JP6605185B1 - Numerical control apparatus and chatter vibration occurrence determination method - Google Patents

Abstract

The numerical control device (1) includes a drive command unit (15) that gives operation commands to the spindle (101) and the feed shaft (102) of the machine tool (100), and a tool or an object to be processed attached to the machine tool (100). Based on the sensor signal (200) that detects the vibration of the sensor signal (200), the sensor signal processing unit (11) that generates a plurality of types of state quantities, and the timing signal (207) periodically at a timing synchronized with the rotation of the spindle (101). ) And a timing signal generator (16) for generating and outputting a dimensionless quantity indicating a plurality of types of state quantities in the state space for each timing signal (207) The occurrence of chatter vibration in the machine tool (100) is determined based on the phase difference calculation unit (12) for calculating the phase difference information (203) indicating the difference and the variation of the phase difference information (203). Motion determination module (13), characterized in that it comprises a.

Description

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

  There is a machine tool that removes a workpiece to a desired shape by changing the relative position between the workpiece and the tool. A machine tool represented by a milling machine and a lathe performs machining by mounting a tool or a workpiece on a spindle and rotating the spindle. During processing, vibration called “chatter vibration” may occur. If chatter vibration occurs, the accuracy of the finished surface may deteriorate or the tool may be damaged.

  In Patent Document 1, vibration is measured twice at a predetermined time interval during processing, and the second measurement result has a larger frequency domain amplitude and a frequency domain phase than the first measurement result. A method is disclosed in which chatter vibrations are determined to have occurred when they are different.

JP 2013-7647 A

  However, the technique described in Patent Document 1 has a problem that it takes a long time to determine whether or not chatter vibration occurs during machining. 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. For this reason, in order to obtain a frequency resolution ΔF sufficient for the determination of chatter vibration, the data acquisition time becomes long. Further, in the technique described in Patent Document 1, since it is necessary to perform measurement twice with a predetermined time, it takes a long time to measure vibration during processing.

  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 reducing the time required for chatter vibration determination.

  In order to solve the above-described problems and achieve the object, a numerical control device according to the present invention includes a drive command unit that gives an operation command to a main spindle and a feed shaft of a machine tool, and a tool or an object to be processed attached to the machine tool. A sensor signal processing unit that generates a plurality of types of state quantities based on the sensor signal that has detected the vibration of the motor, 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 dimensionless quantity indicating a plurality of types of state quantities in the state space for each timing signal, and calculates phase difference information indicating a difference between phases of the dimensionless quantity; and phase difference information And a vibration determination unit that determines the occurrence of chatter vibration in the machine tool based on the variation of.

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

The figure which shows the function structure of the numerical control apparatus concerning Embodiment 1 of this invention. The figure for demonstrating the filter characteristic of the filter process part shown in FIG. The figure which shows the relationship between the timing signal which the timing signal generation part shown in FIG. 1 outputs, and the angle command of a spindle The figure which shows the dimensionless quantity which the phase difference calculating part shown in FIG. 1 calculates The figure which shows an example of transition of the phase difference which the phase difference calculating part shown in FIG. 1 calculates when chatter vibration has occurred The figure which shows an example of transition of the phase difference which the phase difference calculating part shown in FIG. 1 calculates when chatter vibration has not occurred This is an experimental result when chatter vibration occurs, and shows the waveform of acceleration generated during machining The figure which shows the phase difference of the dimensionless quantity calculated | required from the experimental result shown in FIG. This is an experimental result when chatter vibration does not occur, and shows the waveform of acceleration generated during machining The figure which shows the phase difference of the dimensionless quantity calculated | required 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 function structure of the numerical control apparatus concerning Embodiment 2 of this invention. The figure which shows the 1st example of the relationship between the timing signal which the timing signal generation part shown in FIG. 13 outputs, and the angle command of a main axis | shaft. The figure which shows the 2nd example of the relationship between the timing signal which the timing signal generation part shown in FIG. 13 outputs, and the angle command of a main axis | shaft. The figure which shows the function structure of the numerical control apparatus concerning Embodiment 3 of this invention. The figure which shows the function structure of the numerical control apparatus concerning Embodiment 4 of this invention. The figure which shows the function structure of the numerical control apparatus concerning Embodiment 5 of this invention. The figure which shows the function structure of the numerical control apparatus concerning Embodiment 6 of this invention. The figure which shows the hardware for exclusive use for implement | achieving the function of the numerical control apparatus concerning Embodiment 1-6 of this invention. The figure which shows the structure of the control circuit for implement | achieving the function of the numerical control apparatus concerning Embodiment 1-6 of this invention.

  Hereinafter, a numerical control device and a chatter vibration occurrence determination method according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

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

  The machine tool 100 has a main shaft 101 and a feed shaft 102 provided with a motor driven by an operation command 208. In the present embodiment, a workpiece is installed on the main shaft 101, and a 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 main shaft 101 and the feed shaft 102 to the numerical controller 1. In the present 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 workpiece to the numerical controller 1. The sensor 103 is attached to the main shaft 101 or the feed shaft 102 of the machine tool 100. The position where the sensor 103 is attached may be a position where the vibration of the tool or the workpiece can be detected, and is preferably in the vicinity of the point where the tool and the workpiece are in contact. The type of the sensor 103 may be any sensor that can detect the vibration of the tool or the workpiece. The sensor 103 is, for example, a displacement sensor, a speed sensor, an acceleration sensor, an angular velocity sensor, or the like. The sensor 103 may be a force sensor that detects a cutting reaction force or a microphone that detects a cutting sound during processing. Alternatively, at least one of the position, speed, and motor current of the main shaft 101 and the feed shaft 102 included in the operation information instead of the sensor 103 is used to detect the vibration of the tool or the workpiece to be processed. Then, information indicating the detected vibration may be output as the sensor signal 200.

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

  The filter processing unit 10 filters the sensor signal 200 output from 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 a 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 in FIG. 2 indicates the frequency, and the vertical axis indicates the amplitude. FIG. 2 shows chatter vibration components, cutting components, and the passband of the filter in the frequency domain. The cutting component is mainly a vibration component having a frequency obtained by multiplying the number of rotations of the spindle by the number of blades of the tool, and a harmonic component thereof. The filter processing unit 10 removes a band including each cutting component with a predetermined bandwidth. For example, the predetermined bandwidth can be about several Hz near the cutting component. The filter processing unit 10 can be designed using a known bandpass filter, notch filter, a combination of a plurality of bandpass filters, a combination of a plurality of notch filters, a comb filter, or 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 and 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 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 from 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 a state quantity obtained by differentiating the chatter vibration component signal 201 once in time. The sensor signal processing unit 11 sets a chatter vibration component signal 201 and a signal obtained by time-differentiating the chatter vibration component signal 201 once as a time series signal as a state quantity signal 202.

  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 a state quantity obtained by time differentiation of the chatter vibration component signal 201 P times, and the second state quantity is a state quantity obtained by Q time differentiation. Here, P and Q are integers. In this case, the difference between P and Q may be an odd number. Furthermore, the dimension of the first state quantity and the second state quantity may be a dimension obtained by integrating the chatter vibration component signal 201 with time. As a specific example, the first state quantity may be acceleration, and the second state quantity may be speed. Alternatively, the first state quantity may be jerk, which is a differential value of acceleration, and the second state quantity may be the position. The sensor signal processing unit 11 includes, for example, two or more types of state quantities among a sensor signal 200, a state quantity obtained by time differentiation of the sensor signal 200, and a state quantity obtained by time integration of the sensor signal. Can be generated.

  When the timing signal generator 16 determines that the angle command of the spindle 101 has passed a predetermined angle based on the spindle operation command 206 output from the drive command unit 15, it outputs a timing signal 207 to the phase difference calculator 12. To do. Details of the method of generating the timing signal 207 will be described.

  FIG. 3 is a diagram illustrating a relationship between the timing signal 207 output from the timing signal generation unit 16 illustrated in FIG. 1 and the angle command of the spindle 101. The angle command for 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 from 0 degrees to 360 degrees and returns to 0 degrees when it reaches 360 degrees. The timing signal generator 16 outputs a timing signal 207 every 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 an arbitrary angle as long as it is determined at one position while the main shaft 101 rotates once, and can be, for example, the angle ψ1 of the main shaft 101 during the orientation of the main shaft 101. The main shaft orientation is a reference angle at which the main shaft 101 is stopped.

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

  The phase difference calculation unit 12 receives the timing signal 207 output from the timing signal generation unit 16 and the state quantity signal 202 output from the sensor signal processing unit 11. Based on the timing signal 207 and the state quantity signal 202, the phase difference calculation unit 12 generates, for each timing signal 207, a dimensionless quantity indicating a plurality of types of state quantities in the state space. The phase difference information 203 indicating the difference 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 a prior machining experiment, or may be the maximum value of each state quantity obtained in a 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. The phase difference calculation unit 12 normalizes the state quantity signal 202 at time t2 similarly to time t1, and sets the normalized value as the second dimensionless quantity N2.

  FIG. 4 is a diagram showing dimensionless amounts 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, the dimension of the first state quantity of the state quantity signal 202, and the second state quantity. It is expressed in a state space consisting of dimensions. The phase difference calculation unit 12 calculates an angle θ between the first dimensionless quantity N1 that is the previous dimensionless quantity, the origin of the state space, and the second dimensionless quantity N2 that is the current dimensionless quantity, The phase difference between the first dimensionless quantity N1 and the second dimensionless quantity N2 is calculated. 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 phase difference information 203 indicating the calculated phase difference to the vibration determination unit 13.

  FIG. 5 is a diagram illustrating an example of transition of the phase difference calculated by the phase difference calculation unit 12 illustrated in FIG. 1 when chatter vibration is occurring. The dimensionless quantities N10 to N13 are dimensionless quantities calculated at times t10 to t13 when the timing signal 207 is received. At this time, t13> t12> t11> t10. 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 an angle formed by the dimensionless quantity N12, the origin of the state space, and the dimensionless quantity N13.

  When chatter vibration is occurring, the trajectories of the dimensionless quantities N10 to N13 in the state space are circular, and the angle between each dimensionless quantity is constant. Therefore, the angle θ at each time when the timing signal 207 is received is constant.

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

  Here, an experimental result for confirming the difference in the angle θ due to 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 periphery of the round bar was machined by turning. The tool used was a cemented carbide tool, and the acceleration during machining was measured by installing an acceleration sensor on the tool.

  The machining conditions when chatter vibration occurs are as follows: spindle speed 2000 (RPM), feed per tooth 0.1 (mm), radial cut 1.0 (mm), workpiece protrusion 200 (mm) from the chuck It is.

  FIG. 7 is an experimental result when chatter vibration is generated, and is a diagram illustrating a waveform of acceleration generated during machining. FIG. 8 is a diagram showing a dimensionless amount of phase difference obtained from the experimental results shown in FIG. 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 from the acceleration sensor as the sensor signal 200. The dimensional quantity and angle θ were calculated.

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

  The timing signal generator 16 outputs a timing signal 207 every time the angle command of the spindle 101 passes the spindle angle at the time of spindle orientation. The phase difference calculation unit 12 normalizes the state quantity signal 202 and calculates dimensionless quantities N101 to N106 at times t101 to t106 when the timing signals 207 are 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 an angle formed by the dimensionless quantity N103, the origin of the state space, and the dimensionless quantity N104. The angle θ104 indicates an angle formed by the dimensionless quantity N104, the origin of the state space, and the dimensionless quantity N105, and the angle θ105 indicates an 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 is occurring, the trajectory of the dimensionless amount in the state space is 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 rotation speed 2000 (RPM), feed per tooth 0.1 (mm), radial cut 1.0 (mm), and workpiece protrusion 100 from the chuck. (Mm).

  FIG. 9 is an experimental result when chatter vibration is not generated, and is a diagram illustrating a waveform of acceleration generated during machining. FIG. 10 is a diagram showing a dimensionless amount of phase difference obtained from the experimental result 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 from the acceleration sensor as the sensor signal 200, as shown in FIG. Dimensionless quantity and angle θ were calculated.

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

  The timing signal generator 16 outputs a timing signal 207 every time the angle command of the spindle 101 passes the spindle angle at the time of spindle orientation. The phase difference calculation unit 12 normalizes the state quantity signal 202 and calculates dimensionless quantities N201 to N206 at times t201 to t206 at which the timing signals 207 are received. Here, t206> t205> t204> t203> t202> t201.

  FIG. 10 shows dimensionless quantities N201 to N206 in the state space. The angle θ201 indicates an angle formed by the dimensionless quantity N201, the origin of the state space, and the dimensionless quantity N202, and the angle θ202 indicates an angle formed by the dimensionless quantity N202, the origin of the state space, and the dimensionless quantity N203, The angle θ203 indicates an angle formed by the dimensionless quantity N203, the origin of the state space, and the dimensionless quantity N204. The angle θ204 indicates an angle formed by the dimensionless quantity N204, the origin of the state space, and the dimensionless quantity N205, and the angle θ205 indicates an 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 trajectory of the dimensionless amount 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 the angle θ, which is a phase difference, from the phase difference calculation unit 12, and determines chatter vibration using the following procedure. The vibration determination unit 13 determines whether 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 vibration determination information 204 to the command value correction unit 14. Details of the vibration determination unit 13 will be described.

  The vibration determination unit 13 records the phase difference information 203 output from 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 a difference of the recorded angle θ, and determines that chatter vibration is occurring when the difference of the angle θ is below a predetermined threshold, and sets 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, the phase difference calculation unit 12 outputs the angle θ within a range of ± 180 degrees. When chatter vibration does not occur, the angle θ takes an indefinite value within a range of ± 180 degrees, so the difference of the angle θ takes a value of ± 360 degrees. Further, when chatter vibration is occurring, the angle θ has a constant value, so the difference in the angle θ is zero. However, the actual angle θ includes an error derived from a measurement error. For this reason, if the threshold 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 that is repeatedly received. If the standard deviation of the angle θ is below a predetermined threshold, chatter vibration is generated. It is determined that FIG. 11 is a diagram illustrating a first example for explaining processing of the vibration determination unit 13 illustrated in FIG. 1. The vibration determination unit 13 calculates the standard deviation using the angle θ acquired between time t3 and 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 standard deviation threshold. For this reason, the vibration determination unit 13 can determine that chatter vibration has not occurred. FIG. 12 is a diagram illustrating a second example for explaining the processing of the vibration determination unit 13 illustrated in FIG. 1. In the second example shown in FIG. 12, the standard deviation of the angle θ is less than the standard deviation threshold. For this reason, the vibration determination unit 13 can determine that chatter vibration is occurring.

  A method for determining the standard deviation threshold will be described. When chatter vibration occurs, the angle θ has a constant value, and therefore the difference in the angle θ is zero. However, an error derived from a measurement error or the like exists in the actual angle θ. Therefore, the presence or absence of chatter vibration can be determined by setting a value sufficiently larger than the error included in the angle θ as the threshold value. For example, when the error of the angle θ is ± 10 degrees, the standard deviation threshold value can be a value larger than 10 degrees, for example, 20 degrees.

  As another example, the vibration determination unit 13 may determine the presence or absence of chatter vibration 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 that is repeatedly received. it can. In this case, the dispersion 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 using a 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 difference between the calculated maximum value and the minimum value is determined in advance. When it is smaller than the threshold value, it can be determined that chatter vibration has occurred.

  When receiving 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 for changing 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 main shaft 101 so that the rotation speed of the main shaft 101 coincides with 1 / integer of the resonance frequency of the mechanical structure calculated in advance by finite element analysis. . Note that the resonance frequency of the mechanical structure may be a value identified not by finite element analysis but by a prior experiment.

  Further, the correction signal 205 may be a signal for changing the speed command location of the feed shaft 102 by a predetermined ratio. Specifically, the correction signal 205 can be a signal that decreases 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 based on the sensor signal 200 that detects the vibration of the tool or workpiece to be mounted on the machine tool 100. Is generated. 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 dimensions of the dimensionless quantity, is calculated. Generation of chatter vibration in the machine tool 100 is determined based on the variation in the phase difference information.

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

  Further, the numerical control device 1 determines chatter vibration based on the phase difference information 203 which is a dimensionless amount. As a conventional method, for example, there is a method of determining chatter vibration based on the amplitude of chatter vibration. When using the amplitude of chatter vibration, the magnitude of the amplitude varies depending on the machining conditions, so an amplitude threshold must be provided according to the machining conditions. On the other hand, the numerical control apparatus 1 that determines chatter vibration based on the phase difference information 203 that is a dimensionless amount can determine chatter vibration without depending on the processing condition, and can determine a threshold value according to the processing condition. Need not be provided.

  The machine tool 100 according to the first embodiment has a configuration in which a workpiece is installed on the spindle 101. However, for example, as represented by a milling machine and a lathe, a tool is installed on the spindle 101. Can achieve the same effect.

  In the first embodiment, one sensor 103 is used. However, the sensors 103 may be installed at a plurality of locations on the machine tool 100. In this case, it is possible to determine the occurrence of chatter vibration by performing the processing described in Embodiment 1 for all the installed sensors 103. In the case where the sensors 103 are installed at a plurality of locations, even if chatter vibration occurs at a 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 chatter vibration without being affected by a quantization error accompanying differentiation or integration.

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

Embodiment 2. FIG.
In the first embodiment, the 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 a tool is two or more will be described.

  FIG. 13 is a diagram illustrating 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. -1 and a tool information recording unit 17.

  The numerical control device 2 includes 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 instead of the timing signal generation unit 16 of the numerical control device 1. And a timing signal generator 16-1. In the following, portions different from the numerical control device 1 will be mainly described.

  The tool information recording unit 17 records tool information 210 that 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. Furthermore, the tool information 210 may include information indicating a tool shape such as a type of a tool such as an end mill or a tool, 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 cut simultaneously, the number of blades is the same as the number of tools. For example, when the machine tool 100 has a lower turret and an upper turret and performs machining with a turning tool attached to each of the turrets, the tool information recording unit 17 has two blades. The tool information 210 indicating this is output.

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

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

  First, the case where α = 2 will be described. FIG. 14 is a diagram illustrating a first example of a relationship between the timing signal 207 output from the timing signal generation unit 16-1 illustrated in FIG. 13 and the angle command of the main shaft 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 every time the angle command of the main shaft 101 passes through a plurality of angles ψ1 and ψ2, which are predetermined angles. That is, the timing signal 207 is output twice, which is the same number as the number of teeth, while the main shaft 101 rotates once. The angle ψ1 may be an arbitrary angle as long as the angle ψ1 is set to 1 while the main shaft 101 rotates once. For example, the angle ψ1 can be a main shaft angle at the time of main shaft 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 illustrating a second example of the relationship between the timing signal 207 output from the timing signal generation unit 16-1 illustrated in FIG. 13 and the angle command of the spindle 101. The timing signal 207 is output each time through the angle [psi _beta angle command of the main shaft 101 is predetermined. β is a natural number of 2 or more and α or less. The timing signal 207 is output α times while the main shaft 101 rotates once. ψ1 may be an arbitrary angle as long as it is 1 or predetermined while the main shaft 101 rotates once. Between ψ1 and ψβ-1, there is a restriction expressed by the following formula (2). In other words, the timing signal generator 16-1 outputs the timing signal 207 every time the spindle 101 rotates by an angle obtained by dividing 360 degrees by the number of blades α.

  Note that the timing signal generation unit 16-1 may generate the timing signal 207 using the speed command of the spindle 101 included in the spindle operation command 206. In this case, the timing signal generator 16-1 generates a timing signal 207 for each time T2 calculated from the speed command S (rpm) of the spindle 101 using the following 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, the number of tools attached to the machine tool 100 is plural. However, as in the first embodiment, it is possible to shorten the time required for the determination of chatter vibration, that is, the time from the occurrence of chatter vibration to the determination of the occurrence of chatter vibration.

  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.
FIG. 16 is a diagram illustrating 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. -2. The numerical control device 3 includes a timing signal generation unit 16-2 instead of the timing signal generation unit 16 of the numerical control device 1. In the following, portions different from the numerical control device 1 will be mainly described.

  The machine tool 100 includes an angle information sensor 104 attached to the main shaft 101 in addition to the configuration described in the first embodiment. The angle information sensor 104 is a sensor that measures a spindle angle, and for example, an encoder, a potentiometer, or the like can be used. The angle information 211 is a signal including at least an actual measurement 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 controller 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 by which the timing signal generation unit 16-2 generates the timing signal 207 is the same as in the first embodiment, but instead of using the angle command for the main shaft 101, an actual measured value of the main shaft angle is used.

The angle information sensor 104 may be a sensor that detects an actual measurement value of the spindle speed. In this case, the angle information sensor 104 is an angular velocity sensor. The timing signal generator 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 generator 16-2 sets the timing signal 207 for each time T3 calculated using the following equation (4) from the actual spindle speed S _ref (rpm) with the initial time t0 as a reference time. Output.

  As described above, according to the third embodiment of the present invention, the timing signal 207 is generated based on the actually 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, even when the control tracking error occurs between the angle command of the spindle 101 and the actual angle, the numerical control device 3 is the time required for chatter vibration determination, that is, as in the first embodiment, that is, The time from the occurrence of chatter vibration to the determination of the occurrence of chatter vibration can be shortened.

  In the third embodiment, the example in which the timing signal 207 is generated using the actual measurement value of the main shaft angle or the main shaft speed has been described. However, the timing signal generation unit 16-2 uses the main shaft angle command and the actual measurement value of the main shaft 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.
FIG. 17 is a diagram illustrating 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 includes 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- 3. In the following, portions 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 from the angle information sensor 104 and the tool information 210 output from the tool information recording unit 17, and generates the generated timing signal 207. It outputs to the phase difference calculating part 12. The timing signal generator 16-3 can generate the timing signal 207 by the same method as the timing signal generator 16-1 of the second embodiment. At this time, the timing signal generator 16-3 generates the timing signal 207 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 generated between the angle command of the spindle 101 and the actual angle. In addition to the effect that the signal 207 can be generated, as in the second embodiment, even when the number of blades is plural, as in the first embodiment, the time required for the determination of chatter vibration, that is, The time from the occurrence of chatter vibration to the determination of the occurrence of chatter vibration can be shortened.

Embodiment 5 FIG.
FIG. 18 is a diagram illustrating a functional configuration of the numerical control device 5 according to the fifth embodiment of the present invention. The numerical controller 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. -4. Further, the numerical control device 5 can acquire the machining program information 212 including the spindle rotational speed command 213 from the machining program 18 for controlling the machine tool 100. In the following, portions different from the numerical control device 1 will be mainly described.

  The spindle speed command 213 is output to the timing signal generator 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 rotational speed command 213 extracted from the machining program information 212. The timing signal generator 16-4 uses the initial time t0 as a reference time, and outputs a timing signal 207 for each time T4 calculated using the spindle rotational speed command 213 and the following formula (5). Note that S _cmd in Expression (5) indicates the spindle speed indicated by the spindle 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 rotational speed command 213 included in the machining program 18. Even when the timing signal 207 is generated using the machining program 18, as in the first embodiment, the time required to determine chatter vibration, that is, the occurrence of chatter vibration after the chatter vibration is generated is determined. The time until it can be shortened.

Embodiment 6 FIG.
FIG. 19 is a diagram illustrating 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. -5 and a tool information recording unit 17. The numerical control device 6 includes a tool information recording unit 17 in addition to the configuration of the numerical control device 5, and includes a timing signal generation unit 16-5 instead 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 rotational 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, the timing signal 207 for each time T5 calculated using the following formula (6), the number of blades α, and the spindle rotation speed _Scmd. Is output.

  As described above, according to the sixth embodiment of the present invention, in addition to the effects of the fifth embodiment, the occurrence of chatter vibration can be determined even when the number of blades of the tool is plural. It becomes possible.

  Next, 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 controllers 1 to 6 is realized by a processing circuit. These processing circuits may be realized by dedicated hardware, or may be a control circuit using a CPU (Central Processing Unit).

  When the above processing circuit is realized by dedicated hardware, these are realized by the processing circuit 90 shown in FIG. FIG. 20 is a diagram illustrating dedicated hardware for realizing the functions of the numerical controllers 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 application specific integrated circuit (ASIC), a field programmable gate array (FPGA), 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 configured as shown in FIG. FIG. 21 is a diagram illustrating 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, processing unit, arithmetic unit, microprocessor, microcomputer, DSP (Digital Signal Processor), or the like. The memory 93 is, for example, a nonvolatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), Magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs (Digital Versatile Disks), and the like.

  When the processing circuit is realized by the control circuit 91, the processor 92 is realized by reading and executing a program stored in the memory 93 and 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 described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other 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 control device, 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 generation unit, 17 Tool information recording unit, 18 Machining program, 90 processing circuit, 91 control circuit, 92 processor, 93 memory, 100 machine tool Machine, 101 spindle, 102 feed axis, 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 speed command.

Claims (13)

A drive command section that gives operation commands to the spindle and feed axis of the 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 workpiece to be mounted on 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 a dimensionless quantity indicating the plurality of types of state quantities in the state space for each of the timing signals, and calculates phase difference information indicating a difference between phases of the dimensionless quantity;
A vibration determination unit that determines occurrence of chatter vibration in the machine tool based on variation in the phase difference information;
A numerical control device comprising: A command value correction unit that outputs a correction signal for changing the operation command to the drive command unit when the vibration determination unit determines that chatter vibration has occurred;
The numerical control apparatus according to claim 1, further comprising: A filter processing unit for removing, from the sensor signal, 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;
Further comprising
The numerical control device according to claim 1, wherein the sensor signal processing unit generates the plurality of types of state quantities based on the sensor signal output from the filter processing unit. A tool information recording unit for recording blade number information indicating the number of blades of a tool attached to the machine tool;
Further comprising
4. The numerical value according to claim 1, wherein the timing signal generation unit outputs the timing signal every time the spindle rotates by an angle obtained by dividing 360 degrees by the number of blades. 5. Control device.   The sensor signal processing unit includes two or more kinds of state quantities among the sensor signal, a state quantity obtained by differentiating the sensor signal with respect to time, and a state quantity obtained by time integrating the sensor signal. The numerical controller according to claim 1, wherein the numerical controller is generated.   6. The phase difference calculation unit repeatedly calculates the phase difference information indicating an angle formed by a previous dimensionless quantity, an origin of the state space, and a current dimensionless quantity. The numerical control device according to any one of the above.   The vibration determination unit determines that chatter vibration has occurred when a difference between the plurality of pieces of phase difference information repeatedly received is lower than a predetermined value. The numerical control apparatus according to item 1.   The vibration determination unit determines that chatter vibration has occurred when a standard deviation of a plurality of pieces of phase difference information that are repeatedly received is less than a predetermined value. The numerical control device according to item.   The vibration determination unit calculates a difference between the maximum value and the minimum value of the phase difference information received during a predetermined length period, and the difference between the maximum value and the minimum value is determined in advance. The numerical control apparatus according to claim 1, wherein when the value is less than the value, it is determined that chatter vibration has occurred.   10. The numerical value according to claim 1, wherein the timing signal generation unit generates the timing signal based on at least one of an angle command of the spindle and a speed command of the spindle. Control device.   The numerical control device according to claim 1, wherein the timing signal generation unit generates the timing signal based on at least one of an actual angle and an actual speed of the spindle.   The said timing signal generation part produces | generates the said timing signal based on the spindle speed command described in the machining program for controlling the said machine tool, The any one of Claim 1 to 9 characterized by the above-mentioned. The numerical control device described in 1. A chatter vibration occurrence determination method executed by a numerical control device having a drive command unit that gives operation commands to a spindle and a feed axis of a machine tool,
Generating a plurality of types of state quantities based on sensor signals output by vibration sensors attached to the machine tool;
Periodically generating a timing signal at a timing synchronized with the rotation of the spindle;
Generating a dimensionless quantity indicating the plurality of types of state quantities in the state space for each of the timing signals, and calculating phase difference information indicating a difference between phases of the dimensionless quantity;
Determining the occurrence of chatter vibration in the machine tool based on variation in the phase difference information;
A method for determining the occurrence of chatter vibration, comprising:

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