Introduction to the design of portable vibration analyzer

introduction

Traditional vibration analysis instruments have the characteristics of complex structure, large size, and inconvenient operation; while the vibration acquisition and analysis instrument based on single-chip microcomputer is small in size, its analysis ability is limited and often cannot meet the special requirements of vibration analysis and diagnosis.

The vibration analyzer designed in this paper uses CompactRIO as the acquisition device and Labview as the software development platform. It is not only small in size and light in weight, but also has powerful and flexible professional analysis capabilities. It is suitable for testing occasions where the measurement points are scattered and continuous detection is not required.

System Structure

The system adopts a host-server structure. The host computer transmits the collected speed and vibration signals to the host computer through the TCP/IP protocol, and the host computer saves and analyzes the data. The structure is shown in Figure 1.

Figure 1 System structure diagram

Through the online analysis tool, the operator can detect in real time whether the engine vibration exceeds the standard, and the offline analysis tool can help the operator determine the cause of abnormal vibration.

System Design and Features

The system is designed to pursue five major characteristics of flexible testing technology: reliability, accuracy, scalability, adaptability and flexibility.

System adaptability

The system is portable, rainproof, drop-proof and vibration-proof, making the vibration meter suitable for field testing.

In order to make the whole system easy to carry, the vibration meter is designed with hardware that can meet the test requirements and is lightweight. For example, the acquisition device is CompactRIO, which is relatively small in weight and size. The whole system is small in size and light in weight (about 11Kg), making it easy to carry.

The host computer uses a military notebook, which is rainproof. In addition, the notebook bracket is also designed to be rainproof, with a groove on the left side. The interface and fan outlet are all installed in the groove, which can effectively prevent rain and is suitable for rainy day operations. The interface panel is shown in Figure 2.

Figure 2 Interface panel description

In addition, the equipment box is made of military box, which is sturdy and durable and can effectively protect the equipment inside the box from damage.

System scalability

The system can directly increase or decrease FPGA hardware by plugging and unplugging, and can add offline analysis algorithms according to user requirements to facilitate the increase of system functions.

In the design, programs with relatively concentrated functions and high application frequency are designed into modules. The coupling between modules is small, making the system easy to maintain. If there is a problem with any part, check the specific module. The system is easy to expand, and other modules can be added to the system to expand the system's functions. In addition, CompactRIO hardware is divided into Host and FPGA modules. In order to achieve the scalability of FPGA devices, the port reading of all possible boards is written into the program at one time, and then the data of the corresponding board is read according to the board information obtained under the Host to meet the requirements of adding and reducing boards. [page]

The system is divided into upper computer software and lower computer software. The upper computer software is divided into TCP/IP module, system configuration module, data processing module and storage module. The lower computer software is divided into TCP/IP module, Order manage module and data acquisition module.

The lower computer software can test 2-way speed signals and 4-way vibration signals. Among them, the TCP/IP module is responsible for communicating with the upper computer, receiving and processing the commands of the upper computer, and sending the operating status or collected data to the upper computer; the Order manage module is responsible for receiving the commands received by the TCP/IP thread, returning the status information to the TCP thread, and driving the acquisition module to collect data; the acquisition module configures the acquisition parameters, collects data and returns the collected data to the Order manage module.

In the upper computer software, the TCP/IP module is responsible for communicating with the lower computer, sending commands to the lower computer and receiving the status and collected data returned by the lower computer; the system configuration module is responsible for collecting channel selection, naming of channel logic names, setting of waveform colors, calibration coefficients and channel thresholds; the data processing module is the core part of the entire software, which can perform real-time online and offline analysis on the collected data; the storage module is responsible for storing the offline analyzed data.

System reliability

The theoretical MTBF index (mean time between failures) of the system design is about 3,500 hours, and the MTTR index (mean time to repair the system) is less than or equal to 30 minutes. To achieve this index, first of all, pay attention to the MTBF index of each hardware in the hardware selection, and then ensure that the MTBF index of the entire system can meet the design requirements through theoretical calculation. In addition, an exhaust fan is installed on the notebook bracket, and the air inlet and exhaust port are designed to discharge the heat generated by CRIO and power supply in time to ensure the normal use of the instrument; secondly, the operating manual of the vibration instrument provides a flowchart of the notebook not working, the signal waveform not displaying, the signal waveform displaying as noise, and the software fault diagnosis method, which can ensure that the MTTR index is within 30 minutes.

System flexibility

Finding abnormal data quickly from data files is the most important thing in the design. This system has designed three methods, namely browsing data waveforms, replaying vibration sounds, and finding data through alarm records.

Browsing waveform data is similar to dragging a cursor to browse a movie in Media Player. When you drag the cursor as shown in Figure 3 with the mouse, the system will read the waveform of the corresponding time period and display it in the waveform chart.

Figure 3 Browsing data waveform interface

Replay vibration sound: Play the vibration data of each channel in a specific time period through sound, and judge whether there is any abnormality in this data segment through hearing.

The alarm record can be used to call up the time when the vibration abnormality recorded by the system, and then enter the time into the start time in the browsing waveform interface, read the data at the time of the abnormality, and conduct targeted analysis.

Analytical skills

The system has professional analysis capabilities. The designed online analysis algorithms include display of time domain waveforms of vibration signals and speed signals, calculation of maximum value of vibration signals, etc. Online analysis requires fast operation speed, which must be faster than the acquisition speed. Reducing the use of attribute nodes and registers can meet the requirements.

Offline analysis can call out the saved data for more detailed and professional analysis, such as time domain waveform maximum value, effective value calculation, axis trajectory analysis, etc. Offline algorithms do not require high computing speed, and algorithms can be added according to users, such as order analysis and axis trajectory analysis.

Order analysis can perform order analysis calculations based on the collected speed signal and vibration signal to find the corresponding relationship between the vibration signal and the speed signal, so as to find the cause and location of the fault more accurately.

The axis trajectory analysis vividly reflects the actual motion status of the rotor and contains rich information about rotating machinery faults. This system calculates the axis trajectory by collecting two vibration signals perpendicular to the axis and the direction of the rotor.

Conclusion

In the portable vibration meter designed in this paper, the lower computer acquisition module uses the small size and weight CompactRIO, the upper computer uses a rugged military notebook, the outer shell uses a military box, anti-vibration and anti-fall, and the external interface is also designed to be rainproof, so that the instrument can adapt to outdoor and harsh environment testing. In addition, the software design also fully considers the user's needs for test system reliability, scalability and flexibility, and can effectively test whether the engine has abnormalities and help operators determine the causes of abnormalities.