JPS592047B2 - Method for monitoring operating conditions of machines and devices driven by electric motors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method for monitoring the operating status of machines and equipment driven by electric motors, in particular for monitoring the operating conditions of one or more specific operating conditions. Suitable for monitoring for abnormalities.

(Prior art and problems) The method that has been widely adopted in the past to measure and monitor the operating status of machines and equipment uses many types of transducers to convert different physical quantities such as displacement, pressure, and velocity into electrical signals. These signals are then compared alone or in combination with a reference value.

Additionally, factors such as tool deterioration have been measured indirectly by measuring things such as vibration and noise. These conventional methods have disadvantages such as requiring many modifications and installations to the machine, which are not only cumbersome and expensive but also easy to damage the machine.

Furthermore, measurements made while a machine is in operation are often difficult to determine the correct value without the use of very complex equipment, and methods that use noise or vibration spectrum analysis do not allow interference with machine components. Or, it was not always possible to obtain accurate results due to noise emitted from the operation of adjacent machines. Monitoring operating conditions also protects many machines or equipment from damage caused by overloading, improper adjustment, or sluggish tools.
This has led to the use of devices for measuring the current or average power consumed by machinery or equipment, which can be used to measure the average or peak power or current consumption during operation due to abnormal conditions. It is based on the assumption that it will cause

Therefore, methods have been proposed in which the current applied to the motor driving the machine during a normal operating cycle is recorded and compared with the current during subsequent operating cycles, but the current supplied to the drive motor or the average In such traditional methods that depend on power, e.g. the current or average power consumption is
In some cases, the peak power may undergo a larger quantitative change than that caused by abnormal conditions, and on the other hand, the peak power may not change effectively even if there is a deviation from normal operation, which limits the range of application. be. In addition, current operated devices such as those used in the prior art are insensitive to power changes manifested as power factor changes at constant voltage.

Additionally, conventionally used power transducers cannot operate properly with power factors significantly less than unity, and such low power factors often occur in industrial machinery and equipment settings.

OBJECTS OF THE INVENTION The general object of the invention is a method for economically and reliably overcoming the various problems mentioned above for the control and protection of electrically powered machines or devices.

A more specific object of the invention is to provide machines and devices involving electric machines, such as metal cutting Y-shines including multi-blade single-blade cutters, milling machines, and trilink machines, and register presses, stamping/drawing ink presses, etc. The present invention relates to a new method for monitoring the operation of metal forming machines or electrical fluid machines and equipment such as injection molding machines and powder metallurgy presses.

Arrangements of the Present Invention The present invention compares true power characteristic changes applied to electric motors driving machines and devices with power characteristic changes under standard operating conditions for a particular operating parameter in that machine or device.

Abnormalities in various physical operating parameters in machines and equipment, such as an impactful increase in the load on a press, a decline in proper powder forming ability due to wear of metal cutting tools, synchronous changes in various events in the machine process, and changes in material A change in quality or quantity causes a corresponding temporal power change.

Such changes include changes in the amount of applied power from one moment in the cycle to another, changes in the characteristic frequency components of the applied power, changes in the amount of power demanded during particular time intervals, and the like. Therefore, the present invention detects a frequency component that is related to time, is independent of power factor change, and can appropriately observe a fast transient phenomenon from an instantaneous power waveform that is related to a specific operating parameter, and uses that variation as a reference. It is compared with the fluctuation value.

(Example) In FIG. 1, 1 is an electric motor, and 2 is a machine or device driven by the electric motor 1, such as any machine or device such as a metal cutting machine or an injection molding machine. In the case of an injection molding machine, the electric motor 1 is a hydraulic pump electric motor.

3 is a power source, which is connected to the electric motor 1 through a conductor 4;

5 is a current transformer, and 6 is a multiplier that outputs applied power based on the voltage applied to the motor 1 and the current value from the current transformer 5.

R and 8 are band-pass filters, each with a specific frequency F,
・Let F pass through. 9 and 10 are differential amplifiers, and 11 is a reference deviation amount setter.

FIG. 2 shows an example of the instantaneous power waveform applied to the motor 1. Curve A represents the instantaneous power waveform for one cycle of operation output from the multiplier 6 when the machine 2 is in a normal operating state. represent

Curve B is an instantaneous power waveform showing an example when one or more of the operating parameters of machine 2 is changed by a predetermined amount,
For example, it shows the instantaneous power waveform of one cycle when the operation parameter is such that the wear amount of the cutting tool reaches a certain value. FIG. 3 shows the spectrum of frequency components 1 to F6 of the curves A and B, and the characteristic curve C
is the spectrum of waveform A, and characteristic curve D is the spectrum of waveform B.

In the examples shown in FIGS. 2 and 3, features appear in f1 and F of the frequency components of waveforms A and B, ~F6.

That is, there is no discernible change in F, and there is a significant increase in F. Other frequency components show slight changes. Therefore, if the frequency band of the band-pass filter 7 in FIG. , the same instantaneous power waveform as curve B is obtained from the multiplier 6, and the frequency component D1 is obtained from the bandpass filter 7I8.
・D, is output, and the difference ΔD is detected via the differential amplifier 9.

The standard deviation amount setter 11 is set with a standard deviation obtained by adding a necessary margin value to the difference ΔC between F, ·F, obtained from the characteristic curve C, and the difference between this standard deviation and the differential amplifier 9 is set. When the detected difference ΔD is compared with the differential amplifier 10, an output signal E is detected. This indicates that the value of frequency component 3 has increased by more than the standard deviation amount ΔC than that of frequency component 1, and indicates that an abnormal state of tool wear has occurred. This signal E can be used for control such as stopping the device, and is also used as a display and alarm for the operator. In the above embodiment, wear of the cutting tool was used as an example of an operating parameter, but it is sufficient to detect in advance in which frequency band a characteristic change occurs for other parameters, and when multiple parameters are combined. The same is true.

When monitoring multiple abnormal operating conditions, it is sufficient to have multiple differential amplifiers that select and combine the outputs of characteristic frequency bands in each abnormal operating condition from each frequency band, and also to use a computer. By dividing into many frequency bands, the characteristics can be made more precise.
Alternatively, waveform analysis of many types of abnormal states can be performed.

(Effects of the Present Invention) As described above, the present invention provides various methods for changing the frequency spectrum distribution of the instantaneous power waveform applied to the drive motor in the standard operating state of a machine or device, and one or more operating parameters. Compare the frequency spectrum distribution of the instantaneous power waveform applied to the 1-drive motor under abnormal operating conditions, and select frequency components that exhibit characteristic changes such as small and large changes for each abnormal operating condition. , extracting the difference between the selected frequency components among the frequency components in the instantaneous power waveform applied to the drive motor in the operating state to be monitored, and establishing a standard according to the difference in the frequency components in the standard rotation state. By comparing the frequency component with the deviation and detecting that the selected frequency component is in an abnormal operating condition by exceeding the standard deviation, abnormal conditions can be monitored during operation without making any changes to the machine or equipment itself. If the characteristics of an abnormal state that have been set in advance are met, the occurrence of the same abnormality is detected, so that appropriate monitoring can be performed.

In addition, a specific frequency component is extracted from the instantaneous power waveform for each cycle during continuous operation, and the number of cycles during continuous operation can be counted.
It is also possible to measure the number of processed products.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a characteristic curve diagram showing an example of an instantaneous power waveform, and FIG. 3 is a frequency spectrum distribution characteristic curve diagram of the waveform shown in FIG. 1 is a drive motor, 2 is a device, 3 is a power supply, 5 is a current transformer, 6
1 is a multiplier, 7 and 8 are band pass filters, 9 and 10 are differential amplifiers, and 11 is a reference deviation amount setter.

Claims (1)

[Claims] 1. The frequency spectrum distribution of the instantaneous power waveform applied to the drive motor in the standard operating state of the machine or device,
By comparing the frequency spectrum distribution of the instantaneous power waveform applied to the drive motor in various abnormal operating states in which one or several operating parameters have changed to an abnormal state, we can determine the characteristic changes for each abnormal operating state. A change in the selected frequency component among the frequency components of the instantaneous power waveform applied to the drive motor in the operating state to be monitored is a change in the frequency component in the abnormal operating state and a change in the frequency component in the abnormal operating state. A method for monitoring operating conditions of machines and devices driven by electric motors, which detects abnormal operating conditions with matching characteristics.