JP2012047707A - Vibration detector, vibration suppression device, and vibration information display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration detector for appropriately transmitting waveform data of a frequency region of vibration even when a transfer capability is low.SOLUTION: A vibration detector 5 is applied to a vibration suppression device or the like in machine tools. The vibration detector 5 detects chattering vibration occurring while processing with vibration sensors 2a to 2c and calculates vibration data of a frequency region by performing Fourier transformation operation of signals from the vibration sensors 2a to 2c by Fourier transformation operation means 6. The vibration detector 5 divides vibration data in the frequency region calculated in frequency intervals set by frequency division operation means 9 and, with respect to a plurality of divided frequency ranges, outputs vibration data largest in the respective frequency ranges as vibration data in the frequency interval, and reduces data volume by the frequency division operation means 9.

Description

  The present invention relates to a vibration suppression device used in the field of machine tools, for example, a vibration suppression device mounted on a machine tool that performs processing while moving a tool relative to a workpiece by holding a tool on a rotatable spindle. The present invention relates to an applicable vibration detection device, a vibration suppression device equipped with the vibration detection device, and a vibration information display device.

  The vibration suppression device is a device that suppresses chatter vibration by detecting chatter vibration generated during machining in a machine tool, calculating an optimum rotation speed of the tool from the detected value, and changing the rotation speed.

  FIG. 5 is a block diagram showing a configuration of a conventional vibration suppressing device. FIG. 6 is a view showing the rotary shaft unit 11 to be subjected to vibration suppression from the side, and FIG. 7 is a view showing the rotary shaft unit 11 from the axial direction.

  The vibration suppressing device includes a rotating shaft unit including the rotating shaft 13, vibration sensors 12 a to 12 c, and a control device 15. The vibration sensors 12a to 12c are attached to the rotary shaft unit as shown in FIGS. 6 and 7, and the vibration sensors detect vibration acceleration in a direction perpendicular to the other sensors. For example, the vibration sensors 12a to 12c detect vibration accelerations in the time domain in the X-axis, Y-axis, and Z-axis directions that are orthogonal to each other.

  On the other hand, the control device 15 includes an FFT (Fast Fourier Transform) computing device 20 and a parameter computing device 21.

  The FFT operation device 20 includes an FFT operation means 16. The FFT calculation means converts the vibration acceleration in the time domain detected by the vibration sensors 12a to 12c into the vibration acceleration in the frequency domain, and extracts and outputs the vibration acceleration in the frequency domain and its frequency.

  The parameter calculation device 21 includes parameter calculation means 17 and rotation speed control means 18. The parameter calculation means 17 calculates the optimum rotation speed from the data calculated by the FFT calculation device 20. The rotation speed control means 18 controls the rotation speed of the rotary shaft 13 based on the optimum rotation speed calculated by the parameter calculation means 17.

  The function of the vibration suppression device will be described in detail. For the vibration acceleration signal constantly detected during rotation by the vibration sensors 12a to 12c, the FFT calculation means 16 performs the measurement time data set in advance. Fourier transform is performed, and vibration acceleration in the frequency domain is calculated. Next, the parameter calculation means 17 calculates the optimum rotation speed by performing calculation and comparison using a preset number of tool blades and a threshold value. The rotation speed control means 18 changes the rotation speed of the rotating shaft 13 to the calculated optimum rotation speed. As a result, chatter vibration can be suppressed, and finishing accuracy and machining quality of the machined surface can be improved.

  In actual machining, the machine operator sometimes tunes parameters necessary for automatic suppression control of chatter vibration at the initial stage of machining. In this case, it is necessary for the machine operator to display waveform data in the entire frequency region as judgment information for tuning parameters. However, since data in all frequency regions has a large amount of information and requires a high data transfer capability, the cost increases.

  In addition, to avoid this, instead of transmitting the acceleration for all the obtained frequencies in the frequency domain vibration acceleration, the number of points of Fourier transform is reduced and the acceleration at the frequency with coarse resolution is transmitted. Therefore, a method of reducing the amount of information can be considered. However, this method can only obtain average information in the frequency domain within the resolution, so if there are multiple moderate level accelerations in the frequency domain within the resolution, etc., the order of magnitude of vibration acceleration May be changed and information necessary for control may be lost, resulting in incorrect control.

JP 2003-85157 A

  The present invention has a problem that a high transfer capability is required when transmitting waveform data in the entire frequency range, or in order to avoid this, when applying a method of transmitting data with a jumping frequency, the vibration acceleration is reduced. This solves the problem that the order of size is changed, information necessary for control is lost, and erroneous control is performed.

  In order to achieve the above-mentioned object, the vibration detection device of the present invention detects chatter vibration generated during machining, calculates the optimum rotation speed of the tool from the detected value, and suppresses chatter vibration by changing the rotation speed. In the vibration suppression device, the Fourier transform calculation means for calculating the frequency domain vibration data by performing the Fourier transform calculation of the signal from the vibration sensor, and the calculated frequency domain vibration data is divided into preset frequency intervals. A vibration detection device that serves as a frequency division calculation means for outputting vibration data that is maximum in each of the plurality of divided frequency ranges as vibration data of the frequency interval. Reduce the amount.

  According to the present invention, the vibration acceleration in the frequency domain is calculated from the vibration acceleration in the time domain acquired by the vibration sensor, and is divided by a preset frequency width. Then, the maximum vibration acceleration in the data range from the division point to the next division point is extracted and transferred as vibration acceleration data at the division point. As a result, the amount of data can be reduced without losing information necessary for control.

It is a block block diagram which shows an example of the vibration suppression apparatus which is embodiment of this invention. It is a graph which shows the vibration acceleration data of the frequency domain computed by the FFT calculating means. It is a graph which shows the vibration acceleration data of the frequency domain which performed the frequency division process by this embodiment in the frequency width of 30 Hz. It is a graph which shows the data which extracted the vibration acceleration data of the frequency domain of FIG. 2 for every 30 Hz. It is a block block diagram which shows an example of the conventional vibration suppression apparatus. It is explanatory drawing which showed the rotating shaft unit of FIG. 5 from the side surface. It is explanatory drawing which showed the rotating shaft unit of FIG. 5 from the axial direction.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is an explanatory diagram showing a block diagram of data transfer processing according to the present invention relating to a vibration suppression device for a machine tool.

  The vibration suppression device of this embodiment has a configuration in which frequency division calculation means 9 is added to the FFT calculation device 20 of the conventional vibration suppression device illustrated in FIG. Hereinafter, the changed vibration detection device 5 will be described.

  The vibration detection device 5 includes an FFT calculation means 6 and a frequency division calculation means 9. The FFT calculation means 6 converts the vibration acceleration in the time domain detected from the vibration sensors 2 a to 2 c into vibration acceleration in the frequency domain, and outputs it to the frequency division calculation means 9.

  The frequency division calculation means 9 divides the vibration acceleration in the frequency domain calculated by the FFT calculation means by a preset frequency width. Then, the maximum vibration acceleration in the data range from the division point to the next division point is extracted and transferred to the parameter calculation means 7 as vibration acceleration data at the division point.

  The parameter calculation means 7 calculates the optimum rotation speed from the data transferred from the frequency division calculation means 9. The rotation speed control means 8 controls the rotation speed of the rotary shaft 3 based on the optimum rotation speed calculated by the parameter calculation means 7. The parameter calculation means 7, the rotation speed control means 8, the FFT calculation means 6, and the frequency division calculation means 9 function as a vibration suppressing device that suppresses the vibration of the tool.

  The data display means 10 displays the data transferred to the parameter calculation means 7 on the screen. The data display means 10, the FFT calculation means 6, and the frequency division calculation means 9 function as a vibration information display device that displays vibration data in the frequency domain.

  Hereinafter, the frequency division calculation means 9 will be specifically described. For example, the transfer capability between the vibration detection device 5 and the parameter calculation means 7 is set to 128 bytes / 16 msec.

  The vibration sensors 2a to 2c acquire vibration acceleration of 4096 points (measurement time 204.8 msec) with a data size of 1 point 2 bytes by 20 kHz sampling. The acquired data is converted by the FFT calculation means 6 from vibration acceleration in the time domain to vibration acceleration in the frequency domain from 0 to 7.5 kHz. FIG. 2 is a graph showing an example of the calculated vibration acceleration in the frequency domain. If the calculated vibration acceleration in the frequency domain is to be transferred to the parameter calculation means 7, data of about 3 Kbytes (1536 points) is required, and if all data is transferred as it is, (1536 points) × (2 bytes) / ( 128 bytes / 16 msec) = 384 msec is required.

  Thus, if the total number of data points is reduced to 1536 / 6≈250 points by dividing the frequency division operation means with a frequency width of 30 Hz (data point number of 6 points), (250 points) × (2 bytes) / (128 bytes / All data can be transferred at 16 msec) ≈62.5 msec. A waveform transferred by the frequency division processing according to the present embodiment is shown in FIG. By this processing, as described in the background art section, the method of transmitting acceleration at a jumping frequency, for example, the magnitude of vibration acceleration compared to FIG. 4 in which processing for transferring only data for every 30 Hz is performed. Since the order and waveform are not changed, the amount of data can be reduced without losing information necessary for control.

  Further, there are cases where acceleration at many frequency points is not required, such as a use in which vibration acceleration in the frequency domain is used for display instead of control. In that case, the number of transfer data can be reduced without increasing the order of peaks by further widening the frequency width to be divided.

  Further, the data transferred by the frequency division calculation means 9 of the vibration detection device 5 does not need to be data relating to vibration acceleration. The detected data may be data relating to vibration displacement and speed, and the number of transfer data can be reduced. In this embodiment, the frequency is divided every 30 Hz. However, it is not always necessary to divide every 30 Hz, and the division width may be appropriately changed according to the transfer capability.

  DESCRIPTION OF SYMBOLS 1 Rotating shaft unit, 2a-2c Vibration sensor, 3 Rotating shaft, 5 Vibration detection apparatus, 6 FFT calculating means, 7 Parameter calculating means, 8 Rotational speed control means, 9 Frequency division calculating means, 10 Data display means, 11 Rotating shaft Unit, 12a to 12c Vibration sensor, 13 rotation axis, 15 control device, 16 FFT calculation means, 17 parameter calculation means, 18 rotation speed control means, 20 FFT calculation device, 21 parameter calculation device.

Claims (3)

In the vibration detection device that detects chatter vibration that occurs during machining and serially outputs the detected vibration data to an external device,
Fourier transform calculation means for calculating vibration data in the frequency domain by Fourier-transforming the signal from the vibration sensor;
Divide the calculated frequency domain vibration data into preset frequency intervals, and serially output the vibration data that is the maximum in each of the divided frequency ranges as the vibration data of that frequency interval Frequency division calculation means for
A vibration detection apparatus comprising: Vibration detection means for calculating vibration data in the frequency domain based on a signal from a vibration sensor for detecting the vibration of the tool;
Based on the vibration data detected by the vibration detection means, parameter calculation means for calculating the optimum rotational speed of the tool;
A rotational speed control means for controlling the rotational speed of the tool based on the calculated optimal rotational speed;
The vibration detection means comprises
Fourier transform calculation means for calculating vibration data in the frequency domain by Fourier-transforming the signal from the vibration sensor;
Divide the calculated frequency domain vibration data into preset frequency intervals, and serially output the vibration data that is the maximum in each of the divided frequency ranges as the vibration data of that frequency interval Frequency division calculation means for
A vibration suppressing device comprising: Vibration detection means for calculating vibration data in the frequency domain based on a signal from a vibration sensor for detecting the vibration of the tool;
Display means for displaying vibration data in the frequency domain;
The vibration detecting means includes
Fourier transform calculation means for calculating vibration data in the frequency domain by Fourier-transforming the signal from the vibration sensor;
Divide the calculated frequency domain vibration data into preset frequency intervals, and serially output the vibration data that is the maximum in each of the divided frequency ranges as the vibration data of that frequency interval Frequency division calculation means for
A vibration information display device comprising:

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