Control device for a servo motor

Abstract

The present invention provides a servo motor control device capable of suppressing correction delays even when a dead zone is provided. The servo motor control device includes: a motion acquisition unit that acquires the motion of the servo motor; an acceleration acquisition unit that acquires the acceleration of the servo motor; a correction unit that corrects the motion of the servo motor; and a correction start determination unit that determines the start of correction by the correction unit based on the motion of the servo motor. The correction start determination unit includes a dead zone unit that sets a predetermined range of values, i.e., a dead zone range, for the motion of the servo motor, and changes the dead zone range based on the acceleration acquired by the acceleration acquisition unit.

Description

Technical Field

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

[0002] Conventionally, control with a dead zone set has been performed in control devices for machine tools and the like (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 states that “ Figure 3 As shown, when the control correction amount from the filter unit 242 is close to "0", the dead zone processing unit 250 sets the output value to "0". The dead zone processing unit 250 outputs the control correction amount subjected to the dead zone processing to the limit processing unit 260. In addition, Patent Document 2 states that "the adaptive coefficient μm(n) is inversely proportional to the speed and the magnitude of the coupling torque Tc, and a dead zone can be provided so that the adaptive coefficient μm(n) becomes zero when the speed is below a specified value."

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-045702

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-128387 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] A technology is desired that provides a dead zone for not performing correction for the static friction resistance of a servo motor and suppresses a delay in correction when correction is performed.

[0010] Solutions for solving problems

[0011] (1) One embodiment of the present disclosure relates to a control device for a servo motor, comprising: an action acquisition unit that acquires the action of the servo motor; an acceleration acquisition unit that acquires the acceleration of the servo motor; a correction unit that corrects the action of the servo motor; and a correction start determination unit that determines the start of correction of the correction unit based on the action of the servo motor, wherein the correction start determination unit has a dead zone unit that sets a range of prescribed values, i.e., a dead zone range, for the action of the servo motor, and the dead zone unit changes the dead zone range based on the acceleration acquired by the acceleration acquisition unit.

[0012] Effects of the Invention

[0013] According to one embodiment, even if a dead zone is provided, a delay in correction can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram illustrating the configuration of a control device according to one embodiment.

[0015] Figure 2 This is a diagram illustrating a partial configuration of a correction start determination unit of a control device according to an embodiment.

[0016] Figure 3 This is a graph showing the relationship between the dead zone range set by the dead zone setting unit of the control device according to one embodiment and the acceleration amount.

[0017] Figure 4 This is a graph showing a case where there is no dead zone, a slight inversion is within the dead zone range, and inversion correction is performed.

[0018] Figure 5 is a graph showing a case where the start of inversion correction is not delayed in the absence of a dead zone.

[0019] Figure 6 This is a graph showing a case where no reversal correction is performed when a slight reversal is within the dead zone.

[0020] Figure 7 Graph showing a situation where the start of inversion correction is delayed when a dead zone exists.

[0021] Figure 8 This is a graph showing the timing of performing inversion correction when a minute inversion is within the dead band.

[0022] Figure 9 This is a graph showing a state of starting the inversion correction when the dead band range is set to be small in the case where a dead band exists.

[0023] Description of Reference Numerals

[0024] 1: Servo motor control device; 11: Instruction production unit; 12: Friction correction amount generation unit (correction unit); 13: Correction start determination unit; 14: Dead zone calculation unit (dead zone unit); 15: Acceleration amount acquisition unit; 16: Control unit; 17: Servo motor; 131: Dead zone setting unit (dead zone unit); 161: Action acquisition unit. DETAILED DESCRIPTION

[0025] Next, an example of implementation will be described. Figure 1 It is a diagram illustrating the configuration of the control device 1 .

[0026] The servo motor control device 1 is a control device that can perform static friction correction when the servo motor 17 of a machine tool or the like starts to operate (starts up) or when it is reversed. Figure 1 As shown, the control device includes a command generating unit 11 , a friction correction amount generating unit 12 , a correction start determining unit 13 , a dead zone calculating unit 14 , an acceleration amount acquiring unit 15 , a control unit 16 , and an electric motor serving as a servo motor 17 .

[0027] The servo motor 17 rotates, for example, a ball screw (not shown) in the forward and reverse directions based on an electrical signal from the control unit 16 , thereby moving a table (not shown) in the horizontal direction via a nut (not shown).

[0028] The command generation unit 11 generates a position command value for the servo motor 17. The friction correction amount generation unit 12, acting as a correction unit, uses the position command value generated by the command generation unit 11 to determine whether the servo motor 17 has stopped. Furthermore, the friction correction amount generation unit 12 determines whether the servo motor 17 has started from a stopped state or reversed. Specifically, the friction correction amount generation unit 12 detects the start and reverse rotation of the servo motor 17 based on changes in the magnitude or sign of the speed command generated by the command generation unit 11. Furthermore, the friction correction amount generation unit 12 calculates the static friction correction amount for the servo motor 17 and outputs it to the correction start determination unit 13.

[0029] The correction start determination unit 13 includes a dead zone unit that sets a predetermined value range, that is, a dead zone range, for the operation of the servo motor 17. Specifically, the correction start determination unit 13 includes a dead zone setting unit 131 constituting the dead zone unit. Figure 2 As shown, a dead zone having a predetermined dead zone range calculated by a dead zone calculation unit 14 described later is set as the stop position of the servo motor 17. The correction start determination unit 13 determines whether the movement amount of the servo motor 17 is within the dead zone range.

[0030] Figure 2 It is a diagram illustrating a partial configuration of the correction start determination unit 13 of the control device 1 .

[0031] Specifically, when the servo motor 17 stops and then starts, the dead zone range is set to, for example, "a range of 20 μm in one direction from the stopped position" when the servo motor 17 moves in one direction, stops, and then moves in one direction from the stopped position. In addition, when the servo motor 17 is reversed, for example, Figure 8 、 Figure 9As indicated by arrow A in the figure, the range is set to "a range of 20 μm in the opposite direction from the stopped position" when the servo motor 17 moves in one direction, stops, and then starts moving in the opposite direction from the stopped position. As described later, this value of "20 μm" is an appropriate value calculated and determined by the dead zone calculation unit 14 of the dead zone unit, and is not a fixed value.

[0032] When the movement amount of the servo motor 17 acquired by the motion acquisition unit 161 is greater than or equal to the dead band, the correction start determination unit 13 outputs the static friction correction amount from the friction correction amount generation unit 12 to the control unit 16 to start correction based on the static friction correction amount. When the movement amount of the servo motor 17 is within the dead band, the correction start determination unit 13 performs control not to output the static friction correction amount from the friction correction amount generation unit 12 to the control unit 16 so that correction based on the static friction correction amount is not performed.

[0033] The control unit 16 is configured to include a position control unit, a speed control unit, and a current control unit. The position control unit receives a position deviation from the command generation unit 11 and outputs a speed command corresponding to the position deviation to the speed control unit. The speed control unit receives a speed command from the position control unit and outputs a current command corresponding to the speed command to the current control unit. The current control unit receives a current command from the speed control unit, amplifies an electrical signal corresponding to the current command via an amplifier (not shown), and then outputs the signal to the servo motor 17.

[0034] The control loop L1 is used to perform feedback control on the position (specifically, the rotation angle) and the speed (specifically, the rotation speed) of the servo motor 17. The motion acquisition unit 161 of the control unit 16 acquires the motion (the command movement amount) of the servo motor 17 by acquiring the position command value. In addition, the motion acquisition unit 161 acquires the motion (the actual movement amount) of the servo motor 17 via the control loop L1. The acceleration acquisition unit 15 acquires the acceleration based on the command acceleration obtained as the value after differentiating the speed command value. The dead zone calculation unit 14 constituting the dead zone unit calculates a dead zone range suitable for the acceleration based on the acceleration acquired by the acceleration acquisition unit 15. That is, the dead zone calculation unit 14 changes the dead zone range to an appropriate range based on the acceleration acquired by the acceleration acquisition unit 15.

[0035] Specifically, as mentioned above, Figure 2 As shown, the dead zone setting unit 131 sets the dead zone having the dead zone range calculated by the dead zone calculation unit 14 as the stop position of the servo motor 17. For example, the dead zone range calculated by the dead zone calculation unit 14 and set by the dead zone setting unit 131 is a range where the horizontal axis is the command and the vertical axis is the movement amount. Figure 2The range indicated by the arrow A in the graph shown is scaled based on the acceleration acquired by the acceleration acquisition unit 15 .

[0036] In addition, the dead zone range of the movement amount for the acceleration value is appropriately determined based on the performance of the CAD / CAM that creates the instruction. For example, as a graph of the dead zone range value, an appropriate graph such as Figure 3 A straight line sloping downward to the right as shown by the middle straight line B1, or using Figure 3 An inverse proportional curve such as curve B2, or using Figure 3 As shown by the broken line B3, the dead band range is fixed until the acceleration reaches a predetermined value, and the dead band range becomes 0 when the acceleration exceeds the predetermined range.

[0037] Figure 3 It is a graph showing the relationship between the dead zone range set by the dead zone setting unit 131 of the control device 1 and the acceleration amount.

[0038] In all of these graphs, the larger the acceleration, the smaller the dead zone range. In other words, the larger the acceleration, the smaller the dead zone range is set by the dead zone setting unit 131 constituting the dead zone unit.

[0039] The present embodiment described above has the following effects.

[0040] In this embodiment, the control device of the servo motor 17 has a correction start determination unit 13, which determines the start of correction of the friction correction amount generating unit 12 serving as a correction unit based on the action of the servo motor 17. The correction start determination unit 13 has a dead zone unit (dead zone calculation unit 14, dead zone setting unit 131), which sets a range of prescribed values for the action of the servo motor 17, namely, a dead zone range. The dead zone unit changes the dead zone range based on the acceleration acquired by the acceleration acquisition unit 15.

[0041] Thus, the dead zone range can be appropriately changed based on the acceleration acquired by the acceleration acquisition unit 15. Therefore, for example, Figure 8 As shown, the dead zone range ( Figure 8 The width indicated by the arrow A in FIG) is set to include a small reversal in the instruction of the so-called "CAD garbage". As a result, it is possible to avoid overcorrection of the friction resistance of the servo motor 17 for a small reversal (no correction is performed). Figure 6 Inversion correction in C).

[0042] That is, in the conventional structure where no dead zone is provided, Figure 4As shown in FIG. 1 , in the case of a slight reversal in a command including so-called "CAD garbage", the friction resistance of the servo motor 17 is corrected for the slight reversal. However, in this embodiment, since a dead zone is provided, it is possible not to correct the slight reversal in a command including so-called "CAD garbage". Figure 6 The correction is shown by the dotted line in the figure, while the correction for large reversals is Figure 6 、 Figure 8 This can suppress the occurrence of scratches or the like on a machined surface machined by a machine tool equipped with the servo motor 17 .

[0043] Figure 4 This is a graph showing a case where there is no dead zone, a slight inversion is within the dead zone range, and inversion correction is performed. Figure 6 This is a graph showing a case where no reversal correction is performed when a slight reversal is within the dead zone. Figure 8 This is a graph showing the timing of performing inversion correction when a minute inversion is within the dead band.

[0044] Furthermore, when the acceleration is large, the dead zone range ( Figure 8 、 Figure 9 The width indicated by the arrow A in the figure is set to be extremely small, so that correction can be started immediately after the instruction is reversed. Figure 7 As shown, it is possible to suppress the dead zone range ( Figure 7 The width indicated by arrow A in the figure is large, resulting in a delay in the start of correction (arrow D).

[0045] That is, in the conventional structure without setting a dead zone, it is possible to Figure 5 As shown in FIG, the inversion is corrected without causing delay, but when the dead zone is set, as shown in FIG. Figure 7 As shown in FIG, a delay in the start of correction occurs. In particular, when the dead zone range is large, the delay in the start of correction (arrow D) also becomes large. However, in this embodiment, as shown in FIG. Figure 9 As shown, the dead zone range A can be set to be extremely small, and therefore the delay (arrow D) in starting correction can also be minimized.

[0046] Figure 5 is a graph showing a case where the start of inversion correction is not delayed in the absence of a dead zone. Figure 7 Graph showing a situation where the start of inversion correction is delayed when a dead zone exists. Figure 9 This is a graph showing a state of starting the inversion correction when the dead band range is set to be small in the case where a dead band exists.

[0047] In this embodiment, the acceleration is the command acceleration for the servo motor 17. This allows the servo motor 17 to detect whether there is a slight reverse rotation before and after the reverse rotation instruction before and after the reverse rotation instruction, thereby setting an appropriate dead zone range in advance.

[0048] Furthermore, in this embodiment, the motion acquisition unit 161 acquires the commanded movement amount of the servo motor 17, and the correction start determination unit 13 starts correction when the servo motor 17 moves by a movement amount exceeding the dead band range. This allows correction to be used at the start of reversal or startup based on the commanded movement amount, enabling more accurate correction.

[0049] In this embodiment, the dead zone setting unit 131 sets the dead zone range smaller as the acceleration increases. This minimizes delays in the start of correction in high acceleration areas where no delay in the start of correction is particularly required.

[0050] The above describes the present embodiment. 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 modifying it as in the modified examples described below.

[0051] In this embodiment, when the movement amount of the servo motor 17 is outside the dead band range that is changed based on the acceleration amount based on the command acceleration, the correction start determination unit 13 outputs the static friction correction amount from the friction correction amount generation unit 12 to the control unit 16 to start correction using this static friction correction amount. However, this configuration is not limited to this. For example, at least one of the acceleration amount based on the command acceleration, the acceleration amount based on the actual acceleration of the servo motor 17, the torque command for the servo motor 17, and the actual torque of the servo motor 17 may be used as the acceleration amount.

[0052] In this embodiment, the correction start determination unit 13 starts correction using the static friction correction amount generated by the friction correction amount generator 12 when the movement amount (command movement amount) of the servo motor 17 acquired by the motion acquisition unit 161 is greater than or equal to the dead band. However, the present invention is not limited to this. For example, the movement amount of the servo motor 17 acquired by the motion acquisition unit 161 used by the correction start determination unit 13 for determination may be the actual movement amount.

[0053] In addition, the structures of the action acquisition unit, acceleration acquisition unit, correction unit, correction start determination unit, dead zone unit, etc. are not limited to the structures of the action acquisition unit 161, acceleration acquisition unit 15, friction correction amount generation unit 12, correction start determination unit 13, dead zone setting unit 131, dead zone calculation unit 14, etc.

Claims

1. A servo motor control device comprising: a motion acquisition unit for acquiring the motion of the servo motor; an acceleration acquiring unit, configured to acquire the acceleration of the servo motor; a calibration unit that calibrates the operation of the servo motor; and a calibration start determination unit for determining the start of calibration of the calibration unit based on the operation of the servo motor; in, The correction start determination unit includes a dead zone unit that sets a dead zone range, which is a predetermined value range, for the operation of the servo motor. The dead zone unit sets and changes the dead zone range based on the acceleration acquired by the acceleration acquisition unit.

2. The servo motor control device according to claim 1, characterized in that: The acceleration is at least one of a command acceleration for the servo motor, an actual acceleration of the servo motor, a torque command for the servo motor, and an actual torque of the servo motor.

3. The servo motor control device according to claim 1 or 2, characterized in that: The motion acquisition unit acquires a movement amount consisting of a command movement amount or an actual movement amount of the servo motor. The correction start determination unit starts correction when the servo motor operates so that the movement amount is equal to or greater than a dead band range.

4. The servo motor control device according to claim 1 or 2, characterized in that: The dead zone unit sets the dead zone range to be smaller as the acceleration amount is larger.

5. The servo motor control device according to claim 3, characterized in that: The dead zone unit sets the dead zone range to be smaller as the acceleration amount is larger.

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