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This paper addresses a study of fault-tolerant control (FTC) for wireless networked control systems (WNCSs) in industrial automatic processes. The WNCSs is composed of many subsystems, which operate with different sampling cycles. In order to meet the real-time requirements and ensure a deterministic data transmission, the time division multiple access (TDMA) mechanism is adopted in WNCSs. The data in WNCSs are transmitted following a TDMA-based scheduler. According to the periodicity, WNCSs integrated with the scheduler is first formulated as discrete linear time periodic systems (LTPSs). Afterwards, a fault estimation method for LTPSs is developed under a H ∞ performance specification with a regional pole constraint. With the achieved state observer and fault estimator, an FTC strategy for LTPSs is explored. Finally, the proposed methods are verified on a physical experimental WiNC platform. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The problem of residual evaluation for fault detection in nonlinear systems is addressed in this article. Using the factorisation approach, a post-filter is designed and a threshold is computed to achieve an optimal trade-off between fault detectability and the number of false alarms. Furthermore, it is shown that the proposed post-filter also guarantees H-/H∞ multi-objective optimisation of the residual signal. The effectiveness of the proposed method is demonstrated by fault detection of the three-tank benchmark system. [ABSTRACT FROM AUTHOR]

An optimal decentralised fault detection (FD) system is proposed for a class of discrete-time large-scale systems, where limited information exchange among subsystems is enabled with communication networks. Such an FD system consists of two parts in each subsystem: a residual generator (RG) and a residual evaluator. By taking the advantages of network communications, the RGs are designed to match a proper reference model in a stochastic sense such that a best trade-off between the robustness against disturbances and the sensitivity to faults can be achieved. In each residual evaluator, a norm-based evaluation function is selected for evaluating residual signals and a corresponding threshold is calculated for detecting the occurrences of faults. All the solutions are presented in the form of linear matrix inequalities. Finally, a numerical example is given to illustrate the results and the improvement achieved by applying network communications. [ABSTRACT FROM AUTHOR]

The problem of delay-dependent stabilisation for singular linear continuous-time systems with multiple internal incommensurate constant point delays is investigated. The condition when a singular system subject to point delays is regular independent of time delays is given and it can be easily tested with numerical or algebraic methods. Based on the Lyapunov–Krasovskii functional approach and the descriptor integral-inequality lemma, a sufficient condition for delay-dependent stability is obtained. The main idea is to design multiple memory state feedback control laws such that the resulting closed-loop system is regular independent of time delays, impulse free and stable via solving matrix inequality problem. An explicit expression for the desired memory state feedback control law is also given. Finally, a numerical example is presented to illustrate the effectiveness and the availability for the proposed method. [ABSTRACT FROM AUTHOR]

The Mg-3 pct Al-1 pct Zn (AZ31) alloy has been used as a model material for understanding the grain-refinement process of a Mg alloy fabricated by equal-channel angular extrusion (ECAE). The effects of ECAE processing parameters on grain refinement have also been studied; it was found that these effects are quite different from those for fcc metals. A multitemperature extrusion procedure has been developed, which can produce an ultrafine-grained AZ31 alloy having a grain size 0.37 μm. For the AZ31 alloy, this ultrafine-grained alloy has a record high strength accompanied by reasonably good tensile ductility. The success of the development of this ECAE procedure proves that ECAE can offer a good opportunity for the development of high-strength Mg alloys. [ABSTRACT FROM AUTHOR]

We present a proportional, multiple-integral and derivative (PMID) observer technique that can simultaneously estimate system states, fault signals and the finite times derivatives of the faults for a descriptor system with input and measurement faults. Furthermore for a descriptor system with input and measurement faults and unknown disturbances (including modelling errors), a robust PMID observer is designed to simultaneously estimate system states, fault signals, the derivatives of the faults, and attenuate disturbances successfully. Fault-tolerant design is another important issue in this study. By using the obtained estimates of states and faults, and linear matrix inequality technique, a fault-tolerant control scheme is addressed, which ensures the closed-loop plant to be internally proper stable with prescribed H∞ performance index even as unbounded faults occur. Finally, a numerical example is given to illustrate the design procedures, and simulations show satisfactory tracking and fault-tolerant control performance. [ABSTRACT FROM AUTHOR]

A descriptor system approach is introduced to investigate sensor fault reconstruction and sensor compensation for a class of nonlinear state-space systems with Lipschitz constraints. Letting the sensor fault term be an auxiliary state vector, an augmented descriptor system is constructed. Using the linear matrix inequality technique, a state-space nonlinear estimator is designed for the augmented descriptor plant. Accurate asymptotic estimates of the original system state vector and the sensor fault term are thus obtained readily. By subtracting the estimated sensor fault term from the measurement output, sensor compensation is performed, allowing the existing controller for the original plant (without sensor faults) to continue to function normally even when a sensor fault occurs. Robust sensor fault reconstruction and sensor compensation are also discussed in detail for systems with simultaneous sensor faults, input disturbances and output noises. Finally, numerical examples and simulations are given to illustrate the design procedures and demonstrate the efficiency of the approaches. The sensor fault considered may be in any form, and may even be unbounded. As a result, the present work possesses a wide scope of applicability. [ABSTRACT FROM AUTHOR]

The observation data in the B band for BL Lacerate object PKS 0735+178 during 1970–1998 from twenty two publications have been compiled into a light curve. The light curve shows that PKS 0735+178 is very active and exhibits very complicated non-sinusoidal variations. Using both Jurkevich's method and Power spectrum method to analyze these data we have found two periods of 5.26±0.98 years and 1.24±0.05 years for the outbursts in PKS 0735+178. It is of interest to note that the results of the two methods are the same (almost). In addition, these values are in good agreement with the results found by Smith et al.47 and Webb et al.61 We also apply the binary black hole model to explain the central structure of this object and obtain the masses of the primary and secondary black holes are 1.7×109M⊙ and 2.88×107M⊙ respectively. It should be monitored in future to obtain more data for further analysis to test the hypothesis. [ABSTRACT FROM AUTHOR]