Fault-tolerant Scheme Research Articles

An Intelligent Fault Tolerant Data Routing Scheme for Wireless Sensor Network-Assisted Industrial Internet of Things

Safety is a major concern for Industrial 4.0 where different physical parameters are monitored for avoiding uncertain events in the industry. In industries, natural calamities like fire and leakage of harmful gases can cause huge damage to life and property. An Industrial Internet of Things (IIoT) is used to monitor such natural calamities and take timely prompt actions. However, sensors in the IIoT are vulnerable to failures due to energy depletion and hardware malfunctioning. It significantly reduces the reliability of the network. This paper proposes an intelligent fault-tolerant scheme where different faults within the wireless sensor network-assisted IIoT such as node fault and link fault are detected and tolerated in a timely manner. It significantly improves the reliability of the network. Extensive simulations show the out-performance of the proposed scheme in terms of average packet delivery, energy consumption, throughput, network lifetime, communication delay, and recovery speed.

Shared Redundancy Strategy to Improve the Reliability and Fault-Tolerant Capability of Modular Multilevel Converter

Utilizing redundant sub-modules is a well-known strategy to improve the reliability and fault-tolerant capability of the modular multilevel converter (MMC). Redundancy-based fault-tolerant strategy makes it possible to restore the full performance of the converter in the post-fault condition. The main drawback of this strategy is the high cost. In this configuration, each redundant sub-module (RSM) can only be utilized in a specific arm and it cannot be used in other arms. This limitation leads to inefficient utilization of the RSMs in conventional MMC. This paper proposes a shared redundancy strategy which allows RSMs to be used either in upper or lower arms. The derived reliability models in various case studies illustrate that proposed strategy significantly improves the reliability and useful lifetime of MMC. To investigate the effectiveness of the proposed strategy, simulation and experimental results are provided.

A Novel SVPWM Fault-Tolerant Strategy for Torque Ripple Reduction of Seven-Phase Induction Machines Under Single-Phase Open-Circuit Fault

The development of multiphase drives has taken on an accelerated pace in the last decades, and fault-tolerance has been the subject of many classic studies. Traditional space vector pulsewidth modulation (SVPWM) would cause significant torque ripple in the case of open-circuit fault, which in turn degrades the fault-tolerant performance of multiphase machines. This work proposes a novel SVPWM fault-tolerant strategy for seven-phase induction machine under a single-phase open-circuit fault. A deeper insight has been provided into the reconstruction of voltage vectors without using reference current, ensuring the generality for various fault-tolerant principles. Subsequently, an eight-sector-based sector division method is proposed, and five specific nonzero voltage vectors and two zero-voltage vectors in each sector are determined to be candidates. Without confliction of switching state, the symmetric modulation module can still be utilized, which will minimize the modifications after fault occurrence. Besides, the close-loop control for harmonic planes can be fulfilled. Finally, experimental results have demonstrated the effectiveness of the proposed SVPWM fault-tolerant approach under both steady and transient states.

An active fault tolerance framework for uncertain nonlinear high-order fully-actuated systems

This paper presents a novel active fault tolerance framework for uncertain high-order fully-actuated systems (HOFASs). Starting from the uncertain faulty HOFAS model with nonlinear measurement, the advantages of this description are revealed via Lie Derivatives. A HOFAS adaptive observer and controller integration is established and further a closed-loop HOFAS dynamic data modeling structure is derived. This structure uncovers the dynamic characteristics including fault features, and naturally yields a fault detectability condition. Based on the fault information from the dynamic data model, an active fault tolerant control strategy for HOFASs is proposed, which enriches HOFAS control theory. The uniformly bounded stability of the HOFAS model is proved theoretically and illustrated experimentally.

A Robust Fault-Tolerance Scheme with Coverage Preservation for Planar Topology Based WSN

A Robust Fault-Tolerance Scheme with Coverage Preservation for Planar Topology Based WSN

Optimization-Based Maximum-Torque Fault-Tolerant Control of Dual Three-Phase PMSM Drives Under Open-Phase Fault

In this article, a novel optimization-based maximum-torque fault-tolerant control scheme is proposed for the open-phase fault of dual three-phase permanent-magnet synchronous motor drive. First, the relationship between torque output capability and single-phase copper losses under open-phase fault is derived with the consideration of overheating problems. Since the derived expression has multiple optimization goals, a new objective function is designed to simplify the current optimization. Second, particle swarm optimization (PSO) is utilized to obtain the maximum-torque current references based on the designed objective function. Different from the conventional maximum-torque fault-tolerant schemes which limit the current patterns, the proposed fault-tolerant control scheme employs PSO to search for the global optimal result without adding any unnecessary restrictions, such as sinusoidal current patterns. In this way, the proposed fault-tolerant control scheme can achieve the theoretical highest torque output capability of 73.3% with lower total copper loss. Both the theoretical and experimental results are presented to prove the effectiveness and superiority of the proposed optimization-based maximum-torque fault-tolerant control scheme.

An Efficient Fault-Tolerant Protection Method for L0 BTB

Branch prediction structures are increasingly used in space processors due to their crucial role in improving processor performance. Due to radiation effects such as Single Event Upset (SEU) causing system failures, it is necessary to provide protection techniques for branch prediction modules against complex spatial environments. In this paper, we proposed a simple, efficient, low-power, and fault-tolerant design scheme for L0 BTB consisting of a master-slave and a check-decision module. The strategy sets up the L0 BTB structure as a master-slave structure and adds an error check to detect single-bit errors. Experimental results show that we achieve 100% fault tolerance without a loss hit rate. The increase in resource usage is 1.1x, and the path delay increases by 8.1%, superior to other methods. The L0 BTB is a fully-associative structure and multiple entries are accessed simultaneously, which introduces significant power consumption. We added a low-power design for the master-slave module to reduce the query power consumption by 65.9%. In addition, we also applied the scheme to the RAS module. The experimental results demonstrate that our approach is an efficient, generic, fault-tolerant design scheme that can be deployed to different register files.

Current Reconstruction for Dual PMSMs Fed by a Five-Leg Voltage Source Inverter With a Single Current Sensor

The dual-motor system driven by five-leg voltage source inverter (FL-VSI) has been widely studied as a better fault-tolerant scheme. In this paper, a phase current reconstruction strategy based on a single current sensor is proposed to realize the phase currents reconstruction of the dual permanent magnet synchronous motors (PMSM). Firstly, the FL-VSI adopts a centralization modulation strategy to realize independent control of the two motors while expanding the speed range of the motors. Then, a pulse shift strategy applied for the dual-PMSMs system driven by FL-VSI is proposed. The phase currents can be reconstructed when two motors are running in the low modulation region, sector boundary region, or the new phase current reconstruction dead zone by the proposed method. The experimental results show that the reconstructed phase currents can always be consistent with the actual phase currents, which proves the feasibility and effectiveness of the proposed method.

Deadbeat Fault-Tolerant Control Scheme for Dual Three-Phase PMSG With High-Resistance Connection Fault

This article proposes a current deadbeat-based fault-tolerant control scheme for a dual three-phase permanent magnet synchronous generator with a high-resistance connection (HRC) fault. First, the voltage deviation caused by the HRC fault is deduced, and the postfault prediction model is established. Then, the instantaneous active power and reactive power are analyzed considering the negative-sequence voltage and current. To eliminate the fluctuation components and improve the steady-state performance, the fault-tolerant current references are designed under the condition of HRC fault. The deadbeat principle is employed to track the periodic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> current references accurately. The two targets of eliminating output power fluctuations and stabilizing electromagnetic torque are achieved. Finally, the virtual voltage vectors are synthesized to generate the reference voltage and suppress the harmonic current. The proposed method effectively restrains the fluctuations of active power, reactive power, dc-link voltage, and electromagnetic torque. The experimental results verify the effectiveness of the proposed method.

Fault-Tolerant Attitude Control Incorporating Reconfiguration Control Allocation for Supersonic Tailless Aircraft

This paper presents a fault-tolerant attitude control scheme, incorporating reconfiguration control allocation for supersonic tailless aircraft subject to nonlinear characteristics, actuator constraint, uncertainty, and actuator faults. The main idea is to propose an incremental reconfiguration closed-loop control allocation scheme, coupled with a basic backstepping attitude controller, to achieve attitude control. Based on the virtual control input generated by the basic backstepping attitude controller, firstly, the incremental nonlinear control allocation method is adopted to deal with the nonlinear characteristics and actuator constraint. Secondly, a distribution error feedback loop is constructed in the incremental nonlinear control allocation method to enhance the robustness against the uncertainty of the control effectiveness matrix. Thirdly, the control effectiveness matrix is reconstructed by different kinds of fault information to deal with actuator faults, and the proper combination of actuator deflections is generated to achieve accurate command tracking. The stability of the proposed scheme is guaranteed by the Jury stability criterion and the Lyapunov stability analysis. Finally, in comparison with the three existing approaches, the simulation results of two cases are provided to show the effectiveness of the proposed scheme.

Kalman filter-based model predictive control for drag-free satellite under actuator failures and input saturations.

This paper studies the problem of fault-tolerant control for the drag-free satellite subject to actuator failures and input saturations. Particularly, a new Kalman filter-based model predictive control method for the drag-free satellite is proposed. Based on the developed dynamic model and the Kalman filter strategy, a new fault-tolerant design scheme is presented for the challenging situation where the satellite is subject to measurement noise and external disturbance. With the designed controller, the robustness of the system can be guaranteed, and the problem caused by actuator constraints and faults can be solved. Finally, the correctness and effectiveness of the proposed method are verified by numerical simulations.

Adaptive Fault-Tolerant Control for Open-Circuit Faults in Dual Three-Phase PMSM Drives

The traditional fault-tolerant procedure usually comprises fault detection and fault tolerance. Fault detection is adopted to locate the specific fault, which increases the complexity and misdiagnosis risk of fault-tolerant systems. This article introduced an adaptive fault-tolerant control for open-phase faults and open-switch faults in dual three-phase permanent magnetic synchronous machine (PMSM) drives. The proposed fault-tolerant scheme is fulfilled by going through three operation states: healthy operation, transient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> open-loop faulty operation, and fault-tolerant operation. The angle of fault-tolerant reference currents on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> plane is obtained from the transient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> open-loop faulty operation. Unified fault-tolerant reference currents of open-circuit faults are built up by using the above reference angle. After the open-circuit faults occur, the unified fault-tolerant reference currents are directly applied to the drive system without fault localization. Experimental results demonstrate a very smooth switching capability of the developed adaptive fault-tolerant control from the faulty operation to the fault-tolerant operation without extra hardware.

Attitude Fault-Tolerant Control of Aerial Robots with Sensor Faults and Disturbances

In this paper, sensor fault diagnosis and fault tolerant control strategy are investigated for quadcopters under sensor faults and disturbances. We propose the fault diagnosis estimation system and the fault-tolerant control (FTC) method. The fault diagnosis system provides time-varying sensor fault estimation under an unknown bound of disturbances. Moreover, the fault-tolerant control eliminates disturbance that is estimated through the associated disturbance observer. Overall, the proposed FTC guarantees the finite-time tracking convergence using nonsingular fast terminal sliding mode algorithm. Stability of the closed-loop system is validated through the Lyapunov theory. Finally, conventional nonsingular fast terminal sliding mode and adaptive neural network sliding mode control are compared with the proposed method through simulations under sensor faults and disturbances with different scenarios.

Anti-disturbance fault-tolerant control with flexible performance for combined spacecraft attitude tracking under limited thrusts

This paper proposes a novel anti-disturbance fault-tolerant control scheme for prescribed performance attitude tracking of combined spacecraft equipped with thrusters. In practice, the output magnitude of each thruster is limited. When severe actuator faults and/or strong disturbances occur, the remaining active thrusters under limited thrusts may not provide sufficient actuating torques to ensure the satisfaction of prescribed performance. To fill this gap, a tactfully constructed auxiliary system is introduced to generate a series of modification signals, whereby the performance envelops can be actively relaxed when the commanded inputs exceed the thrust limits, while recovering to the nominal level when input saturations disappear. With the modified performance functions (MPFs), a robust adaptive controller is designed to achieve stable attitude tracking of combined spacecraft with flexible performance. Stability analysis shows that the proposed controller can ensure that both the attitude and angular velocity tracking errors evolve strictly within the MPFs, and that all closed-loop signals are uniformly ultimately bounded, despite the presence of external disturbances, thruster faults, and input saturation. Finally, simulation results are provided to show the effectiveness of the proposed method.

Fuzzy observer-based command filtered tracking control for uncertain strict-feedback nonlinear systems with sensor faults and event-triggered technology

For the trajectory tracking problem of nth-order uncertain nonlinear systems with sensor faults, a fuzzy controller based on command filtered and event-triggered technology is designed to improve the tracking error of the system. Concurrently, a fault-tolerant control scheme is introduced to effectively solve the problem of sudden output sensor failure. Additionally, the proposed controller can also greatly avoid complexity explosion problem of derivations of virtual control laws, which makes the design of the controller simpler. Furthermore, an effective observer is designed to solve the problem of system state immeasurability. Therefore, the proposed control scheme makes the design of the controller more convenient and flexible. According to Lyapunov stability theory, it is proved that all closed-loop signals are uniformly and ultimately bounded. Finally, two simulation examples of second-order nonlinear system and single-link robot show the effectiveness of the proposed scheme.

Fault-tolerant control for sensor faults affecting an electromechanical railway track switch

A fault-tolerant control scheme (FTCS) was developed for a novel mechatronic track switch for the first time. The FTCS was first developed and tested on a simulation model of the system, before being applied to an experimental actuation system in the laboratory. Both the simulation and experimental results show that this FTCS works as expected and allows the switch to continue operating as desired under sensor failure, preventing damage to the switch.

Adaptive Fault-Tolerant Tracking Control of Quadrotor UAVs against Uncertainties of Inertial Matrices and State Constraints

This paper presents a study on a quadrotor unmanned aerial vehicle (UAV) fault-tolerant control scheme. According to the attitude model and safety control of the aircraft under the uncertainty of inertial matrix, the attitude state constraint by reinforcement learning is designed to ensure safety. Even if the boundary is crossed, it can be pulled back to the boundary by means of a designed penalty function with reinforcement learning. Meanwhile, in order to inhibit the oscillation caused by immediate reward as usual, an adaptive update law is proposed. Furthermore, considering the coupled actuator fault and system input saturation due to uncertainty of inertial matrix, the Nussbaum-type function is utilized in this work to handle this challenge, which likely causes the singularity of inertia matrix. As a consequence, combined with the Lyapunov stability theory, it is confirmed that the proposed FTC scheme ensures that all the closed-loop signals are bounded. Simulation results are carried out to illustrate the effectiveness and advantage of the proposed control scheme.

Fault Tolerant Control of Drone Interceptors Using Command Filtered Backstepping and Fault Weighting Dynamic Control Allocation

This paper proposes a fault tolerant control strategy for drone interceptors with fixed wings and reaction jets subject to actuator faults. The drone interceptors have both continuous and discrete actuators, which pose a challenge to the control system design. The proposed fault tolerant control system consists of two parts, a nonlinear virtual control law and a dynamic control allocator. To deal with system uncertainty and quantization error, a virtual control law with a parameter update law is designed by command filtered backstepping. Then, a fault weighting dynamic control allocation algorithm is developed to distribute the virtual control signal to the actuators on the drone interceptor. When an actuator fault occurs, the proposed fault weighting dynamic control allocation scheme can redistribute the control signals to the remaining actuators. The effectiveness of the proposed algorithm is confirmed by numerical simulation.

Adaptive Multiple-Model-Based Fault-Tolerant Control for Non-minimum Phase Hypersonic Vehicles With Input Saturations and Error Constraints

In this article, an adaptive multiple-model-based fault-tolerant controller is developed for nonminimum phase air-breathing hypersonic vehicles (HSVs) in the presence of parametric uncertainties, elevator faults, input saturations, and time-varying error constraints. Compared with the existing works, the elevator-to-lift couplings are taken into account, which makes the HSV longitudinal models exhibit unstable internal-dynamics that impedes the applicability of common nonlinear control methods for control design. In order to solve this problem, a two-layer cascade control strategy is proposed in which the external inputs control the external states and the external state deviations control the internal states: 1) A multiple-model linear quadratic control strategy, based on gap metric, is proposed to guarantee the stability of the internal dynamics; 2) a fault-tolerant control scheme, based on tan-barrier Lyapunov functions, is developed by using a low-pass filter and an auxiliary system in conjunction with adaptive backstepping design. In the control law, the uncertain parameters are replaced by their estimates updated by adaptive laws. Additionally, the stability of the whole system is rigidly proved through standard Lyapunov approach, while the other states and signals in the closed-loop system are guaranteed to be bounded. Simulation results are provided to illustrate the effectiveness of the proposed adaptive multiple-model-based fault-tolerant controller.

Adaptive fault-tolerant control for electro-hydraulic servo actuator based on multiple unmodeled dynamics estimation and compensation

The internal leakage fault-tolerant control problem of the electro-hydraulic servo actuator under the influence of multiple unmodeled dynamics is investigated in this paper, and an adaptive fault-tolerant control scheme based on unmodeled dynamics estimation and compensation is proposed. The model of the actuator is divided into two subsystems, which extended-state observers are respectively constructed to estimate the matched and mismatched unmodeled dynamics. Combined with the estimation results of the unmodeled dynamics, an adaptive fault-tolerant controller is designed by using the backstepping method. In which a controller reconfiguration mechanism based on internal leakage fault parameter online adaptation is used to accommodate the fault, and a feedforward compensation strategy is used to suppress the influence of unmodeled dynamics. Semi-physical simulation test of the proposed scheme is conducted under serious cylinder internal leakage. The test result shows that when the maximum internal leakage flow reaches 10.53 L/min, accounting for about 56.77% of the load flow, at the moment the opening of the servovalve is close to the maximum and the proposed scheme can still achieve high-precision position tracking control, where the maximum position tracking errors of fault transient and post-fault steady state are both limited within ±1.5% of the given position.