Using model checking to analyze the system behavior of the LHC production grid

DIRAC (Distributed Infrastructure with Remote Agent Control) is the grid solution designed to support production activities as well as user data analysis for the Large Hadron Collider “beauty” experiment. It consists of cooperating distributed services and a plethora of light-weight agents delivering the workload to the grid resources. Services accept requests from agents and running jobs, while agents actively fulfill specific goals. Services maintain database back-ends to store dynamic state information of entities such as jobs, queues, or requests for data transfer. Agents continuously check for changes in the service states and react to these accordingly. The logic of each agent is rather simple; the main source of complexity lies in their cooperation. These agents run concurrently and communicate using the services’ databases as a shared memory for synchronizing the state transitions. Despite the effort invested in making DIRAC reliable, entities occasionally get into inconsistent states. Tracing and fixing such behaviors is difficult, given the inherent parallelism among the distributed components and the size of the implementation.In this paper we present an analysis of DIRAC with mCRL2, process algebra with data. We have reverse engineered two critical and related DIRAC subsystems, and subsequently modeled their behavior with the mCRL2 toolset. This enabled us to easily locate race conditions and livelocks which were confirmed to occur in the real system. We further formalized and verified several behavioral properties of the two modeled subsystems.     

利用FCS实现除尘控制

FCS2000现场总线控制系统是一种建立在SCADA基础上的通用综合性控制系统.介绍FCS2000系统在除尘控制中的实际应用,同时通过对系统的整体配置、自动控制系统的论述,给出了一种集散控制系统实际应用的设计方案.     

基于组态王的过程控制综合实验测控装置

针对现有过程控制教学的现状，介绍了基于组态王的过程控制综合实验测控装置。该系统是一个小型集散控制系统，装有组态王工控软件的上位计算机完成对被控对象的模拟和监控（SCA—DA），通过RS-232／RS485和下位机PLC串口通信，下位机由西门子PLC（S7—200）组成，实时检测被控对象的温度、压力、液位、流量四个参数，把采集到的数据进行处理和保存，并根据控制要求进行PID运算，运算结果控制执行器动作，执行器为电动调节阀、变频器和电动机。并以串级控制系统为例，说明了过程控制系统的组态及实验步骤。实践证明，该实验装置充分模拟工业控制现场，操作简单，实验效果良好。     

Evolution of system noises in electrodeposition process control

The evolution of source noises in space–time is analysed in this paper. It characterises the global effect of uncertainties in electrodeposition process control, where the source noises have an effect on the concentration field of relevant species in the diffusion layer and the field is controlled by the Neumann boundary using relatively simple boundary controls. The control errors evolve in the diffusion layer and are dependent upon the source noises and applied controls as a random field process. The covariance structure of the field is found analytically and confirmed numerically. The local source noises are incited by the uncertainties from a realistic control system; they are devised by the process physics and a control system structure. This paper demonstrates that even in a relatively simple system, the local uncertainties have a strong tendency to expand in space–time. Some source noises have a dispersed effect on the overall system uncertainty (control error), others are more local and do not expand in the same way. The noise of the mass flux, which is injected through the Neumann boundary, dies out quickly in the diffusion layer.     

Strategies to create platforms for differentiated services from dedicated and opportunistic resources

This paper is proposing a new platform for implementing services in future service oriented architectures. The basic premise of our proposal is that by combining the large volume of uncontracted resources with small clusters of dedicated resources, we can dramatically reduce the amount of dedicated resources while the goodput provided by the overall system remains at a high level. This paper presents particular strategies for implementing this idea for a particular class of applications. We performed very detailed simulations on synthetic and real traces to evaluate the performance of the proposed strategies. Our findings on compute-intensive applications show that preemptive reallocation of resources is necessary for assured services. The proposed preemption-based scheduling heuristic can significantly improve utilization of the dedicated resources by opportunistically offloading the peak loads on uncontracted resources, while keeping the service quality virtually unaffected.     

Experience with remote procedure calls in a real-time control system

This paper describes several years' practical experience with remote procedure calls as a primary tool for application software in a large and complex distributed real-time process control system. We motivate the use of remote procedure calls as an effective technique for the use of local area networks, describe our implementation and discuss its advantages and disadvantages.     

From Flow Logic to static type systems for coordination languages

Coordination languages are often used to describe open-ended systems. This makes it challenging to develop tools for guaranteeing the security of the coordinated systems and the correctness of their interaction. Successful approaches to this problem have been based on type systems with dynamic checks; therefore, the correctness properties cannot be statically enforced. By contrast, static analysis approaches based on Flow Logic usually guarantee properties statically. In this paper, we show how the insights from the Flow Logic approach can be used to construct a type system for statically ensuring secure access to tuple spaces and safe process migration for an extension of the language Klaim.     

并行微处理系统及其在实时控制中的应用

本文介绍了并行处理中广泛应用的Transputer系统及其对工业实时控制的适用性，并论述了实时控制的并行处理方法。     

Adaptive fuzzy control systems with dynamic structure

This article proposes a novel fuzzy system, referred to as a dynamic structure fuzzy system, to address tracking control problems for unknown nonlinear dynamical systems. The fuzzy system is employed to reconstruct the unknown nonlinearities of dynamic systems. In the dynamic structure fuzzy system, the number of fuzzy rules can be either increased or decreased over time based on the required approximation accuracy. The advantage of the dynamic structure fuzzy system is that a suitable-sized fuzzy system can be found to avoid overfitting or underfitting data sets. By using Gaussian radial basis function (GRBF) as a membership function, adaptation laws are presented for tuning all parameters of the parameterized fuzzy system, including the output weights, the widths and the centers of the GRBF's. Global boundedness of the overall control scheme is guaranteed in the sense of Lyapunov. The tracking error converges to the required precision through the adaptive control scheme derived by the Lyapunov synthesis approach. Simulations performed on an underwater vehicle system demonstrate the effectiveness of our scheme.     

凸价格函数下基于堆栈执行的云计算资源调度方案

目前云资源提供商制定了多种定价优惠策略,针对现有云计算任务调度方案没有考虑到动态价格的问题,提出一种在凸价格函数下的资源调度方案。首先,将任务执行区间划分为多个单位子区间。然后,根据子区间中的任务密度,基于任务堆栈执行的思想,在满足任务截止时间下,将低密度区间中的任务重新调度到其它区间。最后,根据任务的最大执行速率,为每个任务分配以最大资源执行,以此获得更多的优惠单价,降低用户租用资源的总成本。实验结果表明,该方案能够有效降低任务执行的总成本。     

利用GIS技术实现军事信息网络资源管理系统

近年来,随着我军信息化水平的提高,军事信息网络的规模越来越大,结构日趋复杂。本文介绍了利用GIS技术建立军事信息网络资源管理系统的实现方法,重点阐述了系统设计的总体思路。     

临近空间信息资源访问控制策略初探*

简要分析了临近空间信息资源的概念特点及在未来应用中的组织形式,明确了对其实行访问控制的需求。阐述了针对访问过程中进行连续、实时、主动控制的概念,提出了SPAC——基于主体偏好知识的主动访问控制模型;详细描述了SPAC概念模型、形式化定义,并对模型框架进行了设计。     

Interactions between control and process design under economic model predictive control

Economic model predictive control (EMPC) is a model-based control scheme that integrates process control and economic optimization, which can potentially allow for time-varying operating policies to maximize economic performance. The manner in which an EMPC operates a process to optimize economics depends on the process dynamics, which are fixed by the process design. This raises the question of how process and EMPC designs interact. Works which have addressed process and control design interactions for steady-state operation have sought to simultaneously develop process designs and control law parameters to find the most profitable way to operate a process that is able to prevent process constraints from being violated and to optimize capital costs in the presence of disturbances. Because EMPC has the potential to operate a process in a transient fashion, this work first focuses on how EMPC and process design interact in the absence of disturbances. Using small-scale process examples, we seek to understand the fundamental nature of the interactions between EMPC and process design, including how these interactions can impact computational complexity of the controller and the design procedure. We subsequently utilize the insights gained to suggest controller design variables which might be considered as decision variables for a simultaneous process and control design problem when disturbances are considered.     

Robust static allocation of resources for independent tasks under makespan and dollar cost constraints

Heterogeneous computing (HC) systems composed of interconnected machines with varied computational capabilities often operate in environments where there may be inaccuracies in the estimation of task execution times. Makespan (defined as the completion time for an entire set of tasks) is often the performance feature that needs to be optimized in such systems. Resource allocation is typically performed based on estimates of the computation time of each task on each class of machines. Hence, it is important that makespan be robust against errors in computation time estimates. In this research, the problem of finding a static mapping of tasks to maximize the robustness of makespan against the errors in task execution time estimates given an overall makespan constraint is studied. Two variations of this basic problem are considered: (1) where there is a given, fixed set of machines, (2) where an HC system is to be constructed from a set of machines within a dollar cost constraint. Six heuristic techniques for each of these variations of the problem are presented and evaluated.     

Passivity-based adaptive inventory control

A new adaptive inventory control strategy is developed by applying online adaptation in the framework of passivity-based control. By using the system model and definition of the inventory, a feedback-feedforward control structure is derived from the passivity theorem. The stability analysis and the extension of the controller to a non-passive system are also given in this paper. This control strategy is demonstrated in a transfer function example and an application to a pressure tank unit in a chemical plant.     

An approach to information requirements specification for process control tasks

This paper discusses the need for designers of process plant supervisory systems to make greater effort in anticipating the information that operators require to carry out their duties. A method for dealing with this problem of information requirements specification in process plant design is proposed. This method translates a task analysis into a set of standard task elements from which standard sets of information, called ‘sub-goal templates’ can be derived. The resultant information requirements specification sets out the operators' information needs in the context of the operating goals that have to be attained. Early trials with the method indicate its promise, but highlight the need for its implementation in a computer tool to assist the designer. The features of such a tool and the further work necessary to develop and test the method are described.