JPWO2020208685A1 - Numerical control device and method for determining the occurrence of chatter vibration - Google Patents

Abstract

The numerical control device (1) includes a drive command unit (15) that gives an operation command to the spindle (101) and the feed shaft (102) of the machine tool (100), and a tool or a machining object attached to the machine tool (100). A timing signal (207) periodically at a timing synchronized with the rotation of the main shaft (101) and the sensor signal processing unit (11) that generates a plurality of types of state quantities based on the sensor signal (200) that detects the vibration of ) Is generated and output for each timing signal (207), and a non-dimensional quantity indicating a plurality of types of state quantities in the state space is generated for each timing signal (207), and between the phases of the non-dimensional quantity. A phase difference calculation unit (12) that calculates the phase difference information (203) indicating the difference, and a vibration determination unit (12) that determines the occurrence of chatter vibration in the machine tool (100) based on the variation of the phase difference information (203). 13) and.

Description

The present invention relates to a numerical control device for determining the occurrence of chatter vibration in a machine tool and a method for determining the occurrence of chatter vibration.

There are machine tools that remove the object to be machined into a desired shape by changing the relative position between the object to be machined and the tool. Machine tools such as milling machines and lathes mount tools or objects to be machined on the spindle and rotate the spindle to perform machining. During processing, vibration called "chatter vibration" may occur. When chatter vibration occurs, the accuracy of the finished surface deteriorates and the tool may be damaged.

In Patent Document 1, vibration is measured twice at predetermined time intervals during processing, and the second measurement result has a larger amplitude in the frequency domain and a phase in the frequency domain as compared with the first measurement result. Disclosed is a method of determining that chatter vibration has occurred when the values are different.

Japanese Unexamined Patent Publication No. 2013-7647

However, the technique described in Patent Document 1 has a problem that it takes a long time to determine the presence or absence of chatter vibration during processing. Specifically, in the technique described in Patent Document 1, frequency analysis is used for vibration analysis. Frequency analysis such as FFT (Fast Fourier Transform) has a restriction that the frequency resolution ΔF is inversely proportional to the data acquisition time T due to its calculation algorithm. Therefore, in order to obtain a frequency resolution ΔF sufficient for determining chatter vibration, the data acquisition time becomes long. Further, in the technique described in Patent Document 1, since it is necessary to perform the measurement twice at a predetermined time, the time for measuring the vibration during processing becomes long.

The present invention has been made in view of the above, and an object of the present invention is to obtain a numerical control device capable of shortening the time required for determining chatter vibration.

In order to solve the above-mentioned problems and achieve the object, the numerical control device according to the present invention includes a drive command unit that gives an operation command to the spindle and the feed shaft of the machine tool, and a tool or a machining object attached to the machine tool. A sensor signal processing unit that generates multiple types of state quantities based on the sensor signal that detects the vibration of the spindle, and a timing signal generation unit that periodically generates and outputs a timing signal at a timing synchronized with the rotation of the spindle. , A phase difference calculation unit that generates a non-dimensional quantity indicating a plurality of types of state quantities in the state space for each timing signal and calculates the phase difference information indicating the difference between the phases of the non-dimensional quantity, and the phase difference information. It is characterized by including a vibration determination unit for determining the occurrence of chatter vibration in a machine tool based on the variation of the above.

According to the present invention, there is an effect that the time required for determining the chatter vibration can be shortened.

The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 1 of this invention. The figure for demonstrating the filter characteristic of the filter processing part shown in FIG. The figure which shows the relationship between the timing signal output by the timing signal generation part shown in FIG. 1 and the angle command of a spindle. The figure which shows the dimensionless quantity calculated by the phase difference calculation part shown in FIG. The figure which shows an example of the transition of the phase difference calculated by the phase difference calculation unit shown in FIG. 1 when chatter vibration occurs. The figure which shows an example of the transition of the phase difference calculated by the phase difference calculation unit shown in FIG. 1 when chatter vibration does not occur. It is an experimental result when chatter vibration occurs, and is a diagram showing the waveform of acceleration generated during machining. The figure which shows the phase difference of the dimensionless quantity obtained from the experimental result shown in FIG. It is an experimental result when chatter vibration does not occur, and is a diagram showing the waveform of acceleration generated during machining. The figure which shows the phase difference of the dimensionless quantity obtained from the experimental result shown in FIG. The figure which shows the 1st example for demonstrating the process of the vibration determination part shown in FIG. The figure which shows the 2nd example for demonstrating the process of the vibration determination part shown in FIG. The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 2 of this invention. The figure which shows the 1st example of the relationship between the timing signal output by the timing signal generation part shown in FIG. 13 and the angle command of a spindle. The figure which shows the 2nd example of the relationship between the timing signal output by the timing signal generation part shown in FIG. 13 and the angle command of a spindle. The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 3 of this invention. The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 4 of this invention. The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 5 of this invention. The figure which shows the functional structure of the numerical control apparatus which concerns on Embodiment 6 of this invention. The figure which shows the dedicated hardware for realizing the function of the numerical control apparatus which concerns on Embodiments 1-6 of this invention. The figure which shows the structure of the control circuit for realizing the function of the numerical control apparatus which concerns on Embodiment 1-6 of this invention.

Hereinafter, the numerical control device and the method for determining the occurrence of chatter vibration according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a functional configuration of the numerical control device 1 according to the first embodiment of the present invention. The numerical control device 1 numerically controls the machine tool 100 by giving an operation command 208 to the machine tool 100.

The machine tool 100 has a spindle 101 and a feed shaft 102 having a motor driven by an operation command 208. In the present embodiment, the object to be machined is installed on the spindle 101, and the tool is installed on the feed shaft 102. Further, the machine tool 100 outputs operation information 209 including at least the positions, speeds, and motor currents of the spindle 101 and the feed shaft 102 to the numerical control device 1. In this embodiment, the number of blades of the tool is one.

A sensor 103 is attached to the machine tool 100. The sensor 103 outputs a sensor signal 200 that detects the vibration of the tool or the object to be machined to the numerical control device 1. The sensor 103 is attached to the structure of the spindle 101 or the feed shaft 102 of the machine tool 100. The position where the sensor 103 is attached may be any position where vibration of the tool or the object to be machined can be detected, and is preferably near the point where the tool and the object to be machined come into contact with each other. The type of the sensor 103 may be any sensor capable of detecting the vibration of the tool or the object to be machined, and the sensor 103 is, for example, a displacement sensor, a speed sensor, an acceleration sensor, an angular velocity sensor, or the like. Further, the sensor 103 may be a force sensor that detects a cutting reaction force or a microphone that detects a cutting sound during machining. Alternatively, instead of the sensor 103, at least one of the positions, speeds, and motor currents of the spindle 101 and the feed shaft 102 included in the operation information is used to detect the vibration of the tool or the object to be machined during machining. Then, information indicating the detected vibration may be output as the sensor signal 200.

The numerical control device 1 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. And have.

The drive command unit 15 receives the operation information 209 from the machine tool 100, outputs the operation command 208 to the machine tool 100 based on the operation information 209, and outputs the spindle operation command 206 to the timing signal generation unit 16. Further, the drive command unit 15 corrects the operation command 208 based on the correction signal 205 output by the command value correction unit 14 described later. The operation command 208 includes at least one of an angle command and a speed command of the spindle 101 of the machine tool 100, and at least one of a position command and a speed command of the feed shaft 102. Further, the spindle operation command 206 includes at least one of an angle command and a speed command of the spindle 101.

The filter processing unit 10 filters the sensor signal 200 output by the machine tool 100 to generate a chatter vibration component signal 201, and outputs the generated chatter vibration component signal 201 to the sensor signal processing unit 11. The filter processing unit 10 removes the cutting component from the sensor signal 200.

FIG. 2 is a diagram for explaining the filter characteristics of the filter processing unit 10 shown in FIG. The horizontal axis of FIG. 2 indicates the frequency, and the vertical axis indicates the amplitude. FIG. 2 shows a chatter vibration component, a cutting component, and a filter pass band in the frequency domain. The cutting component is mainly a vibration component having a frequency obtained by multiplying the spindle rotation speed by the number of blades of the tool, and a harmonic component thereof. The filter processing unit 10 removes a band containing each cutting component with a predetermined bandwidth. For example, the predetermined bandwidth can be about several Hz in the vicinity of the cutting component. The filter processing unit 10 can be designed by using a known bandpass filter, notch filter, combination of a plurality of bandpass filters, a combination of a plurality of notch filters, a comb-shaped filter, and the like. By using the passband filter shown in FIG. 2, the filter processing unit 10 can remove the cutting component from the sensor signal 200 to generate the chatter vibration component signal 201.

Returning to the description of FIG. The sensor signal processing unit 11 generates a plurality of types of state quantities based on the sensor signal 200, and outputs a state quantity signal 202 indicating the generated plurality of types of state quantities to the phase difference calculation unit 12. Specifically, the sensor signal processing unit 11 generates a state quantity signal 202 based on the chatter vibration component signal 201 output by the filter processing unit 10. The state quantity signal 202 includes a first state quantity and a second state quantity. For example, the first state quantity is the chatter vibration component signal 201, and the second state quantity is the state quantity obtained by time-differentiating the chatter vibration component signal 201 once. The sensor signal processing unit 11 simultaneously converts the chatter vibration component signal 201 and the chatter vibration component signal 201 into a state quantity signal 202 as a time-series signal.

The difference in the number of times of time differentiation between the first state quantity and the second state quantity may be any combination as long as it is an odd number. For example, it is assumed that the first state quantity is the state quantity obtained by time-differentiating the chatter vibration component signal 201 P times, and the second state quantity is the state quantity obtained by time-differentiating the chatter vibration component signal 201 Q times. Here, P and Q are integers. In this case, the difference between P and Q may be an odd number. Further, the dimensions of the first state quantity and the second state quantity may be the dimensions obtained by time-integrating the chatter vibration component signal 201. As a specific example, the first state quantity may be the acceleration and the second state quantity may be the velocity. Alternatively, the first state quantity may be a jerk which is a differential value of acceleration, and the second state quantity may be a position. The sensor signal processing unit 11 has, for example, two or more types of state quantities of the sensor signal 200, the state quantity obtained by time-differentiating the sensor signal 200, and the state quantity obtained by time-integrating the sensor signal. Can be generated.

When the timing signal generation unit 16 determines that the angle command of the spindle 101 has passed a predetermined angle based on the spindle operation command 206 output by the drive command unit 15, the timing signal generation unit 16 outputs the timing signal 207 to the phase difference calculation unit 12. To do. The details of the method of generating the timing signal 207 will be described.

FIG. 3 is a diagram showing the relationship between the timing signal 207 output by the timing signal generation unit 16 shown in FIG. 1 and the angle command of the spindle 101. The angle command of the spindle 101 is included in the spindle operation command 206 output by the drive command unit 15. In FIG. 3, the angle command is a signal that takes a value of 0 to 360 degrees and returns to 0 degrees when it reaches 360 degrees. The timing signal generation unit 16 outputs a timing signal 207 each time the angle command of the spindle 101 passes a predetermined angle ψ1. As a result, the timing signal 207 is periodically output at a timing synchronized with the rotation of the spindle 101 of the machine tool 100. The angle ψ1 may be any angle as long as it is determined at one point during one rotation of the spindle 101, and may be, for example, the angle ψ1 of the spindle 101 at the time of orientation of the spindle 101. The spindle orientation is a reference angle at which the spindle 101 is stopped.

Alternatively, the timing signal generation unit 16 can also generate the timing signal 207 by using the speed command of the spindle 101 included in the spindle operation command 206. In this case, the timing signal generation unit 16 outputs the timing signal 207 for each time T1 calculated from the speed command S (rpm) of the spindle 101 using the following mathematical formula (1) with the initial time t0 as the reference time. To do. Further, the timing signal generation unit 16 may use the angle command and the speed command of the spindle 101 together. Here, the timing signal generation unit 16 uses the operation command of the spindle 101 to generate the timing signal 207, but instead of the operation command of the spindle 101 or in addition to the operation command of the spindle 101. , The timing signal 207 may be generated by using the operation command of the feed shaft 102.

The phase difference calculation unit 12 receives the timing signal 207 output by the timing signal generation unit 16 and the state quantity signal 202 output by the sensor signal processing unit 11. The phase difference calculation unit 12 generates a dimensionless quantity indicating a plurality of types of state quantities in the state space based on the timing signal 207 and the state quantity signal 202 for each timing signal 207, and interphases the dimensionless quantity. The phase difference information 203 indicating the difference between the above is calculated. The phase difference calculation unit 12 outputs the generated phase difference information 203 to the vibration determination unit 13.

The phase difference calculation unit 12 normalizes each of the plurality of state quantities included in the state quantity signal 202. The phase difference calculation unit 12 normalizes each state quantity by dividing each state quantity by a predetermined maximum value of each state quantity. The maximum value used here may be the maximum value of each state quantity obtained in the prior machining experiment, or may be the maximum value of each state quantity obtained in the prior simulation.

It is assumed that the phase difference calculation unit 12 receives the timing signal 207 at time t1 and time t2. At this time, t2 is set to a value larger than t1. The phase difference calculation unit 12 normalizes the state quantity signal 202 at time t1, and sets the normalized value as the first dimensionless quantity N1. At time t2, the phase difference calculation unit 12 normalizes the state quantity signal 202 in the same manner as at time t1, and sets the normalized value as the second dimensionless quantity N2.

FIG. 4 is a diagram showing a dimensionless quantity calculated by the phase difference calculation unit 12 shown in FIG. FIG. 4 shows the first dimensionless quantity N1 and the second dimensionless quantity N2 calculated by the phase difference calculation unit 12 as the dimension of the first dimensionless quantity of the state quantity signal 202 and the second state quantity. It is represented in the state space consisting of the dimensions of. The phase difference calculation unit 12 sets an angle θ formed by the first dimensionless quantity N1 which is the previous dimensionless quantity, the origin of the state space, and the second dimensionless quantity N2 which is the current dimensionless quantity. It is calculated as the phase difference between the first dimensionless quantity N1 and the second dimensionless quantity N2. The phase difference calculation unit 12 performs the above calculation for each timing signal 207, and calculates the phase difference between the latest dimensionless quantity and the previous dimensionless quantity. The phase difference calculation unit 12 outputs the phase difference information 203 indicating the calculated phase difference to the vibration determination unit 13.

FIG. 5 is a diagram showing an example of the transition of the phase difference calculated by the phase difference calculation unit 12 shown in FIG. 1 when chatter vibration is generated. The dimensionless quantities N10 to N13 are dimensionless quantities calculated at each time t10 to t13 when the timing signal 207 is received. At this time, t13> t12> t11> t10. Further, the angle θ10 indicates the angle formed by the dimensionless quantity N10, the origin of the state space, and the dimensionless quantity N11, and the angle θ11 indicates the angle formed by the dimensionless quantity N11, the origin of the state space, and the dimensionless quantity N12. The angle θ12 indicates the angle formed by the dimensionless quantity N12, the origin of the state space, and the dimensionless quantity N13.

When chatter vibration occurs, the loci of the dimensionless quantities N10 to N13 in the state space become circular, and the angle between the dimensionless quantities becomes constant. Therefore, the angle θ at each time when the timing signal 207 is received is constant.

FIG. 6 is a diagram showing an example of the transition of the phase difference calculated by the phase difference calculation unit 12 shown in FIG. 1 when chatter vibration does not occur. The dimensionless quantities N20 to N23 are dimensionless quantities calculated at each time t20 to t23 when the timing signal 207 is received. At this time, t23> t22> t21> t20. Further, the angle θ20 indicates the angle formed by the dimensionless quantity N20, the origin of the state space, and the dimensionless quantity N21, and the angle θ21 indicates the angle formed by the dimensionless quantity N21, the origin of the state space, and the dimensionless quantity N22. The angle θ22 indicates the angle formed by the dimensionless quantity N22, the origin of the state space, and the dimensionless quantity N23.

When chatter vibration does not occur, the angle between the locus of the dimensionless quantities N20 to N23 in the state space and the angular dimensionless quantity becomes irregular. Therefore, the angle θ at each time when the timing signal 207 is received is not constant.

Therefore, the phase difference calculation unit 12 calculates a constant value angle θ, that is, a phase difference when chatter vibration occurs, and an irregular value angle θ, that is, when chatter vibration does not occur. The phase difference will be calculated.

Here, the experimental results for confirming the difference in the angle θ depending on the presence or absence of chatter vibration will be described. In this experiment, a round bar of S45C, which is a carbon steel material, was installed on a chuck of a general CNC (Computer Numerical Control) lathe, and the outer circumference of the round bar was machined by turning. A cemented carbide tool was used as the tool, and the acceleration during machining was measured by installing an acceleration sensor on the tool.

Machining conditions when chatter vibration occurs are spindle speed 2000 (RPM), feed per blade 0.1 (mm), radial depth cut 1.0 (mm), and workpiece protrusion amount 200 (mm) from the chuck. Is.

FIG. 7 is an experimental result when chatter vibration occurs, and is a diagram showing a waveform of acceleration generated during machining. FIG. 8 is a diagram showing a phase difference of a dimensionless quantity obtained from the experimental results shown in FIG. 7. In this experiment, the filter processing unit 10, the sensor signal processing unit 11, the timing signal generation unit 16, and the phase difference calculation unit 12 process the acceleration data output by the acceleration sensor as the sensor signal 200, so that the dimensionless unit shown in FIG. 8 is absent. The dimensionless quantity and the angle θ were calculated.

First, the filter processing unit 10 removed 2000/60 = 33.3 (Hz) and a cutting component composed of its harmonics from the acceleration data based on the spindle speed. Next, the sensor signal processing unit 11 calculates and outputs a state quantity signal 202 having the first state quantity as acceleration and the second state quantity as velocity. The velocity, which is the second state quantity, was obtained by integrating the acceleration.

The timing signal generation unit 16 outputs a timing signal 207 each time the angle command of the spindle 101 passes the spindle angle at the time of spindle orientation. The phase difference calculation unit 12 normalized the state quantity signal 202 and calculated the dimensionless quantities N101 to N106 at each time t101 to t106 when each timing signal 207 was received. Here, t106> t105> t104> t103> t102> t101.

FIG. 8 shows dimensionless quantities N101 to N106 in the state space. The angle θ101 indicates the angle formed by the dimensionless quantity N101, the origin of the state space, and the dimensionless quantity N102, and the angle θ102 indicates the angle formed by the dimensionless quantity N102, the origin of the state space, and the dimensionless quantity N103. The angle θ103 indicates the angle formed by the dimensionless quantity N103, the origin of the state space, and the dimensionless quantity N104. The angle θ104 indicates the angle formed by the dimensionless quantity N104, the origin of the state space, and the dimensionless quantity N105, and the angle θ105 indicates the angle formed by the dimensionless quantity N105, the origin of the state space, and the dimensionless quantity N106. The angles θ101 to θ105 are constant. From the above experimental results, it is experimentally shown that when chatter vibration occurs, the locus of dimensionless quantity in the state space becomes circular, and the angles θ101 to θ105 at each time take a constant value. It was.

Subsequently, the machining conditions when chatter vibration does not occur are: spindle speed 2000 (RPM), feed 0.1 (mm) per blade, radial depth cut 1.0 (mm), and workpiece protrusion amount 100 from the chuck. (Mm).

FIG. 9 is an experimental result when chatter vibration does not occur, and is a diagram showing a waveform of acceleration generated during machining. FIG. 10 is a diagram showing a phase difference of a dimensionless quantity obtained from the experimental results shown in FIG. Also in this experiment, the filter processing unit 10, the sensor signal processing unit 11, the timing signal generation unit 16, and the phase difference calculation unit 12 process the acceleration data output by the acceleration sensor as the sensor signal 200, and are shown in FIG. The dimensionless quantity and the angle θ were calculated.

First, the filter processing unit 10 removed 2000/60 = 33.3 (Hz) and a cutting component composed of its harmonics from the acceleration data based on the spindle speed. Next, the sensor signal processing unit 11 calculates and outputs a state quantity signal 202 having the first state quantity as acceleration and the second state quantity as velocity. The velocity, which is the second state quantity, was obtained by integrating the acceleration.

The timing signal generation unit 16 outputs a timing signal 207 each time the angle command of the spindle 101 passes the spindle angle at the time of spindle orientation. The phase difference calculation unit 12 normalized the state quantity signal 202 and calculated the dimensionless quantities N201 to N206 at each time t201 to t206 when each timing signal 207 was received. Here, t206> t205> t204> t203> t202> t201.

FIG. 10 shows dimensionless quantities N201 to N206 in the state space. The angle θ201 indicates the angle formed by the dimensionless quantity N201, the origin of the state space, and the dimensionless quantity N202, and the angle θ202 indicates the angle formed by the dimensionless quantity N202, the origin of the state space, and the dimensionless quantity N203. The angle θ203 indicates the angle formed by the dimensionless quantity N203, the origin of the state space, and the dimensionless quantity N204. The angle θ204 indicates the angle formed by the dimensionless quantity N204, the origin of the state space, and the dimensionless quantity N205, and the angle θ205 indicates the angle formed by the dimensionless quantity N205, the origin of the state space, and the dimensionless quantity N206. From the above experimental results, it is experimentally shown that when chatter vibration does not occur, the locus of dimensionless quantity in the state space is irregular, and the angles θ201 to θ205 at each time take indefinite values. It was.

Returning to the description of FIG. The vibration determination unit 13 receives an angle θ, which is a phase difference, from the phase difference calculation unit 12, and determines chatter vibration using the procedure shown below. The vibration determination unit 13 determines whether or not chatter vibration has occurred based on the phase difference information 203 calculated by the phase difference calculation unit 12. When it is determined that chatter vibration has occurred, the vibration determination unit 13 outputs the vibration determination information 204 to the command value correction unit 14. The details of the vibration determination unit 13 will be described.

The vibration determination unit 13 records the phase difference information 203 output by the phase difference calculation unit 12. This recording is repeated every time the phase difference information 203 is received, and the angle θ included in the phase difference information 203 is recorded as time series data.

Further, the vibration determination unit 13 calculates the difference of the recorded angle θ, and if the difference of the angle θ is less than a predetermined threshold value, determines that chatter vibration has occurred, and uses the vibration determination information 204 as a command value. Output to the correction unit 14. Here, the threshold value used by the vibration determination unit 13 will be described. Here, it is assumed that the phase difference calculation unit 12 outputs the angle θ in the range of ± 180 degrees. When chatter vibration does not occur, the angle θ takes an indefinite value in the range of ± 180 degrees, so the difference in angle θ takes a value of ± 360 degrees. Further, when chatter vibration occurs, the angle θ takes a constant value, so that the difference between the angles θ becomes zero. However, the actual angle θ includes an error due to a measurement error or the like. Therefore, if the threshold value is set to a value sufficiently larger than the error of the angle θ, the presence or absence of chatter vibration can be determined. For example, when the error of the angle θ is ± 10 degrees, the threshold value may be a value larger than 20 degrees, for example, 30 degrees.

Alternatively, the vibration determination unit 13 calculates the standard deviation of the angle θ included in the plurality of phase difference information 203 repeatedly received, and when the standard deviation of the angle θ is less than a predetermined threshold value, chatter vibration occurs. Judge that there is. FIG. 11 is a diagram showing a first example for explaining the processing of the vibration determination unit 13 shown in FIG. The vibration determination unit 13 calculates the standard deviation using the angle θ acquired between the time t3 and the time t4, and determines the presence or absence of chatter vibration. In the first example shown in FIG. 11, the standard deviation of the angle θ exceeds the threshold of the standard deviation. Therefore, the vibration determination unit 13 can determine that chatter vibration has not occurred. Further, FIG. 12 is a diagram showing a second example for explaining the processing of the vibration determination unit 13 shown in FIG. In the second example shown in FIG. 12, the standard deviation of the angle θ is below the threshold of the standard deviation. Therefore, the vibration determination unit 13 can determine that chatter vibration has occurred.

How to determine the standard deviation threshold will be described. When chatter vibration occurs, the angle θ takes a constant value, so the difference between the angles θ becomes zero. However, the actual angle θ has an error due to a measurement error or the like. Therefore, by setting the threshold value to a value sufficiently larger than the error included in the angle θ, it is possible to determine the presence or absence of chatter vibration. For example, when the error of the angle θ is ± 10 degrees, the threshold value of the standard deviation can be a value larger than 10 degrees, for example, 20 degrees.

Further, as another example, the vibration determination unit 13 may determine the presence or absence of chatter vibration by using the dispersion of the angle θ instead of the standard deviation of the angle θ included in the plurality of phase difference information 203 repeatedly received. it can. In this case as well, the variance threshold can be determined in the same manner as in the case of the standard deviation.

As yet another example, the vibration determination unit 13 may determine chatter vibration by using the difference between the maximum value and the minimum value of the angle θ. In this case, the vibration determination unit 13 calculates the difference between the maximum value and the minimum value of the angle θ received during the period of the predetermined length, and the calculated difference between the maximum value and the minimum value is predetermined. If it is smaller than the threshold value, it can be determined that chatter vibration is occurring.

When the command value correction unit 14 receives the vibration determination information 204 from the vibration determination unit 13, the command value correction unit 14 outputs a correction signal 205 instructing the drive command unit 15 to change the operation command 208. The correction signal 205 is a signal that changes the speed command of the spindle 101 by a predetermined ratio corresponding to the current spindle speed.

Alternatively, the correction signal 205 may be a signal for changing the rotation speed of the spindle 101 so that the rotation speed of the spindle 101 matches an integral fraction of the resonance frequency of the mechanical structure calculated in advance by finite element analysis. .. As the resonance frequency of the mechanical structure, a value identified by a preliminary experiment may be used instead of the finite element analysis.

Further, the correction signal 205 may be a signal that changes the speed command location of the feed shaft 102 by a predetermined ratio. Specifically, the correction signal 205 can be a signal that reduces the speed command value of the feed shaft 102 so that the motor current of the feed shaft 102 becomes smaller than a predetermined reference value.

As described above, according to the first embodiment of the present invention, time series data of a plurality of types of state quantities are obtained based on the sensor signal 200 that detects the vibration of the tool or the object to be machined attached to the machine tool 100. Is generated. Then, in the state space, a dimensionless quantity indicating a plurality of types of state quantities is generated for each timing signal 207, and phase difference information indicating an angle θ which is a difference between the phases of the dimensionless quantity is calculated. Based on this variation in the phase difference information, the occurrence of chatter vibration in the machine tool 100 is determined.

Since the numerical control device 1 does not use frequency analysis typified by FFT for determining chatter vibration, it is possible to obtain sufficient frequency resolution for determining chatter vibration without being restricted by the data acquisition time. Therefore, the time required for determining the chatter vibration, that is, the time from the occurrence of the chatter vibration to the determination of the occurrence of the chatter vibration can be shortened. Therefore, the time from the occurrence of the chatter vibration to the suppression of the chatter vibration is shortened, and the chatter vibration can be suppressed at high speed.

Further, the numerical control device 1 determines the chatter vibration based on the phase difference information 203 which is a dimensionless quantity. As a conventional method, for example, there is a method of determining chatter vibration based on the amplitude of chatter vibration. When the amplitude of chatter vibration is used, the magnitude of the amplitude differs depending on the machining conditions, so that the amplitude threshold value must be set according to the machining conditions. On the other hand, in the numerical control device 1 that determines the chatter vibration based on the phase difference information 203 which is a dimensionless quantity, the chatter vibration can be determined without depending on the machining conditions, and the threshold value is determined according to the machining conditions. There is no need to provide.

The machine tool 100 according to the first embodiment has a configuration in which an object to be machined is installed on the spindle 101, but it is a case where a tool is installed on the spindle 101, for example, as represented by a milling machine and a turning machine. Can produce the same effect.

Further, in the first embodiment, one sensor 103 is used, but the sensors 103 may be installed at a plurality of locations of the machine tool 100. In this case, all the installed sensors 103 can be subjected to the process described in the first embodiment to determine the occurrence of chatter vibration. When the sensors 103 are installed at a plurality of locations, even if chatter vibration occurs at the plurality of locations during processing, the chatter vibration can be determined and suppressed.

The sensor 103 installed in the machine tool 100 may detect vibration using two or more types of sensors 103 and output a sensor signal 200 including two or more types of state quantities to the filter processing unit 10. In this case, the sensor signal processing unit 11 can set the two types of sensor outputs as the first state quantity and the second state quantity, respectively. By directly measuring the second state quantity with the sensor 103, it is possible to determine the chatter vibration without being affected by the quantization error associated with the differentiation or integration.

In the first embodiment, the sensor signal processing unit 11 extracts two types of state quantities, but three or more types of state quantities may be extracted.

Embodiment 2.
In the first embodiment, an example in which the number of blades of the tool is one has been described. In the second embodiment, a configuration for determining the occurrence of chatter vibration when the number of blades of the tool is two or more will be described.

FIG. 13 is a diagram showing a functional configuration of the numerical control device 2 according to the second embodiment of the present invention. The numerical control device 2 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. It has a -1 and a tool information recording unit 17.

The numerical control device 2 has a tool information recording unit 17 that outputs tool information 210 in addition to the configuration of the numerical control device 1 according to the first embodiment, and replaces the timing signal generation unit 16 of the numerical control device 1. , Has a timing signal generation unit 16-1. Hereinafter, the parts different from the numerical control device 1 will be mainly described.

The tool information recording unit 17 records the tool information 210, which is information about the tool installed in the machine tool 100, and outputs the recorded tool information 210 to the timing signal generation unit 16-1. The tool information 210 includes at least information indicating the number of blades of the tool. Further, the tool information 210 may include information indicating a tool shape such as a tool type such as an end mill and a tool bit, a tool length, and a tool diameter. When one turning tool is attached to the machine tool 100, the tool information recording unit 17 outputs tool information 210 indicating that the number of blades of the tool is one. Further, even when a turning tool is attached to the machine tool 100, when a plurality of tools are cutting at the same time, the number of blades is the same as the number of tools. For example, when the machine tool 100 has a lower tool post and an upper tool post, and machining is performed with a turning tool attached to both tool stands one by one, the tool information recording unit 17 has two blades. The tool information 210 indicating that is output.

The timing signal generation unit 16-1 determines that the spindle angle has passed a predetermined angle based on the spindle operation command 206 output by the drive command unit 15 and the tool information 210 output by the tool information recording unit 17. , The timing signal 207 is output to the phase difference calculation unit 12 at the determined timing.

The details of the processing of the timing signal generation unit 16-1 will be described. Hereinafter, a case where a tool having α blades is attached to the spindle 101 will be described. α is a natural number of 2 or more.

First, the case of α = 2 will be described. FIG. 14 is a diagram showing a first example of the relationship between the timing signal 207 output by the timing signal generation unit 16-1 shown in FIG. 13 and the angle command of the spindle 101. The angle command is a signal that takes a value between 0 degrees and 360 degrees and returns to 0 degrees when it reaches 360 degrees. The timing signal 207 is output each time the angle command of the spindle 101 passes through a plurality of predetermined angles, the angle ψ1 and the angle ψ2. That is, the timing signal 207 is output twice, which is the same number as the number of blades, while the spindle 101 makes one rotation. The angle ψ1 may be any angle as long as it is set to 1 during one rotation of the spindle 101. For example, the angle ψ1 can be the spindle angle at the time of spindle orientation. Further, the difference between the angle ψ1 and the angle ψ2 is a value obtained by dividing 360 degrees by 2 of the number of tool blades, and ψ2-ψ1 = 180 degrees.

Next, a case where α is an arbitrary natural number will be described. FIG. 15 is a diagram showing a second example of the relationship between the timing signal 207 output by the timing signal generation unit 16-1 shown in FIG. 13 and the angle command of the spindle 101. The timing signal 207 is output each time the angle command of the spindle 101 _{passes through a predetermined angle ψ β.} β is a natural number of 2 or more and α or less. The timing signal 207 is output α times while the spindle 101 makes one rotation. ψ1 may be any angle as long as it is set to 1 during one rotation of the spindle 101. There is a constraint shown in the following mathematical formula (2) between ψ1 and ψβ-1. In other words, the timing signal generation unit 16-1 outputs a timing signal 207 each time the spindle 101 rotates by an angle obtained by dividing 360 degrees by the number of blades α.

The timing signal generation unit 16-1 may generate the timing signal 207 by using the speed command of the spindle 101 included in the spindle operation command 206. In this case, the timing signal generation unit 16-1 generates the timing signal 207 for each time T2 calculated from the speed command S (rpm) of the spindle 101 using the following mathematical formula (3).

As described above, according to the second embodiment of the present invention, since the timing signal 207 is generated based on the tool information 210, there is a case where the number of blades of the tool attached to the machine tool 100 is a plurality. Also, as in the first embodiment, the time required for determining the chatter vibration, that is, the time from the occurrence of the chatter vibration to the determination of the occurrence of the chatter vibration can be shortened.

When the number of blades is 1, the numerical control device 2 can determine and suppress chatter vibration by the same processing as the numerical control device 1.

Embodiment 3.
FIG. 16 is a diagram showing a functional configuration of the numerical control device 3 according to the third embodiment of the present invention. The numerical control device 3 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. It has -2 and. The numerical control device 3 has a timing signal generation unit 16-2 instead of the timing signal generation unit 16 of the numerical control device 1. Hereinafter, the parts different from the numerical control device 1 will be mainly described.

The machine tool 100 has an angle information sensor 104 attached to the spindle 101 in addition to the configuration described in the first embodiment. The angle information sensor 104 is a sensor that measures the spindle angle, and for example, an encoder, a potentiometer sensor, or the like can be used. The angle information 211 is a signal including at least an actually measured value of the spindle angle measured by the angle information sensor 104. The angle information sensor 104 outputs the generated angle information 211 to the numerical control device 3.

The timing signal generation unit 16-2 generates the timing signal 207 based on the actually measured value of the spindle angle included in the angle information 211. The method in which the timing signal generation unit 16-2 generates the timing signal 207 is the same as that in the first embodiment, but the measured value of the spindle angle is used instead of the angle command of the spindle 101.

The angle information sensor 104 may be a sensor that detects the measured value of the spindle speed. In this case, the angle information sensor 104 is an angular velocity sensor. The timing signal generation unit 16-2 can generate the timing signal 207 based on the measured value of the spindle speed instead of the angle command of the spindle 101. The timing signal generation unit 16-2 sets the timing signal 207 for each time T3 calculated from _{the measured value S ref} (rpm) of the spindle speed using the following mathematical formula (4) with the initial time t0 as the reference time. Output.

As described above, according to the third embodiment of the present invention, the timing signal 207 is generated based on the measured value of the spindle angle. Therefore, the timing signal 207 can be generated without being affected by the control tracking error that occurs between the angle command of the spindle 101 and the actual angle. Therefore, the numerical control device 3 is the time required for determining the chatter vibration, that is, even when a control tracking error occurs between the angle command of the spindle 101 and the actual angle, as in the first embodiment. It is possible to shorten the time from the occurrence of chatter vibration to the determination of the occurrence of chatter vibration.

In the third embodiment, an example of generating the timing signal 207 by using the measured value of the spindle angle or the spindle speed has been described, but the timing signal generation unit 16-2 describes the spindle angle command and the measured value of the spindle angle. May be used together, or the spindle speed command and the measured value of the spindle speed may be used together.

Embodiment 4.
FIG. 17 is a diagram showing a functional configuration of the numerical control device 4 according to the fourth embodiment of the present invention. The numerical control device 4 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. -3 and a tool information recording unit 17. That is, the numerical control device 4 has a tool information recording unit 17 in addition to the configuration of the numerical control device 3 described in the third embodiment, and instead of the timing signal generation unit 16-2, the timing signal generation unit 16- Has 3. Hereinafter, the parts different from the numerical control device 2 will be mainly described.

The timing signal generation unit 16-3 generates a timing signal 207 based on the angle information 211 output by the angle information sensor 104 and the tool information 210 output by the tool information recording unit 17, and generates the generated timing signal 207. Output to the phase difference calculation unit 12. The timing signal generation unit 16-3 can generate the timing signal 207 in the same manner as the timing signal generation unit 16-1 of the second embodiment. At this time, the timing signal generation unit 16-3 generates the timing signal 207 by using the measured value of the spindle angle instead of the angle command of the spindle 101.

As described above, according to the fourth embodiment of the present invention, as in the third embodiment, the timing is not affected by the control tracking error that occurs between the angle command of the spindle 101 and the actual angle. In addition to the effect that the signal 207 can be generated, even when the number of blades is a plurality of blades as in the second embodiment, the time required for determining the chatter vibration, that is, as in the first embodiment, that is, It is possible to shorten the time from the occurrence of chatter vibration to the determination of the occurrence of chatter vibration.

Embodiment 5.
FIG. 18 is a diagram showing a functional configuration of the numerical control device 5 according to the fifth embodiment of the present invention. The numerical control device 5 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. It has -4 and. Further, the numerical control device 5 can acquire the machining program information 212 including the spindle rotation speed command 213 from the machining program 18 for controlling the machine tool 100. Hereinafter, the parts different from the numerical control device 1 will be mainly described.

The spindle speed command 213 is output to the timing signal generation unit 16-4, and the machining program information 212 is output to the drive command unit 15. The drive command unit 15 can output an operation command 208 to the machine tool 100 according to the machining program information 212.

The timing signal generation unit 16-4 generates the timing signal 207 based on the spindle speed command 213 extracted from the machining program information 212. The timing signal generation unit 16-4 outputs the timing signal 207 for each time T4 calculated by using the spindle rotation speed command 213 and the mathematical formula (5) shown below with the initial time t0 as the reference time. _{The S cmd} in the mathematical formula (5) indicates the spindle rotation speed indicated by the spindle rotation speed command 213.

As described above, according to the fifth embodiment of the present invention, the timing signal 207 can be generated based on the spindle speed command 213 included in the machining program 18. Even when the timing signal 207 is generated by using the machining program 18, the time required for determining the chatter vibration, that is, the occurrence of the chatter vibration after the chatter vibration is generated is determined as in the first embodiment. It is possible to shorten the time required to do so.

Embodiment 6.
FIG. 19 is a diagram showing a functional configuration of the numerical control device 6 according to the sixth embodiment of the present invention. The numerical control device 6 includes a filter processing unit 10, a sensor signal processing unit 11, a phase difference calculation unit 12, a vibration determination unit 13, a command value correction unit 14, a drive command unit 15, and a timing signal generation unit 16. It has -5 and a tool information recording unit 17. The numerical control device 6 has a tool information recording unit 17 in addition to the configuration of the numerical control device 5, and has a timing signal generation unit 16-5 in place of the timing signal generation unit 16-4.

The timing signal generation unit 16-5 generates a timing signal 207 based on the tool information 210 and the spindle speed command 213, and outputs the generated timing signal 207 to the phase difference calculation unit 12.

The timing signal generation unit 16-5 uses the initial time t0 as a reference time, and uses the following mathematical formula (6), the number of blades α, and the spindle rotation speed S _cmd to calculate the timing signal 207 for each time T5. Is output.

As described above, according to the sixth embodiment of the present invention, in addition to the effect of the fifth embodiment, it is possible to determine the occurrence of chatter vibration even when the number of blades of the tool is a plurality of blades. It will be possible.

Subsequently, the hardware configuration of the numerical control devices 1 to 6 according to the first to sixth embodiments of the present invention will be described. Each functional unit of the numerical control devices 1 to 6 is realized by a processing circuit. These processing circuits may be realized by dedicated hardware, or may be control circuits using a CPU (Central Processing Unit).

When the above processing circuits are realized by dedicated hardware, these are realized by the processing circuit 90 shown in FIG. FIG. 20 is a diagram showing dedicated hardware for realizing the functions of the numerical control devices 1 to 6 according to the first to sixth embodiments of the present invention. The processing circuit 90 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

When the above processing circuit is realized by a control circuit using a CPU, this control circuit is, for example, a control circuit 91 having the configuration shown in FIG. 21. FIG. 21 is a diagram showing a configuration of a control circuit 91 for realizing the functions of the numerical control devices 1 to 6 according to the first to sixth embodiments of the present invention. As shown in FIG. 21, the control circuit 91 includes a processor 92 and a memory 93. The processor 92 is a CPU, and is also called a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like. The memory 93 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), and an EPROM (registered trademark) (Electrically EPROM). Magnetic discs, flexible discs, optical discs, compact discs, mini discs, DVDs (Digital Versatile Disks), etc.

When the above processing circuit is realized by the control circuit 91, it is realized by the processor 92 reading and executing a program stored in the memory 93 corresponding to the processing of each component. The memory 93 is also used as a temporary memory in each process executed by the processor 92.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1,2,3,4,5,6 Numerical controller, 10 Filter processing unit, 11 Sensor signal processing unit, 12 Phase difference calculation unit, 13 Vibration determination unit, 14 Command value correction unit, 15 Drive command unit, 16, 16-1, 16-2, 16-3, 16-4, 16-5 Timing signal generator, 17 Tool information recording unit, 18 Machining program, 90 Processing circuit, 91 Control circuit, 92 Processor, 93 Memory, 100 Machining Machine, 101 spindle, 102 feed shaft, 103 sensor, 104 angle information sensor, 200 sensor signal, 201 chatter vibration component signal, 202 state quantity signal, 203 phase difference information, 204 vibration judgment information, 205 correction signal, 206 spindle operation command , 207 Timing signal, 208 Operation command, 209 Operation information, 210 Tool information, 211 Angle information, 212 Machining program information, 213 Spindle rotation speed command.

Claims (13)

A drive command unit that gives operation commands to the spindle and feed shaft of a machine tool,
A sensor signal processing unit that generates a plurality of types of state quantities based on a sensor signal that detects vibration of a tool or an object to be machined attached to the machine tool.
A timing signal generator that periodically generates and outputs a timing signal at a timing synchronized with the rotation of the spindle,
A phase difference calculation unit that generates dimensionless quantities indicating the plurality of types of state quantities in the state space for each timing signal and calculates phase difference information indicating the difference between the phases of the dimensionless quantities.
A vibration determination unit that determines the occurrence of chatter vibration in the machine tool based on the variation in the phase difference information, and
A numerical control device characterized by comprising. When the vibration determination unit determines that chatter vibration has occurred, the command value correction unit that outputs a correction signal for changing the operation command to the drive command unit,
The numerical control device according to claim 1, further comprising. A filter processing unit that removes a vibration component having a frequency obtained by multiplying the number of blades of a tool attached to the machine tool by the rotation speed of the spindle and a harmonic component of the vibration component from the sensor signal.
With more
The numerical control device according to claim 1 or 2, wherein the sensor signal processing unit generates the plurality of types of state quantities based on the sensor signal output by the filter processing unit. A tool information recording unit that records blade number information indicating the number of blades of a tool attached to the machine tool.
With more
The numerical value according to any one of claims 1 to 3, wherein the timing signal generation unit outputs the timing signal each time the spindle rotates by an angle obtained by dividing 360 degrees by the number of blades. Control device. The sensor signal processing unit performs two or more types of state quantities of the sensor signal, a state quantity obtained by time-differentiating the sensor signal, and a state quantity obtained by time-integrating the sensor signal. The numerical control device according to any one of claims 1 to 4, wherein the numerical control device is generated. Claims 1 to 5 characterized in that the phase difference calculation unit repeatedly calculates the phase difference information indicating the angle formed by the previous dimensionless quantity, the origin of the state space, and the current dimensionless quantity. The numerical control device according to any one of the above items. Any of claims 1 to 6, wherein the vibration determination unit determines that chatter vibration has occurred when the difference between the plurality of phase difference information repeatedly received is less than a predetermined value. The numerical control device according to item 1. Any one of claims 1 to 6, wherein the vibration determination unit determines that chatter vibration has occurred when the standard deviation of the plurality of the phase difference information repeatedly received is less than a predetermined value. The numerical control device described in the section. The vibration determination unit calculates the difference between the maximum value and the minimum value of the phase difference information received during the period of a predetermined length, and the difference between the maximum value and the minimum value is predetermined. The numerical control device according to any one of claims 1 to 6, wherein when the value is lower than the value, it is determined that chatter vibration has occurred. The numerical value according to any one of claims 1 to 9, wherein the timing signal generation unit generates the timing signal based on at least one of the angle command of the spindle and the speed command of the spindle. Control device. The numerical control device according to any one of claims 1 to 9, wherein the timing signal generation unit generates the timing signal based on at least one of the actual angle and the actual speed of the spindle. Any one of claims 1 to 9, wherein the timing signal generation unit generates the timing signal based on the spindle rotation speed command described in the machining program for controlling the machine tool. Numerical control device described in. It is a method for determining the occurrence of chatter vibration executed by a numerical control device having a drive command unit that gives an operation command to the spindle and feed shaft of a machine tool.
A step of generating a plurality of types of state quantities based on a sensor signal output by a vibration sensor attached to the machine tool, and a step of generating a plurality of types of state quantities.
A step of periodically generating a timing signal at a timing synchronized with the rotation of the spindle,
A step of generating dimensionless quantities indicating the plurality of types of state quantities in the state space for each timing signal and calculating phase difference information indicating the difference between the phases of the dimensionless quantities.
A step of determining the occurrence of chatter vibration in the machine tool based on the variation of the phase difference information, and
A method for determining the occurrence of chatter vibration, which comprises.

Images