[毕业论文]美国国家仪器公司的LabVIEW ：一种实验室自动化和测量的编程环境 英文文献翻译.doc

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1、National Instruments LabVIEW: A Programming Environment for Laboratory Automation and Measurement .National Instruments LabVIEW is a graphical programming language that has its roots in automation control and data acquisition. Its graphical representation, similar to a process flow diagram, was crea

2、ted to provide an intuitive programming environment for scientists and engineers. The language has matured over the last 20 years to become a general purpose programming environment. LabVIEW has several key features which make it a good choice in an automation environment. These include simple netwo

3、rk communication, turnkey implementation of common communication protocols (RS232, GPIB, etc.), powerful toolsets for process control and data fitting, fast and easy user interface construction, and an efficient code execution environment. We discuss the merits of the language and provide an example

4、 application suite written in-house which is used in integrating and controlling automation platforms.Keywords: NI LabVIEW； graphical programming；system integration； instrument control；component based architecture； robotics； automation； static scheduling； dynamic scheduling； database.IntroductionCyt

5、okinetics is a biopharmaceutical company focused on the discovery of small molecule therapeutics that target the cytoskeleton. Since inception we have developed a robust technology infrastructure to support our drug discovery efforts. The infrastructure provides capacity to screen millions of compou

6、nds per year in tests ranging from multiprotein biochemical assays that mimic biological function to automated image-based cellular assays with phenotypic readouts. The requirements for processing these numbers and diversity of assays have mandated deployment of multiple integrated automation system

7、s. For example, we have several platforms for biochemical screening, systems for live cell processing, automated microscopy systems, and an automated compound storage and retrieval system. Each in-house integrated system is designed around a robotic arm and contains an optimal set of plate-processin

8、g peripherals (such as pipetting devices, plate readers, and carousels) depending on its intended range of use. To create the most flexible, high performance, and cost-effective systems, we have taken the approach of building our own systems in-house. This has given us the ability to integrate the m

9、ost appropriate hardware and software solutions regardless of whether they are purchased from a vendor or engineered de novo, and hence we can rapidly modify systems as assay requirements change.To maximize platform consistency and modularity, each of our 10 automated platforms is controlled by a co

10、mmon, distributed application suite that we developed using National Instruments (NI) LabVIEW. This application suite described in detail below, enables our end users to create and manage their own process models (assay scripts) in a common modeling environment, to use these process models on any au

11、tomation system with the required devices, and allows easy and rapid device reconfiguration. The platform is supported by a central Oracle database and can run either statically or dynamically scheduled processes.NI LabVIEW BackgroundLabVIEW, which stands for Laboratory Virtual Instrumentation Engin

12、eering Workbench is a graphical programming language first released in 1986 by National Instruments (Austin, TX). LabVIEW implements a dataflow paradigm in which the code is not written, but rather drawn or represented graphically similar to a flowchart diagram Program execution follows connector wi

13、res linking processing nodes together. Each function or routine is stored as a virtual instrument (VI) having three main components: the front panel which is essentially a form containing inputs and controls and can be displayed at run time, a block diagram where the code is edited and represented g

14、raphically, and a connector pane which serves as an interface to the VI when it is imbedded as a sub-VI.Figure1.Example NI LabVIEW VI.The top panel (A) shows the front panel of the VI. Input data are passed through “Controls” which are shown to the left. Included here are number inputs, a file path

15、box, and a general error propagation cluster. When the VI runs, the “Indicator” outputs on the right of the panel are populated with output data. In this example, data include numbers (both as scalar and array), a graph, and the output of the error cluster. In the bottom panel (B) the block diagram

16、for the VI is shown. The outer case structure executes in the “No Error” case (VIs can make internal errors or if called as a sub-VI the caller may propagate an error through the connector pane).Unlike most programming languages, LabVIEW compiles code as it is created thereby providing immediate syn

17、tactic and semantic feedback and reducing the time required for development and testing.2 Writing code is as simple as dragging and dropping functions or VIs from a functions palette onto the block diagram within process structures (such as For Loops, or Case Structures) and wiring terminals (passin

18、g input values, or references). Unit testing is simplified because each function is separately encapsulated; input values can be set directly on the front panel without having to test the containing module or create a separate test harness. The functions that generate data take care of managing the

19、storage for the data. NI LabVIEW supports multithreaded application design and executes code in an inherently parallel rather than sequential manner; as soon as a function or sub-VI receives all of its required inputs, it can begin execution. In Figure1b, all the sub-VIs receive the array input simu

20、ltaneously as soon as the For Loop is complete, and thus they execute in parallel. This is unique from a typical text-based environment where the control flows line by line within a function. When sequential execution is required, control flow can be enforced by use of structures such as Sequences,

21、Events, or by chaining sub-VIs where output data from one VI is passed to the input of the next VI.Similar to most programming languages, LabVIEW supports all common data types such as integers, floats, strings, and clusters (structures) and can readily interface with external libraries, ActiveX com

22、ponents, and .NET framework. As shown in Figure1b, each data type is graphically represented by wires of different colors and thickness. LabVIEW also supports common configuration management applications such as Visual SourceSafe making multideveloper projects reasonable to manage.Applications may b

23、e compiled as executables or as Dynamic Link Libraries (DLLs) that execute using a run-time engine similar to the Java Runtime Environment. The development environment provides a variety of debugging tools such as break-points, trace (trace), and single-step. Applications can be developed using a va

24、riety of design patterns such as Client-Server, Consumer-Producer, and State-Machine. There are also UML (Unified Modeling Language) modeling tools that allow automated generation of code from UML diagrams and state diagrams.Over the years, LabVIEW has matured into a general purpose programming lang

25、uage with a wider user base. NI LabVIEW as a Platform for Automation and InstrumentationOur experience creating benchtop instrumentation and integrated automation systems has validated our choice of LabVIEW as an appropriate tool. LabVIEW enables rapid development of functionally rich applications a

26、ppropriate for both benchtop applications and larger integrated systems. On many occasions we have found that project requirements are initially ill defined or change as new measurements or new assays are developed. There are several key features of the language that make it particularly useful in a

27、n automation environment for creating applications to control and integrate instrumentation, manage process flow, and enable data acquisition.Turnkey Measurement and Control FunctionLabVIEW was originally developed for scientists and engineers .The language includes a rich set of process control and

28、 data analysis functions as well as COM, .NET, and shared DLL support. Out of the box, it provides turnkey solutions to a variety of communication protocols including RS232, GPIB, and TCP/IP. Control structures such as timed While Loops allow synchronized and timed data acquisition from a variety of

29、 hardware interfaces such as PCI, USB, and PXI.DataSocket and VI ServerDeployment of an integrated system with multiple control computers requires the automation control application to communicate remotely with instrument drivers existing on remote computers. LabVIEW supports a distributed architect

30、ure by virtue of enabling seamless network communication through technologies such as VI Server and DSTP (data sockets transfer protocol). DSTP is an application layer protocol similar to http based on Transmission Control Protocol/Internet Protocol (TCP/IP). Data sockets allow easy transfer of data

31、 between remote computers with basic read and write functions. Through VI server technology, function calls can be made to VIs residing on remote computers as though they are residing on the local computer. Both Datasockets and VI server can be configured to control accesses privileges.Simple User I

32、nterface (UI) ImplementationIn addition to common interface controls such as text boxes, menu rings, and check-boxes, LabVIEW provides a rich set of UI controls (switches, LEDs, gauges, array controls, etc.) that are pertinent to laboratory equipment. These have their origins in LabVIEWs laboratory

33、roots and help in development of interfaces which give scientists a clear understanding of a systems state. LabVIEW supports UI concepts including subpanels (similar to the Multiple Document Interface), splitter bars, and XControls (analogous to OCX controls).Multithreaded Programming EnvironmentThe

34、 inherent parallel environment of LabVIEW is extremely useful in the control of laboratory equipment. Functions can have multiple continuous While Loops where one loop is acquiring data rapidly and the other loop processes the data at a much slower rate. Implementing such a paradigm in other languag

35、es requires triggering an independent function thread for each process and developing logic to manage synchronization. Through timed While Loops, multiple independent While Loops can be easily synchronized to process at a desired period and phase relative to one another. LabVIEW allows invoking mult

36、iple instances of the same function with each maintaining its own data space. For instance, we could drag many instances of the Mean sub-VI onto the block diagram in Figure1b and they would all run in parallel, independent of one another. To synchronize or enforce control flow within the dataflow en

37、vironment, LabVIEW also provides functions such as queues, semaphores, and notification functions.NI LabVIEW Application Example: The Open System Control Architecture (OSCAR)OSCAR is a LabVIEW-based (v7.1) automation integration framework and task execution engine designed and implemented at Cytokin

38、etics to support application development for systems requiring robotic task management. OSCAR is organized around a centralized Oracle database which stores all instrumentation configuration information used to logically group devices together to create integrated systems (Fig.2). The database also

39、maintains Process Model information from which tasks and parameters required to run a particular process on a system can be generated and stored to the database. When a job is started, task order and parameter data are polled by the Execution Engine which marshals tasks to each device and updates ta

40、sk status in the database in real time. Maintaining and persisting task information for each system has two clear benefits. It allows easy job recovery in the event of a system error, and it also provides a process audit trail that can be useful for quality management and for troubleshooting process

41、 errors or problems.Figure2.OSCAR component diagram.Each OSCAR component is distributed across the company intranet and communicates with a central database. Collections of physical devices controlled through OSCAR Instrument packages (OIP) make up systems. Users interact with systems through one of

42、 the several applications built on OSCAR. Each application calls the RTM which marshals tasks from the database to each OIP. OSCAR has sets of tools for managing system configurations, creating Process Models, monitoring running processes, recovering error-state systems, and managing plate inventory

43、 in storage devices.OSCAR uses a loosely coupled distributed component architecture, enabled in large part by LabVIEWs DSTP and remote VI technologies that allow system control to be extended beyond the confines of the traditional central control CPU model. Any networked computer or device can be in

44、tegrated and controlled in an OSCAR system regardless of its physical location. This removes the proximity constraints of traditional integrated systems and allows for the utilization of remote data crunchers, devices, or even systems. The messaging paradigm used shares many similarities with curren

45、t Service Oriented Architectures or Enterprise Service Bus implementations without a lot of required programming overhead or middleware; a centralized server is not required to direct the XML packets across the network. An additional benefit to this loosely coupled architecture is the flexibility in

46、 front-end application design. OSCAR encapsulates and manages all functionality related to task execution and device control, which frees the developer to focus on the unique requirements of a given application. For example, an application being created for the purpose of compound storage and retrie

47、val can be limited in scope to requirements such as inventory management and LIMS integration rather than device control, resource allocation, and task synchronization.The OSCAR integration framework consists of multiple components that enable device and system configuration, process modeling, proce

48、ss execution, and process monitoring. Below are descriptions of key components of the framework.Integration PlatformThe Oscar Instrument Package (OIP) is the low level control component responsible for communicating with individual devices. It can support any number of devices on a system (including

49、 multiple independent instances of the same type of device) and communicates to the Runtime Manager (RTM) via serialized XML strings over DSTP. This allows the device controller and RTM components to exist on separate networked computers if necessary. Additionally, the OIP controller communicates with a device instance via LabVIEW remote VI calls which provide a lower level of distribution and allow the device drivers to exist on a separate networked computer from the con