Visualization technology of the hottest virtual in

2022-08-04
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Overview of visualization technology of virtual instrument:

virtual instrument refers to a personal computer instrument with a virtual instrument panel. It is an organic combination of computer resources, modular functional hardware and application software for data analysis, process communication and graphical user interface. It uses software to generate various instrument panels on the screen to complete the data processing, expression, transmission, storage, display and other functions. Compared with traditional instruments, the main advantage of virtual instrument is that it can be defined and designed by users to meet different requirements, make the function of the instrument more powerful and flexible, and it is easy to connect with networks, peripherals and other applications. This not only reduces the price, saves the development and maintenance costs, but also shortens the technology development cycle

one of the key technologies of virtual instrument is application software, because the main function of virtual instrument is embodied by software, that is, "software is instrument". The software development platform of virtual instrument should provide a graphical programming environment. It is worth mentioning LabVIEW and LabWindows of Ni and Vee of HP

the network-based virtual instrument system introduced in this paper is a virtual test platform without data acquisition and bus control system. It is mainly used for post-processing of test data files or real-time simulation testing of tested objects to form a network test simulation system

1. Network based virtual instrument system

the system uses software to generate instrument panel on the computer screen, receives the instrument data to be processed and displayed or the simulation data generated by the software through the data interface, and displays the refresh data, waveform and image in real time. The system has two main characteristics: one is convenient interaction; Second, it realizes the real-time transmission and rendering of network data, and can display different virtual instruments that can be stopped when necessary at different network endpoints, so as to achieve the purpose of multi computer parallel processing

1.1 system composition

the whole software system is divided into two independent subsystems: programming control subsystem and broadcasting subsystem. The system composition is shown in Figure 1

the main work of the programming and control subsystem is to establish and demonstrate the model and control the start and end of the simulation. The programming control subsystem can be divided into two sub modules: module and broadcast control module. Through the module, users can design and establish a virtual instrument model to meet their own needs, and can also modify an existing instrument model. The network simulation function can be realized through the broadcast control module, and the connection relationship with the broadcast subsystem can be established; And continuously receive the external input instrument parameters through the data interface, and send corresponding instructions/data packets to each broadcasting subsystem that has established a connection relationship to update the instrument display status

the broadcast subsystem is responsible for receiving the instructions/data packets (including digital instrument models, various parameters, etc.) sent by the broadcast control system, interpreting the instructions, and constantly refreshing and displaying the current simulation results. In the broadcast subsystem, you can specify whether a visual object is visible, so that the broadcast subsystem running on different computers can display different instrument panels to achieve the purpose of distributed parallel processing

1.2 network transmission of parameters

the system needs to transmit parameters between different computers, so network communication is an essential condition. This system adopts the client/server structure of the application program, this structure is very suitable for distributed processing computer network environment. Because the system is an application oriented to PC platform, Winsock interface based on TCP/IP protocol is used to realize data transmission between networks

2. The virtual instrument panel is the most mature in the industry. For example,

2.1 object-oriented design method

in the visual design process of virtual instruments, object-oriented method is adopted. A virtual instrument system consists of many instruments, and each virtual instrument is controlled by a panel. Therefore, according to the object-oriented design idea, the panel is decomposed into panel objects with inheritance relationship. Each panel object has its own independent properties and behaviors

for a virtual instrument system, its instrument panel objects can be divided into two categories: basic graphic elements and special panel objects, as shown in Figure 2. Basic graphic elements, i.e. primitives, include lines, rectangles, ellipses, polygons, and text; Special panel objects include panel control controls such as buttons, switches, knobs, dynamic regulators, and panel display controls such as indicator lights, digital meters, pointer meters, image displays, oscilloscopes, and other special display controls

2.2 panel object data structure

in the virtual instrument system, the panel object is displayed in the form of graphics, and the system allows users to modify the attribute parameters of the instrument object through human-computer interaction. The object description includes the geometric coordinate data defining the shape of each component of the panel object, the object attributes such as linetype, color, etc., as well as non geometric text or values such as object name and visible information. It is very useful for the use of post-processing programs or interactions

various panel objects have common attributes. Therefore, based on the data types and structures of various panel objects, a common base class data structure can be abstracted. in summary, You can define the base class data structure of panel objects as follows:

class base {

mcsobjectname;  panel object name

mbvisible;  visual information, 0 -- invisible; 1 -- visible

mcrposition;  location information of panel object and size information of its bounding box

mu log break through the low-temperature CO sintering technology brush;  determine the filling attribute

m59141; LOGPEN;  draw the panel object determines the line attribute

}

the data structures of specific panel objects inherit the data structures of the base class. On the basis of the base class, specific panel object data structures can be determined by adding corresponding data types according to the properties and parameters of different panel objects

2.3 virtual instrument instance

users can easily establish a virtual instrument system that meets their own testing needs through the virtual instrument panel object provided by the system and the mouse on the computer screen. Figure 3 shows an example of a virtual instrument operation panel established by using the development platform

3. Visualization design and implementation

the visualization technology of virtual instruments mainly has two aspects: one is the visualization of panel objects and their related parameters, that is, the data is transformed into graphics or images to realize the visualization of panel objects; The second is the graphic user interface (GUI) design based on object-oriented technology, which makes the piston move freely and increases the conflict to the lowest limit, that is, visual interface design

in the system design, the object-oriented direct manipulation graphical interaction mode (i.e. GUI) is adopted to facilitate users to directly manipulate different visible panel object entities on the screen

3.1 panel object entity set

defines an extensible panel object entity set. These objects are abstract representations of panel object graphic attributes and operations. When creating a panel object or its attributes, the user only needs to specify the panel object to directly draw, move, copy, delete and other operations. The object can be redrawn or redrawn by itself, and the user does not need to care about how to draw

3.2 interactive drawing tool class

for interactive feedback, it is not integrated into the panel object, but defines the interactive drawing tool class (a friend of the panel object class) to handle the interactive operations imposed on the panel object, thus ensuring the versatility, independence and expandability. Figure 4 shows the class hierarchy of the interactive drawing tool

3.3 dynamic graphic display of data

data visualization is to display data on the computer screen in a specific

dynamic graphic mode for user monitoring. In the virtual instrument, such as the pointer deflection of the instrument and the waveform change of the oscilloscope, all reflect the dynamic change of the data, that is, the panel object graph has the effect of animation in the test process

data visualization of virtual instrument is to construct a mapping function f:dg → V from data set to panel object set, which needs to describe the visualization semantics of each (DG, V) pair. In this way, for different panel objects, you can establish the functional relationship between the graphics and their corresponding input variables

in the design of the application system, when the data changes frequently, the real-time refresh of the corresponding panel object will cause the screen to flash. In fact, when the data changes, many cells of the panel object graph are fixed, and only some areas with parameter mapping with the data change. Therefore, in the design, a drawing function for displaying dynamic data is constructed

in this system, the data of the virtual instrument test simulation computer is transmitted from the main control computer through the network. The simulation computer runs the broadcast program, starts the panel object display thread, continuously obtains data through the network, assigns data to the panel object, and displays and refreshes the instrument panel screen in real time

under the windows environment, we have developed a virtual instrument visualization general system by using vc++ object-oriented class programming technology. It has a friendly graphical user interface, and users can easily design instrument systems that meet their own needs. At the same time, the system supports network operation mode and realizes network visual simulation. (end)

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