JPH0455821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that uses AE signals to detect abnormalities in a tool during cutting.

Conventional devices that use AE signals to detect tool abnormalities generally output an abnormal signal when the peak value of the sudden AE signal exceeds a certain threshold. Because they may be activated by noise caused by collisions of debris or splashes of cutting oil, they have problems such as insufficient accuracy and complicated and expensive equipment, and they can cause damage to small-diameter tools. It could not be economically detected. In addition, the AE signal detected by the sensor is amplified by a preamplifier, and the output signal from the preamplifier is passed through a full-wave rectifier circuit and an averaging processing circuit.
Extracts the average level of the AE signal and outputs a level abnormal signal when the AE average level exceeds the set threshold,
In addition, the signal from the preamplifier is input to the numerator of the divider through a bandpass filter and a full-wave rectifier circuit, and the entire frequency component of the signal from the preamplifier is inputted as the denominator of the divider through the full-wave rectifier circuit to perform division. It is also conceivable to output a frequency abnormality signal when the obtained frequency component ratio exceeds a set threshold, and to determine that a tool abnormality occurs only when both abnormality signals occur simultaneously. Figure 1 is a graph that records the output of the divider and the output of the averaging processing circuit in that case by changing the positions of the sensor and the tool. does not change, but the signal of the averaged processing output becomes smaller as the sensor moves away from the tool. This is AE when the sensor is separated.
This is thought to be due to signal attenuation. Figure 2 shows the frequency analysis results of the AE signal when the distance between the tool and the sensor is about 10 cm. When the sensor is separated, the relative shape, that is, the ratio of frequency components remains the same, but the overall level decreases, and the frequency Although the divider output, which is the ratio of the components, does not change much, it is thought that the averaging processing output, which represents the magnitude of the AE signal, becomes smaller. Therefore, if the position of the sensor is changed, the level abnormality cannot be detected unless the set value of the comparator that compares the output of the divider and the set threshold value is changed.

The present invention aims to solve these problems, and instead of monitoring the level of the AE signal, it monitors the rate of change in the level from normal cutting to abnormal cutting, that is, the rate at which the level increases, and controls the tool. This device attempts to detect abnormalities and is related to a tool abnormality detection device that detects the rising edge of the AE averaged signal and determines tool abnormality by combining it with the frequency component ratio so that it is not affected by changes in the distance between the tool and the sensor. It is. That is, it is composed of a sensor, a preamplifier, a full-wave rectifier circuit, an averaging circuit, a rise detection section, a bandpass filter, a full-wave rectifier circuit, a divider, a comparator, an AND circuit, and an output circuit.

In other words, the signal after the preamplifier and full-wave rectifier circuit is used as the denominator of the divider, and the preamplifier and bandpass filter (about 100K to about 300KHz, or about 100KHz to
500KHz), the signal after the full-wave rectification circuit is input to the divider as the numerator of the divider, and the output of the divider is compared with the set threshold using a comparator to determine the frequency abnormal output.
In addition, the AE average level signal after the preamplifier, full-wave rectification circuit, and averaging processing circuit is input to the rise detection section, and the obtained signal of sudden change in AE level is compared with the set threshold using a comparator to determine the established threshold. When it exceeds , it is regarded as a rising abnormal output, and the frequency abnormal output and the rising abnormal output are input to an AND circuit, and only when both abnormal outputs occur at the same time, it is determined that the tool is abnormal.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, an AE signal is detected by a sensor 1 and amplified by a preamplifier 2 to an appropriate level. As shown in Figure 2, AE is applied during abnormal cutting.
The level is large, about 100K to 300KHz in frequency components
Or, paying attention to the fact that the frequency of about 100K to 500KHz has a large proportion to the whole, and in order to detect this, the signal from the preamplifier 2 is supplied to the AE level rise abnormality detection section and the frequency abnormality detection section.

The level rise abnormality detection section includes a full-wave rectification circuit 3, an averaging processing circuit 4, and a rise detection section 1 which is a differentiation circuit.
3. It consists of a comparator 9, which extracts the average level of the AE signal from the signal from the preamplifier 2 through a full-wave rectifier circuit 3 and an averaging processing circuit 4, and then extracts the average level of the AE signal from the normal cutting state by a rise detection section 13. A sudden change in the averaging level due to transition to abnormal cutting, that is, a rise is detected. The rate of change in this level, that is, the rate at which the level increases, is input to the comparator 9, and when the rate of change exceeds a set threshold, the comparator 9 outputs a rising abnormality signal of the averaged level.

The frequency abnormality detection section is first divided into two systems, a denominator system and a numerator system of the divider 8. For the denominator system, the entire frequency component is inputted as the denominator X of the divider 8 through the full-wave rectifier circuit 5. The molecular system consists of a bandpass filter 6 of about 100K to 300KHz or about 100K to 500KHz and a full-wave rectifier circuit 7. The bandpass filter 6 extracts the necessary frequency components from the signal from the preamplifier 2, and the full-wave rectifier circuit extracts the necessary frequency components from the signal from the preamplifier 2. 7 and input as the numerator Y of the divider 8. The divider 8 is an analog divider and outputs the value of Y/X. Y/X is a frequency component of 100K to 300KHz or 100K to 800KHz
The value is proportional to the ratio of the total level to the total level.
This frequency comparison Y/X is input to a comparator 10, and when the frequency comparison Y/X exceeds a set threshold, the comparator 10 outputs a frequency abnormality signal.

The level rising abnormality signal of the comparator 9 and the frequency abnormality signal of the comparator 10 are connected to the AND circuit 11.
AND circuit 1 is input only when the level rise abnormal signal and frequency abnormal signal occur simultaneously.
1 determines that there is an abnormality and outputs a tool abnormality signal to the output circuit 12, and the output circuit 12 outputs a control signal such as a relay output.

As described above, the present invention includes the full-wave rectifier circuit 3, the averaging circuit 4, the rise detection section 13 which is a differentiating circuit,
A division system in which the AE signal from the preamplifier 2 is inputted by a denominator system consisting of an AE level rise abnormality detection section consisting of a comparator 9 and a full-wave rectifier circuit 5, and a numerator system consisting of a bandpass filter 6 and a full-wave rectifier circuit 7. It is equipped with a frequency abnormality detection section consisting of a detector 8 and a comparator 10, receives a level rise abnormality signal and a frequency abnormality signal from both detection sections, and outputs a tool abnormality signal to an output circuit 12 only when both signals occur simultaneously. Since the output AND circuit 11 is provided, the AE signal rise abnormality detection section is not affected much by changes in the position of the sensor and the tool, but it may react to impact noise such as hitting the machine and the tool It is not possible to reliably detect abnormalities, and an abnormality detector using a divider removes impact noise and is not easily affected by the position of the sensor and the tool, but it cannot completely detect the AE signal generated from chips. Although there are drawbacks that cannot be removed, by using both at the same time, they compensate for the drawbacks and can more reliably detect tool abnormalities without being affected by the sensor and tool positions. There is no error in judgment due to noise caused by droplets, etc., and the circuit configuration is simple. In addition, since the divider output rises and the detector output is not easily affected by the distance between the sensor and the tool as mentioned above, even if the sensor mounting position is changed, there is no need to change the set value to the comparator, reducing setup time. There are advantages such as:

[Brief explanation of the drawing]

Figure 1 is a graph recording the divider output and averaging processing circuit output by changing the sensor and tool positions.
FIG. 2 is a comparison diagram of AE signal levels during normal cutting and abnormal cutting, and FIG. 3 is a block diagram of an embodiment of the present invention. 1...Sensor, 2...Preamplifier, 3...Full wave rectifier circuit, 4...Averaging processing circuit, 5...Full wave rectifier circuit, 6...Band pass filter, 7...Full wave rectifier circuit, 8 ...Divider, 9...Comparator,
10... Comparator, 11... AND circuit, 1
2...Output circuit, 13...Rise detection section.

Claims (1)

[Claims] 1 A sensor that detects an acoustic emission (hereinafter abbreviated as AE) signal, a preamplifier that amplifies the AE signal from the sensor to an appropriate level, a full-wave rectifier circuit that rectifies the signal from the preamplifier, and a full-wave rectifier circuit that rectifies the signal from the preamplifier. AE by inputting the signal from the wave rectifier circuit
an averaging processing circuit that extracts the average level of the signal;
The signal from the averaging processing circuit is input to the rise detection section that detects sudden changes in the averaged AE level, and the signal from the rise detection section is input and compared with a set threshold to determine the rate of change in the AE level. A rising abnormality signal comparator that outputs a rising abnormal signal when a set threshold is exceeded, a denominator full-wave rectifier circuit that detects the entire frequency component from the signal from the preamplifier and outputs it as the denominator X to the divider, and the preamplifier. A bandpass filter extracts the necessary frequency components from approximately 100KHz to 500KHz from the signal, and a bandpass filter detects the signal from the bandpass filter and sends the numerator Y to a divider.
A divider that inputs the signals of the molecule-based full-wave rectifier circuit, the denominator-based full-wave rectifier circuit, and the molecule-based full-wave rectifier circuit that outputs as and the output of a comparator for a frequency abnormal signal and a comparator for a rising abnormal signal, which input the divider signal and compare it with a set threshold, and output a frequency abnormal signal when the frequency component ratio Y/X exceeds the set threshold. and an AND circuit that inputs the output of the comparator for the frequency abnormality signal and outputs a tool abnormality signal when a rising abnormality signal and a frequency abnormality signal occur simultaneously, and an output that inputs the signal from the AND circuit and outputs a control signal. A tool abnormality detection device comprising a circuit.