Servo control device

Abstract

The present invention provides a servo control device capable of stably performing machining in a swing machining process. The servo control device (20) comprises: a swing command generating unit (23) generating a swing command for swinging a workpiece (W) and a tool (14) relative to each other; any one of a position control unit (22) generating a position command for moving the workpiece (W) and the tool (14) relative to each other, a speed control unit (24) generating a speed command for moving the workpiece (W) and the tool (14) relative to each other, and a current control unit (25) generating a torque command for driving a plurality of axes; and a gain changing unit changing a control gain, wherein the swing command generating unit (23) sends a signal outputted at the start of the swinging action to the gain changing unit, and the gain changing unit changes the control gain.

Description

Technical Field

[0001] The invention relates to a servo control device. Background Art

[0002] Conventionally, there is known an oscillating machining method in which a tool and a workpiece are relatively oscillated in a machining direction (oscillating motion) to thereby crush chips (for example, see Patent Documents 1 and 2).

[0003] Patent document 1 states that "In the tool tip trajectory of the cutting tool 130, the cutting processing portion during the current forward motion overlaps the cutting processing portion during the next reciprocating motion. For example, the circumferential shape of the workpiece W during the n+1th rotation of the spindle 110 includes the circumferential shape of the workpiece W during the nth rotation of the spindle 110. Therefore, the cutting tool 130 produces an idle swing motion without processing the workpiece W. During this idle swing motion, the chips generated from the workpiece W are cut off. The machine tool 100 smoothly processes the outer shape of the workpiece W while cutting off the chips."

[0004] In addition, Patent Document 2 describes "using Figure 2 as well as Figure 3 The control device 8 will be described in detail. Figure 2 As shown, the control device 8 comprises: a central control unit 80, which is composed of a CPU, etc.; an input unit 81, which is composed of a touch panel, etc.; a program information storage unit 82, which stores program information obtained by the user using the input unit 81 for programming; a vibration cutting information storage unit 83, which stores data for making the cutting tool 4 corresponding to the mechanical characteristics such as the mass and motor characteristics on the processing table vibrate at a low frequency, and the data is data that can achieve non-oscillation work even if the gain value is set to a high gain; a motor control unit 84, which controls the action of the cutting tool feed drive motor 7a via the servo amplifier 9; and a display unit 85, which is composed of a liquid crystal monitor, etc. ".

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-005423

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-054689 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] It is desirable to perform machining stably in swing machining.

[0011] An object of the present invention is to provide a servo control device capable of stably performing machining in swing machining.

[0012] Solutions for solving problems

[0013] (1) One embodiment of the present disclosure is a servo control device that controls a machine tool that performs turning processing on a workpiece through the collaborative action of multiple axes, the servo control device comprising: a swing command generating unit that generates a swing command for swinging the workpiece and the tool relative to each other; at least one of a position control unit, a speed control unit, and a current control unit, the position control unit generating a position command for moving the workpiece and the tool relative to each other, the speed control unit generating a speed command for moving the workpiece and the tool relative to each other, and the current control unit generating a torque command for driving the multiple axes; and a gain changing unit that changes a control gain, wherein the swing command generating unit sends a signal output when the swing action starts to the gain changing unit, and the gain changing unit changes the control gain.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide a servo control device capable of stably performing machining in swing machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a diagram for explaining the configuration of a machining system including a servo control device for a machine tool according to the present embodiment.

[0017] Figure 2 This is a diagram showing the relationship between the feed amount and the rotation angle in the swing operation.

[0018] Figure 3 This is a graph showing the gained gain in the state before the control gain is switched during the swing operation.

[0019] Figure 4 This is a graph showing the gain obtained after the control gain is switched during the swing operation.

[0020] Description of Reference Numerals

[0021] 14: tool; 20: servo control device; 21: gain setting unit; 22: position control unit; 23: swing instruction generation unit; 24: speed control unit; 25: current control unit; W: workpiece. DETAILED DESCRIPTION

[0022] Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, in each of the drawings, the same reference numerals are given to the same or corresponding parts.

[0023] Figure 1 1 is a diagram for explaining the configuration of a machining system 1 including a servo control device 20 of a machine tool 10 . Figure 1 The machining system 1 shown includes a machine tool 10 and a servo control device 20 that controls the machine tool 10 .

[0024] The machine tool 10 has a tool 14. The tool 14 performs turning processing on a workpiece W having a cylindrical, cylindrical, conical, or truncated cone shape, for example. Figure 1 In the example of FIG. 1 , the tool 14 performs turning on the outer peripheral surface of the workpiece W. Figure 1 In the example of FIG. 1 , the central axis of the workpiece W, which will be the rotation axis of the workpiece W, is set to the Z axis, and the axis perpendicular to the Z axis is set to the X axis.

[0025] The machine tool 10 is not limited to processing a workpiece W having a linear shape in the direction along the Z axis, but can also process a workpiece W having a tapered shape or an arc shape. In addition, the machine tool 10 is not limited to processing the outer peripheral surface of the workpiece W, but can also process the inner peripheral surface of a cylindrical workpiece W. In addition, the machine tool 10 is not limited to performing turning processing, but can also perform processing such as cutting, grinding, or lapping.

[0026] The machine tool 10 includes a main spindle M0 as a motor 12 and two feed axes M1 and M2 that cooperate with the main spindle M0. The main spindle M0 includes a spindle motor, and the feed axes M1 and M2 include servomotors. The main spindle M0 and the feed axes M1 and M2 are controlled by a servo control device 20.

[0027] The spindle M0 rotates the workpiece W around the central axis (Z axis) of the workpiece W. The feed axis M1 can feed the tool 14 in the Z axis direction (first direction) and reciprocate, i.e., swing, in the Z axis direction. The feed axis M2 can feed the tool 14 in the X axis direction (second direction) and reciprocate, i.e., swing, in the X axis direction.

[0028] When turning a cylindrical or cylindrical workpiece W, the workpiece W is rotated around the central axis (Z axis) of the workpiece W, and the tool 14 is fed only in the Z axis direction (the machining direction in this case) along the generatrix of the outer peripheral surface of the workpiece W.

[0029] On the other hand, when turning a workpiece W having an outer diameter that varies in the Z-axis direction, such as an arc-shaped workpiece W, the workpiece W rotates around the center axis (Z-axis) of the workpiece W, and the tool 14 is fed in an oblique direction (a composite direction of the Z-axis direction and the X-axis direction) (a processing direction in this case) along the generatrix of the outer peripheral surface of the workpiece W. In this case, in order to feed the tool 14 in an oblique direction along the generatrix of the outer peripheral surface of the workpiece W, at least two feed axes M1 and M2 are required. The tool 14 is fed in an oblique direction along the generatrix of the outer peripheral surface of the workpiece W by controlling both the feed axis M1 and the feed axis M2.

[0030] The servo control device 20 is composed of a computer including a memory such as a ROM (read only memory) and a RAM (random access memory) connected to each other via a bus, a CPU (control processing unit), and a communication control unit. The servo control device 20 includes a position control unit 22, a swing instruction generation unit 23, a speed control unit 24, a current control unit 25, and a storage unit (not shown). The functions or operations of these units are realized by the cooperation of the CPU, the memory, and the control program stored in the memory mounted on the above-mentioned computer.

[0031] The storage unit (not shown) stores processing conditions of the workpiece W. The processing conditions of the workpiece W include the relative rotation speed of the workpiece W and the tool 14 around the central axis of the workpiece W, the relative feed speed of the tool 14 and the workpiece W, and position commands of the feed axes M1 and M2.

[0032] A host computer (not shown) such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller) is connected to the servo control device 20, and the aforementioned rotation speed or feed speed can be input from the host computer to a storage unit not shown. In addition, the storage unit or position control unit 22 not shown can be provided not only in the servo control device 20 but also in the host computer.

[0033] Alternatively, a storage unit (not shown) may store a machining program to be executed by the machine tool 10 , and a CPU (not shown) in the servo control device 20 may read the aforementioned rotation speed and feed speed from the machining program as machining conditions and output them to the position control unit 22 and the swing instruction generating unit 23 .

[0034] The position control unit 22 generates a position command for relatively moving the workpiece W and the tool 14. Specifically, the position control unit 22 has a function of generating position commands for the feed axes M1 and M2 based on the relative rotation speed of the workpiece W and the tool 14 around the central axis of the workpiece W and the relative feed speed of the tool 14 and the workpiece W. The position command is a command indicating a target position when the tool 14 and the workpiece W are relatively fed in the direction of the generatrix along the outer peripheral surface of the workpiece W (processing direction).

[0035] The swing instruction generation unit 23 uses the position instruction from the position control unit 22 to generate a swing instruction for swinging the workpiece W relative to the tool 14. Specifically, the swing instruction generation unit 23 generates a swing instruction for the feed axis M1 based on the aforementioned rotation speed and feed speed, so as to obtain a swing frequency that is a positive non-integer multiple of the rotation speed and to cause the tool 14 to intermittently cut the workpiece W. The swing instruction is a periodic instruction generated in an asynchronous manner relative to the rotation speed around the aforementioned center axis, and includes a swing frequency and a swing amplitude. That is, the execution state of the swing action is represented by the swing frequency or the swing amplitude. The value of the S / 60×I item in the equation (1) of the swing instruction described later is equivalent to the swing frequency, and the value of the K×F / 2 item in the equation (1) is equivalent to the swing amplitude.

[0036] Here, intermittent cutting refers to turning the workpiece W while the tool 14 periodically contacts and leaves the workpiece W, which is also called swing cutting or vibration cutting. Figure 1 In the embodiment, the workpiece W rotates and the tool 14 swings relative to the workpiece W, but the tool 14 may rotate around the central axis of the workpiece W and the workpiece W swings relative to the tool 14. Figure 1 In the embodiment, the feed motion and the swing motion of the workpiece W are both performed by one feed axis M1, M2, but the feed motion and the swing motion of the workpiece W may be performed by separate feed axes.

[0037] The subtractor 26 obtains a position deviation between the position command from the position command unit and the position feedback detected by the detector 13. The adder 27 adds the position deviation to the swing command from the swing command generation unit 23 to calculate a composite command. The composite command is provided to the speed control unit 24.

[0038] The speed control unit 24 generates a speed command based on the synthesized command. The subtractor 28 generates a speed deviation by subtracting speed feedback detected by an encoder (not shown) of the motor from the speed command from the speed control unit 24 and supplies the speed deviation to the current control unit 25 .

[0039] The current control unit 25 generates a torque command based on the speed command and the speed deviation, and inputs it to the amplifier. The amplifier supplies the torque command obtained by the conversion by the current control unit 25 to the feed axis M1. The feed axis M1 is controlled based on such a command. A detector 13 composed of an encoder is provided on the feed axis M1. When the feed axis M1 rotates, the detector 13 feeds back the actual position of the feed axis M1 to the subtractor 26. When the difference between the position command value and the position feedback value based on the composite command disappears, the actual position of the feed axis M1 reaches the position command value.

[0040] The gain setting unit 21 sets the servo gains of the servo motors of the feed axes M1 and M2. Regarding the setting of the servo gains, when switching from normal cutting to oscillatory cutting, a signal output at the start of the oscillatory motion can be received from the oscillatory command generation unit 23, thereby changing at least one of the position gain of the position control unit 22, the speed gain of the speed control unit 24, and the current gain of the current control unit 25, which are the control gains described later. The gain setting unit 21 changes the value of the gain by changing the magnification (control gain) multiplied by the gain (Japanese: 利得ゲイン) described later. A preset parameter is used as this magnification, or the gain setting unit 21 calculates this magnification by considering both the execution state of the oscillatory motion and the changed gain, and determining what degree of magnification to multiply. At this time, for example, the execution state of the oscillatory motion is identified by referring to the value represented by the oscillation frequency or the amplitude of the oscillation.

[0041] Next, the oscillatory command generation unit 23 will be described. Figure 2 It is a diagram showing the relationship between the feed amount and the rotation angle in the oscillatory motion.

[0042] Figure 2 In it, the horizontal axis represents the rotation angle of the workpiece W, and the vertical axis represents the feed amount of the tool 14 in the machining direction (i.e., along Figure 1 the generatrix direction of the outer peripheral surface of the workpiece W). Figure 2 It shows a plurality of linearly extending dotted lines C1, C2, C3... extending in an oblique direction.

[0043] As Figure 2 shown, the vertical axis coordinate of the intersection between the dotted line C1 and the vertical axis is equivalent to the vertical axis coordinate of the starting point of the next dotted line C2. Similarly, the vertical axis coordinate of the intersection between the dotted line C2 and the vertical axis is equivalent to the vertical axis coordinate of the starting point of the next dotted line C3. These multiple linearly extending dotted lines C1, C2, C3... represent the trajectory of the tool 14 on the workpiece W in the absence of an oscillatory command. On the other hand, Figure 2The curves A1, A2, A3, etc. shown represent the trajectory of the tool 14 on the workpiece W when there is a swing command. That is, the dotted lines C1, C2, C3, etc. represent only the position command (original command value) before adding the swing command, and the curves A1, A2, A3, etc. represent the position command after adding the swing command. Therefore, the curves A1, A2, A3 represent the commands obtained by adding the position commands represented by the dotted lines C1, C2, C3 to the cosine wave-shaped swing command.

[0044] In addition, curve A1 is the trajectory of the tool 14 during the first rotation of the workpiece W, curve A2 is the trajectory of the tool 14 during the second rotation of the workpiece W, and curve A3 is the trajectory of the tool 14 during the third rotation of the workpiece W. For the sake of simplicity, the illustration of the trajectory of the tool 14 after the fourth rotation of the workpiece W is omitted.

[0045] The swing command generation unit 23 generates the swing command as follows. The swing command generation unit 23 determines the swing frequency to generate commands such as the position commands of the feed axes M1 and M2 generated by the position control unit 22, that is, the curves A1, A2, and A3 with the dotted lines C1, C2, and C3 as reference axes. S / 60×I in the formula (1) described later is the swing frequency.

[0046] When determining the above-mentioned oscillation frequency, it is preferred that Figure 2 As shown in FIG. 1 , the initial phase of the cosine wave curve A2 with a certain dotted line, such as the dotted line C2, as the reference axis is shifted by half a cycle relative to the cosine wave curve A1 with the previous dotted line, such as the dotted line C1, as the reference axis. The reason is that when the phase is shifted by half a cycle, the swing amplitude of the swing command can be set to the minimum limit, resulting in the most effective chip crushing.

[0047] The swing command generation unit 23 determines the swing amplitude of the swing command to generate commands such as curves A1, A2, and A3 with the dashed lines C1, C2, and C3 as reference axes. The value of the K×F / 2 term in the equation (1) described later is the swing amplitude. Figure 2 The curve A1 and the curve A2 shown overlap each other at a position B1 where the rotation angle is approximately 0 degrees and a position B2 where the rotation angle is approximately 240 degrees. Figure 2 It can be seen that at the locations B1 and B2, the maximum value of the curve A1 relative to the dotted line C1 is greater than the minimum value of the curve A2 relative to the dotted line C2. In other words, it is preferable that the swing command generation unit 23 determines the swing amplitude so that the previous curve A1 and the next curve A2 partially overlap each other. In addition, since the feed speed is fixed, the swing amplitudes of the swing commands in the curves A1, A2, and A3 are all the same.

[0048] At the overlapping portions B1 and B2, the tool 14 leaves the workpiece W when machining along the trajectory of the curve A2, so that the workpiece W is not machined. In the present embodiment, such overlapping portions B1 and B2 are generated periodically, so that so-called intermittent cutting can be performed. Figure 2 In the example shown, the operation corresponding to the curve A2 generates chips at the locations B1 and B2. That is, two chips are generated at the curve A2 in the second rotation. Since such intermittent cutting is performed periodically, vibration cutting can be performed.

[0049] Furthermore, the shape of the curve A3 formed with respect to the dotted line C3 is the same as the shape of the curve A1. The curve A2 and the curve A3 overlap at the portion B3 at which the rotation angle is about 120° and the portion B4 at which the rotation angle is about 360°. Through the action corresponding to the curve A3, chips are generated at the portions B3 and B4, respectively. That is, two chips are generated in the curve A3 in the third rotation. After that, two chips are generated every time the workpiece W rotates one circle. However, no chips are generated in the first rotation.

[0050] By determining the swing frequency and the swing amplitude in this way, the swing command generating unit 23 generates a swing command.

[0051] For example, the swing command is expressed as shown in the following equation (1).

[0052]

Number 1

[0053]

[0054] In formula (1), K is the swing amplitude magnification, F is the movement amount of the tool 14 per rotation of the workpiece W, that is, the feed amount per rotation [mm / rev], and S is the rotation speed of the workpiece W around the central axis [min -1 ] or [rpm], I is the swing frequency multiplier. Here, the aforementioned swing frequency is equivalent to the S / 60×I term in formula (1), and the aforementioned swing amplitude is equivalent to the K×F / 2 term in formula (1). Among them, the swing amplitude multiplier K is set to a number greater than 1, and the swing frequency multiplier I is set to a non-integer greater than zero (for example, 0.5, 0.8, 1.2, 1.5, 1.9, 2.3, or 2.5, ... and other positive non-integer). The swing amplitude multiplier K and the swing frequency multiplier I are constants (in Figure 2 In the example, I is 1.5).

[0055] The reason for not setting the oscillation frequency multiplier I to an integer is that when the oscillation frequency is exactly the same as the rotational speed of the workpiece W around the center axis, the aforementioned overlapping parts B1, B2, B3, B4, etc. cannot be produced, and the effect of crushing the chips by oscillating cutting cannot be obtained.

[0056] In addition, according to formula (1), the swing command is a command obtained by subtracting the term (K×F / 2) as an offset value from the cosine wave with the dotted lines C1, C2, and C3 representing the position command as the reference axis. Therefore, the position trajectory of the tool 14 based on the synthetic command value obtained by adding the position command to the swing command can be controlled in the machining direction of the tool 14 with the position based on the position command as the upper limit. Therefore, Figure 2 The curves A1, A2, A3, etc. will not exceed the dotted lines C1, C2, C3, etc. in the + direction (ie, the machining direction of the tool 14).

[0057] And, by setting the swing command as expressed in formula (1), Figure 2 It can be seen from the curve A1 that at the processing starting point of the tool 14 (the position of 0° on the horizontal axis), no large swing will occur in the feed direction of the tool 14 at the beginning.

[0058] In addition, the initial values ​​of the parameters (K, I in the formula (1)) adjusted when determining the swing frequency and the swing amplitude are set to the values ​​stored in the storage unit (not shown) before the machine tool 10 is operated. The rotation speed (S) of the workpiece W is stored in advance in the storage unit (not shown) as a processing condition. The feed rate F is calculated based on the rotation speed (S) and the position command generated by the position control unit 22.

[0059] For example, when the workpiece is machined in a cylindrical or columnar shape, the workpiece W is swung in the feed axis M1 (Z axis) direction along the generatrix of the outer peripheral surface of the workpiece W, that is, in the machining direction.

[0060] On the other hand, when the workpiece processing shape is conical, truncated (tapered) or includes an arc, for example, the swing is performed in the inclined direction along the generatrix along the outer peripheral surface of the workpiece W, that is, the swing is performed in the processing direction which is the combined direction of the feed axis M1 (Z axis) direction and the feed axis M2 (X axis) direction.

[0061] Next, gain change performed by the gain setting unit 21 will be described.

[0062] Here, gain refers to control gain. Specifically, in order to calculate the operating amount used to eliminate the speed deviation in speed control, the speed deviation is amplified by a compensator not shown in the figure. When the amplification is performed, the control gain is calculated by multiplication and integration in the compensator. And, after the operating amount is calculated, the calculated operating amount is input to the control object. And the feedback obtained thereby can be used as a response. In the following description, the ratio of the input to the response at each frequency is called gain gain. In order to calculate the aforementioned operating amount, the amplification factor used when amplifying the deviation is called control gain in the following description. If the control gain is too large, oscillation and overshoot are likely to occur.

[0063] Regarding the position gain of the position control unit 22, the speed gain of the speed control unit 24, and the current gain of the current control unit 25, if the swing cutting is started and the swinging action is performed while maintaining the control gain during normal cutting, the position accuracy of the tool 14 is likely to become unstable and the action is likely to become unstable. This is because, usually, in order to improve the responsiveness of the high-precision servo, a high control gain is often set during normal cutting, and therefore, the value of the gain at the swing frequency is an absolute value deviated from 0 dB (decibel).

[0064] When the machine tool 10 switches from normal cutting to swing cutting, that is, when the swing operation starts, a signal notifying that the swing operation has started is sent from the swing instruction generating unit 23 to the gain setting unit 21. Specifically, Figure 3 As shown in FIG. 1 , in order to maintain accuracy even when driving at a high frequency during normal cutting, the frequency of the point P where the gain with good followability is 0 dB is set to a high value. Here, in the case of the frequency characteristic in the speed gain, good followability means that the gain value reaches -3 dB, and by setting the gain value to a value as close to 0 dB as possible, the followability becomes good.

[0065] Figure 3 This is a graph showing the state before the control gain is switched during the swing operation.

[0066] However, in the normal cutting state, such as Figure 3 As shown in FIG. 1 , at the swing frequency for swing cutting, the value of the gain is a value deviated from 0 dB. In the machine tool 10, when switching from normal cutting to swing cutting, a signal notifying that the swing operation has started is sent from the swing command generating unit 23 to the gain setting unit 21. As a result, the gain setting unit 21 changes the value of the speed gain to be as follows: Figure 4 As shown, the speed gain decreases to approximately 0 dB, and the speed gain is provided to the speed control unit 24. As a result, the value of the gain at the swing frequency becomes approximately 0 dB, the followability of the tool 14 during the swing operation is improved, and the position accuracy of the tool 14 is stabilized and the operation is stable.

[0067] Figure 4 This is a graph showing the state after the control gain is switched during the swing operation.

[0068] The present embodiment described above achieves the following effects.

[0069] In this embodiment, the swing command generation unit 23 sends a signal outputted at the start of the swing operation to the gain setting unit 21 constituting the gain change unit, and the gain setting unit 21 changes the control gain. This allows the value of the gained gain at the swing frequency to be set as close to 0 dB as possible.

[0070] In the present embodiment, the execution state of the swing operation is represented by the frequency or the amplitude. Therefore, by changing the control gain so that the value of the gained gain at the swing frequency becomes close to 0 dB, the amplitude tracking performance of the swing can be improved.

[0071] In addition, in this embodiment, the gain change unit changes at least one of the position gain of the position control unit 22, the speed gain of the speed control unit 24, and the current gain of the current control unit 25 as control gains. For example, the gain change unit only changes the speed gain of the speed control unit 24.

[0072] Therefore, for example, when the current gain is changed to perform current control, there is almost no communication delay from the motor, so the frequency band in which the gain value responds to 0 dB is wide and has no limit, but since the resonance point is also extracted, it is difficult to handle. However, it is possible to easily control by changing only the speed gain without performing such difficult current control.

[0073] In addition, in the present embodiment, the gain changing unit changes the control gain so that the value of the gained gain at the oscillation frequency approaches 0 dB. This improves the followability of the tool 14 performing oscillation cutting, and enables stable machining during oscillation cutting.

[0074] The present embodiment has been described above. The above embodiment is a preferred embodiment, but is not limited to the above embodiment and can be implemented in various modified forms. For example, it can be implemented by deformation as in the modified examples described below.

[0075] That is, the structures of the swing command generating unit, position control unit, speed control unit, current control unit, gain changing unit, etc. are not limited to the structures of the swing command generating unit 23, position control unit 22, speed control unit 24, current control unit 25, gain setting unit 21, etc. in the above-mentioned embodiment.

[0076] In addition, in the above-mentioned embodiment, the gain setting unit 21 changes the speed gain of the speed control unit 24, but the present invention is not limited to this structure. The gain changing unit having the gain setting unit 21 can change at least one of the position gain of the position control unit 22, the speed gain of the speed control unit 24, and the current gain of the current control unit 25, and can also change all three, for example.

[0077] In addition, in the above-mentioned embodiment, the gain setting unit 21 constituting the gain changing unit changes the value of the speed gain so as to make the value of the gain at the oscillation frequency as close to 0 dB as possible, but the present invention is not limited to this configuration. For example, in the case where the value of the gain at the oscillation frequency is low or high precision is required for cutting, the gain changing unit may change the value of the gain at the oscillation frequency so as to make the value of the gain at the oscillation frequency as close to 0 dB as possible so as to increase at least one of the position gain, the speed gain, and the current gain.

Claims

1. A servo control device for controlling a machine tool for turning a workpiece by cooperative action of multiple axes, wherein: The servo control device comprises: a swing command generating unit for generating a swing command for causing the workpiece and the tool to swing relative to each other; at least one of a position control unit, a speed control unit, and a current control unit, wherein the position control unit generates a position command for relatively moving the workpiece and the tool, the speed control unit generates a speed command for relatively moving the workpiece and the tool, and the current control unit generates a torque command for driving the plurality of axes; as well as A gain changing section that changes a control gain, The swing command generating unit sends a signal outputted when the swing operation starts to the gain changing unit, and the gain changing unit changes the value of the gained gain by changing a control gain multiplied by the gained gain.

2. The servo control device according to claim 1, characterized in that: The execution state of the swing action is represented by frequency or amplitude.

3. The servo control device according to claim 1 or 2, characterized in that: The gain changing unit changes at least one of a position gain of the position control unit, a speed gain of the speed control unit, and a current gain of the current control unit as the control gain.

4. The servo control device according to claim 3, characterized in that: The gain changing unit changes only the speed gain of the speed control unit.

5. The servo control device according to claim 1 or 2, characterized in that: The gain changing unit changes the control gain so that a value of the gained gain at the swing frequency approaches 0 decibel.

6. The servo control device according to claim 3, characterized in that: The gain changing unit changes the control gain so that a value of the gained gain at the swing frequency approaches 0 decibel.

7. The servo control device according to claim 4, characterized in that: The gain changing unit changes the control gain so that a value of the gained gain at the swing frequency approaches 0 decibel.

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