Torque correction data acquisition device

Abstract

The purpose of the present disclosure is to make it possible to automatically acquire a plurality of cogging torque data items and automatically select torque correction data from among the acquired cogging data items. This torque correction data acquisition device comprises a count designation unit, a waveform data acquisition unit, a calculation unit, and a selection unit. A program transmission unit transmits an operation program to a motor control unit that controls a motor. The count designation unit designates the number of times the operation program is to be executed. The waveform data acquisition unit acquires cogging torque waveform data for each execution of the operation program. The calculation unit acquires a plurality of cogging torque data items by calculating cogging torque data from the acquired waveform data. The selection unit selects, from the acquired plurality of cogging torque data items, torque correction data for correcting the torque of the motor.

Description

Torque correction data acquisition device

[0001] The present disclosure relates to an apparatus for acquiring torque correction data for correcting torque of a motor that generates cogging torque.

[0002] Some machines, such as machine tools, are equipped with motors that generate cogging torque, such as synchronous motors. In many of these machines, after the motor is installed, it is necessary to correct the torque command value to cancel out fluctuations in the motor's output torque due to the cogging torque. Among devices that acquire torque correction data for this purpose, there are some that calculate the torque correction data from waveform data of the cogging torque.

[0003] JP 2011-135645 A

[0004] The inventors have found that in order to obtain such torque correction data with higher accuracy, it is preferable to obtain the torque correction data in the following manner. That is, the motor is caused to perform operations according to a predetermined operation program multiple times. For each operation, cogging torque data is calculated from waveform data as predetermined data regarding the cogging torque. From the cogging torque data for each operation, only a portion of the cogging torque data that is deemed appropriate is selected as torque correction data. This method allows for accurate acquisition of torque correction data.

[0005] However, the inventors have also noticed the following problems: It is time-consuming and burdensome for an operator to create an operation program and make the motor execute a predetermined operation multiple times. Furthermore, it is time-consuming and burdensome for an operator to visually and manually select torque correction data from multiple cogging torque data.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to enable multiple cogging torque data to be automatically acquired and to automatically select torque correction data from among them.

[0007] The present disclosure provides a torque correction data acquisition device that acquires torque correction data for correcting the torque of a motor that generates cogging torque, comprising: a program transmission unit that transmits an operation program to a motor control unit that controls the motor; a number designation unit that designates the number of times the operation program is executed; a waveform data acquisition unit that acquires waveform data of the cogging torque for each execution of the operation program; a calculation unit that acquires multiple cogging torque data by calculating cogging torque data as predetermined data for the cogging torque from each of the acquired waveform data; and a selection unit that selects the torque correction data from the acquired multiple cogging torque data.

[0008] 1 is a configuration diagram showing a torque correction data acquisition device and its periphery according to a first embodiment; FIG. 2 is a graph showing the transition of the rotation angle of a motor; FIG. 3 is a graph showing the transition of cogging torque; FIG. 4 is a diagram showing a selection result screen; FIG. 5 is a diagram in which cogging torque data is plotted on a phase x amplitude plane; FIG. 6 is a diagram in which a second line is further drawn; FIG. 7 is a diagram in which a third line and a fourth line are further drawn; FIG. 8 is a diagram in which a convex hull and an outlier candidate circle are further drawn; FIG. 9 is a diagram in which a convex hull and a selection circle are drawn on a phase x amplitude plane; FIG. 10 is a diagram in which another convex hull and a selection circle are drawn; FIG. 11 is a diagram in which another convex hull and a selection circle are drawn; FIG. 12 is a diagram in which another convex hull and a selection circle are drawn; FIG. 13 is a diagram in which another convex hull and a selection circle are drawn;

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments and can be appropriately modified and implemented within the scope of the present disclosure.

[0010] First Embodiment As shown in FIG. 1 , a torque correction data acquisition device 30 is provided for a numerical control device 20 of a machine tool 10 .

[0011] The machine tool 10 includes a spindle 11, a motor 12, and a moving device 15. A tool for cutting a workpiece is attached to the spindle 11. The motor 12 is configured to be able to drive the spindle 11 to rotate. The moving device 15 is configured to be able to move the spindle 11 relative to the workpiece. Specifically, for example, the moving device 15 is configured to drive the spindle 11 in some of five axial directions excluding the direction around the spindle 11, and to drive the workpiece in the remaining direction of the five axial directions.

[0012] The numerical control device 20 performs the desired cutting on the workpiece by controlling the motor 12 and the moving device 15 in accordance with the input machining program. Therefore, from a functional perspective, the numerical control device 20 comprises a motor control unit 22 that controls the motor 12 and a movement control unit 25 that controls the moving device 15.

[0013] The motor 12 is a synchronous motor that includes a rotor with a permanent magnet and a stator that rotates the rotor. As a result, a cogging torque cT is generated in the motor 12 as the rotor rotates. Specifically, the cogging torque cT has a sinusoidal waveform, for example, as shown in FIG. 3.

[0014] 1 needs to correct the torque command value so as to eliminate fluctuations in the output torque of the motor 12 caused by the cogging torque cT. The device that acquires the torque correction data D for this purpose is the torque correction data acquisition device 30.

[0015] Cogging torque cT is expressed by the formula "cT = A sin(Bθ + C)." In this formula, "A" is the amplitude A of cogging torque cT as shown in FIG. 3. "B" is a constant determined by the number of poles and slots in the motor 12, i.e., a constant specific to the motor 12, such as "4." "θ" is the rotation angle θ of the rotor in the motor 12. Note that the rotation angle θ changes with elapsed time t as shown in FIG. 2. "C" is the initial phase C of cogging torque cT. In other words, it is the phase of cogging torque cT when the rotor rotation angle θ is "0°."

[0016] Hereinafter, the predetermined data regarding the cogging torque cT will be referred to as "cogging torque data Q." The cogging torque data Q includes data on the initial phase C of the cogging torque cT and data on the amplitude A of the cogging torque cT. Note that the "initial phase C" here may be read as "information regarding the phase."

[0017] The torque correction data acquisition device 30 includes an acquisition device main body 30a, an input operation unit (not shown), and a display 30b. The acquisition device main body 30a is mainly composed of a computer. The input operation unit includes, for example, a keyboard, a mouse, etc., and is configured to be operable by an operator. The display 30b displays various information based on commands from the acquisition device main body 30a.

[0018] The acquisition device main body 30 a is provided with, in terms of function, a number of times designation unit 31 , a program transmission unit 32 , a waveform data acquisition unit 33 , a calculation unit 34 , a selection unit 35 , and an output unit 36 ​​.

[0019] The program transmission unit 32 is configured to be able to transmit a predetermined operation program Pg to the motor control unit 22. The predetermined operation program Pg is a program for performing a predetermined test operation to acquire waveform data Wd of the cogging torque cT, for example, as shown in FIG.

[0020] 1 displays a predetermined input screen G1 on the display 30b. The number of times designation unit 31 is configured to be able to designate the number of times N to execute the operation program Pg based on an input by the operator along the input screen G1.

[0021] Each time the operating program Pg is executed, the waveform data acquiring unit 33 receives the waveform data Wd of the cogging torque cT from the motor control unit 22. The motor control unit 22 is configured to be able to acquire the waveform data Wd of the cogging torque cT based on a feedback value from the motor 12 or the like.

[0022] The calculation unit 34 calculates the cogging torque data Q from each piece of waveform data Wd acquired by the waveform data acquisition unit 33. In this way, a plurality of pieces of cogging torque data Q are acquired.

[0023] The selection unit 35 removes outliers from all of the acquired cogging torque data Q and selects all of the remaining cogging torque data Q as torque correction data D. The selection algorithm will be described below. Note that, in the following, "plotting" and "drawing" referring to the selection unit 35 refer to "plotting" and "drawing" on the algorithm. Therefore, this does not mean that "plotting" or "drawing" is actually performed in a manner that can be visually recognized by an operator or the like.

[0024] Hereinafter, as shown in FIG. 5, a two-dimensional coordinate plane in which data indicating the initial phase C of the cogging torque cT is one dimension (horizontal axis) and data indicating the amplitude A of the cogging torque cT is another dimension (vertical axis) will be referred to as a "phase x amplitude plane CA."

[0025] The selection unit 35 first plots q of the cogging torque data Q for each execution of the operating program Pg on the phase x amplitude plane CA as shown in Fig. 5, and also draws a convex hull α1 of the set of the plots q as shown in Fig. 8. The specific procedure will be described below with reference to Figs. 5 to 8.

[0026] First, as shown in Fig. 5, the selection unit 35 selects the plot q with the smallest value of amplitude A as the first plot q1. Hereinafter, as shown in Fig. 6, a line that passes through the first plot q1 and extends in the horizontal direction will be referred to as the "first line L1." Next, the selection unit 35 selects the plot q with the smallest counterclockwise position angle Φ2 with respect to the first line L1, centered around the first plot q1, as the second plot q2. Hereinafter, the line connecting the first plot q1 and the second plot q2 will be referred to as the "second line L2."

[0027] Next, as shown in Fig. 7, the plot q having the smallest counterclockwise position angle Φ3 with respect to the extension of the second line L2, centered around the second line q2, is selected as the third plot q3. Hereinafter, the line connecting the second line q2 and the third line q3 is referred to as the "third line L3." Next, as shown in Fig. 7, the plot having the smallest counterclockwise position angle with respect to the extension of the third line L3, centered around the third line q3, is selected as the fourth plot q4.

[0028] Similar selection is repeated until the first plot q1 is selected, as shown in Figure 8. Next, as shown in Figure 8, the selected plots q1 → q2 → q3 → q4 → q5 → q1 are connected in the order of selection to draw the convex hull α1. In other words, the convex hull α1 is the smallest convex polygonal area that includes all the plots q.

[0029] Next, the selection unit 35 draws an outlier candidate circle β1 that is a circle that circumscribes three predetermined vertices of the convex hull α1 and that does not include any part of the convex hull α1, as shown in Fig. 8. Specifically, in this embodiment, the outlier candidate circle β1 circumscribes the first plot q1, the second plot q2, and the fourth plot q4.

[0030] Next, the selection unit 35 selects some or all of the cogging torque data Q corresponding to the three plots q1, q2, and q4 circumscribing the outlier candidate circle β1 as outliers. On the other hand, the selection unit 35 selects all other cogging torque data Q as torque correction data D.

[0031] 9 , the selection unit 35 selects the cogging torque data Q corresponding to the first plot q1 as an outlier, and selects the cogging torque data Q corresponding to all plots q other than the first plot q1 as torque correction data D. Then, the selection unit 35 draws a convex hull α2 for all plots q other than the first plot q1 in the same manner as in the case of the convex hull α1 described above, and draws a selection circle β2 in the same manner as in the case of the outlier candidate circle β1 described above, for all plots q other than the first plot q1. As a result, only the first plot q1 of all plots q for each execution of the operating program Pg is positioned outside the selection circle β2.

[0032] 10 , the selection unit 35 selects the cogging torque data Q corresponding to the second plot q2 as an outlier, and selects the cogging torque data Q corresponding to all plots q other than the second plot q2 as torque correction data D. Then, the selection unit 35 draws a convex hull α2 for all plots q other than the second plot q2 in the same manner as in the case of the convex hull α1 described above, and draws a selection circle β2 in the same manner as in the case of the outlier candidate circle β1 described above. As a result, of all plots q for each execution of the operating program Pg, only the second plot q2 is positioned outside the selection circle β2.

[0033] 11 , the selection unit 35 selects the cogging torque data Q corresponding to the fourth plot q4 as an outlier, and selects the cogging torque data Q corresponding to all plots q other than the fourth plot q4 as torque correction data D. Then, the selection unit 35 draws a convex hull α2 for all plots q other than the fourth plot q4 in the same manner as in the case of the convex hull α1 described above, and draws a selection circle β2 in the same manner as in the case of the outlier candidate circle β1 described above. As a result, only the fourth plot q4 out of all plots q for each execution of the operating program Pg is positioned outside the selection circle β2.

[0034] 12 , the selection unit 35 selects the cogging torque data Q corresponding to two plots q1 and q2, the first plot q1 and the second plot q2, as outliers. The selection unit 35 then selects the cogging torque data Q corresponding to all plots q other than the two plots q1 and q2 as torque correction data D. The selection unit 35 then draws a convex hull α2 for all plots q other than the two plots q1 and q2, in the same manner as in the case of the convex hull α1 described above, and draws a selection circle β2 in the same manner as in the case of the outlier candidate circle β1 described above. As a result, of all plots q for each execution of the operating program Pg, only the two plots q1 and q2 are positioned outside the selection circle β2.

[0035] 13 , the selection unit 35 selects the cogging torque data Q corresponding to three plots q1, q2, and q4, i.e., a first plot q1, a second plot q2, and a fourth plot q4, as outliers. The selection unit 35 then selects the cogging torque data Q corresponding to all plots q other than the three plots q1, q2, and q4 as torque correction data D. The selection unit 35 then draws a convex hull α2 for all plots q other than the three plots q1, q2, and q4, in the same manner as in the case of the convex hull α1 described above, and draws a selection circle β2 in the same manner as in the case of the outlier candidate circle β1 described above. As a result, of all plots q for each execution of the operating program Pg, only the three plots q1, q2, and q4 are positioned outside the selection circle β2.

[0036] Furthermore, for example, the selection unit 35 may draw the above-described outlier candidate circle β1, select one to three outliers, and repeat the process two or more times before drawing the selection circle β2. In this case, four or more plots q can be arranged outside the selection circle β2.

[0037] The selection unit 35 calculates a "torque correction data representative value Dr" as a representative value representing the plurality of torque correction data D selected by the above algorithm. The torque correction data representative value Dr may be, for example, a value corresponding to the center of the selection circle β2 as shown in Fig. 4, or may be an average value of all the torque correction data D as shown in Fig. 13, etc.

[0038] 1 transmits a predetermined signal to the display 30b, thereby causing the display 30b to display a predetermined selection result screen G2, as shown in Fig. 4, for example. The selection result screen G2 includes a display of a plot q for each execution of the operation program Pg, a display of a selection circle β2, and a display of a torque correction data representative value Dr.

[0039] When the operator selects "Apply" using the input operation unit while this selection result screen G2 is displayed, the output unit 36 ​​shown in FIG. 1 outputs the torque correction data representative value Dr to the motor control unit 22. The motor control unit 22 corrects the torque command of the motor 12 in accordance with the torque correction data representative value Dr. In other words, the torque command of the initial phase C and amplitude A corresponding to the torque correction data representative value Dr is superimposed on the original torque command. This eliminates or reduces fluctuations in the output torque of the motor 12 caused by the cogging torque cT.

[0040] The configuration and effects of this embodiment are summarized below.

[0041] 1 specifies the number of times the operation program Pg is to be executed. The waveform data acquisition unit 33 acquires waveform data Wd of the cogging torque cT for each execution of the operation program Pg. The calculation unit 34 calculates the cogging torque data Q from each waveform data Wd, thereby acquiring multiple pieces of cogging torque data Q. As described above, the cogging torque data Q for the specified number of executions can be automatically acquired.

[0042] Moreover, the selection unit 35 selects the torque correction data D from the plurality of cogging torque data Q. Therefore, the torque correction data D can be automatically selected from the plurality of cogging torque data Q.

[0043] As described above, according to this embodiment, it is possible to automatically acquire a plurality of cogging torque data Q and automatically select the torque correction data D from among them. This reduces the burden on the worker compared to when the worker manually acquires the plurality of cogging torque data Q and selects the torque correction data D.

[0044] 1 removes outliers from the plurality of cogging torque data Q. Then, the selection unit 35 selects the remaining cogging torque data Q as the torque correction data D. This allows the torque correction data D to be selected efficiently.

[0045] 4, the output unit 36 ​​displays information about the selection made by the selection unit 35 on the display 30b, so that the worker can visually recognize the information about the selection.

[0046] Specifically, the output unit displays a diagram in which a selection circle β2 is drawn together with plots q of cogging torque data Q on a phase x amplitude plane CA. In the diagram, the cogging torque data Q corresponding to the plots q located outside the selection circle β2 is an outlier. The cogging torque data Q corresponding to the plots q located within the region including the selection circle β2 and its inside is torque correction data D. This allows the operator to efficiently visually recognize the torque correction data D and the outliers.

[0047] For example, as shown in Fig. 8 , when a plurality of cogging torque data Q are plotted on a phase x amplitude plane CA, the selection unit 35 calculates a convex hull α1 of the set of the plots q. The selection unit 35 then calculates a circular outlier candidate circle β1 that circumscribes three predetermined vertices of the convex hull α1 and that does not include any part of the convex hull α1. The selection unit 35 then selects outliers from the cogging torque data Q corresponding to the plots q1, q2, and q4 located at the three vertices. This allows for efficient outlier selection.

[0048] Other Embodiments The above-described embodiment can be modified, for example, as follows.

[0049] One or more of the number of times designation unit 31, program transmission unit 32, waveform data acquisition unit 33, calculation unit 34, selection unit 35, and output unit 36 ​​shown in FIG. 1 may be incorporated into the numerical control device 20 or other devices.

[0050] 1 may acquire torque correction data D for the motor of the moving device 15 instead of or in addition to the torque correction data D for the motor 12 of the main spindle 11. Furthermore, the torque correction data acquiring device 30 may acquire torque correction data D for the motor of a device other than the machine tool 10.

[0051] In cases where the worker does not particularly need to visually confirm information related to the selection made by the selection unit 35, for example, the selection result screen G2 shown in FIG. 4 may not be displayed on the display 30b.

[0052] The outliers may be selected using a method different from that of the first embodiment. Specifically, for example, the selection unit 35 may draw a predetermined provisional selection circle centered on the average value of all plots q shown in FIG. 5 . Then, the plots q lying outside the provisional selection circle may be determined to be outliers. Then, a selection circle β2 may be drawn for all plots q excluding the outliers.

[0053] According to the above embodiment, the torque correction data acquisition device (30) described in Supplementary Notes 1 to 5 below can be realized.

[0054] [Supplementary Note 1] A torque correction data acquisition device (30) that acquires torque correction data (D) for correcting torque of a motor (12) that generates a cogging torque (cT), the torque correction data acquisition device (30) comprising: a program transmission unit (32) that transmits an operation program (Pg) to a motor control unit (22) that controls the motor (12); a number designation unit (31) that designates the number of times the operation program (Pg) is to be executed; a waveform data acquisition unit (33) that acquires waveform data (Wd) of the cogging torque (cT) for each execution of the operation program (Pg); a calculation unit (34) that calculates cogging torque data (Q) as predetermined data for the cogging torque (cT) from each of the acquired waveform data (Wd) to acquire a plurality of the cogging torque data (Q); and a selection unit (35) that selects the torque correction data (D) from the acquired plurality of the cogging torque data (Q).

[0055] [Supplementary Note 2] The torque correction data acquisition device (30) according to Supplementary Note 1, wherein the selection unit (35) excludes outliers from the plurality of cogging torque data (Q) and selects the remaining cogging torque data (Q) as the torque correction data (D).

[0056] [Supplementary Note 3] The torque correction data acquisition device (30) according to Supplementary Note 2, further comprising an output unit (36) that displays information related to the selection by the selection unit (35).

[0057] [Supplementary Note 4] The torque correction data acquisition device (30) described in Supplementary Note 3, wherein each of the cogging torque data (Q) includes two-dimensional data having data relating to the phase of the cogging torque (cT) as one dimension and data indicating the amplitude (A) of the cogging torque (cT) as another dimension, the output unit (36) plots (q) a plurality of the cogging torque data (Q) on the two-dimensional coordinate plane (CA) and displays a diagram depicting a predetermined selection circle (β2), and the cogging torque data (Q) corresponding to the plot (q) located outside the selection circle (β2) is the outlier.

[0058] [Supplementary Note 5] The torque correction data acquisition device (30) according to any one of Supplementary Notes 2 to 4, wherein each of the cogging torque data (Q) includes two-dimensional data having data relating to the phase of the cogging torque (cT) as one dimension and data indicating the amplitude (A) of the cogging torque (cT) as another dimension, and wherein the selection unit (35) calculates a convex hull (α1) of a set of plots (q) of a plurality of the cogging torque data (Q) when the plots (q) are made on the two-dimensional coordinate plane (CA), calculates a circular outlier candidate circle (β1) that circumscribes three predetermined vertices of the convex hull (α1) and no part of the convex hull (α1) extends outside the convex hull, and selects the outlier from the cogging torque data (Q) corresponding to the plots (q) located at the three vertices.

[0059] 12 Motor 22 Motor control unit 30 Torque correction data acquisition device 31 Number of times designation unit 32 Program transmission unit 33 Waveform data acquisition unit 34 Calculation unit 35 Selection unit 36 ​​Output unit A Cogging torque amplitude C Initial phase of cogging torque CA Phase x amplitude plane (two-dimensional coordinate plane) cT Cogging torque D Torque correction data Pg Operation program Q Cogging torque data q Plot of cogging torque data Wd Waveform data α1 Convex hull β1 Outlier candidate circle β2 Selection circle

Claims

1. A torque correction data acquisition device that acquires torque correction data for correcting the torque of a motor that generates cogging torque, comprising: a program transmission unit that transmits an operation program to a motor control unit that controls the motor; a number designation unit that designates the number of times the operation program is to be executed; a waveform data acquisition unit that acquires waveform data of the cogging torque for each execution of the operation program; a calculation unit that acquires a plurality of cogging torque data by calculating cogging torque data as predetermined data for the cogging torque from each of the acquired waveform data; and a selection unit that selects the torque correction data from the acquired plurality of cogging torque data.

2. The torque correction data acquisition device according to claim 1, wherein the selection unit excludes outliers from the plurality of cogging torque data and selects the remaining cogging torque data as the torque correction data.

3. The torque correction data acquisition device according to claim 2, further comprising an output section for displaying information relating to the selection made by said selection section.

4. The torque correction data acquisition device of claim 3, wherein each of the cogging torque data includes two-dimensional data with data relating to the phase of the cogging torque as one dimension and data indicating the amplitude of the cogging torque as another dimension, and the output unit displays a diagram on the two-dimensional coordinate plane in which a plurality of the cogging torque data are plotted and a predetermined selection circle is drawn, and the cogging torque data corresponding to the plots located outside the selection circle are the outliers.

5. The torque correction data acquisition device according to any one of claims 2 to 4, wherein each of the cogging torque data includes two-dimensional data in which data relating to the phase of the cogging torque is one dimension and data indicating the amplitude of the cogging torque is another dimension, and the selection unit calculates a convex hull of a set of plots of a plurality of the cogging torque data when the plots are made on the two-dimensional coordinate plane, calculates a circular outlier candidate circle that circumscribes three predetermined vertices of the convex hull and no part of the convex hull extends outside the hull, and selects the outlier from the cogging torque data corresponding to the plots located at the three vertices.

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