KR101610234B1 - Machine tool including feed forward portion - Google Patents

Abstract

The machine tool apparatus of the present invention includes: a motor position control unit for controlling a position of a motor that transfers a tool or an object; A motor speed control unit connected to a rear end of the motor position control unit and controlling a speed of the motor; A feed forward unit for calculating a correction amount according to a command position input to the motor position control unit and feeding-forwarding the correction amount to the motor position control unit or the motor speed control unit; A tuning unit for automatically tuning the gain of the feedforward unit according to acceleration / deceleration or constant speed operation of the motor; .

Description

[0001] MACHINE TOOL INCLUDING FEED FORWARD PORTION [0002]

TECHNICAL FIELD [0001] The present invention relates to a machine tool apparatus, and more particularly, to a technique in which a servo control unit that controls workpiece transfer of a machine tool apparatus includes a feed forward unit.

The machine tool unit processes the object according to the shape and dimensions determined according to the CNC input data. At this time, a conveying section for conveying the object or the tool is provided, and the conveying section controls the relative speed between the object and the tool by transferring the object or the tool to the precise position designated by the CNC, thereby determining the processing quality of the object.

At this time, the low rigidity of the conveyance portion may be a problem depending on the size of the object and the cutting condition. Further, as the feed speed of the spindle or the tool for rotating the object is increased, the low rigidity of the machine tool may be a problem, and the low rigidity of the machine tool may be a problem in high precision machining.

If the low stiffness is a problem, response delay and accompanying vibration may occur in the control of the position of the conveyance part, which may degrade the processing accuracy.

Korean Patent No. 0575433 discloses a machine tool for ejecting a lubricant, but does not mention a technique for improving the machining state of an object from the viewpoint of compensating for low rigidity.

Korean Patent No. 0575433

The present invention is to provide a machine tool apparatus capable of suppressing response delay and vibration occurrence of the servo control unit when the machine tool apparatus has a low rigidity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise forms disclosed. Other objects, which will be apparent to those skilled in the art, It will be possible.

In one embodiment, the machine tool apparatus of the present invention includes: a motor position control unit for controlling a position of a motor that transfers a tool or an object; A motor speed control unit connected to a rear end of the motor position control unit and controlling a speed of the motor; A feed forward unit for calculating a correction amount according to a command position input to the motor position control unit and feeding-forwarding the correction amount to the motor position control unit or the motor speed control unit; A tuning unit for automatically tuning the gain of the feedforward unit according to acceleration / deceleration or constant speed operation of the motor; .

In one embodiment, the machine tool device of the present invention includes: a mechanical part sensor for measuring a position or a speed of a mechanical part connected to the motor; A mechanical part position control part for receiving a feedback signal regarding the position or speed of the mechanical part from the mechanical part sensor and controlling the position of the mechanical part; .

In one embodiment, the tuning unit sets the gain of the feedforward unit as an inverse of a transfer function modeled by the motor or a mechanical unit connected to the motor.

In one embodiment, the machine tool device of the present invention further includes: a mechanical part position control part for controlling a position of a mechanical part connected to the motor; Wherein at least one of a first filter disposed at an output end of the feed forward unit and a second filter disposed at an output end of the mechanical unit position control unit is provided.

In one embodiment, the tuning unit automatically optimizes the transfer function of at least one of the feedforward unit, the first filter, and the second filter in accordance with operating conditions of the motor or the mechanical unit.

In one embodiment, the tuning unit sets the second filter as a low-pass filter when the first filter is set as a high-pass filter, and sets the second filter as a low-pass filter when the first filter is set as a low- .

In one embodiment, the machine tool apparatus of the present invention includes: a first feedback unit for feedback-controlling a position or speed of a motor; A second feedback unit for feedback-controlling the position or speed of the mechanical unit connected to the motor; A feed forward unit for calculating a correction amount according to a command position input to the first feedback unit and feeding-forwarding the correction amount to the first feedback unit; A tuning unit for automatically tuning a gain of at least one of the feedforward unit, the first feedback unit and the second feedback unit in consideration of low rigidity between the motor and the mechanical unit; .

In one embodiment, the machine tool device of the present invention further comprises: a first filter provided at an output end of the feed forward portion; A second filter provided at an output terminal of the second feedback unit; Wherein the tuning unit sets the first filter to a high pass filter and sets the second filter to a low pass filter.

According to an embodiment of the present invention, the machine tool apparatus further comprises a motor speed control unit for controlling the speed of the motor, wherein the output value of the second filter is removed during acceleration / deceleration of the motor, 1 filter, the high frequency component of the output of the feedforward unit is input to the motor speed control unit, the output value of the first filter is removed at the constant speed operation of the motor, and the output of the second feedback unit Is inputted to the motor speed control section.

In one embodiment, the machine tool apparatus of the present invention includes: a motor position control unit for controlling a position of a motor that transfers a tool or an object; A mechanical part position control part for receiving a feedback signal related to the position or speed of the mechanical part connected to the motor and controlling the position of the mechanical part; A feed forward unit for calculating a correction amount according to the command position and feeding-forwarding the correction amount to the motor position control unit; A first filter provided in the feedforward section as a high pass filter; A second filter provided in the mechanical unit position control unit as a low pass filter; A signal obtained by adding a high frequency component of a speed signal passing through the first filter to a speed signal of the motor output from the motor position control unit during acceleration and deceleration of the motor is inputted and the signal outputted from the motor position control unit A motor speed controller for inputting a signal obtained by adding a low-frequency speed component passing through the second filter to a speed signal of the motor, and controlling the speed of the motor in accordance with the input signal; .

A feedforward unit improves the transient response and the normal response characteristic, and the mechanical control unit is provided in parallel to the motor control unit to implement a full-closed control loop, and the characteristics of the first filter and the second filter are automatically tuned, It is possible to suppress the generation and suppress the occurrence of vibration. Although the response delay is solved when the gain is increased, the tradeoff relationship in which vibration is likely to occur can be solved by adjusting the characteristics of the first and second filters or adjusting the gain of the feedforward part. Further, by setting the gain of the feedforward part to be an inverse number of the system parameter, the operation characteristic of the feedforward part can be improved and the occurrence of vibration can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a main part of a machine tool of the present invention. Fig.
2 is a block diagram showing a servo control unit of the present invention.
3 is a graph showing the degree of vibration reduction in the transient response before and after the operation of the tuning unit of the present invention.
4 is a block diagram illustrating an embodiment of the tuning unit of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience. In addition, terms defined in consideration of the configuration and operation of the present invention may be changed according to the intention or custom of the user, the operator. Definitions of these terms should be based on the content of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a main part of a machine tool of the present invention. Fig. 2 is a block diagram showing the servo control unit 100 of the present invention. 3 is a graph showing the degree of vibration reduction in the transient response before and after the operation of the tuning unit 300 of the present invention. FIG. 4 is a block diagram illustrating an embodiment of the tuning unit 300 of the present invention.

1 to 4, the construction and operation of the machine tool of the present invention will be described in detail.

As the machine tool unit becomes larger, the effect of deformation due to warping, twisting, tensile, etc. between the motor 3 driving the machine unit 7 and the machine unit 7 increases, and the machine becomes closer to a low rigidity system. Further, as the machining accuracy is set higher, the effect of low stiffness is increased even in the same machine tool apparatus. This is collectively referred to as a "low rigidity system".

In the case of the low stiffness system, the amount of deformation due to the low stiffness exhibits an elastic characteristic that increases in proportion to the acceleration in a certain range, so that the motor 3 and the mechanical part 7 can be regarded as being elastically coupled. Therefore, it can be seen that the low stiffness system is not connected between the motor 3 and the mechanical part 7 by a rigid body, but is connected by the damping or the spring 8 intervening. In the low stiffness system, in particular, the acceleration change amount is large in the acceleration / deceleration section in which the transfer of the mechanical section 7 is started, so that the transfer response delay may occur or unexpected vibration may occur.

That is, as the size of the machine increases, vibrations due to low rigidity may occur. The weakened stiffness can cause torsion between the motor 3 and the object. Due to the torsion, a delay occurs in moving to a predetermined position, which may eventually cause vibration. For example, in a large-scale machine tool, positional precision control may be difficult due to such a delay. The present invention suppresses the delay phenomenon due to such weak stiffness and reduces vibration to achieve precise position control.

1, the motor 3 and the mechanical part 7 are connected to each other by a ball screw 7b. In case of a rigid system, according to the data inputted from the CNC part 200, When the position of the motor 3 is rotated so as to correspond to 10 ', the mechanical part 7 is also transferred by' 10 '. However, in a low stiffness system, even if the rotational position of the motor 3 is rotated by, for example, ' 10 ' due to damping or elasticity effects, the feeding position of the mechanical part 7 does not correspond to 10. At this time, it can be seen that the response is delayed and the position of the motor 3 to the mechanical part 7 is 1: 1 and the ripple occurs in the response without a constant relation.

The present invention provides the following means for response delay compensation or vibration suppression in a low stiffness system.

i) the feed forward unit 4,

ii) a full closed loop control is employed by measuring the positional displacement of the mechanical part 7 together with the displacement of the motor 3,

iii) setting the gain of the feedforward unit 4 to the reciprocal of the transfer function modeled by the motor 3 or the mechanical unit 7,

iv) installing a first filter (19) in the feedforward unit (4), installing a second filter (16) in the full closed loop (400)

v) the transfer function of the first filter (19) and the second filter (16) can be optimally tuned according to operating conditions,

(vi) a method of automatically tuning the gain of the feedforward unit 4, the gain of the first filter 19, and the gain of the second filter 16.

As one embodiment, the amount of elastic deformation between the motor 3 and the mechanical part 7 is taken into account with respect to the movement command to the mechanical part 7. [ To this end, a motor sensor 3a for measuring the rotation angle or position of the motor 3 is employed and a first feedback unit 410 for inputting a feedback signal and command position of the motor sensor 3a to the motor position control unit 1 ). The first feedback unit 410 receives a feedback input of the motor sensor 3a.

A mechanical part sensor 7a for measuring the positional displacement of the mechanical part 7 is provided and the difference between the measured value of the mechanical part sensor 7a and the commanded position is referred to as a positional error, 15 for inputting a second feedback signal. The second feedback section 420 receives the feedback input of the mechanical part sensor 7a.

The first feedback unit 410 and the second feedback unit 420 may be installed together to provide a full closed loop 400 receiving the feedback signals of both the motor sensor 3a and the mechanical sensor 7a. ) Is implemented.

The operation of the motor 3 or the mechanical part 7 is performed when the position gain of the mechanical part position control part 15 of the first feedback part 410 or the mechanical part position control part 15 of the second feedback part 420 is small The elastic behavior between the motor 3 and the machine section 7 is stabilized, but the reduction in machining accuracy in the steady state may be a problem. Conversely, when the positional gain of the motor position control section 1 or the mechanical section position control section 15 is large, the operation of the motor 3 or the mechanical section 7 becomes rapid, The elastic effect between the first and second electrodes 7 and 7 may be increased to cause vibration.

This includes the first feedback part 410 relating to the motor 3 and the second feedback part 420 relating to the mechanical part 7 as well as the full closed loop 400 relating to the motor 3 and the mechanical part 7, The same is true.

When the position gains of the motor position control section 1 and the machine position control section 15 are small, the follow-up is delayed and the position error amount obtained by subtracting the measurement position from the command position becomes large and the accuracy decreases. An increase in gain causes vibration or overshoot.

Considering the trade-off relationship of the low stiffness system, a response delay may occur if the gain of the control loop is reduced to suppress the vibration of the mechanical unit 7, and the response delay may degrade the machining accuracy. Vibration may occur if gain is increased to reduce response delay and improve precision. The present invention provides the above-mentioned means in order to achieve two effects of a trade-off relationship of response delay reduction and vibration suppression.

1, assuming that the position value of the motor 3 is Xa, the position value of the mechanical part 7 is X, the acceleration value of the position value X of the mechanical part 7 is differentiated twice twice, The mass of the mechanical part 7 is M, the elastic coefficient of the motor 3 and the mechanical part 7 is K, and the frictional force of the mechanical part 7 is f.

At this time, when MA = K (Xa-X) -f is established and the mechanical part 7 moves at a constant speed, the acceleration A of the mechanical part 7 becomes zero, so f = K (Xa-X). Here, the positional deviation (Xa-X) between the motor 3 and the mechanical part 7 is f / K.

2, the value input to the motor position control unit 1 is the position offset of the motor 3 calculated by the motor position offset calculation unit 10 and the position offset of the motor 3 is M < / RTI > The output value Vcs of the motor position control unit 1 to which the motor 3 position offset is inputted is Kp ([theta] - [theta] m).

Similarly, the value input to the mechanical unit position control unit 15 is the position offset of the mechanical unit 7 calculated by the mechanical unit position offset calculation unit 17, and the position offset of the mechanical unit 7 is (command position?) - ( L) of the mechanical part 7). The output value Vcf of the mechanical unit position control unit 15 to which the position offset of the mechanical unit 7 is inputted is Kp ([theta] - [theta] L).

In one embodiment, the full closed loop 400 of the present invention includes a loop comparator 18 for subtracting the output value of the motor position control unit 1 from the output value of the mechanical unit position control unit 15.

The loop comparator 18 subtracts the output value Vcs = Kp (? -? M) of the motor position control unit 1 from the output value Vcf = Kp (? -? L) of the mechanical unit position control unit 15. The output value of the loop comparator 18 is Vcf - Vcs = Kp (? M -? L). Here, ([theta] m - [theta] L) is an actual positional deviation between the motor 3 and the mechanical part 7 caused by the twist in the low stiffness system. The output value of the loop comparator 18 is obtained by multiplying the actual positional deviation between the motor 3 and the mechanical part 7 by the gain.

The speed command calculation section 21 calculates the speed command value Vcf-Vcs = Kp (? M -? L) outputted from the loop comparator 18 and the output value Vcs of the motor speed control section 2 based on the speed calculated by the feed forward section 4 And outputs a speed command Vc which is a sum of the correction amounts Vof.

The motor speed control section 2 is supplied with the output value Vcs of the motor speed control section 2 and the output value Kp (? M -? L) of the loop comparator 18 as the value generated by the speed command calculating section 21, A speed command Vc obtained by adding the speed correction amount Vof calculated in the step (4) is inputted.

In one embodiment, the output value Kp (? M -? L) of the loop comparator 18 is preferably input to the motor speed control section 2 through the second filter 16.

In one embodiment, the second filter 16 is preferably a low-pass filter that filters the high-frequency components of the output value Kp (? M -? L) of the loop comparator 18. Therefore, only the low frequency component of the output value Kp (? M -? L) of the loop comparator 18 is input to the motor speed control unit 2, which is not a high frequency component generated in the acceleration / Frequency component generated in the steady state of the loop comparator 18 is input to the motor speed control unit 2 as an output value of the loop comparator 18. [

On the other hand, the position command? Is input to the feed forward unit 4. The feedforward offset calculation unit 20 provided at the output end of the feedforward unit 4 subtracts Vcf from the output value of the feedforward unit 4. Therefore, the feed forward offset Vof is a value obtained by subtracting Vcf from the output value of the feed forward unit 4. [

<CASE 1>

When the first filter 19 is a high pass filter and the second filter 16 is a low pass filter, the speed command Vc input to the motor speed control section 2 is expressed by Equation 1 below. Here, H means that only a high frequency component passes through the high pass filter, and L means that only a low frequency component passes through the low pass filter.

&Quot; (1) &quot;

Vc = (Vcs) + H (Vof) + L (Vcf-Vcs)

Since the acceleration / deceleration of the motor 3 is a transient response period, the output L (Vcf-Vcs) of the second filter section 16 is removed. Therefore, the speed command Vc input to the motor speed control unit 2 during acceleration and deceleration of the motor 3 is Vc = (Vcs) + H (Vof), and the motor position control of the first feedback unit 410, which is a semi- (1) and the output Vof of the speed FF section.

Since the Vcf component, which is the full closed loop 400, is removed by the second filter 16, the acceleration / deceleration operation is quickly performed only by the measurement value of the position of the motor 3 of the semi-closed loop and the high frequency component of the feedforward value. .

In the steady state, H (Vof), which is a high frequency component, is removed from the response. Therefore, in the steady state response, the speed command does not require the output value of the feedforward unit 4, so that the control accuracy is improved.

The speed command Vc input to the motor speed control unit 2 in the steady state is Vc = (Vcs) + L (Vcf-Vcs), and Vcs and L (Vcs) do. Therefore, since only the low frequency component of Vcf calculated in the second loop is inputted as the speed command Vc, the steady state error can be reduced and the vibration generating factor can be eliminated.

Case 1 in which the first filter 19 is a high-pass filter and the second filter 16 is a low-pass filter is summarized as follows.

The motor speed control unit (2) The first filter (19) The second filter (16) Speed command Vc When the filter is not used (Vcs) H (Vof) L (Vcf-Vcs) (Vcs) + H (Vof) + L (Vcf-Vcs) Acceleration / deceleration time (Vcs) H (Vof) 0 (Vcs) + H (Vof) Steady state (Vcs) 0 L (Vcf-Vcs) Vcf

<CASE 2>

When the first filter 19 is a low pass filter and the second filter 16 is a high pass filter, the speed command Vc input to the motor speed control section 2 is expressed by the following equation (2). Here, H means that only a high frequency component passes through the high pass filter, and L means that only a low frequency component passes through the low pass filter.

&Quot; (2) &quot;

Vc = (Vcs) + L (Vof) + H (Vcf-Vcs)

Since the acceleration / deceleration of the motor 3 is a transient response period, the output L (Vof) of the first filter 19 is removed. The speed command Vc is Vc = (Vcs) + H (Vcf-Vcs), and (Vcs) is canceled to become Vc = Vcf. That is, only the Vcf calculated by the second feedback section 420 is used as the speed command when the motor 3 accelerates or decelerates.

In the steady state, the high-frequency component H (Vcf-Vcs) is removed from the response.

The speed command Vc input to the motor speed control unit 2 in the steady state is Vc = (Vcs) + L (Vof) and only Vcs calculated in the first loop and low frequency component of Vof estimated in the feedforward unit 4 Is input as a speed command.

CASE 2, which is the case where the first filter 19 is a low-pass filter and the second filter 16 is a high-pass filter, is summarized as follows.

The motor speed control unit (2) The first filter (19) The second filter (16) Speed command Vc When the filter is not used (Vcs) L (Vof) H (Vcf-Vcs) (Vcs) + L (Vof) + H (Vcf-Vcs) Acceleration / deceleration time (Vcs) 0 H (Vcf-Vcs) Vcf Steady state (Vcs) L (Vof) 0 (Vcs) + L (Vof)

When the first filter 19 and the second filter 16 are appropriately selected from among the low-pass filter and the high-pass filter, an appropriate speed command can be generated for the system during acceleration / deceleration in a steady state or transient state. The characteristic of the filter is selected by the tuning unit 300.

In one embodiment, the tuning unit 300 tunes the first filter 19 and the second filter 16 to an optimum value suitable for a steady state or a transient state according to the operating specifications of the system.

Next, the gain tuning of the feedforward unit 4 will be described. In one embodiment, the gain of the feedforward portion 4 may be the reciprocal of the transfer function modeling the motor 3 or the mechanical portion 7 to substantially make the overall transfer function substantially unity.

For example, if the reciprocal of the transfer function of the motor 3 is tuned to the gain of the feedforward unit 4, the time delay due to the feedback can be reduced and the steady state error can be reduced.

Referring to FIG. 4, the tuning unit 300 includes at least one of an FF tuning unit 310, a first filter tuning unit 320, and a second filter tuning unit 300.

In one embodiment, the FF tuning unit 310 sets the gain of the feed forward unit 4 to the reciprocal of the transfer function of the motor 3 or the mechanical unit 7.

In one embodiment, the first filter tuning unit 320 or the second filter tuning unit 300 tunes each of the first filter 19 or the second filter 16 with a high pass filter or a low pass filter, do.

The first filter tuning unit 320 or the second filter tuning unit 300 may adjust the gain of the first filter 19 or the second filter 16 to stop the function of the filter . The gain of the first filter 19 is set to 1 by the first filter tuning unit 320 and the gain of the second filter 16 is adjusted by the tuning unit 300 of the second filter 16 The operation of the first filter 19 is the same as that of the non-off state, and only the second filter 16 operates as a high-pass filter.

Accordingly, when the tuning unit 300 is installed, it is advantageous in that the system can adjust the characteristics of the filter or the amount of the feedforward of the speed according to the state of use or the size of the apparatus, The gain of the filter or the feedforward unit can be automatically tuned without the need to replace the feedforward unit 4 and the operation characteristics of the first feedback unit 410 and the second feedback unit 420 can be adjusted.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

1 ... Motor position control part 2 ... Motor speed control part
3 ... motor
3a ... motor sensor 4 ... feed forward unit
7 ... mechanical part 7a ... mechanical part sensor
7b ... ball screw 8 ... spring
9 ... damper 10 ... motor position offset calculating section
12 ... Torque command generator 15 ... Machine position controller
16 ... second filter 17 ... mechanical part position offset calculating section
18 ... Loop comparator 19 ... First filter
20 ... Feed forward offset calculating section
21 ... Speed command calculation unit 100 ... Servo control unit
200 ... CNC part 300 ... tuning part
310 ... FF tuning section 320 ... first filter tuning section
400 ... Full closed loop
410 ... first feedback section
420 ... second feedback section

Claims (10)

A motor position control unit for controlling a position of a motor that feeds a tool or an object;
A motor speed control unit connected to a rear end of the motor position control unit and controlling a speed of the motor;
A feed forward unit for calculating a correction amount according to a command position input to the motor position control unit and feeding-forwarding the correction amount to the motor position control unit or the motor speed control unit;
A tuning unit for automatically tuning the gain of the feedforward unit according to acceleration / deceleration or constant speed operation of the motor;
A mechanical unit position control unit for controlling a position of a mechanical unit connected to the motor; Lt; / RTI &gt;
At least one of a first filter disposed at an output end of the feed forward unit and a second filter disposed at an output end of the mechanical unit position control unit,
The tuning unit includes:
Setting the second filter as a low pass filter when the first filter is set as a high pass filter,
And sets the second filter as a high pass filter if the first filter is set as a low pass filter.
delete The method according to claim 1,
Wherein the tuning unit sets the gain of the feed forward unit to an inverse number of a transfer function modeled by the motor or a mechanical unit connected to the motor.
delete delete delete A first feedback unit for feedback-controlling the position or speed of the motor;
A second feedback unit for feedback-controlling the position or speed of the mechanical unit connected to the motor;
A feed forward unit for calculating a correction amount according to a command position input to the first feedback unit and feeding-forwarding the correction amount to the first feedback unit;
A tuning unit for automatically tuning a gain of at least one of the feedforward unit, the first feedback unit and the second feedback unit in consideration of low rigidity between the motor and the mechanical unit;
A first filter provided at an output end of the feed forward unit;
A second filter provided at an output terminal of the second feedback unit; Lt; / RTI &gt;
Wherein the tuning section sets the first filter to a high pass filter and sets the second filter to a low pass filter.
delete 8. The method of claim 7,
Wherein the first feedback unit is provided with a motor speed control unit for controlling the speed of the motor,
Wherein an output value of the second filter is removed at the time of acceleration / deceleration of the motor, and a high frequency component of an output of the feed forward unit passed through the first filter is input to the motor speed control unit,
Wherein the output value of the first filter is removed at the constant speed operation of the motor and the low frequency component of the output of the second feedback unit passed through the second filter is input to the motor speed control unit.
A motor position control unit for controlling a position of a motor that feeds a tool or an object;
A mechanical part position control part for receiving a feedback signal related to the position or speed of the mechanical part connected to the motor and controlling the position of the mechanical part;
A feed forward unit for calculating a correction amount according to the command position and feeding-forwarding the correction amount to the motor position control unit;
A first filter provided in the feedforward section as a high pass filter;
A second filter provided in the mechanical unit position control unit as a low pass filter;
A signal obtained by adding a high frequency component of a speed signal passing through the first filter to a speed signal of the motor output from the motor position control unit during acceleration and deceleration of the motor is inputted and the signal outputted from the motor position control unit A motor speed controller for inputting a signal obtained by adding a low-frequency speed component passing through the second filter to a speed signal of the motor, and controlling the speed of the motor in accordance with the input signal; The machine tool comprising:

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