Abstract: In this paper, an observer-based fault-tolerantcontrol (FTC) method is proposed for a class of networked control systems (NCSs) with transfer delays. Markov chain is employed to characterize the transfer delays. Then, such kind of networked control systems are modelled as markovian jump systems. An observer- based FTC scheme using the delayed state information and the estimated fault value is presented to guarantee the stability of the faulty systems. An inverted pendulum example is used to illustrate the efficiency of the proposed method.
Abstract—Fault-tolerantcontrol (FTC) is an integral component in in- dustrial processes as it enables the system to continue robust operation under some conditions. In this paper, an FTC scheme is proposed for interconnected systems within an integrated design framework to yield a timely monitoring and detection of fault and reconfiguring the controller according to those faults. The unscented Kalman filter (UKF)-based fault detection and diagnosis system is initially run on the main plant and pa- rameter estimation is being done for the local faults. This critical infor- mation is shared through information fusion to the main system where the whole system is being decentralized using the overlapping decomposition technique. Using this parameter estimates of decentralized subsystems, a model predictive control (MPC) adjusts its parameters according to the fault scenarios thereby striving to maintain the stability of the system. Ex- perimental results on interconnected continuous time stirred tank reactors (CSTR) with recycle and quadruple tank system indicate that the proposed method is capable to correctly identify various faults, and then controlling the system under some conditions.
In large industrial systems, every component has been designed to accomplish a certain function and the overall system works satisfactorily only if all components provide the usual service they are designed for. The Faulttolerantcontrol (FTC) aims to prevent damage in overall system when a fault occurs in one component. FTC methods is considered in two general approaches: active control and passive control. In active approaches, when a fault occurs after detection, isolation and maybe identification of the fault, proper control law is designed and applied immediately to the faulty plant, but in passive control a fixed fault-tolerant closed-loop structure is already designed for the system such that it’ll be able to tolerate some restricted classes of the faults. Control reconfiguration is an active FTCmethod that has been presented comprehensively in  and . In this method, after detection and isolation of the faults (called “fault diagnosis”), the control law is immediately modified by a new structured controller for the faulty system.
systems in [6-8]. In , a switched discrete-time sys- tem with state delay has been considered. The design method is based on the construction of a filter and a fault estimation approach. In , an adaptive fuzzy tracking controlmethod for a class of switched nonlin- ear systems with arbitrary switchings and with actu- ator faults has been proposed. The proposed control scheme guarantee the stability of the whole switched control system based on the common Lyapunov func- tion stability theory and attenuate the effect of the actuator faults on the control performance by design- ing a new fuzzy controller to accommodate uncertain actuator faults. In , an observer has been built to de- tect the fault when it occurs. The problem of FTC for switchied linear systems is addressed by using a nom- inal control law designed in the absence of any fault, associated with fault detection, localization and recon- figuration techniques to maintain the stability of the system under an arbitrary switching signal in the pres- ence of sensor faults. A state trajectory tracking has been proposed in  for actuator faults and observer bank based on controllers with switching mechanism for sensor faults has been also presented in . A nonlinear observer based controller, adopting the so-
Since nano-spacecraft are small, low cost and do not undergo the same rigor of testing as conventional spacecraft, they have a greater risk of failure. In this pa- per we address the problem of attitude control of a nano-spacecraft that experi- ences different types of faults. Based on the traditional quaternion feedback con- trol method, an adaptive fault-tolerantcontrolmethod is developed, which can ensure that the control system still operates when the actuator fault happens. This paper derives the fault-tolerantcontrol logic under both actuator gain fault mode and actuator deviation fault mode. Taking the parameters of the UKube-1 in the simulation model, a comparison between a traditional spacecraft controlmethod and the adaptive fault-tolerantcontrolmethod in the presence of a fault is undertaken. It is shown that the proposed controller copes with faults and is able to complete an effective attitude control maneuver in the presence of a fault.
Flat differential is an operational technique of physical systems which is based on a unique property in dynamic equations structure  Based on this property, all of the state variables of system could be observed analytically by means of re-expression of governing equations in square differential flatness framework. Thereupon a sort of full nonlinear state observer could be presented by this property. Hence the main disadvantage of almost nonlinear methods could be removed. Also, this property could be considered as a perfect option in faulttolerantcontrol problem, in other to reducing the number of dealing variables. One of the most popular nonlinear control methods which has been investigated based on the flat technique is the Feedback linearization. In feedback linearization method, the control command is applied to the system in such a way that system error dynamic comes in the form of a linear differential set. This method has been used on guidance and control of reentry vehicles  and satellites attitude control  in aerospace engineering.
In sensor FTC architecture, evaluation of redundant sensor systems is generally used in most of the applications. For an example, Chan and Hong  successfully showed how to classify faults under noise using redundant sensors and a modified kohonen network. Furthermore, linear sensor redundancy analysis-based FTC has been recently carried out by Santhosh . In commercial EHAs like VariStroke-I from Woodward (USA), redundant linear displacement transducers have been used for FTC operation. However, the sensor redundancy increases the hardware and FDI designing complexity as well as cost, weights, maintenance effort. Therefore, researchers focused the spot light on the analytical redundancy over hardware redundancy for designing FTC architectures. For an instance, analytical redundancy-based fault diagnosis method by developing a filter with sequential probability ratio test was proposed by Chi and Zhang . In an EHA positioning system, such FTC was carried out by Navid and Nariman . They developed quantitative feedback-based FTC module in which the system was identified by single-input-single- output transfer function. However, the identification of such nonlinear systems with this manner is not feasible. Also, they could not reveal the fault information invoked at the sensors.
Therefore, it is necessary to implement the gain-scheduling control scheme to encompasses the entire flight envelop. The study of LPV systems are motivated by the gain-scheduling control design methodology . The most common method to obtain LPV plant is to apply Jacobian linearization on the nonlinear model at a set of operating points. LPV control has emerged as an effective control technique to accommodate plants that exhibit parameter- dependent dynamics [8, 71]. All synthesis conditions for LPV control could be formulated as parameter-dependent LMIs. For the continuous system parameters, there implies infinite number of inequalities. To effectively solve the control optimization problem, the parameter set will be gridded into finite points and convert the infinite number of synthesis conditions to be finite. In general, the synthesis conditions with parameter-dependent Lyapunov func- tion lead to the controllers scheduled by both system parameters and their variation rate. Successful industrial applications of LPV control include robotic manipulators, automotive and turbo-fan engines, aircraft/missile autopilots, and nuclear reactor problems.
component faults, has received much attention during recent decades, which keeps the system safe to achieve satisfactory performances whenever components are healthy or faulty. The existing fault-tolerant controllers can be divided into two design approaches, i.e., passive approach and active approach. Robust control is useful method in passive approach, in which linear matrix inequality (LMI) methods can be used to describe the performances of fixed gain closed-loop systems [12-17]. While adaptive control is very important technique in active approach, in which the parameters can be adjusted online to ensure reliability of closed-loop systems in the presence of a wide range of unknown faults [18-23].
Due to the computational complexity of the cross-layer optimization problem, various meta-heuristic methods have been proposed in recent studies [23–25]. In , a new routing method named MNSGA-II is pro- posed in which a Genetic Algorithm (GA) procedure is used to extract the best paths with the aims of minimiz- ing the number of transmissions and delay. However, the other objectives and tools are not considered. In , we proposed a GA-based method for power and rate control along with scheduling in the wireless mesh networks. The objective function of this method only in- cludes the minimization of the number of time slots. Moreover, the routing and channel assignment are not considered. The authors in  investigated multicast routing and channel assignment problems simultaneously using a GA-based method in which power control and rate adaptation tools are ignored. In this method, the multicast trees are determined at first using differential evolution technique and then the channel assignment is performed by using a GA-based method. While the throughput maximization and fairness are considered in this reference, the balancing factor is not considered.
The aircraft stability is analysed for icing and normal condition . The simulated aircraft attributes were compared for normal flight and icing flight condition and observed that icing changes the geometry and thus equilibrium point of the aircraft. The controllability analysis of tandem quad-copter was carried out . FDI scheme is developed by comparison of required attitude to the measured attitude . Sensor fusion technique is applied to estimate fault in altitude estimation . The real-time parameters of aerodynamic model were estimated using artificial intelligence . The method of system identification was explained briefly for a small unmanned aircraft . The real-time parameter estimation of aircraft was carried out using recursive least square and batch estimation method  and minimized error in each model. System identification using subscale methods were explained for small flexible aircraft . FDI methods classified as data-driven or model reference approach for diagnosing fault. So far, FTFC has been implemented in control reallocation with FDI or control by nullifying errors using proper corrective measures. The input signal or output performance was estimated for designing FDI.
Wireless networks are mounting increasingly widespread sorting from analog to digital telephony to dependency propagation. Consequently, providing a soaring Quality of Service (QoS) in distributing video, voice and data has turn into obvious as one of the most significant confront. Quality of Service (QoS) is a defined point of presentation in a communications network essential by a kind of network traffic. Severe QoS necessities are identified in numerous network conditions, for instance in decisive communications control and martial communication. An efficient mobile ad-hoc network (MANETs) requires QoS potentials that present fault tolerance and fast revival when links be unsuccessful on an irregular or eternal basis. Quality of service concerned the method to present diverse varieties of priority to diverse users, applications, or data flows. Some of the parameters to be considered are delay and jitter, bit rate, packet dropping possibility or bit error rate. The necessities of QoS have been suffered in the fields such as defense, military and so on. Whenever link has a broken or everlasting source there ought to be a method to present fault tolerance in Mobile Ad Hoc networks. MANET topologies are frequently vulnerable to transform. Node mobility in MANET might basis QoS necessities to develop into unreachable with the swell in node mobility to origin changes in topology. This is said to be combinatorial immovability. It deliberates regarding the combinatorial strength and recoverability feature.
ARM MPCore and IBM Cell are the examples of multicore processors employed in the real time embedded systems. Multicore processors are classified into two parts, (1) homogenous or heterogeneous .  states that most of the existing multicore processors are homogenous. The multicore processor is mainly concern for managing the tasks in such a way to utilize the cores effectively. The scheduler in the operating system is responsible for keeping all the cores in the processor busy during the execution of the real time tasks to improve the total execution time. Faults can be categorised into these main categories: permanent, transient and intermittent faults . Permanent Fault such as wear off of any part which require replacement from the spare part to restore the system functionality. Transient fault are the short term faults and can be distinguished from others with their duration of occurrence and causes. These may occur due to external noise and other sources Intermittent fault occurs happened at interims on account of some inward tedious glitch of the segments like temperature vacillations, power supply and noise . To have fault tolerance in multicore systems task scheduling is done. These fault tolerance scheduling algorithms increase the system reliability. In different faulttolerant system, software which is running on a single core employ redundant execution at different level of abstraction, at instruction and virtual machine level. Methods which operate at instruction level have low error detection latencies compare to hardware level. But methods which work at process level allow error propagation. In multi- threaded programs which are running on multicore processors, Shared memory access is frequent than interrupts or signals. For that achieve efficient execution of replicas is very much difficult. For that different deterministic languages are used. We can perform fault tolerance using redundant execution of software in which replicated copies give same output for given input. This method can be implemented using a user level library so it does not require modification in kernel. The error detection mechanism is optimized to perform memory comparisons of the replicas efficiently in user space . Depends on the use of multiple threads performance can be further increase. For scheduling of soft real time tasks with non-real time tasks two level hierarchical scheduling is used. This method decreases average deadline miss ratio and also support the real time requirements for other tasks. The principle _________________________
One of the biggest disadvantages of the 1 st generation controller is the synchronization method used for the controllers. The global data (i.e. grid voltages, currents, ...) is being acquired by the master controller (synchronizer) and shared between all other controllers through the communication bus. In this case, the master controller must have redundant architecture (static or dynamic) with redundant communication bus to avoid single point of failure. This will make the architecture complicated and increase the required resources for implementation of the system. One of the solutions for this problem is connecting all the controllers in a grid format. In this case, some of the controllers are capable of gathering the global variables and can share them to other controllers through the communication bus. If one of the controllers fails, another one of the controller can take the responsibility and synchronize the whole controllers (figure 3.12). There are two types of controller in this architecture. Some of the controllers have measurement devices for measuring common variables between all the controllers. only one of these controller will act as the master controller to synchronize all other controllers. The controllers that have access to global variables will perform voting algorithms to ensure the correctness of the module that is synchronizing other controllers. If the master controller fails, the next controller will take responsibility of the master controller.
Abstract- Cloud computing is a synonym for distributed computing over a network and means the ability to run a program on many connected computers at the same time. This phase is also more commonly used to refer to network based services which appear to be provided by real server hardware, which in fact are served up by virtual hardware, simulated by software running on one or more real machines. This paper is based on the survey of types of faults-tolerance and different types of fault-tolerance techniques. There are several methods used to avoid the faults before and after it occur.
The resilient propagation (RPROP)  algorithm as implemented in MATLAB 7.2 neural network toolbox is used with the default learning rate and momentum constant. For training the network, 200 samples were generated from the input domain of the functions for training purposes. 5000 epochs of training was conducted for each problem, 30nos. of networks have been trained for each function approximation tasks. Fig. 2-5 represents the behavior of all 30 networks for the sensitivity to weight stuck at zero fault for Fn1-Fn4. From the Fig. 2-5, we may infer that S 2
An efficient distributed fault-tolerant routing algorithm for the hypercube has been described in  on the existence of a complete set of node-disjoint paths between any two nodes. It was presented that when a message is blocked by a node failure, the source node is warned and requested to switch to a different node-disjoint path.
fault. Control theory can be divided into two main areas: conventional and modern control. Conventional control covers the concepts and techniques developed up to 1950. Modern control covers the techniques from 1950 to the present. Conventional control became interesting with the development of feedback theory. Feedback was used in order to stabilize the control system. Feedback systems first used in locomotives. Another example was the use of feedback for telephone signals in the 1920’s. Harold Stephen Black proposed a feedback system that would use feedback to limit the distortion.
critical industrial processes with high standstill cost and safety-aspect concern, a high reliability and survivability of the drive system is very important. Therefore, fault-tolerant operation of multilevel inverters has drawn lots of interest in recent years, and several researchers have addressed the fault-tolerant issues for the popular multilevel topologies, such as neutral-point-clamped (NPC) inverters, flying capacitor inverters, cascaded H- bridge inverters, and generalized inverters . In most fault-tolerant solutions, additional components (such as power devices, fuses, or even phase legs) are required to be added to standard multilevel inverters for fault-tolerant operation. This will increase the cost and may even reduce the reliability of the inverters and drive systems due to employing more components. Moreover, both device open and short failure may occur in the inverters, depending on the characteristics and failure mechanism of power devices; thus, a comprehensive fault-tolerant scheme should consider both failure conditions.
ULTIPHASE machines, compared to the standard three-phase ones, give more advantages in terms of reliability and efficiency, becoming always more suitable for high performance and faulttolerant applications. Multiphase motors allow exploiting more degrees of freedom in the generation of the armature field, which can be useful to obtain a higher torque density and efficiency, and reduced torque ripples . Furthermore, suitable diagnostic and faulttolerant algorithms can be exploited also to detect fault conditions and/or to overcome them -. In general, a multiphase drive requires an “extended field oriented control” able to control the air-gap field harmonic components, and a multiphase modulation technique for the inverter can be used to increase the DC-bus exploitation . Among the different multiphase machine topologies, the multi three-phase one has the advantage to use a standard three-phase inverter technology.