Using formal methods with SysML in aerospace design and engineering

Maintaining design consistency is a critical issue for macro-level aerospace development. The inability to maintain design consistency is a major contributor to cost and schedule overruns. By embedding The Systems Modeling Language (SysML) within a formal logic, formal methods can be used to maintain consistency as a design evolves. SysML, provided with a formal semantics, enables engineers to employ reasoning in the course of a typical model-based development process. Engineers can make use of formal methods within the context of current engineering practice and tools without needing to have special formal methods training. As component subsystems are introduced to refine a design, their assumptions are checked against current assumptions. If new assumptions do not introduce inconsistency, they are added to the model assumptions. If the assumptions render the design inconsistent, they are detected which minimizes potential rework. SysML has a demonstrated capability for top-to-bottom design refinement for large-scale aerospace systems. SysML does not have a formal logic-based semantics. The logical formalism within which SysML is embedded matches the informal semantic of SysML closely. The approach to integrating formal methods with SysML is illustrated with a typical macro-level aerospace design task. The design process produces a design solution which provably satisfies the top level requirements. The example provides evidence that coupling formal methods with SysML can realistically be applied to solve aerospace development problems. The approach results from a number of detailed design trades employing a model-based system development process which used SysML as the model integration framework.     

Dependability analysis of DES based on MARTE and UML state machines models

UML (Unified Modeling Language) is a standard design notation which offers the state machines diagram to specify reactive software systems. The “Modeling and Analysis of Real-Time and Embedded systems” profile (MARTE) enables UML with capabilities for performance analysis. MARTE has been specialized in a “Dependability Analysis and Modeling” profile (DAM), then providing UML with dependability assets. In this work, we propose an approach for the automatic transformation of UML-DAM models into Deterministic and Stochastic Petri nets and the subsequent dependability analysis.     

Evaluating real-time software specification languages

In recent years, many notations and methods in real-time software engineering have been proposed. However, thorough experimentation to evaluate these notations and methods has not been carried out. This paper focuses on real-time software engineering specification languages: Unified Modeling Language (UML), Real-Time Object-Oriented Modeling Language (ROOM), Modecharts, statecharts, Mealy and Moore machines, finite state machines, classical logic, Z, ASTRAL, temporal logic, FNLOG, linear logic, Timed Communicating Sequential Processes (TCSP), Temporal Calculus of Communicating Systems (TCCS), ρ1, and Multilevel Specification. The basis for evaluating these software engineering specification languages is by using the Turing machines and Interaction machines. We classify them based on their computational capabilities.     

基于AADL的航天嵌入式软件Ada代码自动生成方法

模型驱动开发方法逐渐应用于航空航天等领域的安全关键软件设计与实现中。体系结构分析设计语言(Architecture Analysis and Design Language, AADL)是一种标准化的嵌入式软件体系结构描述语言,通过建模、验证以及代码自动生成为安全关键软件的设计与实现提供完整支持。然而,工业界实际代码是运行在具有不同特性的目标平台上的,例如不同的软硬件体系结构和编程接口,而现有AADL代码生成研究主要是通过手工将自动生成的代码集成到平台当中,存在工作繁琐且易出错的问题。为此,本文提出一种基于AADL的航天嵌入式软件Ada代码自动生成方法。首先,给出卫星姿轨控系统的AADL建模;其次,给出AADL到平台相关的Ada代码自动转化规则;最后,给出代码生成原型工具,并对卫星姿轨控系统AADL模型所生成的代码进行航天编码规范检查,并运行在相关仿真环境中,验证了本文所提方法的有效性。     

Synthesizing Distributed Protocol Specifications from a UML State Machine Modeled Service Specification

The object-oriented paradigm is widely applied in designing and implementing communication systems.Unified Modeling Language(UML) is a standard language used to model the design of object-oriented systems.A protocol state machine is a UML adopted diagram that is widely used in designing communication protocols.It has two key attractive advantages over traditional finite state machines:modeling concurrency and modeling nested hierarchical states.In a distributed communication system,each entity of the system has its own protocol that defines when and how the entity exchanges messages with other communicating entities in the system.The order of the exchanged messages must conform to the overall service specifications of the system.In object-oriented systems,both the service and the protocol specifications are modeled in UML protocol state machines.Protocol specification synthesis methods have to be applied to automatically derive the protocol specification from the service specification.Otherwise,a time-consuming process of design,analysis,and error detection and correction has to be applied iteratively until the design of the protocol becomes error-free and consistent with the service specification.Several synthesis methods are proposed in the literature for models other than UML protocol state machines,and therefore,because of the unique features of the protocol state machines,these methods are inapplicable to services modeled in UML protocol state machines.In this paper,we propose a synthesis method that automatically synthesizes the protocol specification of distributed protocol entities from the service specification,given that both types of specifications are modeled in UML protocol state machines.Our method is based on the latest UML version(UML2.3),and it is proven to synthesize protocol specifications that are syntactically and semantically correct.As an example application,the synthesis method is used to derive the protocol specification of the H.323 standard used in Internet calls.     

An innovative software architecture to improve information flow from CAM to CNC

Over the years, machine tool evolution has allowed faster equipment, using new configurations, to manufacture parts that were almost impossible to machine in the past. Despite this tremendous evolution in machine and control technologies, the metalworking industry is still using the old ISO 6983 G-Codes programming interface to control the motion of these machines. This programming interface is not the most flexible or most appropriate for use by new open-architecture machine controllers and object-oriented high-level machining interfaces such as ISO 14649 (STEP-NC). This work proposes an innovative language, the ‘Base Numerical Control Language (BNCL),’ which is based on a low-level simple instruction set-like approach. The architecture is designed around two concepts: the BNCL virtual machine, which acts as a virtual microprocessor, and the BNCL virtual hardware, which is an abstraction of the machine tool. The language is characterised by its simplicity and flexibility, two qualities that are critical in a market in which the capabilities and performance of machines are constantly improving. The proposed architectural concepts are validated through various computer simulation and physical tests, including performance throughput, trajectory driving, and CNC controller extension capabilities.     

Autonomous Language Development Using Dialogue-Act Templates and Genetic Programming

In recent years, the concept of "autonomous mental development" (AMD) has been applied to the construction of artificial systems such as conversational agents, in order to resolve some of the difficulties involved in the manual definition of their knowledge bases and behavioral patterns. AMD is a new paradigm for developing autonomous machines, which are adaptive and flexible to the environment. Language development, a kind of mental development, is an important aspect of intelligent conversational agents. In this paper, we propose an intelligent conversational agent and its language development mechanism by putting together five promising techniques: Bayesian networks, pattern matching, finite-state machines, templates, and genetic programming (GP). Knowledge acquisition implemented by finite-state machines and templates, and language learning by GP are used for language development. Several illustrations and usability tests show the usefulness of the proposed developmental conversational agent     

Parallel architecture overview

An increasing number of parallel computer products are appearing in the market place. Their design motivations and market areas cover a broad spectrum: (i) Transaction Processing Systems, such as Parallel UNIX systems (e.g. SEQUENT Balance), for data processing applications; (ii) Numeric Supercomputers, such as Hypercube systems (e.g. INTEL iPSC), for scientific and engineering applications; (iii) VLSI Architectures, such as parallel microcomputers (e.g. INMOS Transputer), for exploiting very large scales of integration; (iv) High-Level Language Computers, such as Logic machines (e.g. FUJITSU Kabu-Wake), for symbolic computation; and (v) Neurocomputers, such as Connectionist computers (e.g. THINKING MACHINES Connection Machine), for general-purpose pattern matching applications.

This survey paper gives an overview of these novel parallel computers and discusses the likely commercial impact of parallel computers.     

基于工作流驱动的航天产品分布式协同设计环境

在分析目前航天产品研制面临形势和存在问题的基础上,引入了构建分布式协同设计环境的解决途径,同时针对产品协同设计过程中知识、任务、对象、人员和流程的统一描述问题,提出了协同设计环境中定义和运行的唯一数据源——任务统一模型(Task Unified Model,简称为TUM)的概念,并对TUM定义、组织、视图转换及运行机制进行了详细论述。然后基于Eclipse RCP和Web Portal技术构建了分布式协同设计环境APEngine,实现了面向产品设计全过程的 TUM 建模、实例化和运行过程。最后通过某航天历史型号设计的工程实际应用,证明了本文研究成果具有较强的工程应用价值。     

A computational model for static data flow machines

Computer architects have been constantly looking for new approaches to design high-performance machines. Data flow and VLSI offer two mutually supportive approaches towards a promising design for future super-computers. When very high speed computations are needed, data flow machines may be relied upon as an adequate solution in which extremely parallel processing is achieved.

This paper presents a formal analysis for data flow machines. Moreover, the following three machines are considered: (1) MIT static data flow machine; (2) TI's DDP static data flow machine; (3) LAU data flow machine.

These machines are investigated by making use of a reference model. The contributions of this paper include: (1) Developing a Data Flow Random Access Machine model (DFRAM), for first time, to serve as a formal modeling tool. Also, by making use of this model one can calculate the time cost of various static data machines, as well as the performance of these machines. (2) Constructing a practical Data Flow Simulator (DFS) on the basis of the DFRAM model. Such DFS is modular and portable and can be implemented with less sophistication. The DFS is used not only to study the performance of the underlying data flow machines but also to verify the DFRAM model.     

Topology Optimization in Aircraft and Aerospace Structures Design

Topology optimization has become an effective tool for least-weight and performance design, especially in aeronautics and aerospace engineering. The purpose of this paper is to survey recent advances of topology optimization techniques applied in aircraft and aerospace structures design. This paper firstly reviews several existing applications: (1) standard material layout design for airframe structures, (2) layout design of stiffener ribs for aircraft panels, (3) multi-component layout design for aerospace structural systems, (4) multi-fasteners design for assembled aircraft structures. Secondly, potential applications of topology optimization in dynamic responses design, shape preserving design, smart structures design, structural features design and additive manufacturing are introduced to provide a forward-looking perspective.     

ConData: A Tool for Automating Specification-Based Test Case Generation for Communication Systems

This paper describes a tool called ConData used as test generation for communication protocols specified as extended finite state machines. The strategy for test generation combines different specification-based test methods: (i) transition testing for the control part of a protocol and (ii) syntax and equivalence partitioning for the data part. The tool uses a representation of the protocol in PSL (Protocol Specification Language), which is transformed into a format readable by a Prolog program. This implements the test strategies mentioned above. The text also presents some results obtained in the test generation for the protocol of the Tele-command Communication System of the SACI-1 satellite.     

A course in computer-aided aerospace design

This paper describes a new sophomore course being offered at Purdue University in the area of aerospace design. While the course and the examples used in this presentation deal with aerospace engineering, the overall structure is presented as being applicable in other engineering areas as well. The basic idea is that, with time, more of the design processes will involve the use of a computer and this necessarily will force the design process towards a higher degree of organization. The course is a simple illustrative example within this viewpoint. The basic modules of aerospace engineering of flight mechanics, aerodynamics, structures, propulsion, weights, air transportation, stability and control, and performance are used to formulate a set of constraints, which, in the particular example, are positive static stability, trim, structural integrity, and range. A (paper) aircraft is defined as an element of the set of feasible values of design parameters (geometry, altitude, speed). Then, given the subset of aircraft which satisfies all the constraints, the aircraft, with the optimum index of performance, is defined to be the best aircraft.     

Data management and control-flow aspects of an SIMD/SPMD parallellanguage/compiler

Features of an explicitly parallel programming language targeted for reconfigurable parallel processing systems, where the machine's N processing elements (PEs) are capable of operating in both the SIMD and SPMD modes of parallelism, are described. The SPMD (single program-multiple data) mode of parallelism is a subset of the MIMD mode where all processors execute the same program. By providing all aspects of the language with an SIMD mode version and an SPMD mode version that are syntactically and semantically equivalent, the language facilitates experimentation with and exploitation of hybrid SIMD/SPMD machines. Language constructs (and their implementations) for data management, data-dependent control-flow, and PE-address-dependent control-flow are presented. These constructs are based on experience gained from programming a parallel machine prototype and are being incorporated into a compiler under development. Much of the research presented is applicable to general SIMD machines and MIMD machines     

基于XML的移动设备人机交互引擎

基于传统的移动设备领域人机交互界面的开发的现状以及特点设计了一种移动应用的开发模型。为了提高移动设备应用开发的效率和人机交互界面的质量,结合这种模型,提出了一种引擎设计方案。这种引擎(称为XmlSupervisor)采用面向服务的体系结构（SOA）的思想,通过将界面、逻辑代码和资源相分离的方案进行设计,可以支持利用可扩展标记语言(XML)的良好的扩展性、自描述性、跨平台性、树状存储结构等特点来开发的人机交互界面,为移动设备的人机交互界面的设计和开发提供了参考。     

A control theoretic framework for modular analysis and design of biomolecular networks

Control theory has been instrumental for the analysis and design of a number of engineering systems, including aerospace and transportation systems, robotics and intelligent machines, manufacturing chains, electrical, power, and information networks. In the past several years, the ability of de novo creating biomolecular networks and of measuring key physical quantities has come to a point in which quantitative analysis and design of biological systems is possible. While a modular approach to analyze and design complex systems has proven critical in most control theory applications, it is still subject of debate whether a modular approach is viable in biomolecular networks. In fact, biomolecular networks display context-dependent behavior, that is, the input/output dynamical properties of a module change once this is part of a network. One cause of context dependence, similar to what found in many engineering systems, is retroactivity, that is, the effect of loads applied on a module by downstream systems. In this paper, we focus on retroactivity and review techniques, based on nonlinear control and dynamical systems theory, that we have developed to quantify the extent of modularity of biomolecular systems and to establish modular analysis and design techniques.