Multi-stability in monotone input/output systems

This paper studies the emergence of multi-stability and hysteresis in those systems that arise, under positive feedback, starting from monotone systems with well-defined steady-state responses. Such feedback configurations appear routinely in several fields of application, and especially in biology. Characterizations of global stability behavior are stated in terms of easily checkable graphical conditions.     

Generation and sensitivity of input/output DC plots

A computer program operating in an interactive mode enables input/output DC plots of nonlinear systems to be generated and sensitivity properties to be studied. The computational method is based on the piecewise-linear approach. The technique is applied to simulate transistor curve tracers and to carry out worst-case analysis of transfer characteristics in digital circuits.     

基于输入输出关系的综合黑盒测试方法

主要针对黑盒测试存在的问题,提出一种测试用例设计方法:根据系统规格说明和系统输入输出之间的关系等附加信息,来确定输入参数之间的覆盖和约束关系,并对参数输入域进行约减;接着对各组合进行处理;仅对各个组合中的输入变量进行两两组合覆盖;对各相关组的结果进行水平拼接组合.实践结果表明,该方法在不影响测试检错能力的情况下有效地提高了测试用例的选择效果.     

Identification of a class of non-linear systems from short input/output records

An iterative procedure is presented for the optimization of the estimated parameters of non-linear systems which can be described by a combined Wiener-Hammerstein model, usually referred to as the general model. The procedure enables the efficient and fairly accurate estimation of the parameters from a short input/output record.     

Overcoming controllability problems in distributed testing from an input output transition system

This paper concerns the testing of a system with physically distributed interfaces, called ports, at which it interacts with its environment. We place a tester at each port and the tester at port p observes events at p only. This can lead to controllability problems, where the observations made by the tester at a port p are not sufficient for it to be able to know when to send an input. It is known that there are test objectives, such as executing a particular transition, that cannot be achieved if we restrict attention to test cases that have no controllability problems. This has led to interest in schemes where the testers at the individual ports send coordination messages to one another through an external communications network in order to overcome controllability problems. However, such approaches have largely been studied in the context of testing from a deterministic finite state machine. This paper investigates the use of coordination messages to overcome controllability problems when testing from an input output transition system and gives an algorithm for introducing sufficient messages. It also proves that the problem of minimising the number of coordination messages used is NP-hard.     

Model extraction and test generation from JUnit test suites

In this paper, we describe how to infer state machine models of systems from legacy unit test suites and how to generate new tests from those models. The novelty of our approach is to combine control dependencies and data dependencies in the same model, in contrast to most other work in this area. Combining both kinds of dependencies helps us to build more expressive models, which in turn allows us to produce smarter tests. We illustrate those techniques with real examples produced by our implementation, the James tool, designed to apply these techniques in practice to Java code and tests.     

Nonlinear input/output modelling

This paper gives a highly abbreviated overview of some of the key issues in empirical nonlinear modelling for chemical process applications. This task is complicated by the inherent nature of nonlinearity: the term describes a class of systems by the one feature they lack. In fact, this division — linear vs. nonlinear — suggests a ‘unity’ or ‘homogeneity’ of the class of nonlinear systems that does not exist. Consequently, this review will focus on specific sub-classes of nonlinear models that have analytically useful structural characteristics, and comparisons will be made both between these classes and with the more familiar linear models. Length limitations restrict these discussions somewhat, but it is hoped that the range of examples will be great enough to demonstrate how nonlinear model identification is both similar to and different from linear model indentification. The general conclusion of this paper is that nonlinear input/output modelling is a vitally important practical art with many unresolved issues; the principal objective of this paper is to elucidate some of these issues.     

Identification of systems with cyclostationary input and correlatedinput/output measurement noise

An alternative approach to Wiener's optimum filtering theory for stationary random time series that is applicable when the system input exhibits cyclostationarity is presented. This alternative approach can, in principle, eliminate performance degradation due to input/output corruption. This method of system identification is called the SPECCORR (spectral correlation ratio) method, since the cross spectra in the ratio are actually spectral correlation functions. An application to interference-tolerant time-difference-of-arrival estimation is described and illustrated by simulation results, showing its effectiveness for system identification with severely corrupted input/output measurements. A comparison of Wiener's method to the SPECCORR method shows the superior performance of the latter     

Fixed-order FIR approximation of linear systems from quantized input and output data

The problem of identifying a fixed-order FIR approximation of linear systems with unknown structure, assuming that both input and output measurements are subjected to quantization, is dealt with in this paper. A fixed-order FIR model providing the best approximation of the input–output relationship is sought by minimizing the worst-case distance between the output of the true system and the modeled output, for all possible values of the input and output data consistent with their quantized measurements. The considered problem is firstly formulated in terms of robust optimization. Then, two different algorithms to compute the optimum of the formulated problem by means of linear programming techniques are presented. The effectiveness of the proposed approach is illustrated by means of a simulation example.     

H2 approximation of multiple input/output delay systems

Many physical multivariable processes can be sufficiently described as linear models with multiple input/output delays. To simplify the synthesis and analysis of control problem, a reduced-complexity model is often desired. In this paper, an H₂ model reduction scheme is introduced for stable linear systems with multiple input/output delays. The reduced model can be a finite dimensional linear model, or a linear model with a time delay. In the latter case the approximation can be improved drastically without increasing the order of the finite dimensional part. The stability is preserved in the approximating models by employing a parametrization of linear stable systems. The optimal parameters can be obtained by solving an optimization problem using a gradient-based method. Two chemical numerical examples are used to show the effectiveness of the proposed scheme.     

An adaptive cache coherence protocol specification for parallel input/output systems

Caching has been intensively used in memory and traditional file systems to improve system performance. However, the use of caching in parallel file systems and I/O libraries has been limited to I/O nodes to avoid cache coherence problems. We specify an adaptive cache coherence protocol that is very suitable for parallel file systems and parallel I/O libraries. This model exploits the use of caching, both at processing and I/O nodes, providing performance improvement mechanisms such as aggressive prefetching and delayed-write techniques. The cache coherence problem is solved by using a dynamic scheme of cache coherence protocols with different sizes and shapes of granularity. The proposed model is very appropriate for parallel I/O interfaces, such as MPI-IO. Performance results, obtained on an IBM SP2, are presented to demonstrate the advantages offered by the cache management methods proposed.     

Recursive system identification method from binary input/output measurements

This paper presents two online identification algorithms of finite impulse response (FIR) systems using binary measurements both on the input and on the output. These algorithms are based on the least mean square (LMS) technique and on the estimation of the correlation functions of the input and output from binary data. Note that the second algorithm is a simplified version of the first one in the case of a white noise on the input. The convergence and variance analyses are provided. A numerical example is given to demonstrate the effectiveness of the proposed algorithms.     

Properties of single input,two output feedback systems

We describe properties of linear multivariable feedback systems for which the plant has a single control input and two measured outputs. Particular attention is paid to 'algebraic' design tradeoffs that occur between different feedback properties at the same frequency. To describe these tradeoffs, we use concepts of plant and controller direction and alignment. We show that if plant/controller alignment is poor, then closed loop response to noise and disturbances will be large unless the loop gain is sufficiently small. Moreover, the closed loop system will exhibit large interactions. We also describe a dual set of results that are applicable to feedback systems for which the plant has two control inputs and a single measured output.     

基于输入/输出动作的协议形式化描述和测试用例生成方法

通信协议的形式化描述及在其基础之上的协议测试用例生成,一直是协议工程的重要研究内容。为此尝试将RSL引入协议形式化描述：首先探讨了一种基于输入/输出动作模型的协议形式化描述方法;随后对基于RSL描述的协议测试技术展开了讨论,提出了一种基于输入/输出动作的协议测试序列生成法则以及基于此法则的测试用例生成方法,并对使用该方法生成的测试用例的性质进行了讨论。     

Observer-based output feedback control of discrete-time linear systems with input and output delays

In this paper, we study observer-based output feedback control of discrete-time linear systems with both multiple input and output delays. By generalising our recently developed truncated predictor feedback approach for state feedback stabilisation of discrete-time time-delay systems to the design of observer-based output feedback, two types of observer-based output feedback controllers, one being memory and the other memoryless, are constructed. Both full-order and reduced-order observer-based controllers are established in both the memory and memoryless schemes. It is shown that the separation principle holds for the memory observer-based output feedback controllers, but does not hold for the memoryless ones. We further show that the proposed observer-based output feedback controllers solve both the l₂ and l_∞ semi-global stabilisation problems. A numerical example is given to illustrate the effectiveness of the proposed approaches.     

Stabilization for state/input delay systems via static and integral output feedback

This paper addresses the static and integral output feedback stabilization problems of continuous-time linear systems with an unknown state/input delay. By combining an augmentation approach and the delay partitioning technique, criteria for static and integral output feedback stabilizability are proposed in terms of nonlinear matrix inequalities with a free parameter matrix introduced. These new characterizations possess a special structure, which leads to linearized iterative computation. The effectiveness and merits of the proposed approach are shown through numerical examples.     

Explicit input and output feedback control for discrete-time systems

A new form of output feedback control, referred herein as explicit input and output feedback control (EIOC), is proposed for linear discrete-time systems. Unlike the conventional dynamic output feedback control described by a state-space model, the proposed EIOC has a batch form, where current control is explicitly expressed using current and past system outputs and past control inputs over a recent time horizon. The paper formulates the EIOC law and discusses its features and desirable characteristics. The EIOC is shown to be equivalent to static output feedback control for an augmented system. The coefficients of the EIOC are obtained to achieve the H _∞ performance criterion. Finally, numerical examples are presented to illustrate the effectiveness of the EIOC.     

Improving test quality using robust unique input/output circuit sequences (UIOCs)

In finite state machine (FSM) based testing, the problem of fault masking in the unique input/output (UIO) sequence may degrade the test performance of the UIO based methods. This paper investigates this problem and proposes the use of a new type of unique input/output circuit (UIOC) sequence for state verification, which may help to overcome the drawbacks that exist in the UIO based techniques. When constructing a UIOC, overlap and internal state observation schema are used to increase the robustness of a test sequence. Test quality is compared by using the forward UIO method (F-method), the backward UIO method (B-method) and the UIOC method (C-method) separately. Robustness of the UIOCs constructed by the algorithm given in this paper is also compared with those constructed by the algorithm given previously. Experimental results suggest that the C-method outperforms the F- and the B-methods and the UIOCs constructed by the algorithm given in this paper, are more robust than those constructed by other proposed algorithms.