A practical approach to implementing real-time semantics

This paper investigates implementations of process algebras which are suitable for modeling concurrent real-time systems. It suggests an approach for efficiently implementing real-time semantics using dynamic priorities. For this purpose a process algebra with dynamic priority is defined, whose semantics corresponds one-to-one to traditional real-time semantics. The advantage of the dynamic-priority approach is that it drastically reduces the state-space sizes of the systems in question while preserving all properties of their functional and real-time behavior. The utility of the technique is demonstrated by a case study that deals with the formal modeling and verification of several aspects of the widely-used SCSI-2 bus-protocol. The case study is carried out in the Concurrency Workbench of North Carolina, an automated verification tool in which the process algebra with dynamic priority is implemented. It turns out that the state space of the bus-protocol model is about an order of magnitude smaller than the one resulting from real-time semantics. The accuracy of the model is proved by applying model checking for verifying several mandatory properties of the bus protocol. This revised version was published online in June 2006 with corrections to the Cover Date.     

Proving properties of real-time systems through logicalspecifications and Petri net models

Addresses the problem of formally analyzing the properties of real-time systems. We propose a method based on modeling the system as a timed Petri net and on specifying its properties in TRIO, an extension of temporal logic suitable for dealing explicitly with time and for measuring it. Timed Petri nets are axiomatized in terms of TRIO, so that their properties can be derived as theorems in the same spirit as the classical Hoare method allows one to prove properties of programs coded in a Pascal-like language. The method is also illustrated through an example     

基于时间STM的软件形式化建模与验证方法

状态迁移矩阵(state transition matrix,简称STM)是一种基于表结构的状态机建模方法,前端为表格形式,后端则具有严格的形式化定义,用于建模软件系统行为.但目前STM不具有时间语义,这极大地限制了该方法在实时嵌入式软件建模方面的应用.针对这一问题,提出了一种基于时间STM(time STM,简称TSTM)的形式化建模方法,通过为STM各单元格增加时间语义和约束,使其适用于实时软件行为刻画.此外,针对TSTM给出了一种基于界限模型检测(bounded model checking,简称BMC)技术的时间计算树逻辑(time computation tree logic,简称TCTL)模型检测方法,以验证TSTM时间及逻辑属性.最后,通过对某型号列控制软件进行TSTM建模与验证,证明了上述方法的有效性.     

Development of real-time sketch-based on-the-spot process modeling and analysis system

Contemporary manufacturing processes require faster real-time controls against dynamic and volatile production environments. While a corresponding simulation model is considered a prerequisite system for the real-time control of a contemporary manufacturing process, simulation modeling and relevant analysis have supported these real-time features comparatively less. These issues might cause procrastination of the simulation modeling, and result in wrong decisions and inaccurate controls. In order to overcome these issues, a new real-time simulation modeling and analysis system is proposed. The proposed system supports sketch-based simulation modeling. The simulation model is constructed using modelers’ sketches of predefined simulation symbols. The sketches are converted automatically into a corresponding stochastic queueing network using Self-organizing Map, a type of neural network. Then, the model is simulated and analyzed using the embedded stochastic queueing analyses. The effectiveness of the proposed system is proven with the modeling, simulation and analyses of several real-time manufacturing cases.     

一种FTCSP的服务组合时间建模与分析方法

为了实现适合描述并发和组合系统的经典进程代数对服务组合时间规约的建模与分析,首先,提出了一种模糊时间通信顺序进程(FTCSP),定义了其语法和操作语义,然后提出了基于FTCSP的服务组合时间建模与分析方法,定义了有利于服务组合时间规约分析的模糊时间算子,给出了服务组合时间分析算法.最后,以地下空间环境信息实时发布系统(UEIRS)为例,验证了该方法的有效性.     

Dynamic production system diagnosis and prognosis using model-based data-driven method

Advanced manufacturing systems are becoming increasingly complex, subjecting to constant changes driven by fluctuating market demands, new technology insertion, as well as random disruption events. While information about production processes has been becoming increasingly transparent, detailed, and real-time, the utilization of this information for real-time manufacturing analysis and decision-making has been lagging behind largely due to the limitation of the traditional methodologies for production system analysis, and a lack of real-time manufacturing processes modeling approach and real-time performance identification method. In this paper, a novel data-driven stochastic manufacturing system model is proposed to describe production dynamics and a systematic method is developed to identify the causes of permanent production loss in both deterministic and stochastic scenarios. The proposed methods integrate available sensor data with the knowledge of production system physical properties. Such methods can be transferred to a computer for system self-diagnosis/prognosis to provide users with deeper understanding of the underlying relationships between system status and performance, and to facilitate real-time production control and decision making. This effort is a step forward to smart manufacturing for system real-time performance identification in achieving improved system responsiveness and efficiency.     

Object-oriented specification and formal verification of real-time systems

An object-oriented approach for specification and verification of real-time systems is described in this paper. It is motivated by taking advantage of object-oriented techniques to produce real-time software that is easy to understand, maintain, and reuse. The approach specifies the structural, behavioral, and control aspects of objects in one model with a textual representation as well as a graphical representation. For ease to comprehend and use, the model encapsulates object states and allows an analyst to focus on specifying object operations one at a time. System behavior from individual objects can be deduced and analyzed. For safety considerations, the approach supports specification of failures to object behavior and their resultant faults. The approach also supports modeling of timed temporal constraints for specifying and verifying desirable real-time properties. An object timed temporal logic OTTL is defined for expressing the syntax and semantics of these constraints. Decision procedures for their verification are also presented.     

一种面向主动对象的实时数据模型

针对支持复杂实时应用的实时数据库管理系统,提出了一种面向主动对象的实时数据模型AOORT,将面向对象实时性和主动性更好地集成在一起。模型由对象、关系和规则3部分组成。对象用来对带有时间特性的实体进行建模,扩展了传统对象来提供实时和主动特征;关系描述了对象之间的联系情况;规则体现了数据库的主动性,并集成了时间约束。最后以一个简单网络化控制系统中的实时数据采集和监控子系统为例,展示了AOORT模型的具体应用。     

Designing and modeling cyberworlds using the incrementally modular abstraction hierarchy based on homotopy theory

For designing and modeling complicated and sophisticated systems such as cyberworlds, their mathematical foundation is critical. To realize it, two important properties called the homotopy lifting property (HLP) and homotopy extension property (HEP) are applied for designing and modeling a system in a bottom-up way and a top-down way, respectively. In this paper, an enterprise system and a real-time embedded system are considered as important socially emerging cases of cyberworlds, where the π-calculus processes for describing these behaviors formally, a Petri net for explaining process interactions, and XMOS XC programs are modeled and designed by our approach. The spaces in both properties are specified by the incrementally modular abstraction hierarchy by climbing down the abstraction hierarchy from the most abstract homotopy level to the most specific view level, while keeping invariants such as homotopy equivalence and topological equivalence.     

一种基于物理意义的快速力反馈形变模型及实时力觉响应算法

虚拟物体在受力作用时的形变建模是虚拟环境中力/触觉人机交互的关键.文中提出了一种新的基于物理意义的形变建模方法,不仅计算速度快,满足力反馈的实时性要求,而且能够同时保证接触力和形变的计算具有较高的精度,适用于具有较大变形量的柔性物体的力反馈计算,满足精细作业对虚拟现实系统的要求.     

基于可扩展端口技术的实时领域分层递阶建模方法

在采用模型驱动的开发(MDD)方法对复杂实时系统进行建模设计时,单层的建模方法难以完成对控制系统的清晰和完整描述。针对上述问题提出了一种分层递阶机制的实时多层建模方法,该方法使用可扩展输入端口和输出端口对现有元模型技术进行扩展,采用可扩展标记语言(XML)实现端口的描述,利用基于信道的端口消息传递机制完成不同层模型之间通信。实际实时控制系统建模结果表明,与单层模型相比,分层递阶的建模方法能够有效实现模型驱动设计方法在实时领域内对并行多任务和复杂交互行为的描述,从而提高实时领域模型的可读性和可复用性。     

Compact modeling of spatial continuum robotic arms towards real-time control

This paper presents a compact modeling approach of continuum robotic arms, with limited computations for faster numerical calculations in real-time implementations. It is assumed that the arm includes a backbone made of elastic rods, and the Cosserat rod theory is simplified for numerically faster modeling. The time-taking boundary-value problem (BVP) is detailed, and some numerical methods are introduced to solve the developed equations of modeling. Next, based on physical intuition, a fast and stable method is proposed to solve the BVP, as a moment-based approach. Also, a method to cancel some numerical integration errors with the least required computations and numerical efforts is presented. Next, a Jacobian-based control of multi-segment continuum robotic arms is developed. Finally, this procedure is experimentally verified to show the precision of proposed modeling approach and also to reveal the importance of faster solutions for real-time control.     

灰色动态预测在AUV传感器故障诊断中的应用

针对自主水下机器人(AUV)传感器故障诊断中样本数据少、随机性强、实时性要求高的特点,将灰色动态预测模型的建模原理引用到AUV传感器的故障诊断中。在对传感器进行数据滤波、小样本灰色建模与灰色动态预测的基础上,可以实现AUV传感器的实时故障诊断。文章详细阐述了基于灰色动态预测的传感器故障诊断的具体实现方法和步骤,对AUV传感器中典型的四种故障模式进行了仿真研究。结果表明该方法能快速、准确地诊断出传感器故障,并且在传感器发生故障后的一段时间内能够实现信号恢复。     

A verification framework for spatio-temporal consistency language with CCSL as a specification language

The Spatio-Temporal Consistency Language(STeC)is a high-level modeling language that deals natively with spatio-temporal behaviour,i.e.,behaviour relating to certain locations and time.Such restriction by both locations and time is of first importance for some types of real-time systems.CCSL is a formal specification language based on logical clocks.It is used to describe some crucial safety properties for real-time systems,due to its powerful expressiveness of logical and chronometric time constraints.We consider a novel verification framework combining STeC and CCSL,with the advantages of addressing spatio-temporal consistency of system behaviour and easily expressing some crucial time constraints.We propose a theory combining these two languages and a method verifying CCSL properties in STeC models.We adopt UPPAAL as the model checking tool and give a simple example to illustrate how to carry out verification in our framework.     

Volume-preserving free-form solids

Some important trends in geometric modeling are the reliance on solid models rather than surface-based models and the enhancement of the expressive power of models, by using free-form objects in addition to the usual geometric primitives and by incorporating physical principles. An additional trend is the emphasis on interactive performance. In this paper, we integrate all of these requirements into a single geometric primitive by endowing the tri-variate tensor-product free-form solid with several important physical properties, including volume and internal deformation energy. Volume preservation is of benefit in several application areas of geometric modeling, including computer animation, industrial design and mechanical engineering. However, previous physics-based methods, which have usually used some form of “energy”, have neglected the issue of volume (or area) preservation. We present a novel method for modeling an object composed of several tensor-product solids while preserving the desired volume of each primitive and ensuring high-order continuity constraints between the primitives. The method utilizes the Uzawa algorithm for non-linear optimization, with objective functions based on deformation energy or least squares. We show how the algorithm can be used in an interactive environment by relaxing exactness requirements while the user interactively manipulates free-form solid primitives. On current workstations, the algorithm runs in real-time for tri-quadratic volumes and close to real-time for tri-cubic volumes     

An event-based approach for formally verifying runtime adaptive real-time systems

Real-time and embedded systems are required to adapt their behavior and structure to runtime unpredicted changes in order to maintain their feasibility and usefulness. These systems are generally more difficult to specify and verify owning to their execution complexity. Hence, ensuring the high-level design and the early verification of system adaptation at runtime is very crucial. However, existing runtime model-based approaches for adaptive real-time and embedded systems suffer from shortcoming linked to efficiently and correctly managing the adaptive system behavior, especially that a formal verification is not allowed by modeling languages such as UML and MARTE profile. Moreover, reasoning about the correctness and the precision of high-level models is a complex task without the appropriate tool support. In this work, we propose an MDE-based framework for the specification and the verification of runtime adaptive real-time and embedded systems. Our approach stands for Event-B method to formally verify resources behavior and real-time constraints. In fact, thanks to MDE M2T transformations, our proposal translates runtime models into Event-B specifications to ensure the correctness of runtime adaptive system properties, temporal constrains and nonfunctional properties using Rodin platform. A flood prediction system case study is adopted for the validation of our proposal.

     

Automated verification and refinement for physical-layer protocols

This paper demonstrates how to use a satisfiability modulo theories (SMT) solver together with a bounded model checker to verify properties of real-time physical layer protocols. The method is first used to verify the Biphase Mark protocol, a protocol that has been verified numerous times previously, allowing for a comparison of results. The techniques are extended to the 8N1 protocol used in universal asynchronous receiver transmitters. We then demonstrate the use of temporal refinement to link a finite state specification of 8N1 with its real-time implementation. This refinement relationship relieves a significant disadvantage of SMT approaches—their inability to scale to large problems. Finally, capturing the impact of metastability on timing requirements is a key issue in modeling physical-layer protocols. Rather than model metastability directly, a contribution of our models is treating its effect as a constraint on non-determinism.     

基于时间自动机的信息物理融合系统建模与验证

信息物理融合系统的建模和验证是当前研究的一个热点。本文通过分析信息物理融合系统的体系结构,利用时间自动机为建模工具,将该结构中的各个组件分别进行建模,以表现它们的分布性和实时性。这些时间自动机组成一个网络模型,用于刻划整个系统之间的并发通信和协作过程。最后,提出一组该系统要满足的性质(包括时间约束),运用模型检测工具UPPAAL自动验证本系统的正确性。     

Knowledge-based modeling for disruption management in urban distribution

Disruption management in urban distribution is the process of achieving a new distribution plan in order to respond to a disruption in real time. Experienced schedulers can respond to disruptions quickly with common sense and past experiences, but they often achieve the new distribution plan by a fuzzy, sometimes inconsistent, and not well-understood way. The method is limited when the problem becomes large scale or more complicated. In this case, optimization techniques consisting of models and algorithms may complement it. However, as the distribution system’s state changes constantly with the plan-executing process and disruptions are diversified, real-time modeling is very difficult. Hence in order to achieve the real-time modeling process, the research in the paper focuses on a knowledge-based modeling method, which combines the knowledge of experienced schedulers with the OR knowledge concerning models and algorithms. Policies, algorithms and models are represented by proper knowledge representation schemes in order to support automated or semi-automated modeling by computers. The modeling process is demonstrated by a case to show how the different kinds of knowledge representation schemes cooperate with each other to support the modeling process. In the knowledge-based modeling process, based on the knowledge of experienced schedulers, a qualitative policy for handling the disruption based on the current distribution system’s state is achieved firstly; and then based on OR knowledge, the corresponding model and algorithm are constructed to quantitatively optimize the policy. The integration of the two kinds of knowledge not only effectively supports the real-time modeling process, but also combines the advantages of both to achieve more practical and scientific solutions to different kinds of disruptions occurring under different distribution system’s states.     

无人机吊挂空运系统的自适应控制设计

针对四旋翼无人机吊挂空运系统存在的模型不确定性及欠驱动性问题,本文提出了一种基于能量耦合的自适应控制设计.首先,基于能量整形控制方法构造了一种新型的能量存储函数以处理状态耦合.然后利用神经网络对系统未建模动态特性进行在线估计,同时设计参数自适应律在线估计模型中的未知参数,并采用基于符号函数的鲁棒控制算法补偿神经网络的估计误差.本文运用李雅普诺夫方法和拉塞尔不变性原理对闭环系统的稳定性进行了证明,并且证明了负载摆动和无人机位置误差的渐近收敛性.最后,在室内实验平台上进行了飞行实验.实验结果表明,本文提出的非线性控制方法能够在有效抑制吊挂负载摆动的同时,实现无人机位置的精确控制.