JPH0123267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling equipment that can detect occurrence and suppression of abnormal vibrations caused by various causes such as overload, and can always operate at maximum load.

This applies to machine tools such as lathes, drills, and milling machines, generator rotors, valves in chemical plants, and other equipment that generates abnormal vibrations due to overload, self-excitation, or wear and tear of mechanical parts. Abnormal vibrations can cause product deterioration and, in extreme cases, serious damage to equipment. On the other hand, it is clear that low-load operation without the possibility of abnormal vibrations will lead to a decrease in productivity.

The present invention utilizes the phenomenon that when abnormal vibration occurs, a certain frequency component strongly appears in the vibration waveform (for example, noise) corresponding to the vibration, and the peaks of the vibration waveform appear at approximately the same period. In this case, it is determined that abnormal vibration has occurred, and the load is reduced or operation is stopped. When the peak periodicity of the vibration waveform disappears due to load reduction, it is determined that abnormal vibration has been suppressed and the loaded state is maintained. The purpose of this invention is to obtain a control method for equipment that allows the equipment to be operated at the limit maximum load without causing abnormal vibrations.

A detailed explanation will be given below with reference to the drawings.

FIG. 1 shows a block diagram when the present invention is applied to cutting using a lathe.

A noise signal, which is one of the vibration waveforms of the lathe L, is detected by the microphone MC. This signal may be detected from the device itself, such as the acceleration signal of the bite, but
For example, a detection signal from a cutting tool includes a strong periodic component even before the abnormal vibration occurs, and the determination of when abnormal vibration (chatter vibration) occurs may lack accuracy. However, this signal extraction portion is appropriately selected depending on the application.

The detected signal is amplified, a bandpass filter removes the DC component and high frequency noise, a half-wave rectifier circuit cuts off the negative part, and a second
Only the positive portion shown in the figure is sent to the AD converter. The AD converter digitizes the above signal according to the sampling rate specified by the oscillation circuit, inputs it to the interface, and determines whether chatter vibration is generated or suppressed by the CPU.

The determination of occurrence of chatter vibration is made as follows. The peak point of the signal shown in FIG. 2 is detected as the point where the signal changes from an increasing trend to a decreasing trend.
Then, the time interval between peak point appearances is measured.
The interval between peak points P _o-1 and P _o is D _o-1 , and the peak point P _{o
Let the interval between} Shall have. When a peak having the same period as defined above appears N times in succession, it is determined that chatter vibration has occurred.

Among the above, the optimum values of the allowable ratio Q and the number of times N are determined experimentally. When cutting with a lathe, chatter marks are left on the cutting surface due to chatter vibration. Figure 3 plots the elapsed time from the start of cutting on the vertical axis, and shows how the time when chatter occurs when Q and N are changed compared to the true chatter occurrence time determined from the chatter mark above. An example of how this changes is shown. In the case shown in the figure, the allowable ratio Q is 10≦Q≦20%, and the number of peak interval matches is N.
It turns out that it is better to set it to 4 or 5. It goes without saying that the optimum values of Q and N must be determined for each object to which the present invention is applied.

When chatter vibration occurs as determined above, the CPU outputs a load reduction signal to the lathe control unit, and the lathe control unit reduces the depth of cut until the chatter vibration is suppressed. This reduction in load can be achieved by reducing the feed per tooth in milling, drilling, etc., but when the depth of cut is reduced in a lathe, steps are formed on the cutting surface, so the depth of cut is reduced. It is necessary to store the amount of decrease and its position in memory.

Judgment regarding suppression of chatter vibration is made as follows.

As mentioned above, the interval between two consecutive peak values D _o
Periodicity defined by the above equation is not observed during D _o+1 , and it is determined that chatter vibration is suppressed when such a relationship occurs M times in succession. In the above example, M=8 is experimentally set. When chatter vibration is suppressed, the vibration appears and disappears for a while. Therefore, it is generally required that the periodic component is not repeated a considerable number of times, M=8.

By suppressing this chatter vibration, the CPU issues a stop signal for the load reduction operation to the lathe control unit, maintains this state, and continues subsequent cutting.

In the above operation, if the load must be reduced until cutting becomes impossible, it is determined that an abnormal situation such as tool breakage has occurred, and the operation of the equipment is stopped.

If the target is a lathe, reducing the cutting depth of the cutting tool as described above will result in uncut parts, so after cutting is completed with chatter vibration suppressed as described above, the memorized cutting tool will be A predetermined cutting surface can be obtained by re-cutting at the depth of cut corresponding to the amount of retraction of the cutting tool stored from the retraction position or slightly before the retraction position.

As described above, according to the present invention, by applying the present invention, various types of equipment can be automatically operated at maximum loads without causing abnormal vibrations, resulting in high productivity.

Regardless of the appropriate load, if the equipment is set at the start of operation, such as by cutting the required amount and feeding the maximum bit, the equipment will be automatically reset to the appropriate load, making it easier to handle the equipment.

Since signal detection is performed using a microphone, it is possible to create a versatile and inexpensive control device.

Since it does not put an unreasonable load on the equipment,
Damage to equipment due to overload can be avoided.

It is possible to achieve remarkable effects such as:

[Brief explanation of drawings]

Figure 1 is a block diagram when the present invention is implemented on a lathe, Figure 2 is a waveform diagram of the output signal from the pre-processing circuit, and Figure 3 shows the slowness of judgment depending on the allowable ratio Q and the number of peaks N to sample. It is a diagram.

Claims (1)

[Claims] 1. Detecting a signal corresponding to vibrations such as noise generated by the operation of equipment, detecting a peak of a specific period in the signal waveform, and detecting a peak of a specific period in the signal waveform, and detecting a peak that appears in the same period a certain number of times. 1. A method for controlling equipment, comprising: reducing the load on the equipment when the peak periodicity is lost a certain number of times in succession; 2. Detect a signal corresponding to the vibration that occurs with the operation of the equipment, detect the peak in the signal waveform,
The device is characterized in that when the peak appears a certain number of times in the same period, the load on the device is reduced, and when the periodicity of the peak is still detected even after the load becomes almost zero, the operation of the device is stopped. How to control equipment. 3. In a machine tool, when the noise generated by cutting is detected, the peak of a specific period in the noise is detected, and the peak appears in the same period a certain number of times,
While decreasing the cutting depth, the amount and position of the decrease are memorized, and the reduction in the cutting depth is continued until the periodicity of the peaks is lost a certain number of times in succession, and then the memorized position is A control method for a machine tool, characterized in that cutting is performed again from a slightly earlier position using a memorized amount of decrease in depth of cut as the depth of cut.