KR20080063572A

KR20080063572A - Built-in digital vibration monitor

Info

Publication number: KR20080063572A
Application number: KR1020070000140A
Authority: KR
Inventors: 최현
Original assignee: 시그널링크 주식회사
Priority date: 2007-01-02
Filing date: 2007-01-02
Publication date: 2008-07-07

Abstract

The present invention relates to a vibration measurement technology, and more particularly, to a device that can be attached to the body of the machine at all times and continuously monitor the state of the machine by continuously measuring vibration during operation of the machine.

The present invention is a casing (10) that looks and built up or attached components, a sensor 20 for detecting the vibration of the machine, an amplifier to amplify a signal received from the sensor, a filter for removing noise from the amplified signal, and noise Signal adjustment module 30 including an AD converter for digitizing the removed signal, a memory for storing a signal received from the signal adjustment module, and a DSP for calculating, comparing, and determining a signal received from the memory and processing the signal. And an input unit 50 for inputting data to a memory and a filter, and an output unit 60 for displaying and outputting information necessary for vibration monitoring of the machine.

The present invention, the built-in digital vibration monitor is capable of monitoring a variety of accurate vibration compared to the product using an analog circuit, can be manufactured at a very low cost, high reliability because it is not affected by noise, and is very easy to operate.

Description

Built-in Digital Vibration Monitor

1 is an external perspective view of a vibration monitor according to the present invention.

2 is a signal processing system diagram.

3 is a schematic diagram of signal operation inside the DSP.

※ Main component number

10: case, 20: sensor, 30: signal adjustment module,

40: signal processing module, 50: input unit, 60: output unit

The present invention relates to a vibration measurement and analysis technology for monitoring the state of the machine, and more specifically, it is attached to the body of the machine at all times and can continuously monitor the state of the machine by continuously measuring vibration during operation of the machine. Device.

Rotating machines such as pumps, motors, and engines, or machines equipped with such rotating machines, inevitably generate vibrations due to the effects of unbalance mass of the rotating body, shaft deflection, bearing wear, and gear tooth damage. . Such vibrations, when there is a sign of a failure in the machine, increase the vibration of a particular frequency component that is related to the cause of the failure. Therefore, by measuring the overall vibration value of the machine or the vibration value of a certain frequency continuously or periodically, by observing the vibration pattern occurring in the machine, it is possible to predict the failure of the machine, and to predict the cause of the failure in advance, so as to prevent preventive maintenance, etc. Appropriate action can be taken. This technique is called vibration monitoring. Vibration monitoring prevents critical machines from breaking down unexpectedly, causing unintended fatal damages such as stopping the entire production process and physical damage to nearby personnel. have.

In order to monitor the vibration as described above, conventionally, an expensive vibration accelerometer or other sensor is attached to a machine that causes vibration, and the sensor is connected to a signal processing device or a computer capable of processing a signal using a signal cable. A separate vibration monitoring system was provided to monitor the vibration of the machine.

In the case described above, signal conditioning devices such as sensors, amplifiers, and signal processing devices are very expensive, and noise is introduced into a long connected signal cable (noise), thereby reducing reliability. In other words, the system was complicated, and there was a problem that only a high-level man with considerable knowledge of vibration could operate. Thus, until now, vibration monitoring has been carried out only on very expensive large facilities.

As mentioned above, the conventional vibration monitoring system is expensive, has low reliability, and requires high manpower for operation. Therefore, it is inexpensive, reliable, and very simple. There is a need for a vibration monitoring system that can detect conditions.

The present invention is a vibration monitor that realizes the above technical problem, and is a built-in digital vibration monitor that can be individually attached to a machine to be monitored to directly monitor the state of the machine.

The built-in digital vibration monitor of the present invention comprises a case 10, a sensor 20, a signal adjustment module 30, a signal processing module 40, an input unit 50, and an output unit 60, the sensor, signal adjustment The module and the signal processing module are composed of one circuit board and mounted inside the case, and the output unit is attached to the case so as to be exposed to the outside. A battery for supplying electricity required for the operation of the vibration monitor may be provided, and a monitor on / off switch may be provided.

As shown in FIG. 1, the case 10 is in the form of a small box, and has an indicator such as an arrow ↑ indicating a vibration sensing direction on an outer surface thereof and is attached to a machine to be subjected to vibration monitoring. The case may be attached to the body of the machine to be monitored by firmly attaching the vibration detection direction indication to the direction in which the vibration is to be measured. Any method such as attaching a screw or attaching an adhesive may be used.

Each module for processing the vibration signal sensed by the sensor and the signal transmission system between the modules are as shown in FIG.

As the sensor 20, a chip type acceleration sensor (MEMS acceleration sensor) is used. The acceleration sensor 20 is attached to the circuit board so that the direction of acceleration detection coincides with the direction indicated on the case 10.

The signal adjustment module 30 includes an amplifier 31 for amplifying the vibration signal detected and sent out by the sensor, a filter 32 for removing noise, and an AD converter 33 (Analog-Digital Converter). It is composed. The amplifier 31 amplifies the weak electrical signal detected by the sensor to an extent easy to process in the signal processing module 40. In addition, the filter 32 removes noise unrelated to the vibration signal generated from the machine. A filter 32 uses a band pass filer for removing high frequency signal components and low frequency signal components, or high frequency noise removing components. A high pass filer and a low pass filer for removing high frequency noise may be connected in series. In this filter, the frequency range to be filtered by the input unit 50 may be input. The AD converter 33 samples the analog signal received from the filter 32 at high speed, converts it into digital, and sends the analog signal to the signal processing module 40.

The signal processing module 40 includes a digital signal processor (DSP) 41 and a memory 42. DSPs and memories are manufactured and marketed in the form of chips. The signal received from the signal adjustment module 30 is once stored in the memory 42 and then sent to the DSP 41 for various operations. The operation structure of the DSP is as shown in Fig. 3, the frequency conversion of the measured signal received from the AD converter by the FFT (Fast Fourier Transformation) conversion method, by integrating the vibration acceleration signal as necessary, the vibration speed or vibration displacement value Then, the measured value is compared with the reference value input to the memory 42 through the input unit 50 to determine whether the limit value is exceeded, and the result is sent to the output unit 60. In addition, when the vibration of the machine exceeds a large reference value, it is possible to send a signal for interrupting the operation by shutting off the power of the monitoring target machine through the output unit 60.

The DSP 41 may add a function of sampling an analog signal at high speed and converting it into digital data, and a digital filtering function for removing noise in a digital manner. When such a function is added, an AD converter may be added to the signal adjustment module. Reference numeral 33 and the filter 32 can be omitted. However, since an aliasing error occurs during sampling with digital data, it is preferable to remove high frequency noise using at least a low pass filter rather than not using the filter 32 completely.

The memory 42 stores other data including the tolerance reference value of the vibration input through the input unit 50, the gain of the sensor, the measurement data, and the like, and the DSP uses the data necessary for this memory.

The input unit 50 is provided with a button or other input means for directly inputting numbers or letters into the memory 42 through the DSP 41 or selecting specific functions from the prepared menu.

The output unit 60 includes one or both of the LCD display window 61 and the output port 62. The LCD display window includes a measurement value received from the DSP 41, a reference value stored in the memory 42, an input menu, Data necessary for monitoring such as an input value input through the input unit 50 is displayed in the form of numbers, tables, graphs, and the like. The output port 62 receives alarm signals, measured data, and the like when the measured vibration of the machine exceeds the reference value from an external device, and is provided with a power supply line and a data input signal line to supply electricity from the outside. Alternatively, instead of using the input unit 50, a separate convenient input means such as a computer may be used to input an input signal through this output port.

Operation and operation of the present inventors built-in digital vibration monitor is as follows.

In consideration of the vibration characteristics of the monitoring target machine, the vibration monitor inputs the sensor gain, the permissible vibration value per frequency, and other data necessary for vibration monitoring, and attaches the case 10 of the vibration monitor to the target machine according to the vibration sensing direction. Then, when the vibration monitor is turned on, the vibration monitor continuously measures the vibration of the target machine through the sensor 20, and the DSP 41 continuously compares the vibration measurement value with the allowable reference value stored in the memory 42. Then, the result is sent to the output unit 60 to display the vibration state of the current machine. If the vibration measurement exceeds the reference value, a signal is sent to the output port 62 to turn on a warning light, sound a warning sound, or shut down the target machine. In this way, the monitored machine can be monitored individually.

The monitoring of the machine vibration can be performed by directly using time domain data of the measured vibration signal or by using frequency domain data by performing frequency analysis on the measured vibration signal.

As a monitoring method using time domain data, a crest factor is used as a criterion for abnormality. The crest factor is defined as a ratio of peak value to peak value (Peak / RMS) as shown in FIG. 4.

Crest Factor detects and monitors signals caused by impulse signal components or short events, and can be diagnosed by detecting momentary vibration changes caused by bearing breakage or gear breakage. Element. Table 1 shows the crest factors of vibration signals generated when there is a problem with a general signal and a machine. By calculating the crest factor of the measured vibration signal, it is possible to know whether the bearing is abnormal as shown in this table.

Case Crest factor Unit sine 1.414 Random noise Good bearing 2.5 to 3.5 Damaged Bearing > 3.5 Failure > 7

References: Fundamentals of noise and vibration analysis for engineers, M. P. Norton, Cambridge University Press, 1989.

Monitoring methods using frequency domain data include Peak test method, Band test method and Overall test method.

The peak test method is a method of determining whether an amplitude of a vibration value corresponding to a specific frequency component is abnormal or not, and as shown in FIG. 5, when the frequency of the vibration signal generated from the machine is a constant value (eg, AC The magnetic vibration component of 120 Hz in the motor is dominant).

As shown in FIG. 6, the band test method is a method of determining whether the sum of vibration values calculated at a specific specific frequency bandwidth is an abnormality criterion.

As shown in FIG. 7, the overall inspection method is a method of determining whether the sum of all vibration values (overall values) measured in the inspection frequency band is abnormal.

An advantage of the digital vibration monitor is that it is possible to set the various inspection conditions as described above to maximize the performance and effect of the vibration monitoring through the external input device 50, and input the same to the monitor to monitor the exact state of the machine. to be.

An example of monitoring condition setting is shown in Table 2 below.

Inspection code Set value Measures test results Remarks A1 0.1g 0.08g OK Frequency Domain Inspection … … … … … C1 6.0 m / sec 13.2 m / sec NG Time domain inspection

The vibration monitor of the present invention can be operated individually as described above, but the output port 62 may be interfaced with the central monitoring or control system provided in the situation room or the like by wire or wirelessly to monitor a plurality of machines in a centralized manner. .

When monitoring the vibration of the machine as described above, the failure of the machine and its cause can be predicted in advance. This prevents catastrophic losses due to sudden breakdown of the machine through proper preliminary maintenance, and prepares spare parts in advance to secure the expensive machine and the entire equipment in which the machine is used. It can be operated economically and economically.

Since the inventors of the present invention built-in digital vibration monitor can be manufactured at a very low cost, it can be individually attached to each machine to be monitored to perform individual monitoring for each machine. In addition, the vibration characteristics of the individual machine to be monitored can be input in advance and attached to the machine, and by measuring the vibration state of the machine by itself, it outputs appropriate countermeasures. Can easily operate a monitoring system.

Compared with the conventional analog monitoring system, the built-in digital vibration monitor of the present invention can set various inspection conditions to maximize the performance and effect of the vibration monitoring through the external input device 50, and time before frequency analysis. It is possible to set various inspection conditions using area data and frequency analysis results (frequency spectrum) as monitoring elements.

The inventors of the present invention built-in digital vibration monitor because it directly detects the vibration of the individual machine to monitor it is not affected by noise and high reliability.

The built-in digital vibration monitor of the present invention is economical because it can be directly applied to vibration monitoring of other homogeneous or heterogeneous machines by modifying and inputting the input information recorded in the memory.

The built-in digital vibration monitor of the present invention can be easily used to centrally monitor a plurality of machines by interfacing the output port with a central monitoring or control system provided in a situation room or the like by wire or wirelessly.

Claims

A case 10 which houses or attaches the following components;

Sensor 20 for detecting the vibration of the machine;

A signal adjustment module 30 including an amplifier for amplifying the signal received from the sensor;

A signal processing module comprising a memory for storing the signal received from the signal adjustment module and a DSP for digitally converting the signal received from the memory, removing noise, calculating, comparing, and determining the signal, and processing the signal into information necessary for monitoring. 40;

An input unit 50 for inputting data into the memory;

And, the output unit 60 for displaying and outputting information necessary for the vibration monitoring of the machine, such as vibration status received from the signal processing module, the presence or absence of the machine, alarm signal;

Vibration monitor is configured to include.

The method of claim 1,

The signal adjustment module 30 is a signal adjustment module 30 further comprising a filter for removing noise from the amplified signal and an AD converter for digitizing the signal from which the noise is removed;

The DSP of the signal processing module (40) is a vibration monitor, characterized in that the function to digitalize the signal is omitted.

The method according to claim 1 or 2,

The output unit 60, characterized in that the output unit further comprises an output port for interfacing the information necessary for monitoring with external equipment, including the alarm signal received from the signal processing module 40, vibration data, Vibration monitor.