JP2021056868A - Machine tool, feedback control method and computer program - Google Patents

Abstract

To provide a machine tool, a feedback control method and a computer program that can control rotation speed of a main spindle according to the magnitude of a load acting on a tool.SOLUTION: A machine tool comprises a control apparatus that performs feedback control of rotation speed of a main spindle on which a tool is mounted. The control apparatus comprises: an acquisition unit that acquires a circumferential position of the main spindle; and a creation unit that creates a gain map which indicates a relationship between speed loop gain associated with main spindle rotation and a circumferential position of the main spindle, and controls the rotation speed of the main spindle on the basis of the circumferential position of the main spindle acquired by the acquisition unit and the gain map created by the creation unit.SELECTED DRAWING: Figure 3

Description

The present art relates to machine tools, feedback control methods and computer programs that control the rotational speed of the spindle on which the tool is mounted.

When machining a workpiece with a tool mounted on the spindle, the tool may vibrate. When the amplitude of vibration becomes large, the roughness of the machined surface of the work becomes large, and the quality of the product deteriorates. Conventionally, a machine tool has been proposed in which an increase / decrease pattern of a spindle rotation speed is stored in a control device of a machine tool, and the rotation speed of the spindle is changed based on the stored increase / decrease pattern. By changing the rotation speed of the spindle, the amplification of vibration can be suppressed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-144580

The machine tool changes the rotation speed of the spindle even when the load acting on the tool is small, as in the case where the load is large. That is, even when the vibration of the tool is small, the machine tool changes the rotation speed of the spindle in the same manner as when the vibration of the tool is large. If the vibration of the tool is small, the roughness of the machined surface of the work may increase due to the change in the rotation speed.

The present disclosure has been made in view of such circumstances, and provides a machine tool, a feedback control method, and a computer program capable of controlling the rotation speed of the spindle according to the magnitude of the load acting on the tool. The purpose.

The machine tool according to the embodiment of the present disclosure is a machine tool including a control device for feedback-controlling the rotation speed of a spindle on which a tool is mounted. It is provided with a creation unit that creates a gain map showing the relationship between the speed loop gain related to the rotation of the spindle and the circumferential position of the spindle, and is created by the circumferential position of the spindle acquired by the acquisition unit and the creation unit. The rotation speed of the spindle is controlled based on the obtained gain map.

In one embodiment of the present disclosure, a gain map is created and the rotation speed of the spindle is controlled based on the created gain map. Therefore, the amount of control of the rotation speed is large or small according to the magnitude of the load acting on the tool. It becomes.

In the machine tool according to the embodiment of the present disclosure, the creating unit creates a gain map based on the number of blades of a tool mounted on the spindle.

In one embodiment of the present disclosure, since the gain map is based on the number of blades of the tool, the speed loop gain corresponding to each blade can be set.

In the machine tool according to the embodiment of the present disclosure, the speed loop gain is a speed loop proportional gain or a speed loop integrated gain.

In one embodiment of the present disclosure, by setting the speed loop proportional gain or the speed loop integrated gain, it is possible to realize the control of the rotation speed according to the magnitude of the load acting on the tool.

In the machine tool according to the embodiment of the present disclosure, the control device has a determination unit for determining whether or not the target rotation speed of the spindle is equal to or lower than a predetermined rotation speed, and the speed loop determined based on the gain map. A storage unit for storing a second speed loop gain different from the gain is provided, and when the determination unit determines that the rotation speed is equal to or lower than the predetermined rotation speed, the rotation speed of the spindle is controlled based on the gain map. When the determination unit determines that the rotation speed is not equal to or lower than the predetermined rotation speed, the rotation speed of the spindle is controlled based on the second speed loop gain.

In one embodiment of the present disclosure, when the rotation speed of the spindle is not equal to or less than a predetermined rotation speed, that is, when the spindle is rotating at high speed, an inertial force acts on the spindle, so that it is difficult to change the speed of the spindle. Therefore, when the spindle is rotating at high speed, the rotation speed of the spindle is appropriately controlled based on the second speed loop gain.

In the feedback control method according to the embodiment of the present disclosure, in the feedback control method of the rotation speed of the spindle, the rotational position of the spindle is acquired, and the rotation of the spindle is based on the number of blades of a tool mounted on the spindle. A gain map showing the relationship between the speed loop gain and the circumferential position of the spindle is created, and the rotation speed of the spindle is controlled based on the acquired circumferential position of the spindle and the created gain map.

In one embodiment of the present disclosure, a gain map is created and the rotation speed of the spindle is controlled based on the created gain map. Therefore, the amount of control of the rotation speed is large or small according to the magnitude of the load acting on the tool. It becomes.

The computer program according to the embodiment of the present disclosure is a computer program that can be executed by a control device that feedback-controls the rotation speed of the spindle, wherein the control device acquires the circumferential position of the spindle and is mounted on the spindle. Based on the number of blades of the tool to be used, a gain map showing the relationship between the speed loop gain related to the rotation of the spindle and the circumferential position of the spindle is created, and based on the acquired circumferential position of the spindle and the created gain map. , The rotation speed of the spindle is controlled.

In one embodiment of the present disclosure, a gain map is created and the rotation speed of the spindle is controlled based on the created gain map. Therefore, the amount of control of the rotation speed is large or small according to the magnitude of the load acting on the tool. It becomes.

In the machine tool, the feedback control method, and the computer program according to the embodiment of the present disclosure, a gain map is created and the rotation speed of the spindle is controlled based on the created gain map, so that the load acting on the tool is applied. The amount of control of the rotation speed also becomes large or small according to the size of.

It is a vertical sectional view of the machine tool which concerns on Embodiment 1. FIG. It is a block diagram which illustrates the control device of a machine tool. It is a block diagram of a spindle control circuit, a spindle motor, an encoder and a differentiator. It is a flowchart explaining the map creation process which creates the gain map which shows the relationship between the velocity loop gain about the rotation of a spindle, and the circumferential position of a spindle. It is a schematic diagram which shows a tool and a work. It is a figure which shows an example of the gain map of the velocity loop proportional gain G1 with respect to the rotation angle of a spindle. It is a figure which shows an example of the gain map of the velocity loop integral gain G2 with respect to the rotation angle of a spindle. It is a flowchart explaining the drive processing of a spindle by a CPU. It is a timing chart of the output torque P1 of the spindle, the rotation speed S1 of the spindle, the velocity loop proportional gain G1, and the velocity loop integrated gain G2 when the first load T1 acts on the tool. It is a timing chart of the output torque P2 of the spindle, the rotation speed S2 of the spindle, the velocity loop proportional gain G1, and the velocity loop integrated gain G2 when the second load T2 acts on the tool. It is a flowchart explaining the drive processing of the spindle by the CPU which concerns on Embodiment 2.

(Embodiment 1) Hereinafter, the present invention will be described with reference to a drawing showing a machine tool according to the first embodiment. FIG. 1 is a vertical cross-sectional view of a machine tool. In the following explanation, the up, down, left, right, front and back indicated by the arrows in the figure are used. As shown in FIG. 1, the machine tool includes a rectangular base 1 that is long in the front-rear direction. The vertical pillar 2 is fixed to the rear part of the base 1. A work holding portion 10 for holding the work is provided on the front portion of the base 1. The work holding portion 10 includes a Y-direction moving portion 11 that moves in the front-rear direction, an X-direction moving portion 12 that moves in the left-right direction, and a base 13 that fixes the work. The Y-direction moving unit 11 includes a Y-axis motor 16 (see FIG. 2), and the Y-direction moving unit 11 moves back and forth by driving the Y-axis motor 16. The X-direction moving unit 12 includes an X-axis motor 23 (see FIG. 2), and the X-direction moving unit 12 moves left and right by the X-axis motor 23.

The Y-direction moving portion 11 is provided on the base 1, and the X-direction moving portion 12 is provided on the Y-direction moving portion 11. The table 13 is provided on the moving portion 12 in the X direction. The left-right front-back movement of the X-direction moving portion 12 and the Y-direction moving portion 11 determines the left-right front-back position of the work fixed to the table 13.

The spindle head 3 that can move in the vertical direction is provided on the front surface of the vertical column 2. The Z-axis motor 33 (see FIG. 2) is provided on the vertical column 2, and the Z-axis motor 33 moves the spindle head 3 up and down. The spindle head 3 rotatably holds a spindle (not shown) extending vertically. The spindle motor 8 is provided at the upper end of the spindle head 3, and the spindle is rotated by driving the spindle motor 8. The two support plates 7 project forward from the vertical column 2 and are arranged side by side. The support plate 7 supports the tool magazine 6, and the tool magazine 6 holds the tool 5. By driving the magazine motor 60 (see FIG. 2), the tool magazine 6 is rotated to send a predetermined tool 5 to the lowest position, that is, the replacement position.

FIG. 2 is a block diagram illustrating a control device 50 of a machine tool. As shown in FIG. 2, the control device 50 includes a CPU 51, a storage unit 52, a RAM 53, and an input / output interface 54. The storage unit 52 is a rewritable memory, such as EPROM or EEPROM. The storage unit 52 stores a machining program for machining the work, an operation program for the spindle head 3 and the tool magazine 6, a gain used for a tapping operation, a spindle positioning operation, and the like, a program for creating a gain map described later, and the like. The control device 50 controls the machine tool based on the program stored in the storage unit 52. The CPU 51 sequentially reads a plurality of commands constituting the machining program and executes the read commands. The control device 50 may include a ROM in which a program is stored in advance.

When the operator operates the operation unit 14, a signal is input from the operation unit 14 to the input / output interface 54. The operation unit 14 is a keyboard, a button, a touch panel, or the like. The input / output interface 54 outputs a signal to the display unit 15. The display unit 15 displays characters, figures, symbols, and the like. The display unit 15 is, for example, a liquid crystal display panel.

The control device 50 includes an X-axis control circuit 55 corresponding to the X-axis motor 23, a servo amplifier 55a, and a differentiator 23b. The X-axis motor 23 includes an encoder 23a. The X-axis control circuit 55 outputs a command indicating the amount of current to the servo amplifier 55a based on a command from the CPU 51. The servo amplifier 55a receives the command and outputs a drive current to the X-axis motor 23. The encoder 23a outputs a position feedback signal to the X-axis control circuit 55. The X-axis control circuit 55 executes position feedback control based on the position feedback signal. The encoder 23a outputs a position feedback signal to the differentiator 23b, and the differentiator 23b converts the position feedback signal into a velocity feedback signal and outputs the position feedback signal to the X-axis control circuit 55. The X-axis control circuit 55 executes speed feedback control based on the speed feedback signal. The current detector 55b detects the value of the drive current output by the servo amplifier 55a. The current detector 55b feeds back the value of the drive current to the X-axis control circuit 55. The X-axis control circuit 55 executes current control based on the value of the drive current.

The control device 50 includes a Y-axis control circuit 56 corresponding to the Y-axis motor 16, a servo amplifier 56a, a differentiator 16b, and a current detector 56b, and the Y-axis motor 16 includes an encoder 16a. The Y-axis control circuit 56, the servo amplifier 56a, the differentiator 16b, the Y-axis motor 16, the encoder 16a, and the current detector 56b are the same as those of the X-axis, and the description thereof will be omitted. The control device 50 includes a Z-axis control circuit 57 corresponding to the Z-axis motor 33, a servo amplifier 57a, a current detector 57b, and a differentiator 33b. The Z-axis motor 33 includes an encoder 33a. The Z-axis control circuit 57, the servo amplifier 57a, the differentiator 33b, the Z-axis motor 33, the encoder 33a, and the current detector 57b are the same as those of the X-axis, and the description thereof will be omitted. The control device 50 includes a magazine control circuit 58 corresponding to the magazine motor 60, a servo amplifier 58a, a current detector 58b, and a differentiator 60b. The magazine motor 60 includes an encoder 60a. The magazine control circuit 58, the servo amplifier 58a, the differentiator 60b, the magazine motor 60, the encoder 60a, and the current detector 58b are the same as those of the X-axis, and the description thereof will be omitted.

The control device 50 includes a spindle control circuit 79, a servo amplifier 79a, a current detector 79b, and a differentiator 80b corresponding to the spindle motor 8. The spindle motor 8 includes an encoder 80a. The servo amplifier 79a, the differentiator 80b, the spindle motor 8, the encoder 80a, and the current detector 79b are the same as those of the X-axis, and the description thereof will be omitted. The spindle control circuit 79 is basically the same as that of the X-axis, but has a configuration different from that of the X-axis as described below.

FIG. 3 is a block diagram of the spindle control circuit 79, the spindle motor 8, the encoder 80a, and the differentiator 80b. The block diagram is shown in the Laplace transform format. In FIG. 3, the description of the servo amplifier 79a and the current detector 79b is omitted. The spindle control circuit 79 includes a first adder 70, a first transfer element 71, a second adder 72, a second transfer element 73, a third adder 74, an integrator 75, and a third transmission element 76. The spindle control circuit 79 may include a differentiator 80b.

The position command value is input from the CPU 51 to the first adder 70, and the position feedback command value is input from the encoder 80a. The first adder 70 subtracts the position feedback command value from the position command value and outputs it to the first transmission element 71.

The first transmission element 71 has a position loop proportional gain G0, and the output value of the first adder 70 is multiplied by G0 and output to the second adder 72. The output value from the first transmission element 71 and the speed feedback command value from the differentiator 80b are input to the second adder 72. The second adder 72 subtracts the speed feedback command value from the output value of the first transmission element 71, and outputs the speed feedback command value to the second transmission element 73 and the integrator 75.

The second transmission element 73 stores, for example, the velocity loop proportional gain G1, multiplies the output value of the second adder 72 by G1, and outputs the output to the third adder 74. The integrator 75 integrates the output value of the second adder 72 and outputs it to the third transmission element 76. The third transmission element 76 stores, for example, the velocity loop integral gain G2, multiplies the output value of the integrator 75 by G2, and outputs the output to the third adder 74.

The third adder 74 adds the output values of the second transmission element 73 and the third transmission element 76 and outputs them to the spindle motor 8. The encoder 80a is rotated by driving the spindle motor 8, and the output value of the encoder 80a, that is, the position feedback command value is input to the differentiator 80b and the first adder 70.

FIG. 4 is a flowchart for explaining a map creation process for creating a gain map showing the relationship between the speed loop gain related to the rotation of the spindle and the circumferential position of the spindle, and FIG. 5 is a schematic diagram showing the tool 5 and the work 40. When the user operates the operation unit 14 and inputs a command to create a gain map, the CPU 51 creates a gain map. The CPU 51 creates gain maps for G1 and G2, respectively.

The CPU 51 determines whether or not the number of blades of the tool 5 has been input (S1). The user operates the operation unit 14 and inputs the number of blades n. If there is no input for the number of blades (S1: NO), the process is returned to S1. For example, as shown in FIG. 5, when the number of blades of the tool 5 is four, n is four.

When the number of blades is input (S1: YES), the CPU 51 calculates the angle for changing the gain (S2). The CPU 51 calculates 360 degrees / n, assuming that the phase intervals of the blades of the tool 5 are evenly spaced. For example, when n is 4, 90 degrees is calculated.

The CPU 51 creates a gain map in which a gain of a different magnitude is set every 90 degrees, stores it in the storage unit 52 (S3), and ends the process.

FIG. 6 is a diagram showing an example of a gain map of the velocity loop proportional gain G1 with respect to the rotation angle of the spindle, and FIG. 7 is a diagram showing an example of a gain map of the velocity loop integrated gain G2 with respect to the rotation angle of the spindle. For example, as shown in FIG. 6, the storage unit 52 stores a gain map for changing G1 in a value A and a value B larger than the value A every 360 / n degrees, and as shown in FIG. A gain map for changing G2 is stored in a value C and a value D larger than the value C every 360 / n degrees.

When positioning the tool 5, the CPU 51 associates the circumferential position of the spindle with the circumferential position of the blade of the tool 5. In addition, the circumferential position of the spindle is associated with the angle at which the gain value in each gain map is changed. That is, the circumferential position of the spindle and the angle at which the gain value in each gain map is changed are associated with each other.

FIG. 8 is a flowchart illustrating a spindle drive process by the CPU 51. The CPU 51 determines whether or not the variable setting for the driving process of the spindle is completed (S11). The user operates the operation unit 14 to set variables. If the variable setting is not completed (S11: NO), the process is returned to S11.

When the variable setting is completed, the CPU 51 determines whether or not the spindle rotation command is being executed from the command of the machining program currently being executed (S12). When the spindle rotation command is executed (S12: YES), the CPU 51 acquires the spindle angle, that is, the circumferential position from the encoder 80a (S13).

The CPU 51 determines whether or not the spindle rotation command being executed is a normal rotation command (S14). The normal rotation command is a rotation command for cutting, and corresponds to, for example, the M3 and M4 commands of the M code. The rotation command for tapping, for example, the G63 or G74 command of the G code, or the command for positioning, for example, the M19 command of the M code, is a rotation command different from the normal rotation command.

In the case of a normal rotation command (S14: YES), the CPU 51 refers to the maps of G1 and G2 (see FIGS. 6 and 7), and sets the values of G1 and G2, that is, the gain, according to the spindle angle acquired in S13. Acquire (S15).

When it is not a normal rotation command (S14: NO), the CPU 51 refers to the storage unit 52 and acquires the speed loop proportional gain and the speed loop integrated gain corresponding to the command being executed (S16). The storage unit 52 stores in advance, for example, the speed loop proportional gain G3 and the speed loop integrated gain G4 corresponding to the rotation command for tapping or the command for positioning. The values of G3 and G4 are, for example, constants.

After acquiring the gain in S15 or S16, the acquired gain is set in the second transmission element 73 and the third transmission element 76, and the feedback control of the spindle motor 8 is performed (S17). When the gains G1 and G2 are acquired in S15, the gain G1 is set in the second transmission element 73, and the gain G2 is set in the third transmission element 76. When the gains G3 and G4 are acquired in S16, the gain G3 is set in the second transmission element 73, and the gain G4 is set in the third transmission element 76.

After executing the feedback control in S17 or in S12, when it is determined that the spindle rotation command is not executed (S12: NO), the CPU 51 determines whether or not there is a reset request (S18).

When there is no reset request (S18: NO), the CPU 51 returns the process to S12, reads the next command of the machining program, and determines whether or not the spindle rotation command is being executed. When there is a reset request (S18: YES), the CPU 51 returns the process to step S11.

FIG. 9 is a timing chart of the output torque P1 of the spindle, the rotation speed S1 of the spindle, the velocity loop proportional gain G1, and the velocity loop integrated gain G2 when the first load T1 acts on the tool 5. SA in FIG. 9 shows the target rotation speed of the spindle. The first load T1 can be expressed as torque.

As shown in FIG. 9, when the gain G1 is B, the response speed of the output torque P1 of the spindle is faster than when the gain G1 is A, and the torque approximate to the first load T1 is output, and the rotation speed is increased. The decrease is also slight. Further, when the gain G2 is D, the response speed of the output torque P1 of the spindle is faster than when the gain G2 is C, the torque approximate to the first load T1 is output, and the decrease in the rotation speed is slight. ..

FIG. 10 is a timing chart of the output torque P2 of the spindle, the rotation speed S2 of the spindle, the velocity loop proportional gain G1, and the velocity loop integrated gain G2 when the second load T2 acts on the tool 5. SA in FIG. 10 shows the target rotation speed of the spindle. The second load T2 can be expressed as torque and is smaller than the first load T1.

As shown in FIG. 10, when the gain G1 is B, the response speed of the output torque P2 of the spindle is faster than when the gain G1 is A, and the torque approximate to the second load T2 is output, and the rotation speed is increased. The decrease is also slight. Further, when the gain G2 is D, the response speed of the output torque P1 of the spindle is faster than when the gain G2 is C, the torque approximate to the second load T2 is output, and the decrease in the rotation speed is slight. ..

As shown in FIGS. 9 and 10, by periodically changing the value of the gain G1 or the gain G2, the rotation speed is periodically changed, and the spindle repeats high-speed rotation and low-speed rotation. Therefore, the amplification of the vibration of the tool 5 can be suppressed.

As shown in FIGS. 9 and 10, when the second load T2 acts on the tool 5, the amount of fluctuation in the rotational speed of the spindle is smaller than when the first load T1 acts on the tool 5. That is, the amount of control of the rotation speed of the spindle also increases or decreases according to the magnitude of the load acting on the tool 5, and the rotation speed becomes stable.

Since the gain map is based on the number of blades of the tool 5, the speed loop gain corresponding to each blade can be set. Further, by setting the speed loop proportional gain G1 or the speed loop integrated gain G2, it is possible to realize the control of the rotation speed according to the magnitude of the load acting on the tool 5.

(Embodiment 2)
Hereinafter, the present invention will be described with reference to the drawings showing the machine tool according to the second embodiment. Of the configurations according to the second embodiment, the same configurations as those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The storage unit 52 of the machine tool stores the speed loop proportional gain G5 and the speed loop integrated gain G6 in advance. The speed loop proportional gain G5 is different from the speed loop proportional gain G1 determined by the gain map shown in FIG. The velocity loop integrated gain G6 is different from the velocity loop integrated gain G2 determined by the gain map shown in FIG. The values of G5 and G6 are, for example, constants, and G5 and G6 are larger than G1 and G2, respectively. The storage unit 52 stores the threshold rotation speed V in advance. The velocity loop proportional gain G5 and the velocity loop integrated gain G6 constitute the second velocity loop gain.

FIG. 11 is a flowchart illustrating a spindle drive process by the CPU 51. S21 to S24 in FIG. 11 are the same processes as S11 to S14 in FIG. 8, S25 is the same process as S16 in FIG. 8, and S30 is the same process as S18 in FIG. Omit. Here, S26 to S29 will be described.

When it is determined in S24 that the spindle rotation command being executed is a normal rotation command, the CPU 51 determines whether or not the target rotation speed of the spindle rotation command is equal to or less than the threshold rotation speed V (S26). When the target rotation speed is not equal to or less than the threshold rotation speed V (S26: NO), the CPU 51 acquires the speed loop proportional gain G5 and the speed loop integrated gain G6 from the storage unit 52 (S27). The threshold rotation speed is 1500 rpm when the number of blades is 4.

When the target rotation speed is equal to or less than the threshold rotation speed V (S26: YES), the CPU 51 refers to the maps of G1 and G2 (see FIGS. 6 and 7), and is proportional to the speed loop according to the spindle angle acquired in S23. The gain G1 and the velocity loop integrated gain G2 are acquired (S28).

After acquiring the gain in S25, S27 or S28, the acquired gain is set in the second transmission element 73 and the third transmission element 76, and the feedback control of the spindle motor 8 is performed (S29). When the gains G1 and G2 are acquired in S28, the gain G1 is set in the second transmission element 73, and the gain G2 is set in the third transmission element 76. When the gains G3 and G4 are acquired in S25, the gain G3 is set in the second transmission element 73, and the gain G4 is set in the third transmission element 76. When the gains G5 and G6 are acquired in S27, the gain G5 is set in the second transmission element 73, and the gain G6 is set in the third transmission element 76.

When the rotation speed of the spindle is not equal to or less than the threshold rotation speed V, that is, when the spindle is rotating at high speed, it is difficult to change the speed of the spindle because the inertial force acts on the spindle. Therefore, when the spindle is rotating at high speed, the rotation speed of the spindle is appropriately controlled based on the velocity loop proportional gain G5 and the velocity loop integrated gain G6, that is, the second velocity loop gain. By setting G5 and G6 to a constant larger than G1 and G2, it becomes easy to appropriately control the spindle rotating at high speed.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The technical features described in each example can be combined with each other and the scope of the invention is intended to include all modifications within the claims and scope equivalent to the claims. Will be done.

5 Tools 8 Spindle motor 14 Operation unit 50 Control device 51 CPU
52 Storage unit 54 Input / output interface 71 First transmission element 73 Second transmission element 75 Integrator 76 Third transmission element 79 Main axis control circuit 79a Servo amplifier 80a Encoder 80b Differentiator

Claims (6)

In a machine tool equipped with a control device that feedback-controls the rotation speed of the spindle on which the tool is mounted.
The control device is
An acquisition unit that acquires the circumferential position of the spindle, and
It is provided with a creation unit that creates a gain map showing the relationship between the velocity loop gain related to the rotation of the spindle and the circumferential position of the spindle.
A machine tool that controls the rotational speed of the spindle based on the circumferential position of the spindle acquired by the acquisition unit and the gain map created by the creation unit. The machine tool according to claim 1, wherein the creating unit creates a gain map based on the number of blades of a tool mounted on the spindle. The machine tool according to claim 1 or 2, wherein the speed loop gain is a speed loop proportional gain or a speed loop integrated gain. The control device is
A determination unit for determining whether or not the target rotation speed of the spindle is equal to or less than a predetermined rotation speed,
It is provided with a storage unit for storing a second speed loop gain different from the speed loop gain determined based on the gain map.
When the determination unit determines that the rotation speed is equal to or lower than the predetermined rotation speed, the rotation speed of the spindle is controlled based on the gain map.
The machine tool according to any one of claims 1 to 3, wherein when the determination unit determines that the rotation speed is not equal to or lower than the predetermined rotation speed, the rotation speed of the spindle is controlled based on the second speed loop gain. In the feedback control method of the rotation speed of the spindle,
Obtain the circumferential position of the spindle and
Based on the number of blades of the tool mounted on the spindle, a gain map showing the relationship between the velocity loop gain related to the rotation of the spindle and the circumferential position of the spindle is created.
A feedback control method for controlling the rotation speed of the spindle based on the acquired circumferential position of the spindle and the created gain map. In a computer program that can be executed by a control device that feedback-controls the rotation speed of the spindle
In the control device
Acquire the circumferential position of the spindle,
Based on the number of blades of the tool mounted on the spindle, a gain map showing the relationship between the speed loop gain related to the rotation of the spindle and the circumferential position of the spindle is created.
A computer program that controls the rotation speed of the spindle based on the acquired circumferential position of the spindle and the created gain map.

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