Application of virtual instrument in displacement test system
With the increasingly complex development of displacement test systems and the expansion of virtual instrument applications, the paper uses virtual instruments as a technology platform to write programs using LabVIEW software to design hydraulic system displacement test systems. The hardware composition and design process of the test system are introduced. The program block diagram and the intuitive front panel diagram are given. The system has strong scalability. The test system can realize data acquisition, transmission, storage and recall of displacement signals. Analysis and display. And through field tests, the system has strong practicability, reliability and convenient operation. Can meet the needs of teaching and industry.
Displacement testing technology has a wide range of applications in industrial production. Displacement detection is the basis of mechanical quantity detection. It is one of the important components of mechatronics technology to convert mechanical quantity into displacement quantity. The detection of displacement not only provides important data for improving product quality and production safety, but also provides a basis for the detection of other parameters. In the hydraulic test rig, the traditional static electro-hydraulic measurement control method can not meet the current requirements of the hydraulic system in terms of performance, operation, online monitoring and fault diagnosis, so the development of online monitoring and analysis system is particularly important. In order to ensure the stability, accuracy and low accident operation of the system, this paper develops a displacement test system, which can display its displacement waveform soldier in real time, and can also perform signal processing on it.
1 Introduction to Virtual Instruments and LabVIEW
The virtual instrument (referred to as VI) consists of hardware devices and interfaces, device driver software, and virtual instrument panels. The underlying device driver software communicates with the real instrument system and displays various controls corresponding to the real instrument panel operation elements on the computer screen in the form of a virtual instrument panel. The user's operation of the virtual instrument panel with the mouse is as real and convenient as operating a real instrument.
Test software is the core of virtual instruments. IabVIEW is a rich and concise virtual instrument development software from National Instruments, a graphical programming language. Using its powerful graphical programming environment, using visualization techniques, select the desired objects from the control module and place them on the front panel of the virtual instrument. Utilizing the powerful computing power of the computer and the powerful function library of the virtual instrument development software can greatly improve the data analysis and processing capability of the virtual instrument system and save development time.
2 hardware structure of the displacement test system
This paper uses a hydraulic test bench as a test platform, consisting of a hydraulic power source and an electrical control system. Its hydraulic power source consists of a power oil pump and a power actuator oil motor. Connect the virtual instrument to the hydraulic test bench, select the working condition, measuring point, install the displacement sensor, and start the data acquisition after debugging and processing. The axial displacement of the hydraulic test bench gear pump was tested. The hardware composition is shown in Figure 1.
2.1 Sensor selection The key to achieving displacement measurement is the conversion of the signal, that is, the selection of the sensor. In this paper, the axial displacement signal acquisition of the gear pump under the normal working condition of the hydraulic circuit of the information acquisition experimental platform is carried out, and the waveform display and analysis of the signal are performed. The waveform curve is changed with time, and the correctness and effectiveness of the data display program of the displacement test platform are verified by the waveform display and the analysis result.
In this system, the displacement sensor uses the eddy current displacement sensor CWY-DO-504, the measuring range is 4mm, and the probe is φ14mm. This is a non-electrical electrical measuring device that converts mechanical displacement or vibration amplitude into electrical signal output. It is convenient for dynamic measurement of rotating bodies such as rotating shafts. The probe can work in media such as water and oil. In the displacement measurement, the displacement signal is adjusted by the matching displacement signal conditioner. The detection system can convert the displacement into a voltage signal for the data acquisition card. When the actuator drives the displacement sensor to move, the voltage signal can be collected. Finally, the voltage signal is converted into a corresponding displacement signal by calibration to realize the displacement measurement. Its shape is shown in Figure 2.
2.2 Selection of Data Acquisition Card The chassis used in this experimental platform is an 8-slot PXI-1050 chassis from National Instruments, and its operating temperature is 0-50 °C. There are four slots for SCXI modules in integrated signal conditioning. With DC power supply and integrated signal conditioning. Four SCXI slots integrate the signal conditioning module into the PXI system. The PXI-6251 multi-function data acquisition card produced by NI is used in this design. The main parameters are as follows: 16 analog input channels, 16-bit precision, 1.25 MS/s sampling rate; 2 analog outputs, 16-bit precision. , 2.8MS / s output speed; 24 digital I / O, 2 channel timing counter, to meet the needs of displacement signal acquisition, the displacement signal is converted into voltage signal output.
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