Fault-tolerant Capability Research Articles

The AAPF fault-tolerant method for small and complex product assembly

Fault-tolerant control should be considered during assembly to ensure stability and efficiency of the assembly process. The paper proposes a fault-tolerant method to improve stability and efficiency during the assembly of small and complex products. The fault-tolerant method model was initially constructed, then an adaptive artificial potential field control algorithm (AAPF) was introduced to control related assembly tasks based on changes in assembly information. Next, active and passive fault tolerance methods were integrated using a least squares support vector machine (LS-SVM). Finally, the assembly of a 2P circuit breaker controller assembly with leakage protection was used as an example to verify the proposed assembly method. The experimental results demonstrated that the AAPF fault-tolerant method showed promising fault-tolerance capabilities for the assembly of small and complex products. Not only could it coordinate the number of tasks for each assembly robot, but it also effectively reduced the number of tasks that accumulated due to faults. The method proposed in this paper could effectively guarantee assembly stability and efficiency during small and complex product assembly.

Submodule fault-tolerant control based adaptive carrier-PDPWM for modular multilevel converters

The modular multilevel converter (MMC) is considered a very promising candidate for medium-voltage and/or high-power grids. One of the major concerns in half-bridge MMCs, especially with large number of levels, is the fault occurs at the converter submodule (SM). Hence, an appropriate control with an SM fault tolerance of the MMC is required to enhance its reliability. This paper addresses the issue and proposes a fault tolerant control-based adaptive carrier phase disposition pulse width modulation (AC-PDPWM) technique for MMCs with superior symmetrical and asymmetrical fault-tolerant capabilities. The proposed control-based AC-PDPWM acts to regulate the flow of energy between arms, rebalance the SM capacitors, and redistribute the pulses to the SM switches. In this study, a single-phase grid connected MMC having both symmetrical and asymmetrical fault conditions is investigated. Compared with other control methods, the proposed control can tolerate the SM fault conditions without requiring redundant SMs or additional computational burden, which decreases the cost and volume of the MMC design and simplifies its control. Simulation and experimental results are included to verify the fault-tolerant capability of the proposed control.

Design and Analysis for Multi-Disc Coreless Axial-Flux Permanent-Magnet Synchronous Machine

The multi-disc axial flux permanent magnet synchronous machine (AFPMSM) can provide high fault tolerance capability in applications requiring high reliability. Firstly, a topological structure of coreless AFPMSM is proposed, the magnetic circuit and the air-gap flux intensity are discussed in detail to improve stable operation of machine in this paper. The relationship between air-gap flux density and the parameters of rotor are clarified respectively based on finite element algorithm (FEA). Furthermore, the winding structure and power driver topology with fault tolerance are presented. And the 3D FEA analyzes the operation characteristics and stress of the machine. Finally, the prototype is manufactured. The results are demonstrated that the torque output and fault tolerance performance is better.

Image Compression Software Design for Zhurong Mars Exploration Rover

Because of the limited number of information transmission channels and high bit error rate in Mars image transmission, a method of image compression software design and realization of Mars rover was proposed. The characteristics of rover image data management were analyzed, and the three capabilities that the rover image compression software needed to have were concluded: uniform file management capability, high-efficiency compression capability, and high fault tolerance capability. For uniform file management capability, a file system for uniform management of multiple types of image data was proposed. To meet the high efficiency and high fault tolerance requirements of the compression algorithm, based on run-length coding algorithm of first-1 bit, the three important processes of multi-load image unification processing, color image preprocessing, and segmented bit-plane image coding were expanded, to improve compression performance and fault tolerance. Then a complete set of image compression software design schemes was formed, using FPGA+DSP, and the complete set of software was realized. Finally a simulation verification system was used to verify the compression effect. Verification results show the effectiveness of the algorithm. This software has been verified by China’s Zhurong Mars rover and can effectively meet the needs of Mars exploration missions. The software design can be used as a reference for image compression in subsequent ultra-long-distance deep space explorations.

Signal reconstruction and disturbance observer-based fault-tolerant control for civil aircrafts

PurposeThis paper aims to focus on the sensor fault-tolerant control (FTC) for civil aircraft under exterior disturbance.Design/methodology/approachFirst, a three-step cubature Kalman filter (TSCKF) is designed to detect and isolate the sensor fault and to reconstruct the sensor signal. Meanwhile, a nonlinear disturbance observer (NDO) is designed for disturbance estimation. The NDO and the TSCKF are combined together and an NDO-TSCKF is proposed to solve the problem of sensor faults and bounded disturbances simultaneously. Furthermore, an FTC scheme is designed based on the nonlinear dynamic inversion (NDI) and the NDO-TSCKF.FindingsThe method is verified by a Cessna 172 aircraft model under bias gyro fault and constant angular rate disturbance. The proposed NDO-TSCKF has the ability of signal reconstruction and disturbance estimation. The proposed FTC scheme is also able to solve the sensor fault and disturbance simultaneously.Research limitations/implicationsNDO-TSCKF is the novel algorithm used in sensor signal reconstruction for aircraft. Then, disturbance observer-based FTC can improve the flight control system performances when the system with faults.Practical implicationsThe NDO-TSCKF-based FTC scheme can be used to solve the sensor fault and exterior disturbance in flight control. For example, the bias gyro fault with constant angular rate disturbance of a civil aircraft is studied.Social implicationsSignal reconstruction for critical sensor faults and disturbance observer-based FTC for civil aircraft are useful in modern civil aircraft design and development.Originality/valueThis is the research paper studies on the signal reconstruction and FTC scheme for civil aircraft. The proposed NDO-TSCKF is better than the current reconstruction filter because the failed sensor signal can be reconstructed under disturbances. This control scheme has a better fault-tolerant capability for sensor faults and bounded disturbances than using regular NDI control.

Fault-tolerant optimal pitch control of wind turbines using dynamic weighted parallel firefly algorithm

With steadily increasing interest in utilizing wind turbine (WT) systems as primary electrical energy generators, fault-tolerance has been considered decisive to enhance their efficiency and reliability. In this work, an optimal fault-tolerant pitch control (FTPC) strategy is addressed to adjust the pitch angle of WT blades in the presence of sensor, actuator, and system faults. The proposed scheme incorporates a fractional-calculus based extended memory (EM) of pitch angles along with a fractional-order proportional–integral–derivative (FOPID) controller to enhance the performance of the WT. A dynamic weighted parallel firefly algorithm (DWPFA) is also proposed to tune the controller parameters. The efficiency of the proposed algorithm is evaluated on the test functions adopted from 2017 IEEE congress on evolutionary computation (CEC2017). The merits of the proposed fault-tolerant approach are tested on a 4.8-MW WT benchmark model and compared to conventional PI and optimal FOPID approaches. Corresponding comparative simulation results validate the effectiveness and fault-tolerant capability of the proposed control paradigm, where it is observed that the proposed control scheme tends to be more consistent in the power generated at a given wind speed.

Model predictive control for reusable space launcher guidance improvement

This work aims to demonstrate the benefits and limitations of an on-board Guidance for reusable launch vehicles, as well as to tradeoff different Model Predictive Control (MPC)-based Guidance and Control (G&C) architectures, exploiting, in particular, recent advances on successive convexification algorithms for optimization problems. Leading space agencies and private companies are investing on the development of reusable space launchers to reduce the cost to access the space. Indeed, that cost is one of the major deterrents in space exploration and space utilization. Reusability is, therefore, the unanimous solution to lower costs, and get a reliable and fast space access. Among many technological enhancements, the guidance, navigation, and control plays a crucial role: precise pinpoint landing capabilities or mid-air recovery, in fact, are mandatory. Indeed, the capability for generating re-optimized guidance trajectories on-board in real-time based on current flight conditions promises to improve the system performance, allows for fault tolerance capabilities, and reduces mission preparation costs. The work focuses especially on the implementation of a successive convexification Model Predictive Control guidance algorithm which solves the 6 Degree-of-Freedom (DoF) Powered Descent Guidance problem (PDG). The novelty of that work is applying a model predictive-based technique to a complex dynamic environment, trading off different solutions to the problem and relying on results obtained by using an industrial simulation framework. The robustness of the proposed approach is tested in several operative scenarios and the feasibility of real-time implementation is studied. For what concerns the trajectory optimization routine, the formulation of the problem, while initially being non-convex, is convexified. This is performed by implementing a successive convexification algorithm, which obtains a sub-optimal solution of the original problem in a fraction of the time required by a global optimizer, by solving a Second Order Cone Programming (SOCP) problem. This method allows coping with different kinds of dynamics nonlinearities, as well as cost functions and constraints. By presenting the approach and critically discussing the obtained results, the work provides an overview of the different methodologies available in the literature and assesses the limits of those approaches when applied to highly nonlinear scenarios, with large dispersions of uncertain parameters, as it is the case of reusable launch vehicles.

Development and performance analysis of switched reluctance motor for E-rickshaw

Objectives: The main purpose of this study is to investigate switched reluctance motor for E-rickshaw propulsion system. Methods: The paper gives details of Literature review of current system incorporated in electric three wheeled propulsion, selection process of SRM, the design procedure of 8/6, 48V, 0.5 kW, 2000 rpm Switched reluctance motor for E-Rickshaw. Design validation and performance estimation is done by virtue of finite element analysis (FEA) tool using Ansys Maxwell Software. Findings: In this present work we found that it is possible to deploy SRM instead of current existing brushless direct current motors (BLDC) and PMSM (Permanent magnet synchronous motors) which are used in power train of electric three wheelers. Incorporating SRM would boost to promote “MAKE IN INDIA” and thus the country would become independent in electric vehicle market, hardware of the proposed SRM is also developed and tested. Novelty: The work done with investigation of SRM for E-rickshaw has not been studied until now although it possesses various advantages over existing system like high reliability and wide torquespeed range which is the basic requirement of propulsion motor in electric vehicles. SRM also provides several benefits like simple construction, high speed, resilience and good fault tolerance capability as all phases function independently. Keywords: ERickshaw; Brushless direct current motors; finite element analysis; Ansys Maxwell Software; Switched reluctance motor; Make in India

Decentralized adaptive tracking control for nonlinear large‐scale systems with unknown control directions

AbstractThis article investigates decentralized adaptive tracking problems for nonlinear large‐scale systems with strong interconnections, unknown control directions and actuator faults. In the presence of measurable system states, a decentralized state feedback control algorithm with a certain inherent fault tolerance capabilities is developed using the dynamic surface control and adaptive techniques. Particularly, a special Nussbaum gain is introduced in the control laws to compensate unknown control directions and unknown bounds of actuator efficiency factor. Using the graph theory and Lyapunov analysis method, it is proved that the designed fault‐tolerant state feedback controller can drive the tracking error for each subsystem to a small neighborhood of the origin while keeping the semiglobal uniform ultimate boundedness for all other closed‐loop signals. When the system states are unmeasurable, an output feedback fault‐tolerant control framework is also formed by introducing a new K‐filters with adjustable parameters and constructing appropriate coordinate transformations. Finally, the effectiveness of the proposed fault‐tolerant control algorithms is verified by simulating two system models.

Adaptive Fault-Tolerant System and Optimal Power Allocation for Smart Vehicles in Smart Cities Using Controller Area Network

Nowadays, the power consumption and dependable repeated data collection are causing the main issue for fault or collision in controller area network (CAN), which has a great impact for designing autonomous vehicle in smart cities. Whenever a smart vehicle is designed with several sensor nodes, Internet of Things (IoT) modules are linked through CAN for reliable transmission of a message for avoiding collision, but it is failed in communication due to delay and collision in communication of message frame from a source node to the destination. Generally, the emerging role of IoT and vehicles has undoubtedly brought a new path for tomorrow’s cities. The method proposed in this paper is used to gain fault-tolerant capability through Probabilistic Automatic Repeat Request (PARQ) and also Probabilistic Automatic Repeat Request (PARQ) with Fault Impact (PARQ-FI), in addition to providing optimal power allocation in CAN sensor nodes for enhancing the performance of the process and also significantly acting a role for making future smart cities. Several message frames are needed to be retransmitted on PARQ and fault impact (PARQ-FI) calculates the message with a response probability of each node.

A Remedial Control for Short-Circuit Fault in NPC/H-Bridge Inverters without Redundant Component

In this paper, a five-level neutral-point-clamped (NPC) inverter with short-circuit fault-tolerant capability is presented. Based on the proposed approach, in order to ensure service continuity subsequent to a short-circuit fault event in a switch, two steps are carried out. First of all, destructive consequences arising from short-circuit fault in a power switch is prevented. Afterwards, according to the defected component, remedial actions are taken. The proposed strategy does not require any redundant component. The service continuity is acquired by applying a remedial control and modifying switching commands applied to the power switches. Using the proposed approach helps to restore the rated voltage and rated current at the terminal, and there is no limit for modulation index during fault-tolerant operation under remedial control. Furthermore, compared to healthy operation, harmonic content of the terminal voltage and current is not deteriorated during fault-tolerant operation. Moreover, additional components, such as bidirectional switches and contactors, are not employed in this strategy. Only some fast fuses are placed in the converter circuit for protection purposes which do not impose a noticeable cost compared to the bidirectional switches and contactors.

Fault-Tolerant Control of a Three-Phase Permanent Magnet Synchronous Motor for Lightweight UAV Propellers via Central Point Drive

This paper deals with the development and the performance characterization of a novel Fault-Tolerant Control (FTC) aiming to the diagnosis and accommodation of electrical faults in a three-phase Permanent Magnet Synchronous Motor (PMSM) employed for the propulsion of a modern lightweight fixed-wing UAV. To implement the fault-tolerant capabilities, a four-leg inverter is used to drive the reference PMSM, so that a system reconfiguration can be applied in case of a motor phase fault or an inverter fault, by enabling the control of the central point of the three-phase connection. A crucial design point is to develop Fault-Detection and Isolation (FDI) algorithms capable of minimizing the system failure transients, which are typically characterized by high-amplitude high-frequency torque ripples. The proposed FTC is composed of two sections: in the first, a deterministic model-based FDI algorithm is used, based the evaluation of the current phasor trajectory in the Clarke’s plane; in the second, a novel technique for fault accommodation is implemented by applying a reference frame transformation to post-fault commands. The FTC effectiveness is assessed via detailed nonlinear simulation (including sensors errors, digital signal processing, mechanical transmission compliance, propeller loads and electrical faults model), by characterizing the FDI latency and the post-fault system performances when open circuit faults are injected. Compared with reports in the literature, the proposed FTC demonstrates relevant potentialities: the FDI section of the algorithm provides the smallest ratio between latency and monitoring samples per electrical period, while the accommodation section succeeds in both eliminating post-fault torque ripples and maintaining the mechanical power output with negligible efficiency degradation.

18‐Sided polygon voltage space vector fed nine‐phase induction machine drive for high power applications

The advantages such as better fault-tolerant capability, less space harmonic content, and requirement of power semiconductor devices with reduced voltage ratings etc., made the multi-phase induction machines drives (IMD) best desirable for the high power applications. However, as the number of phase increases, the improvement in the LMR of the multi-phase IMDs is not significant using the conventional SVPWM techniques provided in the literature. To address the above-mentioned limitation, 18-sided polygon (octadecagon) based voltage space vector generation for a nine-phase IMD is proposed in this article without compromising in the torque harmonic profile. Using the proposed octadecagonal voltage space vector generation technique, the LMR of nine-phase IMD is significantly improved by 26.03%, 24.28%, and 9.15% in comparison to the nine-phase sinusoidal pulse width modulation, nine-phase SVPWM and individual hexagonal SVPWM techniques, respectively. Efficacy of the proposed control technique is substantiated using the results obtained from ANSYS Maxwell simulation and experimentation on 5-hp nine-phase IMD prototype in the laboratory.

Predictive current control based pseudo six-phase induction motor drive

Asymmetrical six-phase induction machines are widely used in high-power safety-critical applications. The so-called pseudo six-phase winding layout has recently been proposed as a promising contender for high power medium voltage applications in terms of torque density, phase current quality, simple single-layer-based stator winding design, and fault-tolerant capability. This winding layout employs quadruple three-phase stator winding sets connected to provide only six terminals, while being fed from two three-phase inverters. Therefore, the same conventional six-phase-based control structure can still be employed. Among the different control techniques, model predictive current control is considered as one of the cutting-edge technologies for multiphase drive systems, thanks to its simplicity and flexibility in defining new control objectives. This paper investigates how the available 64 voltage vectors of a six-phase inverter are classified among different subspaces when employing a pseudo six-phase stator winding. Moreover, the required modifications to classical predictive current control (PCC) are introduced in order to properly control the machine in a manner similar to conventional asymmetrical six-phase machines while ensuring minimum circulating xy current components. The concept of virtual voltage vectors (VVVs) has also been employed to further enhance the stator current quality. The proposed controller is validated using a 2Hp prototype pseudo six-phase machine under different operating conditions. An experimental comparative study with an asymmetrical six-phase machines is also carried out to verify the claimed equivalence.

Performance enhancement of SRM using smart bacterial foraging optimization algorithm based speed and current PID controllers

In modern era, the switched reluctance motors (SRM) are gaining attraction due to its inherent features such as robustness, low cost, simple, rugged structure, excellent fault tolerance and temperature withstanding capability. With these specialized advantages, the accurate and efficient energy analysis is still a challenging one since they operated at variable reluctance and oscillating excitation characteristics resulting in nonlinear characteristics. This paper focused on the energy improvement and performance analysis inclusive of smooth control in speed and minimized torque ripples of SRM by introducing the novel Bio- inspired methodology named Bacterial Foraging Optimization Algorithm (BFOA) for the selection of optimal parameters of the PID speed and current controllers. By minimizing the torque ripples, it increases the average torque which in turn increases the energy conversion. The performance of the SRM is measured in terms of speed, current, power and efficiency and BFOA efficiency has been verified with genetic algorithm (GA) and conventional PID controller using Euler forward approximation method. This paper discusses the modeling, controlling strategy using BFOA, GA and Euler forward approximation method and a comprehensive analysis of energy using optimized selection of controlling parameters. The performance evaluation objectives in this work, is to minimize Integral Square Error of both current and speed controller and also the reduction of torque ripples. The results obtained in this method are also compared with the Genetic Algorithm and Euler forward approximation-based controllers. The proposed algorithm employs individual and social intelligences, which in turn search the responses between the local optima along with global optimums of the problem adaptively. The outmost dynamic response increased average torque and minimized current ripple can be obtained when the parameters of PID controllers are optimized using BFOA.

Improved direct model predictive control for variable magnitude variable frequency wave energy converter connected to constant power load

Archimedes wave swing (AWS) is the first direct-drive wave energy converter (WEC). The AWS is coupled to a linear permanent magnet synchronous generator (LPMSG) and generates a variable magnitude, variable frequency voltage. This paper presents an improved version of direct model predictive control (DMPC) which called improved DMPC (I-DMPC) for a hybrid system containing WEC, supercapacitor (SC) energy storage system (ESS), and constant power load (CPL). This method is implemented based on discrete incremental model of generator and modified objective function, therefor steady-state error is reduced. Simulation results in the MATLAB/SIMULINK environment show the proposed control can maintain stability of the system under different CPL demand and systems faults and improve robustness and fault-tolerant capability of the system in regular and irregular waves. The Comparing results with the conventional DMPC indicate, that by using I-DMPC, d-axis and q-axis errors under regular wave can be reduced 37.5% and 50%, respectively. Also, under irregular wave, I-DMPC reduce the peak of q-axis errors from 73A to 1.5 A when loss of one leg occurred.

Optimal Design of a Six-Phase Permanent-Magnet-Assisted Synchronous Reluctance Motor to Convert into Three Phases for Fault-Tolerant Improvement in a Traction System

A six-phase motor with a high degree of freedom can be converted into a three-phase motor in order to be used in a traction system. In addition, when phase-change technology is applied, it is possible to establish an efficient control strategy tailored to the driving environment of the EVs. Therefore, in this paper, a down-scaled 3 kW permanent-magnet-assisted synchronous motor (PMa-SynRM) capable of phase switching was designed, and its driving states in controlled fault modes were analyzed through experiments. The PMa-SynRM selected for this study was a machine that had good fault-tolerance capabilities and was less expensive than an IPMSM with the same performance; it was designed using the lumped-parameter method (LPM) having a fast calculating speed and a genetic algorithm. In addition, the effectiveness of the optimal design was verified by comparing the analytical results of the FEM and the LPM. Lastly, a phase switching experiment was conducted to analyze the steady-state and transient-state characteristics, and the results are presented.

EGG+: A graph grammar formalism with uncertain structure processing mechanism

Abstract Extended from string grammars, graph grammar is a 2D formal method, which could specify the syntax structures of visual programming languages intuitively yet formally. However, the graph matching conditions in most graph grammars are too strict in specified applications, influencing the flexibility and fault tolerant capability of graph grammar. To solve the problems, this paper introduces an uncertain structure processing mechanism into graph grammar formalism and proposes a new graph grammar named EGG+. Different from traditional graph grammars, EGG+ defines a class of special edges named uncertain edges to specify the uncertain relationships between graphical elements. Each graph with uncertain edge is defined an uncertain graph, as a prototype of a set of graphical structures. By the new terms and definitions, EGG+ productions are divided into two categories: certain productions and uncertain productions, where certain productions specify the structures with strict matching requirements and uncertain productions are used to ignore specified syntactical errors during derivation and reduction, providing fault tolerant capability for the accessible non-isomorphic structures. Moreover, a redex searching algorithm with polynomial time complexity is designed for the convenience of grammatical application in the new formalism.

Research on Redundant Design Technique for USV Autonomous Control System

In the field of USV autonomous control system design, redundant design technology is the important method to improve system reliability. In order to solve the problem of insufficient reliability when USV carrying out long endurance and open sea task, this paper analyzes the critical design elements of autonomous control system redundant configuration, presents a high reliable hybrid redundant structure for USV autonomous control system, and realizes redundant strategy and fault-tolerant control. This paper forms the USV autonomous control system redundant configuration scheme comply with the fault-tolerant capability and redundant rank of USV autonomous control system. Redundancy management strategies and algorithms are used to implement USV autonomous control based on hybrid redundant design. The reliability analysis and computation validate task reliability of the autonomous control system based on hybrid redundant structure.

Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active power filter supplied by a photovoltaic source

<span>This paper presents a novel shunt active power filter (SAPF). The power converter that is used in this SAPF is constructed from a four-leg asymmetric multi-level cascaded H-bridge (CHB) inverter that is fed from a photovoltaic source. A three-dimensional space vector modulation (3D-SVPWM) technique is adopted in this work. The multi-level inverter can generate 27-level output with harmonic content is almost zero. In addition to the capability to inject reactive power and mitigating the harmonics, the proposed SAPF has also, the ability to inject real power as it is fed from a PV source. Moreover, it has a fault-tolerant capability that makes the SAPF maintaining its operation under a loss of one leg of the multi-level inverter due to an open-circuit fault without any degradation in the performance. The proposed SAPF is designed and simulated in MATLAB SIMULINK using a single nonlinear load and the results have shown a significant reduction in total harmonics distortion (THD) of the source current under the normal operating condition and post a failure in one phase of the SAPF. Also, similar results are obtained when IEEE 15 bus network is used.</span>