JP2009115538A - Vibration monitor by wireless sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration monitor by a wireless sensor, which performs high-precision vibration measurement without increasing transmission time for a digital signal of vibration acceleration by controlling a plurality of amplifiers. <P>SOLUTION: The amplification factor of an amplification section which amplifies an analog output signal from a vibration acceleration sensor is set in a switchable manner. The analog output signal from the amplification section is A/D converted to be wirelessly transmitted to a vibration monitoring section. The vibration monitoring section determines the value of the received digital signal, and when it has received the same value successively, the amplification factor of the amplification section is switched. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vibration monitoring device that remotely monitors the vibration state of a rotary machine such as an electric motor or blower in various industrial plants by wireless communication.

Conventionally, in industrial plants where a large number of rotating machines such as electric motors, blowers and fan devices are used, vibration monitoring is performed on major rotating machines in order to prevent shutdown due to sudden failure of equipment. .
According to the method, a maintenance man of the facility periodically visits, carries a vibration meter, manages the tendency of the vibration level, and determines whether there is any abnormality. Also, in large-scale plants, vibration changes are constantly monitored online, vibration data is collected constantly or at regular intervals using a computer, etc., and vibration level changes over time (trend management) and frequency analysis is performed. Therefore, vibration abnormality diagnosis is performed. In recent years, in large-scale industrial plants, there is an abnormality monitoring system in which a wireless tag is installed in a detection unit in order to avoid long-distance cable installation (see Patent Documents 1 and 2).
In the vibration sensor used for these vibration monitoring, the signal of the acceleration sensor is usually amplified using an amplifier, and a signal in a necessary frequency region is selected using a filter according to the frequency range to be measured, and an integration circuit Is used to convert to vibration speed and vibration displacement. In the case of the wireless tag, an analog signal obtained by amplifying the acceleration signal from the acceleration sensor is converted into a digital signal by an A / D converter, transmitted to a receiving device equipped with a computer by a wireless transceiver, and the digital signal is transmitted by a computer. The frequency analysis is carried out by the motor and converted into the vibration speed and vibration displacement, and the vibration level of the rotating machine is monitored by managing the tendency of vibration level and diagnosing vibration abnormality.
JP 2005-24441 Japanese Patent Laid-Open No. 10-19655

However, in these vibration monitoring devices, an amplifier is used to amplify the signal of the acceleration sensor. However, since the acceleration of vibration is proportional to the square of the rotational frequency of the rotating machine, the rotational speed of one amplifier is low. In a small acceleration region, the S / N ratio of the vibration acceleration after amplification becomes worse. As a method for improving the S / N ratio, when converting to a digital signal, the number of bits of the A / D converter can be increased to increase the resolution, but in this case, the number of data increases according to the number of bits. For this reason, there is a drawback that the transmission time for wireless transmission to the outside becomes long.
In addition, when the number of rotations is high, the acceleration is large, and the analog signal of the amplified acceleration exceeds the limit of the input voltage when performing A / D conversion. There is a drawback that the acceleration range is limited. As a method for solving this problem, a variable gain amplifier is used to automatically control the amplification factor to improve the S / N ratio. However, the vibration sensor unit cannot be applied to vibration monitoring using a battery-powered wireless tag due to increased power consumption and cost.
The present invention has been made in view of the above circumstances, and vibration monitoring by a wireless sensor that enables highly accurate vibration measurement without increasing the transmission time of a vibration acceleration digital signal by controlling a plurality of amplifiers. An object is to provide an apparatus.

In order to achieve the above object, a vibration monitoring apparatus using a wireless sensor according to the present invention includes a vibration acceleration sensor, an amplifying unit for amplifying an analog output signal from the vibration acceleration sensor, and an A / D conversion for digitally converting the amplified signal. Unit, a storage unit for storing the A / D converted digital signal, a wireless transmission / reception unit for wireless transmission of the digital signal stored in the storage unit, a wireless sensor provided with a power supply unit for each unit, and the wireless sensor In the vibration monitoring device using a wireless sensor comprising the vibration monitoring unit that receives the output signal and monitors the vibration, the amplification unit is configured so that the amplification magnification can be switched, and the vibration monitoring unit receives from the wireless transmission / reception unit. A determination unit is provided for determining a numerical value of the digital signal and transmitting a control signal for switching the amplification factor of the amplification unit to the wireless sensor when the numerical value continues for a predetermined number of times. And wherein the door.
Further, in the above configuration, the vibration monitoring unit uses the digital signal to calculate a frequency analysis in a frequency range to be monitored, a vibration velocity effective value, and a vibration displacement at a predetermined frequency, and display and determine a state. To do.

As a result, according to the present invention, since the magnification of the amplifier is automatically switched according to the magnitude of vibration acceleration input to a wireless sensor installed in a vibrating part, an analog signal from a small acceleration level to a large acceleration level is obtained. As a result, an A / D converter with a lower number of bits can obtain a higher resolution and a digital signal transmission time required for vibration measurement can be reduced.
In addition, data transmission time can be shortened, vibration frequency components and vibration levels can be displayed, trend management and judgment can be performed, so wireless sensor costs can be reduced, circuits can be downsized, and battery life can be extended. It can contribute to the expansion of the maintenance interval.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an internal configuration of an RFID tag 1 and a vibration monitoring unit 7 as an example of a wireless sensor of the present invention. In the figure, an RFID tag 1 includes a vibration acceleration sensor 2 using a piezoelectric element, an amplification unit 3 that amplifies an analog output signal from the vibration acceleration sensor 2, and converts an analog signal from the amplification unit 3 into a digital signal. A / D conversion unit 4 for data storage, a data storage unit 5 for temporarily storing the converted digital signal, a wireless transmission / reception unit 6 for wireless transmission of the stored digital signal based on a command from the outside, and a power source by a battery It is comprised with the supply part 7. FIG.
The amplifying unit 3 includes a charge amplifier 31 that converts the charge output of the vibration acceleration sensor 2 into a voltage, a low-pass filter 32 that uses the output signal of the charge amplifier 31 as a cutoff frequency near the upper limit of the vibration monitoring frequency range, and its output voltage. Voltage amplifiers 33 and 34 for amplifying the signal are provided.
The voltage amplifier 33 has a bypass circuit, and the bypass circuit is effective when the amplification factor of the amplifier 3 is changed.
Here, the analog signal output from the voltage amplifier 34 is digitally converted by the A / D conversion unit 4, stored in the data storage unit 5, and used as a transmission command signal from the transmission / reception unit 81 provided along with the vibration monitoring unit 8. Is transmitted from the wireless transmission / reception unit 6 and taken into the vibration monitoring unit 7.

The determination unit 82 of the vibration monitoring unit 8 determines that the amplifier is saturated and changes the amplification factor of the amplifier when the same numerical value is continued twice in the acceleration digital signal captured by the transmission / reception unit 81. Transmitting a control signal to the RFID tag 1 In the RFID tag 1 that has received this control signal, the output signal of the low-pass filter 32 is input to the voltage amplifier 34 by bypassing the voltage amplifier 33 in order to lower the amplification factor. As a result, since the amplification factor is lowered, the determination unit 82 of the vibration monitoring unit 8 does not have the same numerical value twice in the acceleration digital signal captured by the transmission / reception unit 81.
As described above, since the amplification factor of the amplifying unit 3 is automatically switched according to the magnitude of the vibration acceleration input to the RFID tag 1, the amplification factor that does not saturate the analog signal from a small acceleration level to a large acceleration level. In addition, a high resolution can be obtained even with an A / D converter having a lower number of bits, and the transmission time of a digital signal necessary for vibration measurement can be reduced.
Further, the vibration analysis unit 83 performs frequency analysis of the digital signal taken in by the frequency analysis unit 81 up to a half frequency of the sampling frequency 4fo set to four times the upper limit f ₀ of the monitoring target frequency, as shown in FIG. As shown in the analysis flow shown, the effective value of the vibration speed of ₀ to f ₀ Hz is calculated, and the vibration fluctuation in the integral multiples f1, 2f1, and 3f1 of the rotational frequency component f1 of the rotating machine is calculated in the effective value. The state determination is displayed by comparing the calculated effective value and vibration fluctuation with a reference value (threshold value) set in advance based on the JIS standard. Further, the calculated effective value and vibration fluctuation are stored in a memory, and the numerical graph is displayed on a trend screen (not shown).

The block diagram which shows the internal function of the RFID tag and vibration monitoring apparatus of this invention. The analysis flowchart which shows the main functions of the vibration monitoring apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... RFID tag 2 ... Vibration acceleration sensor 3 ... Amplification part 4 ... A / D conversion part 5 ... Data storage part 6 ... Wireless transmission / reception part 7 ... Power supply part 31- ..Charge amplifier 32 ... Low pass filter 33, 34 ... Voltage amplifier 8 ... Vibration monitoring unit 81 ... Transmission / reception unit 82 ... Determination unit 83 ... Vibration analysis unit

Claims (2)

Vibration acceleration sensor, amplification unit for amplifying an analog output signal from the vibration acceleration sensor, A / D conversion unit for digitally converting the amplified signal, storage unit for storing the A / D converted digital signal, the storage unit A wireless transmission / reception unit that wirelessly transmits a digital signal stored in the wireless sensor, a wireless sensor including a power supply unit to each unit, and
In the vibration monitoring device by the wireless sensor comprising the vibration monitoring unit that receives the output signal of the wireless sensor and monitors the vibration,
The amplification unit is configured so that the amplification magnification can be switched, and
The vibration monitoring unit is provided with a determination unit that determines a numerical value of the digital signal received from the wireless transmission / reception unit and transmits a control signal to the wireless sensor to switch the amplification factor of the amplification unit when the numerical value continues a predetermined number of times. A vibration monitoring apparatus using a wireless sensor. 2. The vibration monitoring device according to claim 1, wherein the vibration monitoring unit uses the digital signal to calculate a frequency analysis in a frequency range to be monitored, a vibration velocity effective value, and a vibration displacement at a predetermined frequency, and display and state determination. A wireless sensor vibration monitoring device.

Images