Fault coupling in finite bijective functions

Fault-based testing attempts to show that particular faults cannot exist in software by using test sets that differentiate between the original program (hypothesized to be correct) and faulty alternate programs. The success of this approach depends on a number of assumptions, notably that programmers are competent insofar as they only commit relatively trivial faults, and that faults only couple infrequently. Fault coupling occurs when test sets are able to differentiate between the original program and faulty alternate programs when faults occur in isolation, but not when they occur in combination; it is a complicating factor in fault-based testing. Fault coupling is studied here within the context of finite bijective functions. A complete mathematical solution of the problem is possible in this simplified case; the results indicate that fault coupling does indeed occur infrequently, and are thus in agreement with the empirical results obtained by others in the field. One surprising result is that certain kinds of test set are able to avoid fault coupling altogether.     

Distributed fault‐tolerant control design for spacecraft finite‐time attitude synchronization

This paper develops two distributed finite‐time fault‐tolerant control algorithms for attitude synchronization of multiple spacecraft with a dynamic virtual leader in the presence of modeling uncertainties, external disturbances, and actuator faults. The leader gives commands only to a subset of the followers, and the communication flow between followers is directed. By employing a novel distributed nonsingular fast terminal sliding mode and adaptive mechanism, a distributed finite‐time fault‐tolerant control law is proposed to guarantee all the follower spacecraft that finite‐time track a dynamic virtual leader. Then utilizing three distributed finite‐time sliding mode estimators, an estimator‐based distributed finite‐time fault‐tolerant control law is proposed using only the followers' estimates of the virtual leader. Both of them do not require online identification of the actuator faults and provide robustness, finite‐time convergence, fault‐tolerant, disturbance rejection, and high control precision. Finally, numerical simulations are presented to evaluate the theoretical results. Copyright © 2015 John Wiley & Sons, Ltd.     

Fault‐tolerant formation control of multiple UAVs in the presence of actuator faults

In order to counteract actuator faults in formation flight of multiple unmanned aerial vehicles (UAVs), this paper presents a fault‐tolerant formation control (FTFC) design methodology, in which the reference generator and the finite‐time convergence of FTFC gains are explicitly considered. Feasible references in response to actuator faults can be generated by considering the health and mission conditions of an overall team of UAVs. Moreover, by applying an auxiliary integrated regressor matrix and vector method, FTFC gains can converge within a finite amount of time to facilitate the fault accommodation process. Thus, the negative effects resulting from failed actuators can be compensated by the healthy/redundant actuators in UAVs. Simulation studies of UAV formation flight are carried out to exemplify the effectiveness of this design approach. Copyright © 2015 John Wiley & Sons, Ltd.     

Adaptive robust actuator fault compensation for linear systems using a novel fault estimation mechanism

This paper investigates the problem of adaptive fault‐tolerant control for a class of linear systems with time‐varying actuator faults. The outage and loss‐of‐effectiveness fault cases are covered. An active fault compensation control law was designed in two steps. Firstly, the time‐varying fault parameters were estimated based on a novel adaptive observer. Compared with the traditional adaptive observer, the actuator fault estimations are faster and the high‐frequency oscillations can be attenuated effectively. Such oscillations are usually caused by increasing the gains of adaptive laws to deal with abrupt changes in system dynamics. Then, based on online estimations of the fault parameters, an adaptive fault‐tolerant controller was constructed to compensate for the loss of actuator effectiveness and to eliminate the effect of fault estimation error. The asymptotic stability and an adaptive performance of a closed‐loop system can be guaranteed, even in the case of actuator faults and disturbances. Simulation results are given to verify the effectiveness and superiority of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.     

协议被动测试的错误标识

被动测试不仅能够检测协议实现是否有错误,而且利用检测过程中的症状信息能够标识错误.提出一种扩展了的被动测试错误标识算法,它能够在标记错误过程中记录该错误所导致的系统状态;又给出了一种以上述状态为初始状态继续向前观察多步以区分错误的算法.所提方法能够区分等价错误;继续向前测试步数不受限制,应用该方法对一个简化的BGP协议状态机模拟器进行错误标识,实验结果表明在观察步骤数足够多的情况下所提方法能够高效定位系统实现错误.     

Input‐output based fault estimation for linear systems with partially dynamic uncertainty and actuator faults

This paper is concentrated on the problem of fault estimation for a class of linear systems with partially dynamic uncertainty and actuator faults. A novel input–output‐based fault estimation approach is proposed, by which the estimates can asymptotically converge to the magnitudes of the actuator faults, and the asymptotic convergence of the estimation is theoretically proved. Some important properties related to the corresponding fault errors are obtained. The proposed input–output‐based fault estimation method can exponentially weaken the effects of the fault derivatives on the fault error dynamics. Based on the online estimates, a corresponding robust fault‐tolerant control policy is designed, so that the closed‐loop system is asymptotically stable and the control output curves can asymptotically trace to the normal control output curves. Finally, three examples are given to show the effectiveness, merits, and applications of the proposed methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Finite‐horizon fault estimation for time‐varying systems with multiple fading measurements under torus‐event–based protocols

In this paper, the issue of the finite‐horizon H_∞ fault estimation is dealt with for a class of discrete time‐varying systems subject to randomly occurring faults and multiple fading measurements. The missing phenomena may occur in a random way from different sensors, which is represented by an individual stochastic variable meeting a certain probability distribution. Furthermore, in order to alleviate the communication burden, the torus‐event–based protocols are adopted to schedule the data transmissions only when some significant events occur. Our aim of the presented issue is to estimate the fault such that, with multiple fading measurements via the received information governed by torus‐event–based protocols, the H_∞ index is satisfied over a given finite horizon. Sufficient conditions are obtained for the desired time‐varying estimator in terms of the technique of stochastic analysis and the methods of completing squares. The desired estimator gains are calculated by working out two backward recursive Riccati difference equations. Finally, a numerical simulation is given to verify the usefulness of our designed fault estimation approach.     

Observer‐based fault‐tolerant control for a class of hybrid impulsive systems

This paper investigates the fault‐tolerant control (FTC) problem for a class of hybrid nonlinear impulsive systems. Two kinds of faults are considered: continuous faults that affect each mode and discrete faults that affect the impulsive switching. The FTC strategy is based on the trade‐off between the frequency of switching and the decreasing rate of Lyapunov functions along the solution of the system, which maintains the stability of overall hybrid impulsive systems in spite of these two kinds of faults. A switched reluctance motor example is taken to illustrate the applicability of the proposed method. Copyright © 2009 John Wiley & Sons, Ltd.     

Sliding mode fault‐tolerant control of uncertain system: A delta operator approach

This paper is concerned with the sliding mode control of uncertain nonlinear systems against actuator faults and external disturbances based on delta operator approach. The nonlinearity, actuator fault, and external disturbance are considered in this study, and the bounds of Euclidean norms of the nonlinearity and the specific lower and upper bounds of the actuator faults and the disturbances are unknown knowledge. Our attention is mainly focused on designing a sliding mode fault‐tolerant controller to compensate the effects from the nonlinearity, unknown actuator fault, and external disturbance. Based on Lyapunov stability theory, a novel‐adaptive fault‐tolerant sliding mode control law is deigned such that the resulting closed loop delta operator system is finite‐time convergence and the actuator faults can be tolerated, simultaneously. Finally, simulation results are provided to verify the effectiveness of the proposed control design scheme. Copyright © 2017 John Wiley & Sons, Ltd.     

Adaptive fault‐tolerant time‐varying formation tracking for multiagent systems with multiple leaders

In this paper, an adaptive fault‐tolerant time‐varying formation control problem for nonlinear multiagent systems with multiple leaders is studied against actuator faults and state‐dependent uncertainties. Simultaneously, the followers form a predefined formation while tracking reference signal determined by the convex combination of the multiple leaders. Based on the neighboring relative information, an adaptive fault‐tolerant formation time‐varying control protocol is constructed to compensate for the influences of actuator faults and model uncertainties. In addition, the updating laws can be adjusted online through the adaptive mechanism, and the proposed control protocol can guarantee that all the signals in the closed‐loop systems are bounded. Lyapunov‐like functions are addressed to prove the stability of multiagent systems. Finally, two examples are provided to demonstrate the effectiveness of the theoretical results.     

Test suite minimization for testing in context

Testing a component embedded into a complex system, in which all other components are assumed fault‐free, is known as embedded testing. This paper proposes a method for minimizing a test suite to perform embedded testing. The minimized test suite maintains the fault coverage of the original test suite with respect to faults within the embedded component. The minimization uses the fact that the system is composed of a fault‐free context and a component under test, specified as communicating, possibly non‐deterministic finite state machines (FSMs). The method is illustrated using an example of telephone services on an intelligent network architecture. Other applications of the proposed approach for testing a system of communicating FSMs are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

基于定值-引用链的测试用例优先级排序算法

测试用例优先级排序作为一种高效实用的回归测试技术,通常以测试用例的覆盖度作为优先级排序的量化指标,忽略了测试用例的其他测试性能。针对该问题,提出一种基于DU链的测试用例优先级排序算法。该算法 综合考虑 测试用例的DU链覆盖度和回归测试的错误检测能力,对测试用例优先级进行量化。与已有算法相比,该算法基于数据流覆盖,充分利用了测试执行的历史信息和程序模块的耦合信息,在排序过程中动态计算测试用例的优先级量化值。实验结果表明,采用优先级排序算法的测试用例集能在测试过程中以较短的时间发现更多的错误,有效地提高了回归测试的检错效率。     

Fault detection and estimation for a class of PIDE systems based on boundary observers

In this paper, we propose a simultaneous state estimation and fault estimation approach for a class of first‐order hyperbolic partial integral differential equation systems. Specifically, we consider the multiplicative boundary actuator and sensor faults, ie, unknown fault parameters multiplying by the boundary input or boundary state (ie, output). As a consequence, two difficulties arise immediately: (1) simultaneous estimation of both plant state and faults is a nonlinear problem due to the multiplication between fault parameters and plant signals; (2) no prior information is available to determine the type (actuator or sensor) of faults. To overcome these difficulties, this paper develops adaptive fault parameter update laws and embeds the resulting laws into the plant state observer design. First, we propose new approaches to estimate actuator fault and sensor fault, respectively. Next, we develop a novel method to simultaneously estimate actuator and sensor faults. The proposed observer and update laws, designed using only one boundary measurement, ensure both state estimation and fault parameter estimation. By choosing appropriate Lyapunov functions, we prove that the estimates of state and fault parameters converge to an arbitrarily small neighborhood of their true values. Numerical simulations are used to demonstrate the effectiveness of the proposed estimation approaches.     

Adaptive disturbance observer‐based finite‐time continuous fault‐tolerant control for reentry RLV

The control effectors of reusable launch vehicle (RLV) can produce significant perturbations and faults in reentry phase. Such a challenge imposes tight requirements to enhance the robustness of vehicle autopilot. Focusing on this problem, a novel finite‐time fault‐tolerant control strategy is proposed for reentry RLV in this paper. The key of this strategy is to design an adaptive‐gain multivariable finite‐time disturbance observer (FDO) to estimate the synthetical perturbation with unknown bounds, which is composed of model uncertainty, external disturbance, and actuator fault considered as the partial loss of actuator effectiveness in this work. Then, combined with the finite‐time high‐order observer and differentiator, a continuous homogeneous second‐order sliding mode controller based on the terminal sliding mode and super‐twisting algorithm is designed to achieve a fast and accurate RLV attitude tracking with chattering attenuation. The main features of the integrated control strategy are that the adaptation algorithm of FDO can achieve non‐overestimating values of the observer gains and the second‐order super‐twisting sliding mode approach can obtain a more elegant solution in finite time. Finally, simulation results of classical RLV (X‐33) are provided to verify the effectiveness and robustness of the proposed fault‐tolerant controller in tracking the guidance commands. Copyright © 2017 John Wiley & Sons, Ltd.     

A low‐complexity design for distributed containment control of networked pure‐feedback systems and its application to fault‐tolerant control

This paper addresses a low‐complexity distributed containment control problem and its extension to fault‐tolerant control for networked nonlinear pure‐feedback systems under a directed graph. The multiple dynamic leaders are neighbors of only a subset of the followers described by completely non‐affine multi‐input multi‐output pure‐feedback dynamics. It is assumed that all followers' nonlinearities are heterogeneous and unknown. The proposed containment controller is implemented by using only error surfaces integrated by performance bounding functions and does not require any differential equations for compensating uncertainties and faults. Thus, compared with the previous containment control approaches for multi‐agent systems with unknown non‐affine nonlinearities, the distributed containment control structure is simplified. In addition, it is shown that the proposed control scheme can be applied to the fault‐tolerant containment control problem in the presence of unexpected system and actuator faults, without reconstructing any control structure. It is shown from Lyapunov stability theorem that all followers nearly converge to the dynamic convex hull spanned by the dynamic leaders and the containment control errors are preserved within certain given predefined bounds. Copyright © 2016 John Wiley & Sons, Ltd.     

Retrofit fault‐tolerant tracking control design of an unmanned quadrotor helicopter considering actuator dynamics

This paper presents a retrofit fault‐tolerant tracking control (FTTC) design method with application to an unmanned quadrotor helicopter (UQH). The proposed retrofit fault‐tolerant tracking controller is developed to accommodate loss‐of‐effectiveness faults in the actuators of UQH. First, a state feedback tracking controller acting as the normal controller is designed to guarantee the stability and satisfactory performance of UQH in the absence of actuator faults, while actuator dynamics of UQH are also considered in the controller design. Then, a retrofit control mechanism with integration of an adaptive fault estimator and an adaptive fault compensator is devised against the adverse effects of actuator faults. Next, the proposed retrofit FTTC strategy, which is synthesized by the normal controller and an additional reconfigurable fault compensating mechanism, takes over the control of the faulty UQH to asymptotically stabilize the closed‐loop system with an acceptable performance degradation in the presence of actuator faults. Finally, both numerical simulations and practical experiments are conducted in order to demonstrate the effectiveness of the proposed FTTC methodology on the asymptotic convergence of tracking error for several combinations of loss‐of‐effectiveness faults in actuators.     

基于先锋光纤通道交换网的故障监测与诊断的研究与设计

基于先锋网的天气预报系统对先锋网的可靠性和可管理性提出了要求。分析了先锋网的原理后,我们设计了先锋网故障监测与诊断子系统,并在分析了SNMP下目前故障诊断方法的基础上,提出了主动式的根据各硬件设备的关系收集信息来确定故障源的诊断算法;系统采用以太网与光纤网双型网络,能依据设备之间的关系,经过主动的测试、推断和排除来确定故障的位置,具有很高的智能性,特别是当光纤通路出现故障时,系统还能利用第二条通路进行详细的诊断;系统采用的诊断算法能够根据各部分间的关系对可能出现故障的部分进行主动测试,收集需要的测试信息,从而确定故障源。     

Adaptive multivariable finite‐time continuous fault‐tolerant control of rigid spacecraft

The problem of fault‐tolerant attitude tracking control for rigid spacecraft in the presence of inertia uncertainties, actuator faults, and external disturbances is investigated in this paper. A novel adaptive finite‐time continuous fault‐tolerant control strategy is developed by combining the fast nonsingular terminal sliding mode surface and the adaptive multivariable super‐twisting algorithm, which improves the robustness while preserving high accuracy and finite‐time convergence. The main features of the control strategy are the double‐layer adaptive algorithm based on equivalent control, which ensures nonoverestimation of the control gain and the continuous controller, which maintains better property of chattering reduction. Finally, the efficiency of the proposed controller is illustrated by numerical simulations.     

Fault detection for output feedback control systems with actuator stuck faults: A steady‐state‐based approach

The paper studies the fault detection problem for output feedback control systems with bounded disturbances and nonzero constant reference inputs. A steady‐state‐based approach is proposed which can be used to detect small actuator stuck faults including actuator outage (the stuck value is zero). These small stuck faults, especially the outage faults, cannot be detected effectively using the existing techniques. A dynamic output feedback controller and a weighting matrix are designed simultaneously. The dynamic output feedback controller stabilizes the closed‐loop system for both fault‐free and faulty cases and attenuates the effects of disturbances. By manipulating the steady‐state values of system states with the detection weighting matrix, a residual is then generated, through which actuator stuck faults including actuator outages can be detected effectively. Simulation results are included to demonstrate our design procedure. Copyright © 2009 John Wiley & Sons, Ltd.     

一种随机TBFL方法

许多学者研究了运用测试集对程序错误语句定位的问题,并提出了许多行之有效的方法,这些方法统称为TBFL(testing based fault localization)方法。后来人们发现,测试集里如果出现冗余,则这些冗余测试用例会伤害这些定位方法的功效。为了解决这个问题,Hao等人提出了SAFL(similarity aware fault localization)方法。实际上完全避免冗余是不可能的,因此从另一个角度构造了一个新的TBFL方法,称为随机TBFL方法。该方法的基本思想是:测试前对程序的语句错误概率进行先验分布,并把测试集看成随机变量,用测试用例反映的程序语句有关信息对程序语句的概率作一些调整,调整后的概率称为后验校正概率,最后根据这个后验概率对错误语句进行定位。将传统的TB-FL方法如Dicing方法、TARANTULA方法、SAFL方法纳入随机信息分析并通过几个实例进行分析和比较,结果表明,随机TBFL方法不仅能够正确定位错误语句,而且冗余对该方法的功效伤害不大。