Motor control device and industrial machine

Abstract

The present application provides a kind of motor control device and industrial machine.Electric motor control device has: position instruction part, it generates position instruction for control object;Position detection part, it detects the position of control object or the position of motor for driving control object;And position control part, it controls the position of motor based on position instruction, and the position of control object or motor detected, wherein, at least one of position instruction part and position control part has vibration suppression filter, which is used to approximate the inverse characteristics of vibration characteristics generated between motor and control object, vibration suppression filter changes vibration suppression frequency according to at least one of the position and mass of control object.

Description

Technical Field

[0001] This invention relates to an electric motor control device and industrial machinery, and more particularly to an electric motor control device and industrial machinery for suppressing vibration. Background Technology

[0002] The following issue has long been a concern: when machining workpieces using machine tools that generate low-frequency vibrations, such as those below 100 Hz, stripes corresponding to the vibrations are produced on the workpiece. The following literature is known as a technique for suppressing these low-frequency vibrations.

[0003] Japanese Patent Application Publication No. 2009-15448 discloses a motor control device for a semi-closed-loop control system that performs feedback control on the position and speed of a motor. The device includes a band-stop filter that detects the natural frequency of the controlled object and removes the component of the detected natural frequency.

[0004] Japanese Patent Application Publication No. 2016-163397 discloses a motor control device for a fully closed-loop control system that performs feedback control on the position of a machine, wherein the position control unit includes a filter that approximates the reverse characteristics of the transmission characteristics from the motor to the machine.

[0005] Japanese Patent Application Publication No. 2019-9958 discloses a motor control device for a semi-closed-loop control system that performs feedback control on the speed of an electric motor, wherein the speed control unit includes a filter that approximates the reverse characteristics of the transmission characteristics from the electric motor to the machine. Summary of the Invention

[0006] In methods that remove only specific vibration components by detecting the natural frequency of the machine, the vibration suppression function for changes in vibration characteristics is more likely to be delayed. In addition, it is easy to remove components other than the target vibration component, which sometimes makes the motor control unstable.

[0007] Therefore, there is a need for a technology that can more quickly and accurately apply vibration suppression functions to changes in vibration characteristics.

[0008] One aspect of this disclosure provides an electric motor control device comprising: a position command unit that generates a position command for a controlled object; a position detection unit that detects the position of the controlled object or the position of a motor used to drive the controlled object; and a position control unit that controls the position of the motor based on the generated position command and the detected position of the controlled object or the motor, wherein at least one of the position command unit and the position control unit includes a vibration suppression filter for approximating the inverse characteristics of vibration characteristics generated between the motor and the controlled object, and the vibration suppression filter changes the vibration suppression frequency according to at least one of the position and mass of the controlled object.

[0009] Other aspects of this disclosure provide an industrial machine comprising: an electric motor; a self-shaft driven by the electric motor; a control object capable of movement via the self-shaft; and the aforementioned electric motor control device.

[0010] Another aspect of this disclosure provides an industrial machine comprising: an electric motor; a self-shaft driven by the electric motor; a other-shaft driven by an electric motor different from the electric motor; a control object capable of movement via at least one of the self-shaft and the other-shaft; and the aforementioned electric motor control device. Attached Figure Description

[0011] Figure 1 This is a structural diagram of the motor control device of a semi-closed-loop control system in one implementation method.

[0012] Figure 2 This is a structural diagram of the motor control device of a fully closed-loop control system in one implementation method.

[0013] Figure 3A This is an explanatory diagram showing the torsional vibration characteristics of a ball screw.

[0014] Figure 3B This is an explanatory diagram showing the torsional vibration characteristics of a ball screw.

[0015] Figure 4 This is an explanatory diagram showing the vibration characteristics of a leaf spring in a ball screw.

[0016] Figure 5 It is a structural diagram of an industrial machine with a self-shaft driven by an electric motor.

[0017] Figure 6 It is a structural diagram of industrial machinery that has a separate shaft driven by a motor different from the electric motor. Detailed Implementation

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same or similar constituent elements are labeled with the same or similar reference numerals. Furthermore, the embodiments described below are not intended to limit the technical scope and meaning of the terms used in the claims. In addition, in this specification, "feedforward" is referred to as "FF," and "feedback" is referred to as "FB."

[0019] Figure 1 The structure of the motor control device 1 in a semi-closed-loop control system is shown. The motor control device 1 includes: a position command unit 10 that generates position commands for the controlled object 3; a position control unit 11 that controls the position of the motor 2 based on the generated position commands and the detected position of the motor 2; and a position detection unit 13 directly mounted on the motor. The position detection unit 13 includes, for example, a rotary displacement sensor such as an encoder, a resolver, or a Hall sensor. The controlled object 3 includes, for example, the worktable, spindle head, or conveyor of industrial machinery such as machine tools or conveying machinery.

[0020] The motor control unit 1 may also include a servo control unit 12 for speed and torque control. However, the position control unit 11 may also function as the servo control unit 12. In the latter case, the position control unit 11 directly outputs torque commands to the motor 2. Furthermore, the position command unit 10, the position control unit 11, and the servo control unit 12 may also include processors such as a CPU (central processing unit) or an FPGA (field-programmable gate array). The position control unit 11 includes a vibration suppression filter 20a, a position FF controller 21, a subtraction unit 22, a position FB controller 23, and an addition unit 24.

[0021] The vibration suppression filter 20a is a filter that approximates the inverse characteristics of the vibration characteristics generated between the motor 2 and the controlled object 3. Since the motor control device 1 is a semi-closed-loop control system, the vibration suppression filter 20a compensates for the vibration characteristics generated outside the position FB loop (i.e., between the motor 2 and the controlled object 3). Therefore, the vibration suppression filter 20a can be a position command filter that corrects the position command and is located outside the position FB loop. Alternatively, the vibration suppression filter 20a can be located in the position command unit 10 instead of the position control unit 11.

[0022] The position FF controller 21 differentiates the position command to generate a first speed command. The subtraction unit 22 subtracts the position command from the detected motor position to generate a position deviation. The position FB controller 23 multiplies the position deviation by the position FB gain to generate a second speed command. The addition unit 24 adds the first speed command and the second speed command to generate a motor speed command.

[0023] Figure 2 The structure of the motor control device 1 of the fully closed-loop control system is shown. The motor control device 1 differs from the motor control device 1 described above in that it includes a position detection unit 13 installed on industrial machinery. The position detection unit 13 includes, for example, a linear displacement sensor such as a strain gauge or a laser displacement sensor. The position control unit 11 controls the position of the motor 2 based on the position command generated in the position command unit 10 and the detected position of the controlled object 3.

[0024] Since the motor control device 1 is a fully closed-loop control system, the vibration suppression filter 20b compensates for the vibration characteristics generated inside the position FB loop (especially between the motor 2 and the controlled object 3). Therefore, the vibration suppression filter 20b can be a position FB filter located inside the position FB loop. The vibration suppression filter 20b can be a second speed command filter located after the position FB controller 23 to correct the second speed command, or it can be a motor speed command filter located immediately after the adder 24 to correct the motor speed command. Furthermore, the vibration suppression filter 20b can also be a position deviation filter located before the position FB controller 23 to correct the position deviation.

[0025] Alternatively, in addition to the vibration suppression filter 20b, the position control unit 11 may also have a vibration suppression filter 20c outside the position FB loop, or the position control unit 11 may replace the vibration suppression filter 20b with a vibration suppression filter 20c outside the position FB loop. The vibration suppression filter 20c may be a position FF filter disposed outside the position FB loop. The vibration suppression filter 20c may be a first speed command filter disposed after the position FF controller 21 to correct the first speed command, or it may be a position command filter disposed before the position FF controller 21 to correct the position command. By disposing of the vibration suppression filter 20c outside the position FB loop, the frequency components in the first speed command that cause vibration can be reduced, allowing the controlled object to move without vibration.

[0026] The vibration suppression filters 20a-20c described above possess a filter F(s) that approximates the inverse characteristic (Equation 2) of the vibration characteristics (Equation 1) generated between the motor 2 and the controlled object 3, as shown in the following equations. In these equations, ω0 is the anti-resonance frequency (i.e., the vibration suppression frequency), ζ is the vibration attenuation coefficient, and s is the Laplace operator.

[0027]

[0028]

[0029] In the vibration suppression filter F(s) shown in Equation 2, the numerator polynomial is key, and the denominator polynomial can also be a suitable low-pass filter. As low-pass filters, first-order low-pass filters, second-order low-pass filters, etc., can be listed. The first-order low-pass filter is an ideal form and can be described, for example, as shown in the following equation. In the following equation, ω adj It is a parameter that can be adjusted for a specific anti-resonance frequency.

[0030]

[0031] A second-order low-pass filter is a mount-type filter, which can be described, for example, as shown in the following formula. A second-order low-pass filter is suitable for situations where only the vibration components of the target are suppressed.

[0032]

[0033] The anti-resonance frequency ω0 (i.e., the vibration suppression frequency) in these vibration suppression filters F(s) varies according to the physical changes of the controlled object 3 (i.e., changes in at least one of its position and mass). Therefore, the vibration suppression filters 20a-20c in this example are characterized in that, as described later, the vibration suppression frequency is changed according to at least one of the position and mass of the controlled object 3.

[0034] Generally, in industrial machinery, power is transmitted to the controlled object 3 via power transmission elements such as shafts, gears, conveyor belts, chains, cams, and chain links. Therefore, the vibration frequency of the controlled object 3 can be described by the torsional vibration characteristics of the power transmission elements, the vibration characteristics of the leaf springs, and their combinations.

[0035] As an example of torsional vibration characteristics, refer to Figure 3A and Figure 3BLet's illustrate the torsional vibration characteristics of the ball screw 31. In this example, assume the following: the controlled object 3, acting as a worktable, moves on the ball screw 31, which is cantilevered by the support element 32, and the ball screw 31 generates torsional vibration V1. The ball screw 31 has a length L, a diameter d, and a lateral spring constant G. Ignoring the mass of the ball screw 31, the spring constant k1 of the ball screw 31 is described by the following formula.

[0036]

[0037] According to this formula, the spring constant k1 varies depending on the length L of the ball screw, which is equivalent to the position of the controlled object 3. When... Figure 3B When the position of the controlled object 3 changes as shown, thus changing the spring constant k1, the angular frequency ω1 (i.e., the vibration frequency) of the controlled object 3 also changes as shown in the following formula. In the following formula, J L It is the inertia of control object 3.

[0038]

[0039] According to this formula, it can also be known that the angular frequency ω1 of the controlled object 3 is based on the inertia J, which is equivalent to the mass M of the controlled object 3. L And change. When the controlled object 3 has a mass M and is driven by a ball screw 31 with a pitch p [m], the inertia J of the controlled object 3 changes. L The mass M of the controlled object 3 can be transformed into the mass M using the following formula.

[0040]

[0041] In addition, as an example of the vibration characteristics of a leaf spring, refer to Figure 4 Let's illustrate the leaf spring vibration characteristics of the ball screw 31. In this example, assume the following: the controlled object 3 is at the top of the ball screw 31, the ball screw 31 is cantilevered by the support element 32, and the ball screw 31 generates leaf spring vibration V2. The ball screw 31 has a length L, a diameter d, and a Young's modulus E. Ignoring the mass of the ball screw 31, the spring constant k2 of the ball screw 31 is described by the following formula.

[0042]

[0043] According to this formula, the spring constant k2 varies with the length L of the ball screw 31, which is equivalent to the position of the controlled object 3. When the position of the controlled object 3 changes, thus changing the spring constant k2, the angular frequency ω2 (i.e., the vibration frequency) of the controlled object 3 also changes as shown in the following formula. In the following formula, M is the mass of the controlled object 3.

[0044]

[0045] According to this formula, it can also be seen that the angular frequency ω2 of the controlled object 3 varies with the mass M of the controlled object 3.

[0046] Refer again Figure 1 and Figure 2 Regarding the position of the controlled object 3 (i.e., the length L of the ball screw), it can be input from the position detection unit 13 to the vibration suppression filters 20a-20c, as shown by the dashed arrow, or it can be input from the position command unit 10 to the vibration suppression filters 20a-20c. On the other hand, regarding the mass M of the controlled object 3, it can be pre-input by the operator to the motor control device 1, or it can be estimated based on the relationship between the torque and acceleration of the controlled object 3 or the motor 2 by causing a slight movement (e.g., vibration) of the motor 2.

[0047] Figure 5 This illustrates an industrial machine 30 equipped with a self-shaft 31 driven by an electric motor 2. The industrial machine 30 includes an electric motor 2, a self-shaft 31 driven by the electric motor 2, a control object 3 capable of movement via the self-shaft 31, and an electric motor control device 1 for controlling the electric motor 2. The electric motor 2 is, for example, a servo motor; the self-shaft 31 is, for example, an X-axis ball screw defining the X-axis direction; and the control object 3 is, for example, a worktable. The self-shaft 31 is cantilevered by a support element 32, but it can also be supported at both ends.

[0048] The motor control device 1 is equipped with either a fully closed-loop control system or a semi-closed-loop control system. Figure 1 or Figure 2 The vibration suppression filters 20a-20c are shown. Torsional vibration V1 is generated on the self-axis 31, and the characteristics of this torsional vibration vary depending on the position Lx of the controlled object 3 in the X-axis direction. Therefore, the vibration suppression filters 20a-20c, based on the position Lx of the controlled object 3 on the self-axis 31, calculate the angular frequency ω1 of the torsional vibration V1 according to Equation 6. Based on the calculated angular frequency ω1, the vibration suppression frequency ω0 of F(s), which approximates the inverse characteristics of the torsional vibration, is changed. Then, the vibration suppression filters 20a-20c output the changed F(s).

[0049] Figure 6The diagram shows an industrial machine 30 that also includes a secondary shaft 33 driven by a motor 4, which is different from the motor 2. The industrial machine 30 includes a motor 2, a primary shaft 31, a secondary shaft 33, a control object 3 capable of movement via at least one of the primary shaft 31 and the secondary shaft 33, and a motor control device 1 for controlling the motor 2 and the motor 4. The primary shaft 31 is, for example, a Y-axis ball screw defining the Y-axis direction, the secondary shaft 33 is, for example, a Z-axis ball screw defining the Z-axis direction, and the control object 3 is, for example, a spindle head. The primary shaft 31 is cantilevered by a support element 32, but may also be supported at both ends; the secondary shaft 33 is cantilevered.

[0050] The motor control device 1 is equipped with either a fully closed-loop control system or a semi-closed-loop control system. Figure 1 or Figure 2 The vibration suppression filters 20a-20c are shown. Torsional vibration V1 is generated on the self-axis 31, and the characteristics of this torsional vibration vary depending on the position Ly of the controlled object 3 in the Y-axis direction. Leaf spring vibration V2 is generated on the other axis 33, and the characteristics of this leaf spring vibration vary depending on the position Lz of the controlled object 3 in the Z-axis direction. The vibration suppression filters 20a-20c calculate the angular frequency ω1 of the torsional vibration V1 using Equation 6 based on the position Ly of the controlled object 3 on the self-axis 31. Based on the calculated angular frequency ω1, the vibration suppression frequency ω0, which approximates the reverse characteristic of the torsional vibration F1(s), is changed. Furthermore, the vibration suppression filters 20a-20c calculate the angular frequency ω2 of the leaf spring vibration V2 using Equation 9 based on the position Lz of the controlled object 3 on the other axis 33. Based on the calculated angular frequency ω2, the vibration suppression frequency ω0, which approximates the reverse characteristic of the leaf spring vibration F2(s), is changed. Then, the vibration suppression filters 20a-20c output the modified F1(s)×F2(s).

[0051] According to the above implementation, the vibration suppression filters 20a-20c are changed according to the physical changes of the controlled object 3 (i.e., changes in at least one of the position and mass of the controlled object), so the vibration suppression filters 20a-20c can be applied more quickly and accurately to changes in vibration characteristics.

[0052] Alternatively, the program executed by the aforementioned processor can also be provided by recording on a computer-readable, non-transitory recording medium such as a CD-ROM.

[0053] Various embodiments have been described in this specification, but the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the above claims.

Claims

1. An electric motor control device, comprising: The position command unit generates position commands for the controlled object; A position detection unit detects the position of the controlled object or the position of the motor used to drive the controlled object; and The position control unit controls the position of the motor based on the generated position command and the detected position of the controlled object or the motor. in, At least one of the position command unit and the position control unit includes a vibration suppression filter, which is used to approximate the reverse characteristics of the vibration characteristics generated between the motor and the controlled object. The vibration suppression filter changes the vibration suppression frequency based on at least one of the position and mass of the controlled object. The vibration suppression frequency is varied based on the torsional vibration characteristics and the leaf spring vibration characteristics. Using a spring constant k1 that varies according to the position of the controlled object and the inertia J of the controlled object. L The torsional vibration characteristics are described by the following formula for the angular frequency ω1 of the controlled object: ， The spring constant k1 is described by the following formula, based on the length L of the ball screw, the diameter d of the ball screw, and the lateral elastic coefficient G of the ball screw, which are equivalent to the position of the controlled object: ， The inertia J is described by the following formula based on the mass M of the controlled object and the pitch p of the ball screw. L : ， Furthermore, the vibration suppression filter has filter characteristics obtained by multiplying a first vibration suppression filter that approximates the inverse characteristics of the torsional vibration characteristics with a second vibration suppression filter that approximates the inverse characteristics of the leaf spring vibration characteristics.

2. The motor control device according to claim 1, wherein, The weight of the controlled object is either pre-input by the operator or estimated based on the relationship between the torque and acceleration of the controlled object or the motor.

3. The motor control device according to claim 1, wherein, The vibration characteristics of the leaf spring are described by the following formula, based on the spring constant k2 that varies with the position of the controlled object, the mass M of the controlled object, and the angular frequency ω2 of the controlled object: 。 4. The motor control device according to claim 1, wherein, The motor control device is a semi-closed-loop control system, and the vibration suppression filter is a position command filter located outside the position feedback loop.

5. The motor control device according to claim 1, wherein, The motor control device is a fully closed-loop control system, and the vibration suppression filter is a position feedback filter located inside the position feedback loop.

6. The motor control device according to claim 5, wherein, The motor control device is a fully closed-loop control system, and the vibration suppression filter is a position feedforward filter located outside the position feedback loop.

7. An industrial machine, comprising: Electric motor; A self-shaft driven by the electric motor; A separate shaft driven by a motor different from the motor mentioned above; A control object capable of movement via the self-axis and the other-axis; and The motor control device according to any one of claims 1 to 6.

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