Virtual Instrumentation For Test, Control And Design
Virtual instrumentation has been widely adopted in test and measurement areas. It has gradually increased addressable applications through continuous innovation and hundreds of measurement hardware devices. The benefits that have accelerated test development are beginning to accelerate control and design.
Virtual Instrumentation for Test
Test has been a long-proven field for virtual instrumentation. As the pace of innovation has increased, so too has the pressure to get new, differentiated products to market quickly. Consumer expectations continue to increase; in electronics markets, for example, disparate function integration is required in a small space and at a low cost. All of these conditions drive new validation, verification and manufacturing test needs. A test platform that can keep pace with this innovation is not optional; it is essential. The platform must include rapid test development tools adaptable enough to be used throughout the product development flow. The need to get products to market quickly and manufacture them efficiently requires high-throughput test. To test the complex multifunctional products that consumers demand requires precise, synchronized measurement capabilities. And as companies incorporate innovations to differentiate their products, test systems must quickly adapt to test the new features.
Virtual instrumentation is an innovative solution to these challenges. It combines rapid development software and modular, flexible hardware to create user-defined test systems. Virtual instrumentation delivers as shown in Figure 1.13 user-defined instruments and customizable hardware for test systems:
- Intuitive software tools for rapid test development
- Fast, precise modular I/O based on innovative commercial technologies
- A PC-based platform with integrated synchronization for high accuracy and throughput
Figure: User-defined instruments and customizable hardware for test systems.
Engineers and scientists have always been able to use virtual instrumentation software to create highly integrated user-defined systems using modular I/O, but they can now extend custom configurability to the hardware itself. This degree of user-configurability and transparency will change the way engineers build test systems.
Virtual Instrumentation for Industrial I/O and Control
PCs and PLCs both play an important role in control and industrial applications. PCs bring greater software flexibility and capability, while PLCs deliver outstanding ruggedness and reliability. But as control needs become more complex, there is a recognized need to accelerate the capabilities while retaining the ruggedness and reliabilities. Independent industry experts have recognized the need for tools that can meet the increasing need for more complex, dynamic, adaptive and algorithm-based control. The Programmable Automation Controllers (PACs) provide multidomain functionality (logic, motion, drives and process) and the concept of PAC supports multiple I/O types. Logic, motion and other function integrations are a requirement for increasingly complex control approaches. PACs deliver PC software flexibility with PLC ruggedness and reliability. LabVIEW software and rugged, real-time, control hardware platforms are ideal for creating a PAC.
Virtual Instrumentation for Design
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The same design engineers that use a wide variety of software design tools must use hardware to test prototypes. Commonly, there is no good interface between the design phase and testing/validation phase, which means that the design usually must go through a completion phase and enter a testing/validation phase. Issues discovered in the testing phase require a design-phase reiteration as shown in Figure 1.14. The simulation test plays a critical role in the design and manufacture of today’s electronic devices.
Figure: Simulation test plays a critical role in the design and manufacture.
In reality, the development process has two very distinct and separate stages—design and test—which are two individual entities. On the design side, Electronic Design Automation (EDA) tool vendors undergo tremendous pressure to interoperate from the increasing semiconductor design and manufacturing group complexity requirements. Engineers and scientists are demanding the capability to reuse designs from one tool in other tools as products go from schematic design to simulation to physical layout. Similarly, test system development is evolving towards a modular approach. The gap between these two worlds has traditionally been neglected, first noticeable in the new product prototype stage. Traditionally, this is the stage where the product designer uses benchtop instruments to sanity-check the physical prototypes against their design for correctness. The designer makes these measurements manually, probing circuits and looking at the signals on instruments for problems or performance limitations. As designs iterate through this build-measure-tweak-rebuild process, the designer needs the same measurements again. In addition, these measurements can be complex—requiring frequency, amplitude and temperature sweeps with data collected and analyzed throughout. Because these engineers focus on design tools, they are reluctant to invest in learning to automate their testing. Systems with intrinsic-integration properties are easily extensible and adapt to increasing product functionality. When new tests are required, engineers simply add new modules to the platform to make the measurements. Virtual instrumentation software flexibility and virtual instrumentation hardware modularity make virtual instruments a necessity to accelerate the development cycle.
Virtual Instrumentation in The Engineering Process
Virtual instruments provide significant advantages in every stage of the engineering process—from research and design to manufacturing test.
Research and Development
In research and design, engineers and scientists demand rapid development and prototyping capabilities. With virtual instruments, we can quickly develop a program, take measurements from an instrument to test a prototype and analyze results—all in a fraction of the time required to build tests with traditional instruments. When we need flexibility, a scalable open platform is essential, from the desktop to embedded systems to distributed networks. The demanding requirements of research and development (R&D) applications require seamless software and hardware integration. Whether we need to interface stand-alone instruments using GPIB or directly acquire signals into the computer with a data acquisition board and signal conditioning hardware, virtual instrumentation software makes integration simple. With virtual instruments, we also can automate a testing procedure, eliminating the possibility of human error and ensuring the consistency of the results by not introducing unknown or unexpected variables.
Development Test and Validation
With the flexibility and power of virtual instruments, one can easily build complex test procedures. For automated design verification testing, one can create test routines in virtual instrumentation software and integrate software such as National Instruments Test Stand, which offers powerful test management capabilities. One of the many advantages these tools offer across the organization is code reuse. We develop code in the design process and then plug these same programs into functional tools for validation, test or manufacturing.
Decreasing test time and simplifying development of test procedures are primary goals in manufacturing test. Virtual instruments combined with powerful test management software deliver high performance. These tools meet rigorous throughput requirements with a high-speed, multithreaded engine for running multiple test sequences in parallel. TestStand easily manages test sequencing, execution and reporting based on routines written in virtual instrumentation software. TestStand integrates the creation of test code in virtual instrumentation software. TestStand also can reuse code created in research and development or design and validation. If we have manufacturing test applications, we can take full advantage of the work already done in the product life cycle.
Manufacturing applications require software to be reliable, high in performance and interoperable. Virtual instruments offer all these advantages by integrating features such as alarm management, historical data trending, security, networking, industrial I/O and enterprise connectivity. With this functionality, we can easily connect to many types of industrial devices such as PLCs, industrial networks, distributed I/O and plug-in data acquisition boards. By sharing code across the enterprise, manufacturing can use the same applications developed in research and development or validation, and integrate seamlessly with manufacturing test processes.
Virtual Instruments beyond Personal Computer
Recently, commercial PC technologies have begun migrating into embedded systems. Examples include Windows CE, Intel x86-based processors, PCI and Compact PCI buses and Ethernet for embedded development. Virtual instrumentation relies on commercial technologies for cost and performance advantages; it has also expanded to encompass more embedded and real-time capabilities. LabVIEW runs on Linux as well as the embedded ETS real-time operating system from VenturCom on specific embedded targets. The option of using virtual instrumentation as a scalable framework that extends from the desktop to embedded devices should be considered a tool in the complete toolbox of an embedded systems developer. Ethernet now dominates as the standard network infrastructure for companies worldwide. In addition, the popularity of the Web interface in the PC world has overflowed into the development of cell phones, PDAs, and now industrial data acquisition and control systems. Embedded systems at one time meant stand-alone operation, or at most interfacing at a low level with a real-time bus to peripheral components. The increased demand for information at all levels of the enterprise (and in consumer products) requires you to network embedded systems while continuing to guarantee reliable and often real-time operation.
Virtual instrumentation software can combine one development environment for both desktop and real-time systems using cross-platform compiled technology; you can capitalize on the built-in Web servers and easy-to-use networking functionality of desktop software and target it to real-time and embedded systems. For example, you can use LabVIEW to simply configure a built-in Web server to export an application interface to defined secure machines on the network on Windows, and then download that application to run on a headless embedded system that can fit in the user’s hand. This procedure happens with no additional programming required on the embedded system. You then can deploy that embedded system, power it, connect to the application from a remote secure machine via Ethernet, and interface to it using a standard Web browser. For more sophisticated networking applications, you can graphically program TCP/IP or other methods with which you are already familiar in LabVIEW and then run them in the embedded system.
Embedded systems development is one of the fastest growing segments of engineering, and will continue to be for the foreseeable future as consumers demand smarter cars, appliances, homes, and so on. The evolution of these commercial technologies will propel virtual instrumentation into being more applicable to a growing number of applications. Leading companies that provide virtual instrumentation software and hardware tools need to invest in expertise and product development to serve this growing set of applications. Virtual instrumentation software platform, LabVIEW, includes the ability to scale from development for desktop operating systems, to embedded real-time systems to handheld personal digital assistant targets, to FPGA-based hardware, and even to enabling smart sensors.
Next-generation virtual instrumentation tools need to include networking technology for quick and easy integration of Bluetooth, wireless Ethernet and other standards. In addition to using these technologies, virtual instrumentation software needs a better way to describe and design timing and synchronization relationships between distributed systems in an intuitive way to help faster development and control of these often embedded systems. The virtual instrumentation concepts of integrated software and hardware, flexible modular tools, and the use of commercial technologies combine to create a framework upon which we can rapidly complete our systems development and also maintain them for the long term. Because virtual instrumentation offers so many options and capabilities in embedded development, it makes sense for embedded developers to understand and review these tools.