Virtual instrument, virtual oscilloscope, virtual instrument technology, virtual instrument software, virtual instrument development, virtual instrument composition

I. Introduction

At present, multimedia computer, information superhighway and computer network are three important development directions of computer information science. They are interrelated, mutually promoted and developed together, and have penetrated into all aspects of people's daily work, life, study and entertainment, and gradually moved from offices and laboratories to families.

Virtual reality is an important application field of multimedia computer, and multimedia technology is the technical basis of virtual reality. Virtual reality is a simulated reality environment with vivid vision, hearing, touch and smell generated by multimedia computer technology. Users can interactively experience this virtual reality with human natural skills, and the results they experience-the response of this virtual reality is similar or exactly the same as the results they experience in the corresponding real reality. The concept of virtual reality includes the following three levels of meaning:

1. Virtual reality is a real entity generated by computer technology. People have real three-dimensional vision, stereo hearing, touch and smell for this entity.

2. People can talk with virtual reality through natural skills, that is, people's head, eyes, limbs and other actions are realistic in virtual reality.

3. Virtual reality technology often relies on some three-dimensional sensing devices to complete interactive actions, such as helmet-mounted stereoscopic display, data gloves, data clothing, three-dimensional manipulator and so on.

Although virtual reality technology is still in its infancy, it has been applied to scientific visualization, computer-aided design, aircraft/automobile/surgical simulation, virtual instruments and other fields. It has shown broad application prospects in aerospace, national defense and military, biomedicine, education and training, entertainment and games, tourism and other fields.

Virtual instrument (VI) is an important application of virtual reality in the field of instruments and meters, and it has risen quietly all over the world. Virtual instrument is a special instrument based on multimedia computer, which uses graphical interface programming technology to simulate the panel, function and operation of the actual instrument, thus generating various tasks.

Due to the high development of science and technology, various powerful and increasingly complex instruments are constantly emerging, many of which are based on computers, and there is a trend of computerization of instruments, mainly as follows:

1, hardware and computer interface standardization

2. Hardware and software

3. Software modularization

4. Modularization

5. System synthesis

6, graphical programming

7. Visualization of scientific calculation

8. Hardware interface software driver

Due to the continuous development of computer software and hardware technology and the need of practical application, people are more and more interested in virtual instruments, and it is possible to develop virtual instruments. The development of virtual instruments mainly stems from the following purposes:

1, saving time and money for instrument development.

2. Make full use of the data processing and analysis functions of the computer.

3. Unify the user interface of the instrument

4. Enhance the function and application scope of the instrument.

5, the demand for comprehensive instruments

6, make the instrument easy to expand

Virtual instrument is mainly composed of the following parts:

1, interface control library

2. Data input and output

3, data processing method library

4. Data representation library

5. Data storage and management

6. Any signal appears

7, graphical interface programming environment

The interface control library includes some panel components of commonly used instruments, such as indicators, meters, light-emitting diodes, buttons, dials, dials, sliders and so on. Each control has programmable functions and properties.

Data input and output refers to obtaining data from external devices to enter the computer or outputting data from the computer to control the external devices. It is necessary to establish driver software for communication with data acquisition board, serial port and other standardized interfaces (IEEE-488, GPIB, RS-232, RS-422, SCSI, VXI, etc.). ), thus expanding the application scope of the instrument.

Scope and application field.

There are many data processing methods in the data processing method library, such as FFT calculation, filtering, modeling, parameter estimation and so on. And provides programming interfaces for these processing methods. All kinds of complex tasks can be accomplished by simply combining these methods.

Data representation refers to displaying data and processing results in a certain way, including digital display, curve display, histogram, scatter plot, two-dimensional graph, three-dimensional grid graph, three-dimensional filled graph, four-dimensional graph, image and even dynamic graph or image, which makes data representation very intuitive and easy to understand.

Data storage and management mainly refers to providing data storage formats, data query methods and data browsing methods.

Signal generation refers to the generation of arbitrary signals according to needs, some of which can be used for instrument testing and self-inspection.

Graphical programming environment refers to a kind of tool, and users can arbitrarily combine controls and methods to connect them into a whole to form a special tool. Using virtual instruments, users can quickly generate all kinds of instruments they need like building blocks.

Second, the existing examples of virtual instruments and integrated environment

1, MATLAB: high-performance numerical calculation and data analysis software.

MATLAB is a high-performance numerical calculation and data analysis software developed by Mathworks Company in the United States. It has become an industrial standard for engineering and scientific research. It has the characteristics of unique user interface, complex numerical calculation, powerful data analysis, flexible scientific graphics, fast calculation and convenient expansion. It is the first choice software for high-yield and creative scientific research.

The basic functions of MATLAB are:

Matrix operation ※

Matrix decomposition ※

Calculation of eigenvalue and eigenvector of matrix ※

Signal convolution ※

Frequency spectrum estimation ※

Complex number operation ※

One-dimensional and two-dimensional fast Fourier transform ※

Filter design and filtration ※

Curve fitting ※

Cubic spline fitting ※

Bessel function ※

Nonlinear optimization ※

The solution of linear equations ※

Differential equation ※

MATLAB includes the following toolbox:

Digital signal processing toolbox ※

Control system design toolbox ※

System identification toolbox ※

Self-expanding toolbox ※

MATLAB includes drawing function:

Histogram ※

Scatter plot ※

Curve graph ※

Three-dimensional grid diagram ※

Three-dimensional filling map ※

Contour map ※

Polar coordinate graph ※

X-y diagram ※

Image display ※

2.DADiSP: data analysis and graphics software for scientists and engineers.

DADiSP software is developed by American DSP development company, which is mainly used as a tool for scientists and engineers to analyze data and display graphics. It includes the following functions:

Matrix operation ※

Calculation of eigenvector and eigenvalue ※

One-dimensional and two-dimensional FFT and convolution ※

Two-dimensional, three-dimensional and four-dimensional graphic display ※

Medical image processing ※

Satellite remote sensing image processing ※

Seismic signal processing ※

Statistical analysis and processing ※

Experimental design ※

Hypothesis test ※

Filter design ※

Signal processing of sonar radar ※

Voice and communication signal processing ※

Vibration analysis ※

3.MP 100: Medical Signal Acquisition and Processing System

MP 100 is a medical signal acquisition and processing system developed by BIOPAC Systems, USA. It runs with AcqKnowledge software, providing a flexible and easy-to-use modular system, enabling you to complete data collection and analysis tasks at will. AcqKnowledge is a powerful and flexible software package. It can design complex data acquisition, simulation, triggering and analysis systems by using drop-down menus and dialog boxes without learning another programming language. It mainly includes real-time data recording, analysis and filtering, off-line data analysis and processing, and various graphic representations of data. The system can be connected with virtual instrument LabVIEW to provide a visual graphical programming environment. Its main application fields are:

Exercise Physiology ※

EMG signal recording ※

ECG recording and analysis ※

EEG recording and analysis ※

Recording and analysis of evoked potentials ※

Analysis of electronystagmography and eye movement ※

Nerve conduction analysis ※

Psychophysiology ※

Pharmacology ※

Telemetry monitoring ※

4.LabVIEW: a virtual instrument for graphic programming.

LabVIEW is a graphical programming virtual instrument system developed by American National Instrument Company. It mainly includes data acquisition, control, data analysis, data representation and other functions. It provides a novel programming method, that is, the software modules are assembled graphically to generate special instruments. LabVIEW consists of panel, flow chart and icon/connector, in which the panel is the user interface, the flow chart is the source code of virtual instrument, and the icon/connector is the calling interface. The flowchart includes an input/output (I/O) component, a computing component and a sub-VI component, which are represented by icons and data streams. I/O components communicate directly with data acquisition board, GPIB board or other external physical instruments; The computing component completes mathematical or other operations and operations; Sub-VI component calls other virtual instruments.

5.LabWindows/CVI:'s virtual instrument programmed with C language.

The function of LabWINDOWS is similar to that of LabVIEW, both of which were developed by the same company. The difference is that it can write virtual instruments in C language.

6. Modular virtual instrument system.

LabLinc V is a modular virtual instrument system developed by COULBOURN INSTRUMENTS. It consists of basic units, signal acquisition and processing, control and other modules, and is mainly used for data acquisition, real-time display and process control in physiology, biomedicine and biomechanics.

7. Design of visual signal processing system.

HyperSignal is a visual signal processing system design software developed by Hyperception Company in the United States, which visualizes the design process and signal processing results of the signal processing system at the same time.

8.Model900: Flexible data acquisition and waveform generation system.

Model900, developed by American Applied Signal Technology Company, provides high-speed and large-capacity data acquisition, waveform generation and other functions, and adopts virtual instrument environment to save development time and money.

9.DASP: Software for automatically acquiring, processing and analyzing large-capacity data.

DASP was developed by Oriental Institute of Vibration and Noise Technology. It is mainly used for recording and analyzing scientific experimental data, collecting and analyzing multifunctional signals, and collecting, displaying, reading, calculating, analyzing, storing, printing and drawing automatic data.

10, LabDoc: integrated instrument software package.

LabDoc, developed by Japan Kangtaike Electronic Technology Co., Ltd., has a variety of measuring instrument functions, and can provide easy-to-operate instrument pictures through graphical user interface and online help. It can be used in laboratory, production line inspection, education and training, etc. The main test functions are:

Digital filtering ※

Pulse generation ※

Function generation ※

Waveform generation ※

Generation of tuning signal ※

Fast fourier transform analysis ※

Frequency meter ※

Above, we have listed ten popular virtual instruments and integrated environment systems, among which the United States has done the best in this respect, while China has just started in this respect and has not yet seen a complete virtual instrument system. As can be seen from the examples listed above, virtual instruments have the following characteristics:

Involving more profound numerical calculation methods. ※

Integrated signal processing and process control algorithms. ※

Software and hardware modules are independent of each other. ※

Have an integrated programming environment for secondary development. ※

It is the product of interdisciplinary and infiltration. ※

Third, the virtual medical signal processing instrument

There are a wide range of medical signals, among which the common medical signals are ECG, EEG, evoked potential, EMG, EMG signal, nerve impulses potential, blood pressure, pulse wave, respiratory wave, body temperature and other signals, and their characteristics are different.

Different from each other, they have their own frequency bands, amplitude ranges and interference sources, which makes medical signal processing very complicated.

No matter what kind of medical signal instrument, it almost involves the same tasks as signal amplification, acquisition, analysis, processing and filtering. At the same time, different signals have their special processing methods. The organic combination of these similarities and particularities forms an integrated environment, which is the basis of virtual instruments.

Due to the need of multi-parameter clinical monitoring and comprehensive diagnosis, medical signal acquisition and processing instruments show an integrated trend, and people turn from developing single-function medical signal instruments to developing multi-functional integrated instruments. However, this integration is not the accumulation and combination of single-function instruments, but to find out the similarities and differences from different single-function instruments, form software and hardware modules, computerize medical signal processing instruments, and form the development environment of medical signal processing instruments, that is, virtual instruments.

Virtual medical signal processing instrument is a promising field, and many medical instrument companies are optimistic about this market prospect, and have invested a lot of manpower, material resources and financial resources in research and development in this field, among which the aforementioned MP 100 medical data acquisition system and LabLinc V modular virtual instrument are outstanding representatives.

Virtual medical signal processor is a tool to develop and produce various medical signal processors. For developers, special instruments can be generated as quickly as building blocks, saving a lot of development time and money; For users, they can spend less money and buy more musical instruments. Virtual medical signal processing instrument lays a foundation for the development of integrated multifunctional instrument, and the latest research results can be applied to the instrument as soon as possible. In addition, virtual medical signal processing instruments can be used to study unknown signals and unknown characteristics of signals, so as to achieve the purpose of producing more results quickly. In fact, virtual medical signal processing instruments will also contribute to the current hot research fields, such as telemedicine and medical e-books.

Fourthly, related technologies of virtual instruments.

1, numerical calculation

In virtual instrument, it is necessary to provide flexible data processing methods, which can be realized by programming according to actual needs. In order to simplify the complexity of programming and save a lot of development time, various numerical calculation programs should be provided in the virtual instrument as much as possible, mainly including the following aspects:

Matrix operation (addition, subtraction, multiplication, inversion, transposition) ※

Calculation of eigenvalues and eigenvectors ※

Matrix decomposition ※

Univariate and bivariate interpolation ※

Numerical integration and differentiation ※

The solution of linear algebraic equation ※

Solution of nonlinear equation ※

Fitting and approximation ※

Special function ※

Regression and statistics ※

2. Digital signal processing

Digital signal processing plays an important role in complex instruments, so it is necessary to integrate various digital signal processing methods in virtual instruments. Digital signal processing methods can be divided into several categories:

Signal preprocessing ※

Filter design and filtration ※

Classical spectral estimation ※

Modern spectrum estimation ※

Correlation and convolution ※

Discrete transformation ※

Digital feature calculation ※

Public signal generation ※

Signal modeling ※

Data compression ※

3, computer graphics, graphics

Graphics and images are intuitive representations of a large number of data in complex instruments, such as static and dynamic EEG topographic maps, surface temperature distribution maps of objects, electromagnetic field distribution maps, etc. , which can transform the original very abstract data into an intuitive representation that people can easily understand; In addition, the data and its analysis results are also used to represent curves, histograms, three-dimensional graphs and contour maps. Therefore, in the virtual instrument, it is very necessary to establish the graphic and image representation module of these data.

4. Visualization of scientific calculation

As mentioned above, the graphic and image representation of complex mass data is very important in virtual instruments, but the mapping from data to graphics is not a simple matter, which is a research topic of scientific computing visualization developed in recent years.

The fundamental purpose of scientific computing visualization is to transform a large amount of data obtained from experiments or numerical calculations into computer images that human vision can feel. Using images to organize a large number of abstract data organically, so as to vividly show the contents represented by data and their relationships, help people directly grasp the complex overall situation, better discover and understand the laws, and get rid of the confusion of complex and large amounts of abstract data. Introducing scientific calculation visualization into virtual instrument will show people the infinite charm of the instrument and make it have the ability to process and analyze a large number of complex data.

5. Object-oriented visual programming

Virtual instrument is an integrated programming environment, with which people can quickly generate the complex instruments they need. Therefore, virtual instrument should be programmable and easy to operate, so people introduce object-oriented visual graphic programming technology into virtual instrument. Many powerful components are integrated in virtual instrument, which are represented by intuitive computer graphics, and each component has corresponding controllable attributes, operations and functions. People only need to arrange these components on the computer screen, set the corresponding properties and their relationships with other components, and then they can generate musical instruments with corresponding functions.

Verb (abbreviation of verb) abstract

Virtual instrument is a new research field at home and abroad. Many high-tech companies and research institutes are optimistic about this market application prospect, and have invested a lot of manpower, material resources and financial resources to step up development and research. Virtual instrument is an important application field of multimedia computer, which is the product of interdisciplinary and infiltration, and concentrates many high, precise and sophisticated science and technology. Virtual instrument is not an instrument, but it is higher than the instrument. It greatly shortens the development cycle of new instruments and saves the development cost of instruments. It is not only a tool for developing instruments, but also a powerful means for scientific research. Virtual instrument is the product of instrument computerization, the foundation of integrated instrument and a revolution in instrument industry. Its research and development have far-reaching significance.