JP4842903B2 - Numerical control apparatus and numerical control method - Google Patents

Description

  The present invention relates to a numerical control device and a numerical control method in a feed drive system used for a 5-axis machine tool or the like.

  FIG. 10 is a numerical control device of a 5-axis machine tool having three orthogonal XYZ axes, a rotation axis B axis around the Y axis, and a rotation axis C axis around the Z axis, and FIG. 11 is a schematic diagram of the 5-axis machine tool. Respectively. Since the configuration of each of the five axes is common, only the X axis will be described. In the X axis, the rotational force of the servo motor 43 is converted into a linear motion via the ball screw 51 to drive the X axis table 53 serving as a driven body. A position detector 44 is mounted on the servo motor 43, and feedback control is performed by the output from the position detector 44. In other words, the position detector 44 detects the rotation angle and indirectly detects the position of the X-axis table 53 to perform position control. Then, by moving the X-axis table 53 on which the workpiece 56 is placed to a desired position, the spindle 54 and the workpiece 56 are relatively controlled to process the workpiece 56 with the tool 55. In the numerical controller 45, the current position of the position detector 44 attached to the servo motor 43 is subtracted from the X-axis position command value TPx of the position command value TP generated by the function generator 41 based on the program. The value is input to the controller 42.

In the conventional semi-closed loop type five-axis machine tool shown in FIG. 11, when the axis of the ball screw 51 generating the driving force and the center of gravity of the X-axis table 53 are different, the posture of the X-axis table 53 is changed. Therefore, there is a difference between the two stop positions when the X-axis table 53 is positioned at a predetermined position in the positive direction and when it is positioned in the negative direction. Therefore, this difference when feeding at a certain feed rate is measured, and given in advance to the numerical controller 45 as a backlash correction value, the movement amount is corrected.
For example, Patent Document 1 provides a function that makes it possible to detect a change in the deformation amount of the ball screw and a change in the deformation amount of the table when the table moving direction is reversed. There is described a numerical control device having a function of detecting and correcting a position error based on deformation and a position error based on table deformation and correcting each error. In Patent Document 2, a value obtained by multiplying the acceleration obtained by differentiating the position command twice by a coefficient is obtained as a correction amount, and added to the speed command to correct a position error due to expansion / contraction of the structure during acceleration / deceleration. A control method is described. Furthermore, Patent Literature 3 describes a positioning device that detects the acceleration of a moving body and obtains a correction amount for a target position.

JP-A-6-67716 Japanese Patent No. 3308656 JP-A-8-297508

  However, the methods of Patent Documents 2 and 3 refer to the posture deformation of the driven body due to the lost motion caused by the posture change of the driven body of the linear axis and the correction including the rotation axis orthogonal to the linear axis. Absent. This lost motion occurs because the center of gravity of the driven body does not match the position where the driving force acts.If the feed drive system has sufficient rigidity, such a change in posture can be ignored. It cannot be ignored when it is unavoidable in terms of cost and cannot be rigid, or when the center of gravity of the driven body and the driving position are far apart and the mass of the driven body is large as in a large machine tool. The lost motion value is not a constant value, and changes not only at the time of reversal but also by the change in acceleration / deceleration. However, it is insufficient for correcting the lost motion in the posture change, and the relative position between the spindle and the workpiece cannot be corrected. Japanese Patent Application Laid-Open No. 2003-228561 discloses a technique for detecting a change in the amount of deformation of the table portion when the table moving direction is reversed and correcting the error. It is necessary to provide a sensor, which increases the cost.

  Accordingly, the present invention has been made in view of the above-described problems, and is a numerical control device capable of accurately correcting posture changes occurring on a linear axis including a rotation axis without providing a displacement sensor or the like. And a numerical control method.

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that one or a plurality of linear axes orthogonal to each other for linearly moving the driven body, and another linear axis rotating around any one of the linear axes. In a numerical control apparatus having one or more rotating shafts orthogonal to each other, acceleration / deceleration calculating means for obtaining acceleration / deceleration of the driven body, acceleration / deceleration of the driven body obtained by the acceleration / deceleration calculating means, Posture displacement amount for determining the posture displacement amount of the driven body including at least the posture displacement amount around the rotation axis based on the gravity center position and mass of the drive body and the position where the driving force acts on the driven body. And a rotation correction value calculation unit that obtains at least a correction value of the rotation axis from the posture displacement amount obtained by the posture displacement amount calculation unit.
According to a second aspect of the present invention, in the configuration of the first aspect, when the other linear axis or the rotation axis is mounted on the driven body, the posture displacement amount calculating means is configured to change the other linear axis or the rotation axis. The posture displacement amount of the driven body is obtained using the center of gravity position corrected by taking into account the position of the center of gravity of the shaft as the center of gravity position of the driven body.
According to a third aspect of the present invention, in the configuration of the first or second aspect, the driven body used in the posture displacement amount calculating means is provided with input means for inputting a gravity center position and / or mass of the driven body. The center of gravity position and / or the mass can be arbitrarily changed.

In order to achieve the above object, the invention described in claim 4 is a numerical control method, wherein the acceleration / deceleration of a driven body that is linearly driven by one or a plurality of linear axes orthogonal to each other is obtained and stored in a storage means. Based on the first step, the acceleration / deceleration of the driven body obtained in the first step, the center of gravity position and mass of the driven body, and the position where the driving force acts on the driven body , A second step of obtaining a posture displacement amount of the driven body including a posture displacement amount around one or more rotation axes orthogonal to another linear axis by rotating around any one of the linear axes ; If, from the attitude displacement amount obtained in the second step, is characterized in that a third step of obtaining at least the correction value of the rotary shaft, a.
According to a fifth aspect of the present invention, in the configuration of the fourth aspect, when another linear axis or rotating shaft is placed on the driven body, in the second step, the other linear axis or rotating shaft is The posture displacement amount of the driven body is obtained using the center of gravity position corrected by taking the center of gravity position into account as the center of gravity position of the driven body.
According to a sixth aspect of the present invention, in the configuration of the fourth or fifth aspect, the second step uses the position of the center of gravity and the mass of the driven body obtained by the input means.

In the first and fourth aspects of the invention, for example, the relative position between the spindle and the workpiece can be accurately controlled by correcting the rotation axis based on the posture change generated on the linear axis. In particular, since the posture change amount is obtained from the acceleration and corrected, it can be corrected dynamically.
In the inventions of claims 2 and 5, when a linear axis or a rotation axis is placed on the linear axis to be corrected, even if the position of the center of gravity of the linear axis to be corrected changes due to the movement of the axis placed on the axis And high-precision machining can be realized.
According to the third and sixth aspects of the present invention, even when the size and weight of the workpiece are greatly different, the operator can respond to the change of the workpiece by inputting the information on the workpiece into the numerical control device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Form 1]
FIG. 1 is a block diagram of a numerical controller of a 5-axis machine tool, and FIG. 2 is an explanatory diagram of the 5-axis machine tool. The basic configurations of the 5-axis machine tool and the numerical control device are the same as those in FIGS. 10 and 11, and only the X-axis will be described here.
First, the numerical control device 5 includes a controller 2, a servo motor 3, and a position detector 4 for each axis drive system in addition to the function generator 1. The difference from FIG. 10 is that the acceleration is obtained from the correction value calculation unit (attitude change amount calculation means and rotation correction value calculation means) 6 for calculating the attitude change amount generated in the X-axis table 13 and the output of the position detector 4. The acceleration calculation unit (acceleration / deceleration calculation means) 7 is newly provided.
In this numerical control device 5, for example, when the X-axis table 13 moves, the correction value calculation unit 6 uses the acceleration AAx of the X-axis table 13 obtained by the acceleration calculation unit 7 and the position command value TP of each axis. Calculates the correction value EP and sends it to each axis. Therefore, a value obtained by subtracting the correction value EP and the current position AP of the position detector 4 attached to the servo motor 3 from the position command value TP is input to the controller 2.

FIG. 2 shows how the X-axis table 13 is pitched as the X-axis table 13 is moved at the acceleration AAx by driving the X-axis ball screw 11. Reference numeral 14 denotes a spindle, and 15 denotes a tool. Further, the distance Hx between the axis of the X-axis ball screw 11 and the center of gravity of the X-axis table 13, the distance Lx between the sliders of the rolling guide 12, the mass Mx of the X-axis table 13, the gravitational acceleration g, and the radial stiffness Kx of the slider are These are recorded in advance in the memory of the correction value calculation unit 6. In FIG. 2, the center of gravity of the X-axis table 13 is at the center between the two sliders 12 (a) and 12 (b). The method of calculating the posture change amount will be specifically described with reference to FIG.
First, the acceleration AAx is obtained by the acceleration calculator 7 (first step of the present invention).
Next, assuming that the radial load load of the front slider 12 (a) is F1, the radial load load of the rear slider 12 (b) is F2, and the tilt amount of the X-axis table 13 is ΔB,

F1 = Mx · g / 2−Mx · AAx · Hx / (2Lx) ·· (Formula 1)
F2 = Mx · g / 2 + Mx · AAx · Hx / (2Lx) ·· (Formula 2)
ΔB = tan ⁻¹ (| F1−F2 | / Kx / Lx) (Expression 3)
It can be expressed as.
That is, as the X-axis table 13 accelerates or decelerates, the term Mx · AAx · Hx / (2Lx) is added to the radial load load of the slider 12, but the sign differs between the front and rear sliders 12. A difference occurs in the position of the X-axis table 13. In the correction value calculation unit 6 of FIG. 1, the correction value EPb = ΔB is calculated from Equation 3, and the B axis turns by correction.

In order to make the X-axis table 13 whose posture is displaced in this way coincide with the position of the blade edge before and after turning, it is necessary to move the X-axis and the Z-axis by ΔX and ΔZ. If the Z-axis command value (in this case, the distance between the X-axis table center of gravity and the B-axis rotation center) is TPz,
ΔX = TPz · sinΔB ·· (Formula 4)
ΔZ = TPz (1−cos ΔB) (5)
It can be expressed as. That is, EPx = ΔX and EPz = ΔZ are correction values, respectively.

  FIG. 3 is a flowchart of the posture displacement correction function of the numerical control device 5. When an X-axis movement is instructed by the program, first, TPx is calculated from the function generator 1 in S1. Next, in S2, the acceleration calculator 7 calculates the X-axis acceleration AAx from the value of the position detector 4 (first step of the present invention). In S3, the X-axis acceleration AAx obtained in S2 and S1 Using the calculated Z-axis command value TPz, the correction value calculation unit 6 calculates the correction values EPx, EPz, and EPb, respectively, as described above (second and third steps of the present invention).

  As described above, according to the numerical control device 5 and the numerical control method of the first aspect, the acceleration calculation unit 7 for obtaining the acceleration of the X-axis table 13, the acceleration of the X-axis table 13 obtained by the acceleration calculation unit 7, X The posture displacement amount of the X-axis table 13 is obtained based on the center of gravity position and mass of the shaft table 13 and the position where the driving force acts on the X-axis table 13, and the X-axis, Z-axis, and B-axis are obtained from the obtained posture displacement amounts. With the correction value calculation unit 6 for obtaining the correction value, it is possible to correct the posture change generated on the linear axis using the rotation axis, and to accurately control the relative position of the spindle and the workpiece. Become. In particular, since the posture change amount is obtained from the acceleration and corrected, it can be corrected dynamically.

[Form 2]
Next, another embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same component as the form 1, and the overlapping description is abbreviate | omitted.
In the numerical control device 5a shown in FIG. 4, the correction value calculation unit 6 is newly provided with a centroid position calculation unit 8 for calculating the centroid position, and when the linear axis or the rotation axis is placed on the linear axis, Even if the position of the center of gravity of the straight axis to be corrected changes due to the movement of the mounted axis, it is possible to cope with it.
FIG. 5 shows the Y-axis of a 5-axis machine tool, 21 is a Y-axis ball screw, 22 is a Y-axis rolling guide for guiding a Y-axis table 29, 23 is a Y-axis crossrail, and 24 is a Y-axis servomotor. , 24 are Y-axis position detectors. Here, a Z-axis which is another linear axis is mounted on a Y-axis table 29 which moves linearly, a Z-axis servo motor 26 and a Z-axis position detector 27 are mounted, and a Z-axis ram 28 as a driven body is mounted. It can be moved up and down.

Here, when the Z-axis ram 28 is lowered, for example, as shown in the lower side of the figure, the position of the center of gravity of the Y-axis Z-axis including the Y-axis table 29 etc. changes from Hyz to Hyz ′. If Hyz ′ is the Y-axis mass My, the Z-axis mass Mz, and the center-of-gravity position Hyz obtained from the Z-axis movement amount ΔTPz,
Hyz ′ = Hyz−Mz · ΔTPz / (My + Mz) (Equation 6)
Can be obtained. Here, the center-of-gravity position calculation unit 8 obtains this Hyz ′.
Therefore, in this numerical controller 5a, as shown in the flowchart of FIG. 6, when a Y-axis movement is commanded by the program, TPy is calculated by generating a function in S11. In S12, the acceleration calculation unit 7 calculates the Y-axis acceleration AAy from the value of the Y-axis position detector 25, and the centroid position calculation unit 8 uses the Z-axis command value TPz to change the YZ-axis centroid position after displacement. Hyz ′ is calculated. Next, in S13, the correction value calculation unit 6 calculates the correction values EPy, EPz, and EPa using the Y-axis acceleration AAy obtained in S12 and the YZ-axis gravity center position Hyz ′.

As described above, also in the numerical control device 5a and the numerical control method of the second embodiment, it is possible to accurately control the relative position between the spindle and the workpiece by correcting the posture change generated on the linear axis using the rotation axis. It becomes possible.
In particular, here, when the Z-axis is placed on the driven body of the Y-axis, the correction value calculation unit 6 sets the center-of-gravity position corrected by taking the center-of-gravity position of the Z-axis into account as the Y-axis center of gravity position Since the posture displacement amount such as 29 is obtained, even when the position of the center of gravity of the linear axis to be corrected is changed due to the movement of the axis placed on it, high-accuracy machining can be realized.

[Form 3]
In the numerical control device 5b shown in FIG. 7, in addition to the configuration of the second form, even when the machine operator inputs workpiece information using an input means such as a keyboard, the size and weight of the workpiece vary greatly. It can be supported. For example, as shown in FIG. 8, when a large workpiece 31 is placed on the X-axis table 13, the mass of the driven body changes from Mx to Mx ′, and the center of gravity changes from Hx to Hx ′. In such a case, by inputting these information (Mx ′, Hx ′) from the machine operator to the correction value calculation unit 6, it is possible to accurately grasp the mass and the gravity center position of the driven body.
Therefore, as shown in the flowchart of FIG. 9, in S21, the operator inputs the mass of the driven body and the position of the center of gravity to the numerical controller 5b based on the height and mass of the workpiece. When the X-axis movement is commanded by the program in S22, TPx is calculated by generating a function in S22. Next, in S23, the acceleration calculator 7 calculates the X-axis acceleration AAx from the value of the position detector 4. In S24, the correction value calculation unit 6 calculates the correction values EPx, EPz, and EPb, respectively, using the X-axis acceleration AAx obtained in S23 and the Z-axis command value TPz calculated in S21. Become.

As described above, also in the numerical control device 5b and the numerical control method according to the third aspect, it is possible to accurately control the relative position between the spindle and the workpiece by correcting the posture change generated on the linear axis using the rotation axis. It becomes possible.
In particular, here, input means for inputting the gravity center position and mass of the X-axis table is provided so that the gravity center position and mass of the X-axis table used in the correction value calculation unit 6 can be arbitrarily changed. Even if the distances are greatly different, the operator can respond to changes in the workpiece by inputting the information on the workpiece into the numerical control device.

In the first to third embodiments, the posture displacement amount of the driven body is obtained using the acceleration obtained by the acceleration / deceleration calculating means. However, the posture change of the driven body using the deceleration during deceleration. The amount may be obtained.
In form 3, the operator changes both the mass of the driven body and the position of the center of gravity, but either one may be used.
And in the said form 1-3, although demonstrated in the example which applied this invention in a 5-axis machine tool, a linear axis and a rotating shaft may be a machine tool fewer than this, and a linear axis, The present invention can be applied to other machine tools and industrial machines as long as they have a rotation axis orthogonal to the linear axis and control the driven body.

It is a block diagram of the numerical control apparatus of form 1. It is explanatory drawing of the 5-axis machine tool of the form 1. It is a flowchart of the attitude | position displacement correction function of the numerical control apparatus of form 1. It is a block diagram of the numerical control apparatus of form 2. It is explanatory drawing of the 5-axis machine tool of the form 2. It is a flowchart of the attitude | position displacement correction function of the numerical control apparatus of the form 2. It is a block diagram of the numerical control apparatus of form 3. It is explanatory drawing of the 5-axis machine tool of the form 3. It is a flowchart of the attitude | position displacement correction function of the numerical control apparatus of the form 3. It is a block diagram of the conventional numerical control apparatus. It is explanatory drawing of the conventional 5-axis machine tool.

Explanation of symbols

  1 ··· Function generator 2 ··· Controller 3 · · Servo motor 4 · · Position detector 5, 5a, 5b · · · Numerical control device 6 · · Correction value calculator 7 · · · Acceleration calculation , 8 .. Center of gravity position calculation unit, 11.. X-axis ball screw, 12.. Slider, 13 ... X-axis table, 14 ... Spindle, 15 ... Tool, 21 ... Y-axis ball screw, 22・ Y-axis rolling guide, 24 ・ ・ Y-axis servo motor, 25 ・ ・ Y-axis position detector, 26 ・ ・ Z-axis servo motor, 27 ・ ・ Z-axis position detector, 29 ・ ・ Y-axis table, 31 ・ ・Large workpiece.

Claims (6)

In a numerical controller having one or a plurality of linear axes orthogonal to each other for linearly moving a driven body and one or more rotational axes that rotate around any linear axis and are orthogonal to other linear axes,
Acceleration / deceleration calculation means for obtaining acceleration / deceleration of the driven body;
Based on the acceleration / deceleration speed of the driven body obtained by the acceleration / deceleration calculating means, the center of gravity position and mass of the driven body, and the position where the driving force acts on the driven body , at least the rotation shaft Posture displacement amount calculating means for obtaining the posture displacement amount of the driven body including the surrounding posture displacement amount ;
Rotation correction value calculation means for obtaining at least a correction value of the rotation axis from the posture displacement amount obtained by the posture displacement amount calculation means;
A numerical control device comprising:   When another linear axis or rotating shaft is mounted on the driven body, the posture displacement amount calculation means calculates the center of gravity position corrected in consideration of the center of gravity position of the other linear axis or rotating shaft. The numerical control apparatus according to claim 1, wherein a posture displacement amount of the driven body is obtained as a center of gravity position of the body.   An input means for inputting a gravity center position and / or mass of the driven body is provided, and the gravity center position and / or mass of the driven body used in the posture displacement amount calculating means can be arbitrarily changed. The numerical control apparatus according to claim 1 or 2. A first step of obtaining an acceleration / deceleration of a driven body that is linearly driven by one or a plurality of linear axes orthogonal to each other and storing the acceleration / deceleration in a storage unit;
Based on the acceleration / deceleration of the driven body obtained in the first step, the center of gravity position and mass of the driven body, and the position where the driving force acts on the driven body , at least about any one of the linear axes A second step of obtaining and storing in the storage means a posture displacement amount of the driven body including a posture displacement amount around one or more rotation axes orthogonal to another linear axis by rotating at
From the attitude displacement amount obtained in the second step, a third step of determining at least the correction value of the rotary shaft,
A numerical control method comprising:   In the case where another linear axis or rotating shaft is mounted on the driven body, in the second step, the center of gravity position corrected by taking the center of gravity position of the other linear axis or rotating shaft into account is determined. The numerical control method according to claim 4, wherein an attitude displacement amount of the driven body is obtained as a center of gravity position.   6. The numerical control method according to claim 4, wherein, in the second step, the position of the center of gravity and the mass of the driven body obtained by the input unit are used.

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