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.
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 with a range of 4 mm and a probe of φ14 mm. 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 National Instruments 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 bits. Accuracy, 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.
3 software composition of the displacement test system
Modular design data acquisition, the design of the data acquisition module has a direct impact on the subsequent data display and analysis results and the realization of the entire system function. This article uses NI DAQ (Data AcQuisition) card and its driver to design this module. Make full use of the integrated and comprehensive DAQ function library and sub-VI, the design can realize the control of data acquisition, including data acquisition module such as trigger control and channel control.
3.1 Program Flow of Displacement Test System 3.2 Main Control Front Panel of Displacement Test System In this displacement test, the front panel can display the original waveform of the displacement signal, and can also perform derivative analysis and processing on the displacement signal, showing at a glance Key information for the original and autocorrelation waveforms – rms, peak-to-peak, and mean.
3.3 VI design of the displacement test system Data storage and recall. When programming, the database is used to store and read data. Establish an Access data source, through the ADO database access technology, make full use of the flexibility of ADO, realize the operation of the database through the programming model, execute user commands, and realize the management of data. LabVIEW database access package using ADO technology - LabSQL, users can directly access the database by calling subVIs in LabVIEW.
4 Field test
Before collecting the data, the system should be debugged to ensure that the collected data is within the specification range of the data acquisition card, and the output waveform of the data acquisition card is consistent with the actual waveform. Only when this requirement is met can the data be collected and protected. The security of the data acquisition card. After debugging, exit directly and perform data acquisition operations. Otherwise, re-commission until the requirements are met before proceeding. The sensor is then mounted on the axially outer edge of the gear pump and the acquired signal is displayed on the front panel of the displacement test system.
From the original waveform of the displacement, it can be seen that the displacement signal is a periodic signal, which can also be judged from the autocorrelation map, because the autocorrelation function waveform is not attenuated, and is a periodic signal of the same frequency.
5 Conclusion
Through the acquisition and analysis of the displacement signal, the signal waveform displayed and analyzed by the designed displacement test system is consistent with the actual operating conditions of the hydraulic system. This proves the effectiveness of this development platform, and provides an intuitive and convenient analysis platform for further operation of the machine and its components, online monitoring and fault diagnosis.
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.
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 with a range of 4 mm and a probe of φ14 mm. 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 National Instruments 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 bits. Accuracy, 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.
3 software composition of the displacement test system
Modular design data acquisition, the design of the data acquisition module has a direct impact on the subsequent data display and analysis results and the realization of the entire system function. This article uses NI DAQ (Data AcQuisition) card and its driver to design this module. Make full use of the integrated and comprehensive DAQ function library and sub-VI, the design can realize the control of data acquisition, including data acquisition module such as trigger control and channel control.
3.1 Program Flow of Displacement Test System 3.2 Main Control Front Panel of Displacement Test System In this displacement test, the front panel can display the original waveform of the displacement signal, and can also perform derivative analysis and processing on the displacement signal, showing at a glance Key information for the original and autocorrelation waveforms – rms, peak-to-peak, and mean.
3.3 VI design of the displacement test system Data storage and recall. When programming, the database is used to store and read data. Establish an Access data source, through the ADO database access technology, make full use of the flexibility of ADO, realize the operation of the database through the programming model, execute user commands, and realize the management of data. LabVIEW database access package using ADO technology - LabSQL, users can directly access the database by calling subVIs in LabVIEW.
4 Field test
Before collecting the data, the system should be debugged to ensure that the collected data is within the specification range of the data acquisition card, and the output waveform of the data acquisition card is consistent with the actual waveform. Only when this requirement is met can the data be collected and protected. The security of the data acquisition card. After debugging, exit directly and perform data acquisition operations. Otherwise, re-commission until the requirements are met before proceeding. The sensor is then mounted on the axially outer edge of the gear pump and the acquired signal is displayed on the front panel of the displacement test system.
From the original waveform of the displacement, it can be seen that the displacement signal is a periodic signal, which can also be judged from the autocorrelation map, because the autocorrelation function waveform is not attenuated, and is a periodic signal of the same frequency.
5 Conclusion
Through the acquisition and analysis of the displacement signal, the signal waveform displayed and analyzed by the designed displacement test system is consistent with the actual operating conditions of the hydraulic system. This proves the effectiveness of this development platform, and provides an intuitive and convenient analysis platform for further operation of the machine and its components, online monitoring and fault diagnosis.
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