The current research is limited in terms of actual implementation. Accurately simulating the environment of outer space on Earth for testing of space hardware is a very difficult challenge. This complicates the process of hardware validation, since hardware performance must be evaluated during each test while performing the function appropriate to that environment, and the cumulative effect of environmental conditions cannot be at once determined. As a result, actual hardware performance data from operating satellites and space hardware is generally considered much more valuable than ground test data, and for most mission-critical hardware, it is preferrable to have been previously flight tested, except in the case of dedicated testing or demonstration missions. We are developing a test bed for the entire closed-loop attitude control system and payload with actual nanosatellite reaction wheel hardware on a 3-axis rotating air bearing 12, 13 to validate the system as shown in Figs. 6 and 7. To overcome faults and noise injected into the hardware, adaptive terminal sliding mode control laws with a fuzzy system, second order sliding mode control laws with a fuzzy system and third order sliding mode control laws with a fuzzy system are developed for discrete time, and tested on the spherical air bearing system. These controller laws can increase the attitude tracking control accuracy without using redundant reaction wheels. The experimental results show the proposed analytical faulttolerantcontrol laws to be effective.
In this paper, also the design steps of the re- covery algorithm, based on a backstepping feedback linearization controller, were presented, in which the fault magnitude estimation accomplished by the FDD algorithm was utilized. As the simulation results revealed, this algorithm provided the compensation ability of the fault eect such that no deviation of the system from the desired pointing attitude occurred. These analytical investigations demonstrated the ro- bustness of the control design to the disturbances, measurement noise and unknown faults, and so the expected performance was achieved. To highlight the potentialities of the proposed algorithms in real applications, hardware in the loop test facility was planned to study the digital implementation of the designed algorithms, and provide more accurate and realistic results. As observed from the test results, the developed algorithms maintained their desired performances, which validated their feasibility in real- time implementations. Future work is planned to study reliability and dependability analyses which are of paramount importance for aerospace applications.
Abstract—In the electro mechanical brake (EMB) system, an improvement of the fault-tolerantcontrol, like invalid protections of sensors and electric systems are the key problems to the development of electric vehicles. The adaptivefault-tolerantcontrol in this paper is focus on the descriptor nonlinear system which contains double time-delays and parameter uncertainties. In fault detection and estimation, construct the controlled system model which contains multi-sensor, double time-delays and parameter uncertainties based on T-S fuzzy model, then design the observer to realize fault detection and estimation in real-time. In building the fault-tolerantcontrol model, the first step is to choose an appropriate sliding surface, and combine the algorithm of sliding control with adaptive generic model control. Then apply the state observer to the designed sliding adaptive generic model, and build the decision model with dynamic fault reconfiguration. And the goal of this paper about the adaptive robust fault-tolerantcontrol for the complex nonlinear controller system is achieved. Numerical SIMULINK simulation examples are given to illustrate the application and the effectiveness of the proposed design method.
Although there are many congestion-aware routing algorithms presented in 2D NoCs, there are a few presented methods in 3D NoCs. MAR  is a partially adaptive routing algorithm in 3D networks based on the Hamiltonian path. It is a simple approach which provides adaptivity without using virtual channels. An extension of turn models from 2D to 3D network is done in 4N-First and 4P-First methods . These algorithms are also partially adaptive routing algorithms and do not require any virtual channels. The planar-adaptive routing algorithm  is a well-known method presented in the realm of interconnection networks. This algorithm requires one, three and two virtual channels along the X, Y and Z dimensions, respectively. The adaptivity of this method is limited to a fully adaptive routing algorithm inside a sequence of 2D planes. In this paper, we present a region-based routing algorithm on a 2D and 3D mesh networks. In these approaches, the network is partitioned into a group of clusters. The clusters are connected to each other via a light weight clustering network to distribute the congestion information. This network is built upon the mesh network where the data packets are propagated. The routing decision relies on the congestion level at the neighbouring clusters rather than
Electronic circuits are increasingly present in automotive, medical, and space applications where reliability is critical. In those applications, the circuits have to provide some degree of fault tolerance. This need is further increased by the intrinsic reliability challenges of advanced CMOS technologies that include, e.g., manufacturing variations and soft errors. A number of techniques can be used to protect a circuit from errors. Those range from modifications in the manufacturing process of the circuits to reduce the number of errors to adding redundancy at the logic or system level to ensure that errors do not affect the system functionality. To add redundancy, a general technique known as triple modular redundancy (TMR) can be used. The TMR, which triplicates the design and adds voting logic to correct errors, is commonly used.
it is a suitable choice to be compared with our pro- posed approach. In , the optimization process is di- vided in two phases. In the first phase, the authors find an optimum time-slot assignment for a scenario with a single shared channel, taking into consider- ation the routing. In the second one, starting from the first phase solution, a complete solution is built up for the multi-channel multi-radio scenario. Since this problem is NP-complete, a heuristic method based on the compatible configurations is proposed in which all the links that are feasible to transmit on the same channel at the same time are extracted. The advantage of the model presented in  is its com- pleteness because it considers all available tools and is the first complete model introduced in this field. However, its disadvantage is that its objective is only throughput maximization and it does not consider the balancing, fairness and robustness against failures that are very important in WMNs. In our proposed model FTTC-TMBF, we have added the balancing, fairness and K-connectivity feature to themodel intro- duced in . In addition, we presented a four-step solu- tion where in first step, a heuristic method and in second to forth ones, a solution based on the genetic algorithm are used. In summary, we have proposed a comprehensive model in FTTC-TMBF to optimize the wireless mesh networks in which the objectives of throughput maximization, balancing, fairness and K-connectivity is considered, in addition to using all available tools; while, the model introduced in , only have considered the ob- jective of throughput maximization. Moreover, in com- parison to , we have proposed HFTTC-TMBF in which a heuristic method and genetic algorithm is used for solv- ing the problem.
Anousha et al.  presented a scheduling system that depends upon estimating the completion time of the tasks on each of resources. The proposed system will generate the scheduling decisions as per the value of estimated completion time. The results show that the proposed scheduling system improves total completion time in comparison to Min-Min strategy. S.K Panda et al.  presented a scheduling system that depends upon utilizing the Round Trip Time (RTT) to discover failures and after identification of failures checkpointing strategy is being used to recover from failures. Results show that the proposed scheduling system improves total completion time and lessen the makespan in comparison to Min-Min and Max-Min strategies. In N.M. Reda et al. , the proposed strategy is based on finding appropriate resources by getting the average value via sorting list of completion time of each task. Finally, the task having the maximum average is allocated to the machine that has the minimum completion time. Results show that the proposed strategy outperforms almost other strategies in terms of resources utilization and makespan. K. Kousalya et al.  proposed a QoS based Task Rescheduling algorithm (QTR) in which scheduled tasks are collected and then rescheduled using Minimum Completion Time(MCT) value. The results of the computations show that the QTR algorithm reduces makespan in comparison to existing strategies. J.Y Maipan et al.  proposed an algorithm MinExt which calculates the average completion time of all tasks. Then tasks having more than average completion time value are scheduled first followed by the set of tasks less than or equal to average completion time value. The results indicate that the proposed strategy minimizes total completion time value and utilizes the idle resources effectively in comparison to existing strategies.
In general, the FTC is a control methodology that ensures the safe operation under acceptable limit of a system when faults occur under FDI system. The FDI problem consists of two sub modules: binary decision making (fault detection) and finding the time variant fault behavior (fault identification). Several procedures were conducted by different researchers for fault detection mechanisms. Chi and Zhang  proposed a fault detection method based on failure and non-failure hypothesis of an aircraft system. Parameter estimation is also a way for fault detection . This is done by measuring the input and output signals if the basic model structure is known. Then the process follows direct estimation or numerical optimization. In another case, passive robust fault detection was presented by Puig and Quevedo  by bounding the uncertainties in intervals, known as ‘interval model’. Process model-based fault detection was also evaluated using residual analysis . Meanwhile, observer-based fault identification was carried out by different researchers [14, 15]. These conducted researches reflect the effectiveness of the FDI in faulttolerantcontrol systems.
systems more robust to electrode shift, including employ- ing a new EMG PR training method , investigating the effects of electrode size and orientation , changing interelectrode distance and electrode configuration , and extracting control signals by linear factorization of multi-channel EMG recordings . Sensinger et al. , Tommasi et al. , and Chen et al.  developed adap- tive learning schemes to deal with variations in EMG sig- nals for reliable EMG pattern classification. Lopez et al.  proposed a robust EMG sensing system by fusing re- dundant information of EMG signals to reduce the sensi- tivity of the control system relative to electrode failures. Tkach et al.  suggested several time-domain features that were resilient to EMG signal change caused by muscle fatigue and exerted force levels. Hahne et al.  employed a spatial filter in high-density EMG signal processing to obtain robustness to sensor noise. Geng et al.  devel- oped a two-stage cascade classifier with the first classifier for limb position identification and the second for limb motion classification to reduce the effect of limb position variation on classification performance. Simon et al.  implemented a decision-based velocity ramp as a postpro- cessing step for the EMG PR algorithm to diminish the ef- fect of misclassifications on the prosthesis movement. Amsuss et al.  proposed a self-correcting EMG PR- controlled system by adding a postprocessing algorithm to the existing EMG PR algorithm to detect and remove mis- classifications of the system.
maintain copies of the system state. Client write operations are applied atomically to all of the replicas so that after detecting a server failure the remaining servers can continue the service. Passive replication, on the other hand, distinguishes one replica as the primary server, which handles all client requests. A write operation at the primary server invokes the transmission of an update message to the backup servers. If the primary fails, a failover occurs and one of the backups becomes the new primary. In general, schemes based on passive replication are simpler and tend to require longer recovery time since a backup must execute an explicit recovery algorithm to take over the role of the primary. Schemes based on active replication do not have to budget for this failover time. However, the overhead associated with managing replication tends to slow down the response to a client request since an agreement protocol must be performed to ensure atomic ordered delivery of messages to all replicas.
If the frame is rotated 90 degrees to the right, the source of light would be in S1, and then rotate to the left until is 90 degrees from the horizontal and the source of light is in S7. During this process the source of light would be passing in order all sectors S1 to S7. If no sensor is faulty the signals LL, LH, H, L, RH and RL suffer only one transaction from 1 to 0 at different time intervals. When one sensor is faulty three signals are wrong and three are correct.
Abstract— Safety-Critical Applications have to function correctly and deliver high level of quality-of-service even in the presence of faults. But radiation problem in embedded system is a serious threat. There is an increasing concern about the mitigation of radiation effects in embedded systems. The protection of processor-based systems to mitigate the harmful effect of transient faults (soft errors) is gaining importance as technology shrinks. This review paper presents various methodologies for facilitating the design of fault- tolerant embedded systems and is supported by an infrastructure that permits to easily combine hardware/software soft errors mitigation techniques. The proposed system combines hardware and a software mitigation technique, which facilitates the design space exploration, developed to support the fault tolerance co-design approach and is added to the most vulnerable parts. A wide industrial consensus about the necessity of a set of safety definitions leads to the introduction of several functional safety standards. To achieve an embedded systems comply with these requirements, thorough testing is needed during early design stages of the integrated device.
Abstract: Cloud computing is one of the emerging technology in the field of business and also in the research field. High performance and high efficiency for 5G systems can be provided by the cloud radio access networks(C-RAN). There is also requirement of higher efficiency and also for the low latency for the 5G mobile networks. Sometimes there is probability of entire system failure due to the fault in some part of the hardware or the software. Hence by developing some of the faulttolerant methods these kind of issues can be avoided. Fault tolerance methods can also increase the use of cloud based services. The main idea of faulttolerant scheduling methods is to involve redundancy , so that all the tasks can be performed even when the system fails. But this may cause overhead for the cloud service providers. Hence various scheduling algorithms can be used to overcome this problem. In this paper, the different kinds of faulttolerant scheduling algorithms are discussed. Hence the suitable methods can be used according to the requirement of the user. This should also lead to increase in the efficiency, performance of the tasks and avoid the system failure in case of minute faults in the system.
In this paper a new approach for dealing faulttolerantcontrol problem on satellite attitude dynamic has been investigated. In order to achieving an active scheme of FTC, a new idea based on separating the main controller from fault compensation has been provided. The main attitude controller has been used from flatness differential property which demonstrated for that dynamics. Nonlinear flatness based observer could estimate all dynamic variables even in fault scenarios with allowable range of error. By this idea active FTC scheme did not required to reconfiguration and possible performance whit 50 percentages fault in actuator was accessible. Consequence of this paper could create an appropriate base for complete intelligent active FTC scheme which require to reconfiguration in systematical fault scenarios.
Alan Burns graduated in 1974 with a first class honours degree in mathematics from Sheffield University; he then received a DPhil degree from the Computer Science Department at the Uni- versity of York. He has worked for many years on a number of different aspects of real-time systems engineering. After a short period of employment at UKAEA Research Centre, Har- well, he was appointed to a lectureship at Bradford University in 1979. He was subse- quently promoted to senior lecturer in 1986. In January 1990, he took up a readership at the University of York in the Computer Science Department. During 1994, he was promoted to a personal chair. Since 1 July 1999, he has been head of the Computer Science Department at York. His research activities have covered a number of aspects of real- time and safety critical systems including requirements for such systems, the specification of safety and timing needs, system architectures appropriate for the design process, the assessment of languages for use in the real-time safety critical domain, distributed operating systems, the formal specification of scheduling algorithms and implementation strategies, and the design of dependable user interfaces to safety critical applications. Professor Burns, together with Professor Wellings, heads the Real-Time Systems research group at the University of York—one of the largest research groups in this area in the world and with a strong international reputation. He has authored/ coauthored more than 350 papers/reports and eight books. Most of these are in the Ada or real-time area. His teaching activities include courses in operating systems, scheduling, and real-time systems. He is a senior member of the IEEE.
(DFIG) Wind turbines can either operate at fixed speed or variable speed. For a fixed speed wind turbine the generator is directly connected to the electrical grid. For a variable speed wind turbine the generator is controlled by power electronic equipment. There are several reasons for using variable-speed operation of wind turbines; among those are possibilities to reduce stresses of the mechanical structure, acoustic noise reduction and the possibility to control active and reactive power. Most of the major wind turbine manufactures are developing new larger wind turbines in the 3- to-5-MW range. These large wind turbines are all based on variable-speed operation with pitch control using a direct driven synchronous generator (without gearbox) or a doubly-fed induction generator (DFIG). The Doubly-Fed Induction Generator (DFIG) is an induction generator with both stator and rotor windings as shown in fig. 2. The DFIG is nowadays widely used in variable-speed wind energy applications with a static converter connected between the stator and rotor. Currently, this topology occupies close to 50% of the wind energy market
power-line inspection, and city surveillance, safety is a big issue to be considered [3, 115]. More recently, the fault-tolerant capability of unmanned systems has begun to draw more and more at- tention in both industrial and academic communities, due to the increased demands for safety and reliability [14, 116, 117]. As argued in [11, 12], the increasing demands for safety, reliability, and high system performance have stimulated research in the area of FTC beneficial from the new de- velopments in control theory, computer technology, actuator and sensor techniques. Fault-tolerant capability is an important feature for safety-critical systems, such as UAVs, chemical processing plants, nuclear power plants, etc. The main objective is to maintain the overall system stability and acceptable degree of performance in the presence of faults in the system . From the point of view of fault occurrence location, fault can be classified into actuator fault, sensor fault, and other system component fault [11, 31]. Partial loss of control effectiveness of an actuator is a common fault occurring in aircraft systems. Since the actuator plays an important role of connecting con- trol signals to physical movements of the system to accomplish specific objectives, actuator fault is considered in this chapter. One way to accommodate this kind of fault is to use the robustness of the control system which does not require on-line detection of fault as opposed to active fault-tolerantcontrol system [11, 118, 119]. This so-called robust controller treats faults as uncertainties in the system, which can be incorporated in the design of a controller . Therefore, a trade-off be- tween system performance and robustness is unavoidable. Moreover, if a large fault is considered during the design stage, it will lead to unacceptable performance in normal (fault-free) conditions due to the big trade-off for taking such a large uncertainty into consideration. Since real systems mostly work under normal conditions and fault does not occur all the time, the consideration of fault during design stage will sacrifice certain degree of performance.
Chapter 3 contains a multiobjective FDI methods to estimate both actuator and sen- sor faults in the LPV plant. First, a general form of faulty LPV plant was introduced by converting the actuator faults into the equivalent sensor faults. Through a multibojective formulation of FDI problem, a bank of FDI filters are constructed such that the effect of dis- turbance on the residual is minimized. In addition, each residual signal will track one of the faults while decoupling it from other faults. This approach not only makes detection and iso- lation of faults possible, but also provides the estimation of fault signals. The multiobjective optimization condition for synthesizing FDI filters is derived in the form of LMIs, and can be solved efficiently using interior point algorithm. The proposed FDI design for the flexible HSV will be demonstrated for different multiple fault cases. The resulted FDI observers for faulty pitch altitude sensor and angle of canard will be applied to the faulty plant of flexible HSV model under two types of altitude tracking commands in the simulation studies. And the FDI performances will compared with another effective FDI algorithm based on PMI observers.
The operational characteristics of the proposed AFR algorithm are practically verified with the help of computer simulations performed using MATLAB software. The proposed AFR algorithm is designed, programmed and simulated using Matlab.As a first task after starting its operation the WF-HVGS initializes all its IFSIC Units for fault free operation. This initialization includes loading the rated parameter values of line voltage, line currents and associated phase deviations into the individual IFSIC Units. The initialization data of the WF-HVGS is given as follows.
The algorithm is evaluated using grid sim toolkit. In Fault-tolerant Scheduling Algorithm for Precedence Constrained Tasks,  failure in a heterogeneous system is discussed. For non- preemptive tasks, each task has two copies that are scheduled on different processors and mutually excluded in time. For tasks with precedence constraints, an overlapping scheme allows the backup copy of a task to overlap with its successors’ primary copies. The paper on FaultTolerant Scheduling in Multicore Systems,  presents a hardware based algorithm which uses triple and double modulo redundancy. Redundant multi-threaded processes are used which helps in soft errors detection and recovery. In Energy Minimization for FaultTolerant Scheduling of Periodic Fixed-Priority Applications  the problem of energy minimization for scheduling periodic fixed- priority applications on multiprocessor platforms with fault tolerance requirements is discussed. Check points are introduced to allow scheduling of an application which tolerates up to k faults on a single processor. The FaultTolerant Global Scheduling  is a backup based algorithm which uses resource reclaiming faulttolerant global scheduling (RRFGTS). This algorithm delays the execution of backup and rescues the resource distributed to backups after the execution. The dynamic faulttolerant scheduling (DFTS) algorithm in multicore systems  is designed to tolerate single or