Vibration control device and vibration control method

Abstract

A vibration control device and a vibration control method for controlling shaft torsional vibration and machine support vibration without installing a specific sensor or measuring instrument are disclosed. The vibration control device (30) includes: an amplification factor changing unit (31) that changes the amplification factor of an amplification unit (24) for amplifying the deviation between a command value and a detection value in a servo amplifier (20), a vibration detection unit (32) that measures the frequency and amplitude of vibration superimposed on a moving part, and a filter changing unit (33) that changes the filter (21) based on the frequency and amplitude detected by the vibration detection unit (32).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Japanese Patent Application No. 2020-006940 filed on January 20, 2020, which is hereby incorporated by reference herein in its entirety including specification, claims, drawings, and abstract. Technical Field

[0003] The present disclosure relates to a servo control device for various machines including, for example, a machine tool, and particularly to a vibration control device that controls vibration superimposed on a moving part. Background Art

[0004] Machines in which a moving part is driven by a servo mechanism are known. For example, in a machine tool, a servo mechanism drives one or both of a workpiece and a tool and causes a relative movement between the workpiece and the tool, thereby machining the workpiece. The moving part is driven by a motor via a ball screw or the like, or directly by a linear motor or the like. Typically, when the moving part is accelerated or decelerated, a large force is applied from the motor, which causes torsional vibrations of the shaft system of the ball screw or vibrations of the machine support. This results in an increase in the positioning stabilization time and a deterioration in the accuracy of the position and the surface quality of the machined surface.

[0005] JP 2004-334772A discloses a positioning control device that calculates the amount of shaft twist of a drive shaft from a position command value and a position detection value of a moving part and corrects the position command value, thereby canceling and controlling a deviation caused by shaft vibration.

[0006] In the technology disclosed in JP 2004-334772A, after the deviation is caused by the shaft torsion, the amount of correction is calculated, and then correction is performed based on the amount of correction, which inevitably causes a delay in correction. In addition, the feedback control system generally has a tracking delay caused by the phase delay, and therefore, a delay is also caused in the operation of correcting the moving part according to the amount of correction, which leads to the problem of insufficiently controlled vibration. If the machine support vibration is generated by the reaction force of the force of the motor driving the moving part, the moving part will vibrate following the vibration of the machine support, and the tip of the tool will vibrate accordingly, resulting in no improvement in the surface quality of the machine processing even in an ideal feedback control system that does not have a tracking delay, can completely correct the shaft torsion, and can match the position command value and the position detection value at any time.

[0007] In addition, in order to control the vibration of the machine support, the vibration of the machine support needs to be detectable. For this purpose, a technique of installing, for example, an acceleration sensor on the machine support and observing the sensor is generally adopted. Summary of the invention

[0008] An object of the present disclosure is to provide a vibration control apparatus and a vibration control method for controlling shafting torsional vibration and machine support vibration without installing a specific sensor or measuring instrument.

[0009] A vibration control device according to the present disclosure is a vibration control device for controlling the vibration of a moving part in a machine, the machine including: a moving part driven by a servo motor, a numerical control device that generates a movement command for the moving part, a filter that shapes the command generated by the numerical control device and limits the frequency to be passed, a detector that detects the position or speed of the moving part, a servo amplifier that controls the force generated by the servo motor or the force transmitted to the moving part so that the deviation between the output from the filter and the detection value detected by the detector becomes 0, the vibration control device including: an amplification factor changing unit that changes the amplification factor of an amplification unit for amplifying the deviation in the servo amplifier, a vibration detection unit that measures the frequency and amplitude of the vibration superimposed on the moving part from the deviation, and a filter changing unit that changes the filter based on the frequency and amplitude detected by the vibration detection unit.

[0010] The amplification factor changing unit may enable the detector to detect the vibration of the moving part by reducing the amplification factor of the amplification unit at the beginning of the operation and restoring the amplification factor to its original state at the end of the operation.

[0011] When the amplitude of the vibration exceeds a predetermined amplitude, the filter changing unit may update the characteristics of the filter so that the gain of the filter at the frequency of the vibration is reduced by at least a ratio of the amplitude of the vibration to the predetermined amplitude.

[0012] The vibration control method according to the present disclosure is a vibration control method for controlling the vibration of a moving part in a machine, the machine comprising: a moving part driven by a servo motor, a numerical control device that generates a movement command for the moving part, a filter that shapes the command generated by the numerical control device and limits the frequency to be passed, a detector that detects the position or speed of the moving part, a servo amplifier that controls the force generated by the servo motor or the force transmitted to the moving part so that the deviation between the output from the filter and the detection value detected by the detector becomes 0, and the vibration control method comprises the following steps: reducing the amplification factor of an amplification unit for amplifying the deviation in the servo amplifier, measuring the frequency and amplitude of the vibration superimposed on the moving part, when the amplitude of the vibration exceeds a predetermined amplitude, reducing the gain of the filter at the frequency of the vibration by at least the ratio of the amplitude of the vibration to the predetermined amplitude, and restoring the amplification factor of the amplification unit for amplifying the deviation to the original amplification factor.

[0013] According to the present disclosure, it becomes possible to control shafting torsional vibration and machine mount vibration without installing specific sensors or measuring instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present disclosure will be described based on the following drawings, in which:

[0015] Figure 1 An example of a general machine tool is shown;

[0016] Figure 2 is a block diagram showing a configuration of a vibration control device according to an embodiment;

[0017] Figure 3 is a flowchart showing the process of a vibration control method according to an embodiment; and

[0018] Figure 4 An example of filter characteristics before and after changing the filter is shown. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0020] Figure 1 An example of a general machine tool is shown.

[0021] The machine tool has a motor 3, a ball screw 4, a guide 5, and a spindle head 6 arranged on the front surface of a structure 2, which stands upright on a base 1 fixed on a floor surface. The torque generated by the motor 3 is converted into a force acting in a linear direction by the ball screw 4, and the force controls the movement of the spindle head 6 movably supported by the guide 5 in the left-right direction in the figure. A similar mechanism controls the movement of the spindle head 6 in the up-down direction in the figure, thereby controlling the movement of the tool attached to the tip of the spindle head 6. The movement of the worktable 7 located on the base 1 is controlled in a direction passing through the paper surface, thereby controlling the movement of the workpiece 8 attached to the top surface of the worktable 7. The workpiece 8 is machined by rotating the tool attached to the spindle head 6.

[0022] The torque generated by the motor 3 is controlled and generated by the servo amplifier 20 so that the position detection value or speed detection value detected by the rotation angle detector 9 attached to the motor 3, by the load position detector 10 attached to the structure 2 for enabling direct detection of the position of the spindle head 6, or by both matches the position command value or speed command value generated by the numerical control device 11.

[0023] Figure 2 : is a block diagram showing the internal configuration of the above-mentioned servo amplifier 20 and the configuration of the vibration control device 30 according to the embodiment of the present disclosure.

[0024] In the servo amplifier 20, the filter 21 shapes the position command value or the speed command value generated by the numerical control device 11. The position detection value or the speed detection value detected by the rotation angle detector 9, the load position detector 10, or both is selected or synthesized by the adjustment unit 22, thereby calculating the position detection value or the speed detection value for control use. The signals output from the filter 21 and the adjustment unit 22 are subjected to subtraction by the subtractor 23, thereby obtaining the deviation Err. The deviation Err is amplified by the amplification unit 24, and then the control unit 25 controls the torque generated by the motor 3 so that the deviation Err=0 is achieved.

[0025] Here, if the ball screw 4 has low rigidity, the shaft torsion of the ball screw 4 causes delay and vibration in the response of the spindle 6 compared with the command value generated by the numerical control device 11. That is, the detection value detected by the load position detector 10 includes superimposed delay and vibration, and generates a deviation Err.

[0026] On the contrary, for example, if the ball screw has high rigidity, and if the amplification unit 24 and the control unit 25 capable of performing sufficient control are implemented, for example, by setting a high amplification factor in the amplification unit 24, the response delay and vibration of the above-mentioned spindle head 6 are reduced, and the deviation Err≒0 can be achieved. However, the reaction force generated when the spindle head 6 is driven is transmitted to the structure 2, and displacement and vibration occur due to the rigidity of the machine support and mechanism. At this time, control is performed to achieve the deviation Err≒0, resulting in displacement and vibration of the spindle head 6 integral with the structure 2.

[0027] In the vibration control device 30, when an operation command is received from a superior device such as the numerical control device 11, the amplification factor changing unit 31 reduces the amplification factor of the amplification unit 24, and the vibration detection unit 32 measures the frequency and amplitude of the vibration included in the deviation Err. If the amplitude of the detected vibration exceeds a predetermined amplitude, the filter changing unit 33 reduces the gain of the filter 21 at the frequency of the vibration detected by the vibration detection unit 32. The predetermined amplitude may be a predetermined amplitude, or may be changed by an administrator or the like. The amplification factor changing unit 31 then restores the amplification factor of the amplification unit 24 to the factor before the amplification reduction, and the vibration control device 30 completes the operation.

[0028] In the above operation, the amplification factor changing unit 31 reduces the amplification factor of the amplification unit 24, and therefore, even if the displacement and vibration are caused by the rigidity of the machine support and the mechanism, the displacement and vibration can be observed using the deviation Err without installing an acceleration sensor or the like. In addition, the vibration detecting unit 32 can identify the frequency and amplitude of the vibration included in the deviation Err by using, for example, an FTT (Fast Fourier Transform) algorithm. In addition, the filter changing unit 33 can reduce the gain at the vibration frequency of the filter 21 by adding a filter having a band-stop characteristic before or after the existing filter 21 and redefining the filter as the filter 21. Alternatively, the gain of the filter 21 can be reduced by setting the order of the filter 21 to a higher order in advance and changing the filter coefficient. The gain at the vibration frequency reduces the ratio of at least the amplitude of the detected vibration to the predetermined amplitude.

[0029] Figure 3 is a flowchart illustrating a process of a vibration control method according to an embodiment of the present disclosure.

[0030] When receiving an operation command from a superior device such as the numerical control device 11, the vibration control device 30 starts to operate and reduces the amplification factor of the amplification unit 24 used to amplify the deviation Err (step 1). The vibration control device 30 then measures the frequency and amplitude of the vibration included in the deviation Err (step 2). If the amplitude of the detected vibration exceeds the predetermined amplitude (yes), the vibration control device 30 reduces the gain of the filter 21 at the frequency of the detected vibration by at least the ratio of the amplitude (step 3). If the amplitude of the detected vibration does not exceed the predetermined amplitude (no), the gain of the filter 21 remains unchanged. The vibration control device 30 then restores the amplification factor of the amplification unit 24 to the factor before reduction (step 4). This completes the operation.

[0031] Figure 4 Examples of filter characteristics before and after the filter 21 is changed are shown.

[0032] Before changing the filter 21, the gain at the vibration frequency is 1, and the relevant frequency component included in the command completely passes through the filter 21. In contrast, after changing the filter 21, the gain at the vibration frequency is reduced so that the gain becomes equal to or less than the predetermined amplitude / vibration amplitude. The relevant frequency component included in the command is also reduced in proportion to the reduction. This also leads to a reduction in the exciting force applied to the mechanical system, and thus leads to a reduction in the vibration caused by the shaft torsion of the ball screw 4 and the vibration caused by the rigidity of the machine bracket and mechanism.

[0033] By using the vibration control device and the vibration control method described above, it is possible to control the shafting torsional vibration and the machine support vibration without installing a specific sensor or measuring instrument.

[0034] Although, in the above-mentioned embodiment, a machine tool equipped with a shaft extending from a motor via a ball screw for driving a spindle head has been described as an example, the above-mentioned embodiment can also be applied to a machine tool driven by a linear motor and can also be applied to industrial machines other than machine tools. This embodiment can be applied not only to a linear driven shaft but also to a rotary driven shaft.

[0035] In addition, for the purpose of explanation, the amplification unit 24 and the control unit 25 have been included as components for controlling the torque generated in the motor 3 based on the deviation Err, and these components can be configured as a single integrated control unit. The detection object to be detected by the vibration detection unit does not necessarily have to be the deviation Err, and the deviation Err can also be replaced by, for example, the detection value of the load position detector 10, as long as it is a signal superimposed with the vibration of the moving part. The vibration control method according to the embodiment of the present disclosure can be used for both manual and automatic processing, regardless of its form.

Claims

1. A vibration control device for controlling the vibration of a moving part in a machine, the machine comprising: The moving part is driven by a servo motor; a numerical control device that generates movement commands for the moving part; a filter that shapes the commands generated by the numerical control device and limits the frequencies to be passed; a detector that detects the position or speed of the moving part; as well as a servo amplifier that controls the force generated by the servo motor or the force transmitted to the moving part so that a deviation between an output from the filter and a detection value detected by the detector becomes 0, wherein The vibration control device comprises: an amplification factor changing unit that changes an amplification factor of an amplification unit for amplifying a deviation in the servo amplifier and enables the detector to detect the vibration of the moving part by reducing the amplification factor of the amplification unit at the beginning of an operation and restoring the amplification factor of the amplification unit to the original amplification factor at the end of the operation, a vibration detection unit that measures the frequency and amplitude of the vibration superimposed on the moving part from the deviation, and A filter changing unit changes the filter based on the frequency and the amplitude detected by the vibration detecting unit.

2. The vibration control device according to claim 1, wherein: When the amplitude of the vibration exceeds a predetermined amplitude, the filter changing unit updates the characteristics of the filter so that the gain of the filter at the frequency of the vibration is reduced by at least a ratio of the amplitude of the vibration to the predetermined amplitude.

3. A vibration control method for controlling vibrations of a moving part in a machine, the machine comprising: The moving part is driven by a servo motor; a numerical control device that generates movement commands for the moving part; a filter that shapes the commands generated by the numerical control device and limits the frequencies to be passed; a detector that detects the position or speed of the moving part; as well as a servo amplifier that controls the force generated by the servo motor or the force transmitted to the moving part so that a deviation between an output from the filter and a detection value detected by the detector becomes 0, wherein the vibration control method includes the following steps: reducing an amplification factor of an amplification unit for amplifying a deviation in the servo amplifier, measuring the frequency and amplitude of the vibrations superimposed on the moving part, When the amplitude of the vibration exceeds a predetermined amplitude, reducing the gain of the filter at the frequency of the vibration by at least a ratio of the amplitude of the vibration to the predetermined amplitude, and The amplification factor of the amplification unit used to amplify the deviation is restored to the original amplification factor.

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