A mathematical model of a digital control system with variable parameters

An approach is suggested for analysis of digital control systems with variable parameters; the approach involves the method of event-driven simulation. In addition, we describe a mathematical model of a discrete-continuous control system, implemented in MATLAB/Simulink/Stateflow.     

Bayesian statistical model checking with application to Stateflow/Simulink verification

We address the problem of model checking stochastic systems, i.e., checking whether a stochastic system satisfies a certain temporal property with a probability greater (or smaller) than a fixed threshold. In particular, we present a Statistical Model Checking (SMC) approach based on Bayesian statistics. We show that our approach is feasible for a certain class of hybrid systems with stochastic transitions, a generalization of Simulink/Stateflow models. Standard approaches to stochastic discrete systems require numerical solutions for large optimization problems and quickly become infeasible with larger state spaces. Generalizations of these techniques to hybrid systems with stochastic effects are even more challenging. The SMC approach was pioneered by Younes and Simmons in the discrete and non-Bayesian case. It solves the verification problem by combining randomized sampling of system traces (which is very efficient for Simulink/Stateflow) with hypothesis testing (i.e., testing against a probability threshold) or estimation (i.e., computing with high probability a value close to the true probability). We believe SMC is essential for scaling up to large Stateflow/Simulink models. While the answer to the verification problem is not guaranteed to be correct, we prove that Bayesian SMC can make the probability of giving a wrong answer arbitrarily small. The advantage is that answers can usually be obtained much faster than with standard, exhaustive model checking techniques. We apply our Bayesian SMC approach to a representative example of stochastic discrete-time hybrid system models in Stateflow/Simulink: a fuel control system featuring hybrid behavior and fault tolerance. We show that our technique enables faster verification than state-of-the-art statistical techniques. We emphasize that Bayesian SMC is by no means restricted to Stateflow/Simulink models. It is in principle applicable to a variety of stochastic models from other domains, e.g., systems biology.     

Generic and reflective graph transformations for checking and enforcement of modeling guidelines

In the automotive industry, the model driven development of software, today considered as the standard paradigm, is generally based on the use of the tool MATLAB Simulink/Stateflow. To increase the quality, the reliability, and the efficiency of the models and the generated code, checking and elimination of detected guideline violations defined in huge catalogs has become an essential task in the development process. It represents such a tremendous amount of boring work that it must necessarily be automated. In the past we have shown that graph transformation tools like Fujaba/MOFLON allow for the specification of single modeling guidelines on a very high level of abstraction and that guideline checking tools can be generated from these specifications easily. Unfortunately, graph transformation languages do not offer appropriate concepts for reuse of specification fragments—a MUST, when we deal with hundreds of guidelines. As a consequence we present an extension of MOFLON that supports the definition of generic rewrite rules and combines them with the reflective programming mechanisms of Java and the model repository interface standard Java Metadata Interface (JMI).     

基于Stateflow和xPC的监控系统实现

Stateflow是MATLAB提供的一种基于有限状态机理论的图形化建模和仿真工具。本文介绍了Stateflow的重要概念和基本用法。并使用MATLAB的Simulink、Stateflow和RTW／xPC工具箱,完成一仓厍监控系统从建模、仿真到实时代码生成的完整过程,大大缩短了监控系统的开发周期。     

Repository mining for changes in Simulink and Stateflow models

Software and Systems Modeling - Model-Based Development (MBD) is widely used for embedded controls development, with MATLAB/Simulink/Stateflow being one of the most used development environments in...     

基于MATLAB的三闭环交流伺服运动控制系统仿真与设计

针对交流伺服运动控制系统,在PMSM伺服系统电流环和速度环的基础上,进行位置环设计,保证伺服电机位置跟踪的精确性。同时,利用S曲线加减速算法进行速度规划,减小电机在加减速过程中的机械振动,以保证控制系统的稳定性和快速性。在MATLAB/Simulink中建立伺服系统仿真模型,仿真结果表明,上述方法能使系统具有很好的精确性、快速性和抗扰动性。     

An operational semantics for Stateflow

We present a formal operational semantics for Stateflow, the graphical Statecharts-like language of the Matlab/Simulink tool suite that is widely used in model-based development of embedded systems. Stateflow has many tricky features but our operational treatment yields a surprisingly simple semantics for the subset that is generally recommended for industrial applications. We have validated our semantics by developing an interpreter that allows us to compare its behavior against the Matlab simulator. We have used the semantics as a foundation for developing prototype tools for formal analysis of Stateflow designs.     

Tree slicing: Finding intertwined and gapped clones in one simple step

Most of software nowadays contain code duplication that leads to serious problems in software maintenance. A lot of different clone detection approaches have been proposed over the years to deal with this problem, but almost all of them do not consider semantic properties of the source code. We propose to reinforce traditional tree-based clone detection algorithm by using additional information about variable slices. This allows to find intertwined/gapped clones on variables; preliminary evaluation confirms applicability of our approach to real-world software.     

Mathematical model of steam generator feed system at power unit of nuclear plant

A mathematical model of a steam generator feed system at a power unit of a nuclear plant with variable values of transfer function coefficients is presented. The model is realized in the MATLAB/Simulink/Stateflow event-driven simulation.     

An approach to clone detection in sequence diagrams and its application to security analysis

Duplication in software systems is an important issue in software quality assurance. While many methods for software clone detection in source code and structural models have been described in the literature, little has been done on similarity in the dynamic behaviour of interactive systems. In this paper, we present an approach to identifying near-miss interaction clones in reverse-engineered UML sequence diagrams. Our goal is to identify patterns of interaction (“conversations”) that can be used to characterize and abstract the run-time behaviour of web applications and other interactive systems. In order to leverage existing robust near-miss code clone technology, our approach is text-based, working on the level of XMI, the standard interchange serialization for UML. Clone detection in UML behavioural models, such as sequence diagrams, presents a number of challenges—first, it is not clear how to break a continuous stream of interaction between lifelines (representing the objects or actors in the system) into meaningful conversational units. Second, unlike programming languages, the XMI text representation for UML is highly non-local, using attributes to reference-related elements in the model file remotely. In this work, we use a set of contextualizing source transformations on the XMI text representation to localize related elements, exposing the hidden hierarchical structure of the model and allowing us to granularize behavioural interactions into conversational units. Then we adapt NICAD, a robust near-miss code clone detection tool, to help us identify conversational clones in reverse-engineered behavioural models. These conversational clones are then analysed to find worrisome interactions that may indicate security access violations.     

Simulink/Stateflow仿真程序的HLA兼容性改造设计

该文从数据结构入手，宏观分析了Simulink／Stateflow仿真模型在进行HLA(高层体系结构)兼容性改造过程中所涉及的主要问题及步骤。主要包括由RTW(实时工作室)所生成的Simulink／Stmeflow模型C代码的通用运行框架，模型程序的SOM(仿真对象模型)开发，模型程序的HLA软件接口设计等。特别是针对HLA软件接口的设计与实现过程中存在许多重复性的工作，提供了一个将Simulink／Stateflow模型程序自动转化为HLA联邦成员且能适用于不同联邦的工具软件框架结构，从而为基于HAL仿真系统的Simulink／Stateflow仿真模型开发提供一条优化途径。     

Search-based automated testing of continuous controllers: Framework,tool support,and case studies

ContextTesting and verification of automotive embedded software is a major challenge. Software production in automotive domain comprises three stages: Developing automotive functions as Simulink models, generating code from the models, and deploying the resulting code on hardware devices. Automotive software artifacts are subject to three rounds of testing corresponding to the three production stages: Model-in-the-Loop (MiL), Software-in-the-Loop (SiL) and Hardware-in-the-Loop (HiL) testing.ObjectiveWe study testing of continuous controllers at the Model-in-Loop (MiL) level where both the controller and the environment are represented by models and connected in a closed loop system. These controllers make up a large part of automotive functions, and monitor and control the operating conditions of physical devices.MethodWe identify a set of requirements characterizing the behavior of continuous controllers, and develop a search-based technique based on random search, adaptive random search, hill climbing and simulated annealing algorithms to automatically identify worst-case test scenarios which are utilized to generate test cases for these requirements.ResultsWe evaluated our approach by applying it to an industrial automotive controller (with 443 Simulink blocks) and to a publicly available controller (with 21 Simulink blocks). Our experience shows that automatically generated test cases lead to MiL level simulations indicating potential violations of the system requirements. Further, not only does our approach generate significantly better test cases faster than random test case generation, but it also achieves better results than test scenarios devised by domain experts. Finally, our generated test cases uncover discrepancies between environment models and the real world when they are applied at the Hardware-in-the-Loop (HiL) level.ConclusionWe propose an automated approach to MiL testing of continuous controllers using search. The approach is implemented in a tool and has been successfully applied to a real case study from the automotive domain.     

Refinement-based verification of implementations of Stateflow charts

Simulink’s Stateflow is a graphical notation widely adopted in industry. Since it is frequently used to model safety-critical systems, correctness of implementations of Stateflow charts is a major concern. In previous work, we have shown how we can generate formal models for refinement of Stateflow charts automatically. Here, we define a refinement strategy that supports the automated verification of implementations with respect to these models. We consider the verification of implementations that follow architectural patterns used in the Stateflow code generator. We present a detailed procedure for application of refinement laws. If the implementation is correct, the procedure succeeds. If a law application fails, the implementation is either incorrect or does not use the expected architectural pattern. The very low proof burden associated with the refinement verification makes a high level of automation possible.     

Towards clone detection in UML domain models

Code clones (i.e., duplicate fragments of code) have been studied for long, and there is strong evidence that they are a major source of software faults. Anecdotal evidence suggests that this phenomenon occurs similarly in models, suggesting that model clones are as detrimental to model quality as they are to code quality. However, programming language code and visual models have significant differences that make it difficult to directly transfer notions and algorithms developed in the code clone arena to model clones. In this article, we develop and propose a definition of the notion of “model clone” based on the thorough analysis of practical scenarios. We propose a formal definition of model clones, specify a clone detection algorithm for UML domain models, and implement it prototypically. We investigate different similarity heuristics to be used in the algorithm, and report the performance of our approach. While we believe that our approach advances the state of the art significantly, it is restricted to UML models, its results leave room for improvements, and there is no validation by field studies.     

AMT车辆雪地模式控制系统的仿真

应用MATLAB/Simulink/Stateflow开发了AMT车辆在雪地模式下的变速性能仿真系统,建立了发动机、传动系统、驾驶员驾驶意图识别以及低附路面上的轮胎力等模型。基于该系统研究了AMT车辆在雪地模式下的控制模式,并通过仿真数据加以验证。     

Formal verification and simulation for platform screen doors and collision avoidance in subway control systems

For hybrid systems, hybrid automata-based tools are capable of verification, while Matlab Simulink/Stateflow is proficient in simulation. We propose a co-verification procedure, in which the verification tool SpaceEx/PHAVer and simulation tool Matlab are integrated to analyze and verify hybrid systems. For the application of this procedure, a platform screen door system (PSDS, a subsystem of the subway control system), is modeled with hybrid automata and Simulink/Stateflow charts, respectively. The models of PSDS are simulated by Matlab and verified by SpaceEx/PHAVer. The simulation and verification results indicate that the sandwiched situation can be avoided under time interval conditions. We improve the model with four trains and four stations on a subway line and analyze the urgent control scenario for the safety distance requirement. In this paper, the Simulink/Stateflow model is a refinement of the SpaceEx/PHAVer model, which is closer to a final implementation. Moreover, the two models are complementary for some features (e.g.,visualization of simulation, correctness proving by verification), stressing different aspects of the overall system and permitting complementary analysis techniques, i.e., verification versus simulation. We conclude that this integration procedure is competent in verifying subway control systems.     

克隆代码分析方法研究

针对已有克隆代码检测工具只输出克隆组形式的检测结果,而无法分析克隆代码对软件质量的影响问题,提出危害软件质量的关键克隆代码的识别方法。首先,定义了克隆代码的统一表示形式,使之可以分析各种克隆检测工具的检测结果;接下来,解析源程序和克隆检测结果,识别标识符命名不一致性潜在缺陷;然后,定义了克隆关联图,在此基础上检测跨越多个实现不同功能的文件、危害软件可维护性的克隆代码;最后,对检测结果进行可视化统计分析。本文的克隆代码分析工具被应用于分析开源代码httpd,检测出了1组标识符命名不一致的克隆代码和44组危害软件可维护性的关键克隆类,实验结果表明,本文方法可以有效辅助软件开发和维护人员分析、维护克隆代码。     

基于MATLAB/Simulink的捷联惯性导航系统仿真

介绍了仿真软件MATLAB/Simulink及先进的仿真系统平台软件RT-Lab,设计了龙格-库塔积分模块,用于解决在使用定步长求解器及数字时钟情况下的积分精度不高的问题;建立了基于MATLAB/Simulink的捷联惯性导航仿真模型;并将系统分解成一系列功能相对独立的模块,如轨迹发生模块,捷联惯导解算模块;并进行了仿真验证,得到的姿态、速度、位置误差与理论值相符,证明了仿真模型建立正确、方法采用得当、有效。     

Automatic library migration for the generation of hardware-in-the-loop models

Embedded systems are widely used in several applications nowadays. As they integrate hard- and software elements, their functionality and reliability are often tested by hardware-in-the-loop methods, in which the system under test runs in a simulated environment. Due to the rising complexity of the embedded functions, performance limitations and practicability reasons, the simulations are often specialized to test specific aspects of the embedded system and develop a high diversity by themselves. This diversity is difficult to manage for a user and results in erroneously selected test components and compatibility problems in the test configuration. This paper presents a generative programming approach that handles the diversity of test libraries. Compatibility issues are explicitly evaluated by a new interface concept. Furthermore, a novel model analyzer facilitates the efficient application in practice by migrating existing libraries. The approach is evaluated for an example from the automotive domain using MATLAB/Simulink.