Fault-tolerant Sensor Research Articles

Development of sensor nodes based on fault tolerance

In the present paper, and a fail-safe system capable of operating in safety side even upon occurrence of failures was designed where internet of things (IoTs)-based sensor nodes allowed fault tolerance based on hardware redundancy. The fault tolerance system masked faults with the application of triple modular redundancy (TMR) system and enabled fail-safe control by using a comparator for fault detection and self-diagnostics. The fault-tolerant sensor nodes presented in the paper were installed outdoors where disasters/calamities could occur and could execute the specified algorithms even upon occurrence of faults allowing the use in areas with poor environments and particularly the application to plant facilities for management of oil and gas pipelines, etc. as the high reliability could be guaranteed.

Hierarchical Combination Reliability Modeling Method for Fault Tolerant Sensor System

According to the architecture feature of the fault tolerant sensor system, a hierarchical combination reliability modeling method was proposed based on the dynamic fault tree analysis and the Markov process. Temporal operators were applied to represent the sequential logic, and the analytic formula for the failure probability of the top event was derived. The FDI (failure detection and isolation) behavior was modeled by the Markov process. The resultant model was compared to the PFCM (perfect fault coverage model). The impact of the parameters on the system reliability was evaluated. The simulation results demonstrate the modeling method is feasible, efficient and more accurate.

Energy-aware topology control for reliable data delivery in solar-powered WSNs

Solar power is a valuable source of power for wireless sensor networks, but it periodically requires an appropriate energy management strategy. We introduce a scheme that constructs and maintains a fault-tolerant wireless sensor network topology that can make the best use of solar energy. This topology control scheme is based on a simple model of the availability of solar energy and matches the connectivity of each node with the energy left in its battery. Operating locally, our scheme constructs and maintains a k-connected backbone of energy-rich nodes that handles most of the network’s traffic reliably, without depleting the reserves of energy-poor nodes. Simulation results demonstrate the effectiveness of our scheme.

Localization-free and energy-efficient hole bypassing techniques for fault-tolerant sensor networks

Nowadays, since wireless sensor networks (WSNs) are increasingly being used in challenged environments such as underground mines, tunnels, oceans and the outer space, fault-tolerance need has become a major requirement for routing protocols. So far, the proposed fault-tolerance methods or algorithms aim to recover the isolated failures which occur at different parts of the network in different times. However, there is another type of failure for WSNs which is more destructive for the applications. By collapsing sensor nodes as a group at the same time, a hole can appear at the network which may cut the data delivery drastically. In the literature, previous studies for bypassing holes are based on localization which may have significant energy and economic costs. In this paper, two localization-free and energy-efficient algorithms are proposed for bypassing the holes formed by group collapse. We realized that when holes are modeled with clusters, hole bypassing can be solved by cluster bypassing. Our algorithms, intra-cluster bypass and inter-cluster bypass, aim to heal the corrupted communication links in the presence of holes. We show the operation of the algorithms, analyze them and provide extensive simulation results in an ns-2 environment. We compare our proposed algorithms with the other approaches and show that our algorithms significantly improve the fault recovery percentages while consuming a reasonable amount of energy even in the presence of high collapse ratio.

Measurement Theory and Experimental Study of Fault-Tolerant Fully Pre-Stressed Parallel Six-Component Force Sensor

To meet the high reliability requirement under complicated environment and overcome the disadvantages of parallel structure six-component force sensor with traditional spherical pairs, the design concepts of fault-tolerance and fully prestressing are proposed to the design of parallel six-component force sensor. A kind of fault-tolerant and fully prestressed parallel structure force sensor using modified spherical pairs is proposed. The structural characteristics of the sensors are analyzed in comparison with traditional Stewart platform-based sensor. The complete mathematic model including the models with and without signal fault is established using screw theory and considering the relations of stiffness and force distribution. The mathematical expression to obtain the lower bound of prestressed force is determined. The static calibration experimental study of a sensor prototype is carried out, and the experimental results prove the superiority of the structure and the correctness of theoretical analysis. Besides, a fault diagnosis method is proposed and verified with a tracking task, which provides a basis for the applied research of the fault-tolerant sensor.

A New Method for Reducing Energy Consumption in Wireless Sensor Networks using Fuzzy Clustering and Fault Tolerance

Nowadays, wireless sensor networks, clustering protocol based on the neighboring nodes into separate clusters and fault tolerance for each cluster exists for sensors to send information to the base station, to gain the best performance in terms of increased longevity and maintain tolerance than with other routing methods. However, most clustering protocols proposed so far, only geographical proximity (neighboring) cluster formation is considered as a parameter. In this study, a new clustering protocol and fault tolerance based on the fuzzy algorithms are able to clustering nodes in sensor networks based on fuzzy logic and fault tolerance. This protocol uses clustering sensor nodes and fault tolerance exist in the network to reduce energy consumption, so that faulty sensors from neighboring nodes are used to cover the errors, work based on the most criteria overlay neighbor sensors with defective sensors, distance neighbor sensors from fault sensor and distance neighbor sensors from central station is done. Superior performance of the protocol can be seen in terms of increasing the network lifetime and maintain the best network tolerance in comparison with previous protocols such as LEACH in the simulation results.

New Fault-Tolerant Scheme for Flight Control System of Unmanned Aerial Vehicles

In complex systems like flight control systems etc., reliability is as important as performance. In order to improve the reliability of flight control system (FCS), the fault- tolerant technique was adopted. Three parts of the FCS which are Flight Control Fault Tolerant Computer, Redundancy sensor and Servo-actuator have been explored. The key techniques have been solved, such as Redundant Disposition, Synchronism of the Redundant Channels, Data link and Communication of Channels, etc. The experimental results show that the system meets with the fly control system’s demand of reliability.

Fault tolerant control of induction motor through observer techniques II

In the design of the control law due to sensor and actuator faults, it is very important to implement the fault tolerant control system. Unknown Input Observers (UIO) can be used in model based fault detection and isolation (FDI) schemes to reduce or almost eliminate the effect of unknown disturbances on the MIMO plant/system. Furthermore, they can be used to generate residuals that are insensitive to unknown disturbances or noise, and thus, lower the false alarm rate. Design of many faults isolation banks of UIOs has been done. To make sure the best detection and isolation of the faults is provided, these banks generate residuals which are sensitive to only one fault. Fault tolerant control is used to compensate both sensor and actuator faults. Key words: Fault tolerant control, actuator fault, and sensor fault unknown input observer, fault detection and isolation, MIMO system, induction motor.

Fault Tolerant Sensor Network Design with Respect to Diagnosability Properties

Interest for more reliable and safety systems is growing as control systems become increasingly complex and encounter various unexpected component failures. Indeed, fault-tolerant control, and fault detection and identification take into account, at the early design stage, unexpected system failures. For this reason, the ability of a system (sensors, actuators, components) to tolerate a fault must be taken from designing. This paper deals with the problem of fault tolerant sensor network design. A new approach based on residual structure analysis is proposed to provide a fault tolerant architecture. The proposed analysis is based on diagnosability properties in case of sensor loss situations; it evaluates the capacity of the system to be fault tolerant. A graph representation is used to study diagnosability, and evaluate fault tolerance capacity in different cases of sensors distribution.

Sensor network design for complex systems

SUMMARY This paper proposes a strategy to design a minimal and fault-tolerant sensor network for observability of complex systems. Complex systems are large-scale dynamic systems composed of interconnected subsystems. The objective is to determine the sensors to be used so that the system is observable while minimizing the number of sensors. The strategy is based on breaking down complex systems into interconnected subsystems. System breakdown helps in treating each subsystem separately and allows using reduced-order observers rather than a large-scale observer for the overall system. An academic example is given to illustrate the proposed strategy.Copyright © 2011 John Wiley & Sons, Ltd.

Research on a Real-Time Fault Tolerant Time Synchronization Algorithm for GSM-R Wireless Sensor Networks Based on Network Materials

Time synchronization is a key technology in wireless sensor networks. In this paper, aim at high-speed railway GSM-R network require higher real time, fault tolerance and band coverage way, presents a real-time fault-tolerant wireless sensor network time synchronization algorithm, using direct forwarding strategy, regression analysis and abnormal data filtering methods to meet the requirements of GSM-R network. Analysis and simulation show that the algorithm has good real-time and fault tolerance to meet the requirements of GSM-R network applications.

Maximising lifetime for fault-tolerant target coverage in sensor networks

Abstract We study the problem of maximising the lifetime of a sensor network for fault-tolerant target coverage in a setting with composite events. Here, a composite event is the simultaneous occurrence of a combination of atomic events, such as the detection of smoke and high temperature. We are given sensor nodes that have an initial battery level and can monitor certain event types, and a set of points at which composite events need to be detected. The points and sensor nodes are located in the Euclidean plane, and all nodes have the same sensing radius. The goal is to compute a longest activity schedule with the property that at any point in time, each event point is monitored by at least two active sensor nodes. We present a (6 + ɛ)-approximation algorithm for this problem by devising an approximation algorithm with the same ratio for the dual problem of minimising the weight of a fault-tolerant sensor cover. The algorithm generalises previous approximation algorithms for geometric set cover with weighted unit disks and is obtained by enumerating properties of the optimal solution that guide a dynamic programming approach.

Sensor Fault Tolerance Method by Using a Bayesian Network for Robot Behavior

This paper presents FTBN, a new framework that performs learning autonomous mobile robot behavior and fault tolerance simultaneously. For learning behavior in the presence of a robot sensor fault this framework uses a Bayesian network. In the proposed framework, sensor data are used to detect a faulty sensor. Fault isolation is accomplished by changing the Bayesian network structure using interpreted evidence from robot sensors. Experiments including both simulation and a real robot are performed for door-crossing behavior using prior knowledge and sensor data at several maps. This paper explains the learning behavior, optimal tracking, exprimental setup and structure of the proposed framework. The robot uses laser and sonar sensors for door-crossing behavior, such that each sensor can be corrupted during the behavior. Experimental results show FTBN leads to robust behavior in the presence of a sensor fault as well as performing better compared to the conventional Bayesian method.

Cooperative federated filtering approach for enhanced position estimation and sensor fault tolerance in ad-hoc vehicle networks

The present study addresses a solution to the position and orientation estimation problem of vehicles in ad-hoc vehicle networks using decentralised filtering. Specifically, a distributed filter operating in a cooperative federated structure for enhancing the estimation accuracy of vehicles state over unreliable wireless communication networks subject to uncertain and limited measurements is proposed. The filter relies on a variety of position measurements obtained from the on-board vehicle positioning system, from other cooperating vehicles in the vicinity, as well as from the immediate roadside environment via communication. Direct distance measurements between vehicles, furthermore, between vehicles and the stationary elements of the infrastructure can be used, if available, as highly accurate reference measurements. The study demonstrates how successfully the novel idea of cooperative federated filtering in addressing the demands of both fault tolerance and enhanced estimation accuracy in ad-hoc vehicle networks can be used.

Estimating the State of Distributed Dynamical Systems Based on Limited Measurements by means of Cooperative Filtering with Application to ad-hoc Vehicle Network

In this paper a decentralized approach to state estimation of distributed dynamical systems over unreliable communication network subject to uncertain and limited measurements is addressed. Specifically, a distributed filtering concept for enhancing the estimation accuracy of vehicles state from uncertain position data in ad-hoc vehicle networks is presented. The filter relies on a variety of position measurements obtained from the on-board vehicle positioning system, from other nearby cooperating vehicles, as well as from the immediate roadside environment via communication. Direct distance measurements between vehicles as well as between vehicles and the static elements of the roadside infrastructure can be used, if available, as highly accurate reference measurements. The paper demonstrates how successfully the idea of cooperative filtering in addressing the demands of both sensor fault tolerance and enhanced estimation accuracy in distributed systems over ad-hoc communication networks can be used.

A Fault-tolerant Adaptive Node Scheduling Scheme for Wireless Sensor Networks *

In wireless sensor networks, the limited battery resources of sensor nodes have a direct impact on network lifetime. To improve energy efficiency, there have been a variety of sensor node scheduling methods to keep only a minimum number of sensor nodes in active mode. However, those existing sensor node scheduling methods mainly focus on the coverage problems, largely ignoring the fault-tolerance issues. In this paper, we proposes a new fault-tolerant sensor node scheduling algorithm, called FANS (Fault-tolerant Adaptive Node Scheduling), that does consider not only sensing coverage but also sensing level. The proposed FANS algorithm enables to preserve sensing coverage, maximize network lifetime and achieve energy efficiency. Experimental results show that the FANS algorithm provides enhanced performance in terms of sensing coverage, energy consumption and the number of control messages.

A novel fault-tolerant sensor system for sensor drift compensation

The conventional fault-tolerant sensor systems would fail when outputs from incorporated sensors are either noisy or drifting. This paper presents a novel real-time fault compensation method, which uses state estimation and compensation techniques, that the sensor system can perform robust measurements even when outputs from every incorporated sensor are noisy and drifting. In a simulation example, the proposed design can detect and correct the sensor errors (dc bias and drift) in real time. For the dc bias, the minimum detectable offset value is 0.1, which is the same as the standard deviation of the sensor noise. The compensated sensor output is biased at values smaller than 0.02. For the sensor drifts, the proposed method can compensate drifts for the change rate of drifts up to four times faster than that of the signal to be measured. The highest change rate of drifts, that can be compensated by this method, is determined by the standard deviation of the sensor noise.

Control and Sensor Fault Tolerance of Vehicle Active Suspension

In this paper, a full vehicle active suspension system is considered with the dynamics of the four force actuators. Being a large-scale and complex nonlinear system, it is physically decomposed into five interconnected subsystems. For each subsystem, a local controller is designed. Each control module is decomposed into functional submodules. In a higher level, a global module is designed to supervise all the submodules. In parallel to this hierarchical structure of control, a fault diagnosis structure is constructed. A local diagnosis module is designed for each subsystem to detect and isolate sensor faults. The local modules are monitored by a global module. Simulation is done to illustrate the system control, diagnosis, and fault tolerance.

Improved robustness and sensor fault tolerance via a generalized internal model-based fault-tolerant controller

In this paper the synthesis of an implicit fault-tolerant control system that is capable of handling multiple sensor faults in addition to modelling uncertainties is presented. The implicit approach allows sensor fault tolerance without the need for accurate information from the fault diagnosis element. Difficulties encountered when solving for a fault-tolerant control problem commonly related to the reliability and accuracy of its fault diagnosis element are thus avoided. Based on extensions to the generalized internal model-based controller (GIMC), the new development proposed in this paper includes the introduction of an Hinfin loop-shaping controller in the structure to facilitate best control performance augmented by standard H∞ controllers as a fault-compensating block to facilitate fault tolerance towards multiple sensor fault conditions and robustness towards modelling uncertainties. Crucial stability and robustness analysis/proofs of the proposed design are conveniently obtained. Sensor faults are modelled as functions within a bounded family of signals and an internal model of this family is embedded into the fault compensating H∞ controller which is cascaded to the H∞ loop-shaping controller. The reliability of operation towards modelling uncertainties is also shown to be guaranteed. Its potential for providing multiple sensor fault tolerance in addition to robustness towards modelling uncertainties is illustrated with a flight control system example; results are significant, as observed in a comparison of control performance with standard H∞ and μ controllers.

Fault-tolerant sensor integration for micro flow-sensor arrays and networks

Distributed micro flow-sensor arrays and networks (DMFSA/N), built from collections of spatially scattered, cooperating intelligent and redundant micro flow-sensor nodes, can improve the accuracy and reliability of system. However, it is unrealistic to expect all the sensor nodes and communication links in the system to function properly all the time. This paper is based on an earlier research, in which a DMFSA/N with a cluster architecture and fault-tolerant time-out Protocol (FTTP) was developed. In this paper, a fault-tolerant sensor integration algorithm (FTSIA) is proposed and evaluated in simulations. Experimental results showed that the FTSIA could always give reliable results even when certain portion of the sensors yielded faulty information. Furthermore, the results from FTSIA were significantly more accurate than the mean of sensor readings (popularly applied in industry) if some of the sensors produced faulty readings. Finally, the application of the proposed FTSIA is illustrated by measuring flow pressure using a pressure sensor array of eight sensors.