controlled to compensate phase loss and to produce the required output torque. The proposed control technique ensures continuous operation of the machines while producing minimum torque ripples and minimum stator ohmic loss. The control technique is based on the instantaneous power balance theory. To set the summation of the phase currents equal to zero, a constraint is incorporated in the derivation of the control technique. A five-phase PM machine is considered to demonstrate the proposed open circuit fault-tolerant control strategy. Simulation and experimental results are provided for validation. [ABSTRACT FROM AUTHOR]

In the paper by Chen et al. (IEEE Trans. Ind. Electron., vol. 66, no. 4, pp. 2837–2846, Apr. 2019), the authors proposed two fault-tolerant control strategies for T-type three-level inverters considering neutral-point (NP) voltage oscillations. However, some basic problems are worth being discussed about the proposed fault-tolerant control methods. This letter presents some comments and results concerning the paper by Chen et al. [ABSTRACT FROM AUTHOR]