外文翻譯--虛擬儀器支持系統(tǒng)（英文）

1、A Virtual Instrumentation Support System 00 Programming Luis F. F. Brito Palma and Adelino R. F. da Silva Concurrent Programming Departamento de Engenharia Electrotecnica Faculdade de Ciencias e Tecnologia, Universid

2、ade Nova de Lisboa, Portugal Contacts: Tel. 351.1.2948339, Fax. 351.1.2948532 Emails: lbp@mail.fct.unl.pt, afs@mail.fct.unl.pt 00 Technology Abstract A Virtual Instrumentation Support System that permits to run seve

3、ral concurrent virtual instruments has been developed. In this paper, we present a Multi-Tasking Graphical Environment (named AGMT) and two main virtual instrumentation applications - a Digital Oscilloscope and a Di

4、gital Image Processor. The AGMT was designed to work in real-time and interact with sensors and actuators via data acquisition boards, and other input-output devices. The AGMT implements a preemptive and priority mul

5、ti-tasking system under the DOS operating system. The AGMT allows the user to define, in run-time, the task scheduling policy of the concurrent applications. The virtual environment may be easily extended to run othe

6、r typical Supervisory Control and Data Acquisition applications. 1. Introduction Virtual Instrumentation Systems have received a lot of attention in recent literature. This is mainly due to the growing interest in Su

7、pervisory Control and Data Acquisition (SCADA) applications, like monitoring systems, control systems and management systems. Several commercial virtual instrumentation systems are available. Some systems run under t

8、he Windows operating system, while others still run under the DOS operating system. Most commercial systems do not have the potential to satisfy real-time constraints [1,2], since neither Windows nor DOS are real-tim

9、e operating systems. Besides, most virtual instrumentation systems do not permit to control the task scheduling policy. In the system we have developed, named AGMT, tasks are conceived as lightweight processes or thr

10、eads of execution associated with the virtual applications [3]. The Multi-Tasking Graphical Environment AGMT [4], results from the integration of two toolkits: the InterworkTM concurrent programming toolkit [5], and

11、 the ZincTM graphical user interface framework [6]. The Interwork toolkit emulates a real-time kernel by supporting priority scheduling and preemptive multi- tasking. In this sense, it is conceived as a real-time

12、extension of the DOS operating system. The Zinc graphical user interface framework has an event manager and a window manager. The event manager controls the events generated by the input devices as well as other inte

13、rnal events of the graphic system. The Graphical User Interfaces window manager controls the visualization of the window objects to be displayed on the screen. Based on these two toolkits, the AGMT system executes th

14、e polling of all event generating devices attached to the event manager, such as the cursor, the keyboard, the mouse, as well as others user-defined devices. The AGMT system was developed with object-oriented (00) t

15、echnology [7] and used the C++ object-oriented programming language [8,9], to permit the incorporation of new virtual instruments in a modular and easy way. Two main virtual instrumentation applications - a Digital

16、Oscilloscope and a Digital Image Processor - have been developed to illustrate the potential of the AGMT system. In the following sections, the underlying concepts of Virtual Instrumentation systems are introduce

17、d, followed by the description of the system design and applications. 2. Virtual Instrumentation Virtual Instrumentation is a knowledge area that integrates several others areas, as illustrated in figure 1: instrume

18、ntation systems [ 10,1 I], concurrent programming, graphical user interfaces [ 121, real-time systems, object-oriented technology, and object-oriented programming. 1 Instrumentation I Systems T A Real-Time U

19、 Systems Fig. 1. Virtual instrumentation related knowledges areas. Instrumentation systems deal with the signals coming from sensors and the signals to control actuators. 301 0-7803-5008-1/98/$10.0001998 IEEE. In fig

20、ure 5, the multi-tasking support system implemented in the AGMT can be observed. This figure shows three tasks: one main task controls the graphical user interface of the AGMT, each other task controls one independen

21、t virtual instrument. However, it is possible to associate more than one task with a single application, or have one task control multiple applications. Control-task of Control-task of Control-task of pq operatin

22、g system Fig. 5. Multi-tasking support model. The granularity of the tasks’ routines must be small, to facilitate the operation of the preemptive task scheduler, as indicated in figure 6. Figure 7 shows a temporal dia

23、gram of the CPU allocation to three different tasks: the main task responsible for controlling the GUI of AGMT, the oscilloscope task, and the color demonstration task. AGMT-Task -.---. OSCILLOSCOPE-Task ----

24、----.__ I -._...___ Fig. 6. Preemptive task scheduling on AGMT. Tasks 4 AGMT-Task OSCILLOSCOPE-Task COLORDEMO-Task Time Fig. 7. Temporal diagram of CPU usage. The AGMT main window has the aspect represented in figure

25、 8. Fig. 8. Main window of AGMT. The AGMT environment was design to permit the definition of the priority and the time-slice allocated to each task. The scheduler uses a time-sliced scheduling policy with two priority

26、 levels. Active tasks, i.e., tasks in the ready state, share the same high priority value “1”. Suspended tasks have the low priority value “0”. This policy is adequate in real-time applications requiring high respons

27、iveness. As regards the AGMT environment, the definition of the task scheduling policy is done in run-time by clicking the button “Prioridades + Time-Slices” (see figure 8). The window related to the task scheduling

28、policy will then appear, as shown in figure 9. The AGMT graphical environment runs in the main task, has a fixed high priority value, and cannot be suspended. The time-slices values range from 1 to 10. A unit of time

29、-slice equals 55 ms - a value imposed by the internal clock of the Interwork toolkit. I Ambiente Gr6fico Multi-’ Ficheiro AplicaCEes-Tarefas UtilitLrios A I Ambiente AGMT: 1 -- Osc i loscopio : p-- II.1 Demo - Co

30、res : r] Fig. 9. Task scheduling policy definition window. The C++ programmer can easily create and add new virtual instruments to the AGMT environment in compile-time. The following main steps must be followed. First

31、, code the application simulating the virtual instrument as a class in C++, using the Zinc primitives. An instance of this class is then added to the event manager and the window manager. Second, add a sub-menu to th

32、e graphical user interface to permit the invocation of the application. Third, insert code in the main menu to fork the task that runs the application. 4. Applications Two main virtual instrumentation applications hav

33、e been developed - a digital oscilloscope and a digital image processor. Two others applications with more educational purposes were developed as well: one clock simulator and a color demonstration application. Two