Fault-tolerant Design Research Articles

Smart Investment for Redundancies Selection Integrated to Reconfigurable Fault-Tolerant Control Design

This paper presents a methodology for the optimal hardware redundancies selection in the context of reconfigurable fault-tolerant control design. Assuming that a nominal controller of reduced dimension has been successfully designed, the objective is to accommodate a presumed set of failures, including partial, total, and simultaneous actuator faults, preserving the system stability and maintaining an acceptable dynamic performance. The methodology is based on a multiobjective optimization framework to obtain a suitable trade-off between conflicting design objectives such as controllability and performance. The selection of additional hardware devices (not included in the nominal controller) is penalized to determine the minimum number of redundancies that should be installed. In addition, the redundancies selection is performed without explicitly considering the type of control structure. The effectiveness of the proposed approach is tested using the well-known Tennessee Eastman benchmark.

Fault Tolerant ALU using Parity Preserving Reversible Logic Gates

Demand of reliable computing has been a major concern since the dawn of the electronic digital computer age. Reliable computing has various applications not only in the field of military, aerospace and communication but even contemporary commercial applications to fulfill today’s automated life style. The tremendous growth in fabrication from small scale integration (SSI) to giant scale integration (GSI) is facing power dissipation as one of the main barriers. To overcome this barrier, researchers need to enter into the reversible logic domain. Making a reversible circuit robust or fault tolerant is much more difficult than a conventional logic circuit. Fault tolerance can be achieved in a system by using parity bits. The main aim of this paper is to come up with a new fault tolerant ALU design based on parity preserving reversible logic gates with improved quantum cost and power overhead as compare to existing fault tolerance based ALU designs. The most stringent requirement for fault tolerant ALU is in real time control system where faulty computation jeopardizes human life or other catastrophic effects.Implentation of proposed design is done using Xilinx ISE design suit 14.2 tool and its performance over existing ALU designs is qualitatively analyzed.

Acceleration-based fault-tolerant control design of offshore fixed wind turbines

Wind turbines (WTs) are basically controlled by varying the generator load torque (with the so-called torque control) and the blade pitch angles (with the so-called pitch control) based on measurement of the generator shaft speed. These two controllers unitedly work to satisfy the control objectives, and it is crucial that they are tolerant to possible faults in the WT system. Passive fault-tolerant control comprises the design of robust controllers against disturbances and uncertainties. This enables the controller to counteract the effect of a fault without requiring reconfiguration or fault detection. In this regard, the main contribution of this paper is to propose new control techniques that not only provide fault tolerance capabilities to the WT system but also improve the overall performance of the system in both fault-free and faulty conditions. Coupling nonlinear aero-hydro-servo-elastic simulations of an offshore WT with jacket platform is carried out for several pitch actuator faults. The jacket platform motions and structural loads caused by fault events with the proposed controllers are compared with loads encountered during normal operation and with respect to a well-known baseline controller in the literature. The proposed controllers are based in the super-twisting algorithm by using feedback of the generator shaft speed as well as the fore-aft and side-to-side acceleration signals of the WT tower.

Active fault tolerant control design for uncertain strict‐feedback non‐linear systems

This study proposes an active fault tolerant control (FTC) scheme for uncertain strict-feedback non-linear systems. Changes in the system dynamics due to faults are modelled as unknown non-linear functions of the measurable state variables. The scheme is composed of fault detection and estimation (FDE) module, accommodation mechanism and nominal controller based on the dynamic surface control (DSC). The FDE module, composed of a diagnostic estimator and an adaptive non-linear-in parameter (NLIP) approximator, generates the residual signal, detects and estimates fault simultaneously. Robust adaptive laws are derived for learning all parameters of an adaptive NLIP approximator. After FDE, accommodation mechanism uses the generated fault information to construct the corrective control law to compensate the fault effects. The proposed active FTC system detects and estimates unknown fault and constructs a corrective control law to reduce the effects of fault on the system without the need for fault isolation module. Unlike most of the traditional active FTC schemes, the proposed scheme requires no prior knowledge about the faulty situations, offline computational cost and fault isolation module. It is proven that all signals of the closed loop system are uniformly ultimately bounded. Simulation results illustrate the effectiveness of the proposed scheme.

Fault-tolerant design approach for reliable offshore multi-megawatt variable frequency converters

Inverters play a key role in realizing reliable multi-megawatt power electronic converters used in offshore applications, as their failure leads to production losses and impairs safety. The performance of high power handing semiconductor devices with high speed control capabilities and redundant configurations helps in realizing a fault-tolerant design. This paper describes the reliability modeling done for an industry standard, 3-level neutral point clamped multi-megawatt inverter, the significance of semiconductor redundancy in reducing inverter failure rates, and proposes methods for achieving static and dynamic redundancy in series connected press pack type insulated gate bipolar transistors (IGBT). It is identified that, with the multi megawatt inverter having 3+2 IGBT in each half leg with dynamic redundancy incorporated, it is possible to reduce the failure rate of the inverter from 53.8% to 15% in 5 years of continuous operation. The simulation results indicate that with dynamic redundancy, it is possible to force an untriggered press pack IGBT to short circuit in <1s, when operated with a pulse width modulation frequency of 1kHz.

Robust fault-tolerant control for wing flutter under actuator failure

Many control laws, such as optimal controller and classical controller, have seen their applications to suppressing the aeroelastic vibrations of the aeroelastic system. However, those control laws may not work effectively if the aeroelastic system involves actuator faults. In the current study for wing flutter of reentry vehicle, the effect of actuator faults on wing flutter system is rarely considered and few of the fault-tolerant control problems are taken into account. In this paper, we use the radial basis function neural network and the finite-time H∞ adaptive fault-tolerant control technique to deal with the flutter problem of wings, which is affected by actuator faults, actuator saturation, parameter uncertainties and external disturbances. The theory of this article includes the modeling of wing flutter and fault-tolerant controller design. The stability of the finite-time adaptive fault-tolerant controller is theoretically proved. Simulation results indicate that the designed fault-tolerant flutter controller can effectively deal with the faults in the flutter system and can promptly suppress the wing flutter as well.

A comparison of fatigue strength sensitivity to defects for materials manufactured by AM or traditional processes

The fatigue behavior of metallic materials fabricated via additive manufacturing processes is currently not well understood and it has been the subject of many experimental investigations in recent years. In this paper we carried out a literature review about the fatigue strength of additively manufactured AlSi10Mg and Ti6Al4V, especially in terms of sensitivity to defects and inhomogeneities. The analysis shows that fatigue properties and key variables (heat treatment, defect size) are very similar to the ones of parts obtained with traditional manufacturing processes. These results confirm that defect tolerant design concepts can be adopted also for AM components.

Speed sensor fault tolerant controller design for induction motor drive in EV

This paper deals with the problem of speed sensor fault tolerant controller (SSFTC) design for Induction Motor (IM) drive in electric vehicle (EV). First, the Takagi-Sugeno (T-S) model approach was adopted to represent the nonlinear dynamic of IM subject to speed sensor faults and unknown bounded disturbance. Next, based on L2 robust fault detection filter design, a Modified Field Oriented Controller (MFOC) is designed. The proposed approach requires the knowledge of the occurring faults which are estimated from a descriptor observer. The observer gains are determined by solving a set of Linear Matrix Inequality (LMI). Finally, simulation results show the effectiveness of the proposed approach evaluated on 7.5kVA Induction Motor.

Dynamic surface active fault tolerant control design for the attitude control systems of UAV with actuator fault

In this paper, an active fault tolerant control (FTC) approach based on transient performance index is proposed for the attitude control systems of unmanned aerial vehicle (UAV) with actuator fault. The nonlinear attitude control system model for UAV with actuator faults is given, which represents the dynamic characteristics of UAV. A fault diagnosis component is used for fault detection and estimation. According to the fault estimation information obtained during the fault diagnosis, the fault tolerant control scheme is developed by adopting the adaptive dynamic surface control technique, which guarantees the asymptotic output tracking and ultimate uniform boundedness of the closed-loop attitude control systems of UAV in actuator faulty case. Further, a prescribed transient performance of the FTC attitude control systems is considered which characterizes the convergence rate and maximum overshoot of the attitude tracking error. Finally, simulation results are shown that the attitude control system states remain bounded and the output tracking errors converge to a neighborhood of zero.

Real-time fault tolerant full adder design for critical applications

In the complex computing system, processing units are dealing with devices of smaller size, which are sensitive to the transient faults. A transient fault occurs in a circuit caused by the electromagnetic noises, cosmic rays, crosstalk and power supply noise. It is very difficult to detect these faults during offline testing. Hence an area efficient fault tolerant full adder for testing and repairing of transient and permanent faults occurred in single and multi-net is proposed. Additionally, the proposed architecture can also detect and repair permanent faults. This design incurs much lower hardware overheads relative to the traditional hardware architecture. In addition to this, proposed design also provides higher error detection and correction efficiency when compared to the existing designs.

WITHDRAWN: Reversible logic adders: Novel low-cost fault-tolerant designs

WITHDRAWN: Reversible logic adders: Novel low-cost fault-tolerant designs

Control Tolerante a Fallas Activo: Estimación y acomodación de fallas en sensores aplicado al modelo LPV de una bicicleta sin conductor

This paper presents an Active Fault Tolerant Control design applied to a riderless bicycle LPV model affected by additive sensor fault and measurement noise. Within the Active Fault Tolerant Control, the detection and diagnostic system is based on the estimations computed by a fault observer, used to determine a fault occurrence. The proposed algorithms, considered as the main contributions in this work, achieves noise-free estimations for the faults and state, in order to compute the fault indicator and control law, respectively. The fault tolerance of the system is guaranteed through the fault accommodation based on a set of observers. The results have been corroborated using a riderless bicycle LPV model, with a controller that aims at keeping it stood-up along its translation motion.

Fault Tolerant Control of an AUV using Periodic Output Feedback with Multi Model Approach

Active thruster control is an important problem in AUV. One of the way to tackle this problem is to make the dynamic system like AUV as adaptive and self-controlling. This article discusses the fault tolerant controller design with periodic output feedback for Autonomous Underwater Vehicle using multi model approach. The entire system is modelled in state space. Assuring high degree of reliability and persisting autonomy under thruster failure the controller has to be designed such that the thrust distribution is effectively controlled if any one of the signals and corresponding thrusters fails. The AUV is modelled in six degrees of freedom having six inputs and six outputs. Four thrusters are used for vertical and horizontal movements in AUV. Fault tolerant controller is designed for depth control of AUV, with periodic output feedback gains with multi model approach. To each thruster failure the multi model is presented with the gain matrix having all off diagonal terms zero. The designed robust fault tolerant controller with periodic output feedback with multi model approach provides satisfactory stabilization to AUV depth system.

Finite-time fault-tolerant control for flutter involving control delay

Many control laws, such as optimal controllers and classical controllers, have seen their applications to suppressing the aeroelastic vibrations of the aeroelastic system. However, those control laws may not work effectively if the aeroelastic system involves control delay and faults. In this paper, we use the finite-time H∞ adaptive fault-tolerant control technique to deal with the flutter problem of the wing, which is subject to control delay, parameter uncertainties and external disturbances. Then actuator faults are considered in the control design. The theory content of this article includes the modeling of wing flutter and fault-tolerant controller design. By using the Lyapunov–Krasovskii function and the linear matrix inequality (LMI), the stability of the finite-time H∞ adaptive fault-tolerant controller is theoretically proved. Simulation results are given to demonstrate the effectiveness of the scheme.

Finite-time fault-tolerant control for flutter of wing

In this paper, we use the radial basis function neural network and the finite-time H∞ adaptive fault-tolerant control technique to deal with the flutter problem of wings with propulsion system, which is affected by input saturation, time delay, time-varying parameter uncertainties and external disturbances. Then sensor and actuator faults are both considered in the control design. The theory content of this article includes the trajectory optimization, modeling of wing flutter and fault-tolerant controller design. The stability of the finite-time H∞ adaptive fault-tolerant controller is theoretically proved. Finally, simulation results are given to demonstrate the effectiveness of the scheme.

A Survey on Design Approaches to Circumvent Permanent Faults in Networks-on-Chip

Increasing fault rates in current and future technology nodes coupled with on-chip components in the hundreds calls for robust and fault-tolerant Network-on-Chip (NoC) designs. Given the central role of NoCs in today’s many-core chips, permanent faults impeding their original functionality may significantly influence performance, energy consumption, and correct operation of the entire system. As a result, fault-tolerant NoC design gained much attention in recent years. In this article, we review the vast research efforts regarding a NoC’s components, namely, topology, routing algorithm, router microarchitecture, as well as system-level approaches combined with reconfiguration; discuss the proposed architectures; and identify outstanding research questions.

Robust adaptive fault-tolerant control for a class of uncertain nonlinear systems with multiple time delays

This study is concerned with the problem of robust adaptive fuzzy fault-tolerant control for a class of uncertain nonlinear systems with mismatching parameter uncertainties, external disturbances, multiple state time delays perturbations and actuator failures, which include loss of effectiveness, outage and stuck modes. A novel direct adaptive fuzzy tracking control scheme is developed to achieve the fault-tolerant control objective. First, by introducing a positive nonlinear control gain function, the effects of state time delays and actuator failures are effectively compensated. Then, a suitable fuzzy logic system (FLS), which is used to approximate the corresponding nonlinear function, is constructed to eliminate the influences on mismatched parameter uncertainty and external disturbance. Moreover, it is shown that all the closed-loop system signals are uniformly bounded and that the tracking error converges to a small neighborhood of the origin via Lyapunov–Krasovskii stability analysis. Finally, the proposed adaptive fuzzy fault-tolerant tracking design approach is illustrated on a two stage chemical reactor system with delayed recycle streams.

Practical relevance of faults, diagnosis methods, and tolerance measures in elastically actuated robots

Elastically actuated robots promise safe human–robot interaction and energy-efficient motions. Yet, increased complexity and critical operation states might increase the practical fault risk. This paper explores faults in such robots using expert data from the field and identifies components that show increased fault occurrence: the highest fault sensitivity occurs in kinematics, electronics, sensors, and software. Since elastic actuators are an active field of research, few cases of industrial application exist and thus most experts in this study have academic background. Beyond assessing fault sensitivity, countermeasures such as redundant design are compiled. A brief literature review discusses fault diagnosis and fault-tolerant design with respect to these insights. Despite the availability of a few promising methods in robotics, neither diagnosis nor tolerance do receive sufficient recognition leaving potential for practical application.

A lumped fluidic model of an anode chamber for fault tolerant strategy design

Water management in Proton Exchange Membrane (PEM) fuel cell systems is a critical point. This article will widely explain the importance of anode exhaust gas management for fuel cell and the issues of liquid water accumulation in the anodic compartment of a dead-ended anode fuel cell system. A 0D model of the water behavior in the anode channels is introduced and an identification procedure of the water diffusion coefficient and a tunable parameter, using the least-square criteria, has been developed. The presented results show good correlation, allowing to extend the model to hydrogen and to validate it with experiments. This model will be useful to elaborate a fault tolerant strategy to mitigate the impact of liquid water accumulation into the anode chamber.

Fault tolerant control design using adaptive control allocation based on the pseudo inverse along the null space

Summary Fault-tolerant control systems are vital in many industrial systems. Actuator redundancy is employed in advanced control strategies to increase system maneuverability, flexibility, safety, and fault tolerability. Management of control signals among redundant actuators is the task of control allocation algorithms. Simplicity, accuracy and low computational cost are key issues in control allocation implementations. In this paper, an adaptive control allocation method based on the pseudo inverse along the null space of the control matrix (PAN) is introduced in order to adaptively tolerate actuator faults. The proposed method solves the control allocation problem with an exact solution and optimized l∞ norm of the control signal. This method also handles input limitations and is computationally efficient. Simulation results are used to show the effectiveness of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.