JP2017027360A - Machine error compensation system, error compensation method, and error compensation program - Google Patents

Abstract

An improvement state of machine motion accuracy and machining accuracy when correction control is performed using a geometric error as a correction parameter can be determined in advance. An error compensation system measures an initial position of a target sphere on a table by a touch probe of a main axis, calculates a command value for calculating a rotation axis at a plurality of angles from the initial position measurement value, and determines the touch probe and the target sphere. A control unit 21, a measurement value acquisition unit 23, a measurement command value generation unit 24, a geometric error identification calculation unit 25 that identifies a geometric error based on the measurement value, and a geometric error identification A correction parameter calculation unit 26 that calculates a correction parameter based on the value; a control unit 21 that performs correction control using the correction parameter; and an expected value of the measured value when the correction control is executed. The accuracy index calculation unit 27 for calculating the accuracy index value from the above and the screen display unit 28 for informing the accuracy index value are included. [Selection] Figure 3

Description

  The present invention relates to an error compensation system, an error compensation method, and an error compensation program for identifying and correcting geometric errors in a machine such as a machine tool having a translation axis and a rotation axis.

  FIG. 1 is a schematic diagram of a 5-axis control machining center having three translation axes and two rotation axes. The spindle head 2 is a translational axis and can move with two degrees of freedom of translation relative to the bed 1 by the X and Z axes orthogonal to each other. The table 3 can move with one degree of freedom of rotation with respect to the cradle 4 by the C-axis that is the rotation axis, and the cradle 4 can move with one degree of freedom with respect to the trunnion 5 with the A-axis that is the rotation axis. Yes, the A axis and the C axis are orthogonal to each other. Further, the trunnion 5 is a translational axis and can move with one degree of freedom of translation relative to the bed 1 by a Y axis orthogonal to the X / Z axis. Accordingly, the spindle head 2 can move with respect to the table 3 with three translational degrees of freedom and two degrees of freedom of rotation. Each feed shaft is driven by a servo motor controlled by a numerical control device (not shown), and a workpiece is fixed to the table 3, a tool is mounted on the spindle head 2, and the workpiece is rotated. Machining can be performed by controlling the relative position and the relative posture.

  Factors that affect the motion accuracy of this 5-axis control machining center include various errors such as the error of the center position of the rotating shaft (deviation from the assumed position) and the tilt error of the rotating shaft (straightness between the axes, parallelism). There is a geometric error between. For example, the five-axis control machining center of FIG. 1 has three types of geometric errors related to the translational axis: a perpendicular angle between XY axes, a perpendicular angle between Y-Z axes, and a perpendicular angle between Z-X axes. Further, there are two types of geometric errors related to the main axis: tool-Y axis perpendicularity and tool-X axis perpendicularity. Further, geometric errors related to the rotation axis include C-axis center position X-direction error, C-A axis offset error, A-axis angle offset error, C-A axis perpendicularity, A-axis center position Y-direction error, A-axis center. There are eight types: position Z direction error, AZ axis perpendicularity, and A-Y axis perpendicularity. Therefore, there are a total of 13 geometric errors.

If there is a geometric error, the movement accuracy of the machine deteriorates, and the machining accuracy of the workpiece deteriorates. For this reason, it is necessary to reduce the geometric error by adjustment, but it is difficult to make it zero, and high-precision machining can be performed by performing control for correcting the geometric error.
In order to perform correction control for the geometric error, it is necessary to measure or identify the geometric error inherent in the machine. As a method for identifying a geometric error of a machine, the present inventor has proposed a method as described in Patent Document 1. In the method of the present invention, the center position of the target sphere fixed on the table is measured using a touch probe mounted on the spindle, and this measurement is performed by rotating and tilting the table at a plurality of angles using the rotation axis. The geometric error of the machine is identified from the obtained measurement result.

However, when the measurement of the geometric error is not normally performed due to a measurement error such as a disturbance, the geometric error identification value includes an error. In this case, since correction control is performed using an incorrect identification value as a correction parameter, the motion accuracy of the machine is not sufficiently improved or deteriorated.
Accordingly, several methods have been proposed as methods for determining measurement errors in geometric error measurement.
For example, in Patent Document 2, the diameter of a sphere is measured together with the center position of the target sphere, and a method of determining a measurement error when the variation of each diameter value exceeds a threshold, or the initial position of the target sphere is measured first. A method of measuring again at the same position after a series of measurements and determining a measurement error when the difference from the first measurement value exceeds a threshold is shown.
Patent Document 3 discloses a method of determining a measurement error when a geometric error identification value or a new correction parameter created from the identification value is greater than or equal to a threshold value.

JP 2011-38902 A JP 2012-30338 A JP2012-107900A

  However, in the inventions of Patent Document 2 and Patent Document 3, it is only necessary to determine a measurement error based on whether a measurement result such as a sphere diameter value or a geometric error identification value exceeds a threshold, and the geometric error identification value itself. It does not determine whether is appropriate. For this reason, when correction control is performed using the identification value of the geometric error as a correction parameter, it cannot be determined whether the motion accuracy of the machine is improved or how much the processing accuracy is.

  Therefore, the present invention provides a machine error compensation system, an error compensation method, and an error compensation method that can determine in advance the improvement state of the machine motion accuracy and machining accuracy when the correction control is performed using the geometric error measured and identified as a correction parameter. The purpose is to provide a compensation program.

In order to achieve the above object, the invention according to claim 1 is provided in a machine having three or more translation axes, one or more rotation axes, a rotatable main shaft, and a table.
An initial position measuring means for measuring an initial position in a three-dimensional space of a jig to be measured attached to the other by means of a position measuring sensor attached to one of the spindle and the table;
Command value calculation means for calculating a command value of the position measurement sensor and the jig to be measured when the rotation axis is calculated at a plurality of angles from the initial position measurement value;
Based on the command value, the position measurement sensor and the jig to be measured are positioned at a plurality of locations, and the measurement value acquisition means for measuring the position of the jig to be measured in a three-dimensional space by the position measurement sensor,
Geometric error identification means for identifying a geometric error related to the translation axis and / or the rotation axis based on the measurement value obtained by the measurement value acquisition means;
Correction parameter calculation means for calculating a correction parameter based on the geometric error identification value obtained by the geometric error identification means;
Control means for correcting and controlling the operation of the machine using the correction parameter, and an error compensation system comprising:
A corrected expected value calculation means for calculating an expected value of the measurement value at each measurement position when the correction control is executed;
An accuracy index value calculating means for calculating an accuracy index value of the geometric error identification value using at least the measured value and the predicted value;
Informing means for informing the accuracy index value.
According to a second aspect of the present invention, in the configuration of the first aspect, the corrected predicted value calculation means includes the command values, the geometric error identification values, and the measured values corresponding to the command values. And calculating an expected value of the measurement value at each measurement position when the correction control is executed.
According to a third aspect of the present invention, in the configuration of the second aspect, the corrected predicted value calculation means calculates an initial position error due to the geometric error at the initial position from the initial position measurement value and the geometric error identification value. When the correction control is executed using the initial position error, the command value for each measurement position, the geometric error identification value, and the measurement value corresponding to each command value An expected value of the measurement value at each measurement position is calculated.
According to a fourth aspect of the present invention, in the configuration of the third aspect, the corrected predicted value calculation means performs homogeneous coordinate conversion between the calculation of the initial position error and the calculation of the predicted value of the measurement value. It is characterized by calculating by.
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the accuracy index value calculating means calculates a norm of a difference vector between the measured value and its predicted value and the command value as an accuracy index value. Are calculated respectively.
According to a sixth aspect of the present invention, in the configuration according to any one of the first to fifth aspects, the notification unit is configured such that the accuracy index value calculated by the accuracy index value calculation unit exceeds a preset threshold value. The accuracy index value is notified, and the fact that the threshold value is exceeded is also notified.
To achieve the above object, the invention according to claim 7 identifies geometric errors in a machine having three or more translation axes, one or more rotation axes, a rotatable main axis, and a table. An error compensation method for performing correction control,
An initial position measuring step for measuring an initial position of the jig to be measured in a three-dimensional space by attaching a position measuring sensor to one of the spindle and the table and a jig to be measured on the other; and
A command value calculating step for calculating a command value of the position measurement sensor and the jig to be measured when the rotation axis is calculated at a plurality of angles from the initial position measurement value;
Based on the command value, the position measurement sensor and the jig to be measured are positioned at a plurality of locations, and a measurement value acquisition step of measuring the position of the jig to be measured in a three-dimensional space by the position measurement sensor,
A geometric error identification step for identifying a geometric error related to the translation axis and / or the rotation axis based on the measurement value obtained by the measurement value acquisition step;
A correction parameter calculation step for calculating a correction parameter based on the geometric error identification value obtained by the geometric error identification step;
A corrected expected value calculation step for calculating an expected value of the measurement value at each measurement position when the operation of the machine is corrected and controlled using the correction parameter;
An accuracy index value calculating step of calculating an accuracy index value of the geometric error identification value using at least the measured value and the predicted value;
And a notification step of notifying the accuracy index value.
In order to achieve the above object, an invention described in claim 8 is a machine error compensation program, which causes a computer to execute the machine error compensation method described in claim 7.

  According to the present invention, it is possible to compare the accuracy index value of the expected value and the current accuracy index value when correction control is performed using the geometric error measured and identified as a correction parameter. Therefore, if the accuracy index value of the predicted value is larger, the geometric error identification value is likely to be inappropriate, and it can be determined that there may have been a measurement error, which is an opportunity to restart the measurement. . Conversely, when the accuracy index value of the predicted value is smaller than the current accuracy index value, it is possible to predict how much the machine motion accuracy and machining accuracy will improve from the smaller amount, and error compensation Performance evaluation can be easily performed.

It is a schematic diagram of a 5-axis control machining center. It is a schematic diagram of a touch probe and a target sphere. It is a block block diagram of the numerical control apparatus provided with the error compensation system. It is a flowchart of the error compensation method from the measurement by a touch probe to displaying an accuracy index value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Here, a five-axis control machining center of FIG. 1 will be described as an example of a machine to which the present invention is applied. However, the machine according to the present invention is not limited to a machining center, and may be a machine tool such as a lathe, a multi-task machine, or a grinding machine. In addition to machine tools, industrial machines and robots may be used. Furthermore, the number of axes is not limited to five, but may be four or six or more. Furthermore, not only the mechanism in which the table 3 has two or more degrees of freedom of rotation by the rotation shaft, but also the mechanism in which the spindle head 2 has two or more degrees of freedom of rotation or the spindle head 2 and the table 3 each have one or more degrees of freedom of rotation. It may be a mechanism.
First, in order to perform measurement for identifying a geometric error, as shown in FIG. 2, a touch probe 11 as a position measurement sensor is attached to the spindle 2 of a 5-axis control machining center, and a measurement target is placed on the table 3. A target sphere 12 as a jig is installed and fixed.

FIG. 3 is a block configuration diagram of a numerical controller provided with an error compensation system in the 5-axis control machining center of FIG.
In FIG. 3, reference numeral 21 denotes a control unit as a control unit that controls each axis based on each axis command value stored in the data storage unit 22, and is acquired by the measurement value acquisition unit 23 in the data storage unit 22. Various data such as measurement values, geometric error identification values, correction parameters, etc. of the target sphere 12 by the touch probe 11 are stored. The control unit 21 and the measurement value acquisition unit 23 function as an initial position measurement unit and a measurement value acquisition unit of the present invention.
The measurement command value generation unit 24 uses the initial position measurement value of the target sphere 12 stored in the data storage unit 22 and the length of the touch probe 11 to set measurement conditions (such as the index angle of each rotation axis). ) To calculate the target sphere center position and touch probe tip position moved by rotating and tilting the rotation axis, and using the calculated three-dimensional position coordinate values at each indexing angle as command values for the three translation axes. Each index angle is calculated as a command value for the rotation axis. That is, it functions as command value calculation means of the present invention.

The geometric error identification calculation unit 25 performs identification calculation of the geometric error of the machine based on each target sphere center position measurement value stored in the data storage unit 22 and a command value at each position. That is, it functions as the geometric error identification means of the present invention. As this identification calculation method, for example, as disclosed in the above-mentioned Patent Document 1, an error or inclination error of the center position of the rotation axis or an inclination of the translation axis from an arc approximated by arc approximation of a plurality of measurement values. This is performed by a known method for calculating the error.
The correction parameter calculation unit 26 adds the geometric error identification value calculated by the geometric error identification calculation unit 25 to the current correction parameter for correction control stored in the data storage unit 22, thereby obtaining a new correction parameter. calculate. That is, it functions as a correction parameter calculation means of the present invention.

  The accuracy index calculation unit 27 uses the measured values, the command values, and the geometric error identification values stored in the data storage unit 22 to control the control unit with new correction parameters calculated by the correction parameter calculation unit 26. The predicted value of the measured value at each measurement position when the correction control 21 is controlled is calculated. Also, a current error vector at each measurement position is calculated from each measurement value and each command value, and an expected error vector at each measurement position is calculated from each predicted value and each command value. From the error vector, an accuracy index value for the geometric error identification value (an index value indicating whether the geometric error identification value is appropriate) is calculated. The accuracy index calculation unit 27 functions as a corrected predicted value calculation unit and an accuracy index value calculation unit of the present invention. The calculated accuracy index value is displayed by the screen display unit 28 as a notification unit.

FIG. 4 is a flowchart showing an error compensation method until the numerical control device of FIG. 3 performs measurement by the touch probe 11 and displays the accuracy index value on the screen display unit 28. The error compensation stored in the data storage unit 22 is shown in FIG. Executed by the program.
First, in S1, the initial center position (initial position) of the target sphere 12 is measured (initial position measurement step). The measurement value is acquired by the measurement value acquisition unit 23 and stored in the data storage unit 22.
Next, in S2, a command value list is created in the measurement command value generation unit 24 (command value calculation step). That is, a three-dimensional position coordinate value calculated at each index angle of the rotation axis is used as a command value for three translation axes, and a command value list is created using each index angle as a command value for the rotation axis. Store.

Next, in S3, the position of the target sphere 12 is measured. That is, based on each axis command value stored in the data storage unit 22, the control unit 21 controls each axis so that the touch probe 11 is positioned directly above the target sphere 12, and the surface of the target sphere 12. The touch probe 11 is brought into contact with four or more points to measure the position at each contact point, and the measurement value acquisition unit 23 obtains the center position measurement value and the diameter measurement value of the target sphere 12 and stores them in the data storage unit 22. (Measurement value acquisition step). Here, by using the diameter value of the target sphere 12 that has been measured in advance, the center position of the target sphere 12 can also be obtained by three-point contact measurement.
Next, in S4, it is determined whether or not all measurement conditions have been completed. If not completed, the process returns to S3 to perform the next measurement, and if completed, the process proceeds to S5.

In S5, geometric error identification calculation unit 25 performs geometric error identification calculation (geometric error identification step). That is, the machine geometric error identification calculation is performed based on the center position measurement value of each target sphere stored in the data storage unit 22 and the command value at each position. The calculated geometric error identification value is stored in the data storage unit 22.
Next, in S6, the correction parameter calculation unit 26 calculates a new correction parameter. That is, a new correction parameter is calculated by adding the geometric error identification value to the current correction parameter for control stored in the data storage unit 22 (correction parameter calculation step). New correction parameters are stored in the data storage unit 22.
Next, in S7, the accuracy index calculation unit 27 calculates an expected value of the measured value when correction control is performed with a new correction parameter (corrected expected value calculation step). Details of this calculation method will be described later. The calculated predicted value is stored in the data storage unit 22.

  Next, in S8, the accuracy index calculation unit 27 calculates the accuracy index value (accuracy index value calculation step). Here, the prediction error vector at each measurement position is calculated from the predicted value of each measurement value stored in the data storage unit 22 and each command value, and the current value at each measurement position is calculated from each measurement value and each command value. An error vector is calculated, and a machine accuracy index value is calculated from each predicted error vector and each current error vector calculated. Details of calculation of each error vector and accuracy index value will be described later. The calculated accuracy index value is stored in the data storage unit 22. Further, the accuracy index calculation unit 27 compares the threshold value stored in the data storage unit 22 with the accuracy index value, and if the accuracy index value exceeds the threshold value, the threshold value stored in the data storage unit 22 Turn over flag ON.

In step S9, the screen display unit 28 displays the accuracy index value stored in the data storage unit 22 on the screen (notification step). At this time, when the threshold over flag stored in the data storage unit 22 is OFF, the accuracy index value is displayed in the standard character color. When the threshold over flag is ON, the accuracy index value is the standard character color. Display in different colors.
For geometric error correction control, the control unit 21 uses a correction parameter stored in the data storage unit 22 and uses a known correction control method disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-104317. Can be used.

Here, the calculation method of the expected value of the measured value in S7 will be described.
In the 5-axis control machining center of FIG. 1, a coordinate system is considered on the spindle head 2, the table 3, and each feed axis. The coordinate system from which the measured value is obtained is the same as the Y-axis coordinate system in the case of this machine, and the measured value (x _Ii , y _Ii , z _Ii ) when there is no geometric error is the touch in the spindle head coordinate system. If the tip point vector of the probe is ^T P, the command positions of the i-th X, Y, Z, A, and C axes are respectively x _i , y _i , z _i , a _i , c _i , and the probe length is t. The following equation 1 can be used. That is, the touch probe tip point vector ^{TP is} subjected to homogenous coordinate transformation from the spindle head coordinate system to the measurement value coordinate system via each axis coordinate system, so that measurement values (x _Ii , y _Ii , _zIi ) is determined.

Each geometric error is considered as a 6-DOF relative minute error between the axes. When the translation error of each geometric error is δx _j , δy _j , δz _j , and the rotation error is α _j , β _j , γ _j , the j-th geometric error conversion matrix ε _j is expressed by the following equation (2).

When there is a geometric error in the machine, measurement values (x _Ri , y _Ri , z _Ri ) when there is a geometric error can be obtained by using the following equation (3). That is, touch the tip of the probe point vector ^{T P,} by taking into account the geometrical errors to the coordinate transformation from the spindle head coordinate system to the measurement coordinate system through each axis coordinate system, measured values of the case where there is a geometric error ( x _Ri , y _Ri , z _Ri ) are obtained.

The angle of the rotation axis in the initial position measurement is 0 °. Here, the C axis 0 ° in the case of the machine of FIG. 1 is an angle at which the target sphere 12 is positioned on the X axis plus side. The measurement value of the initial position measurement includes the influence of geometric error. If each axis command value in the initial position measurement is x ₀ , y ₀ , z ₀ , a ₀ , c ₀ , an error (initial position error) (δx _ini , δy _ini , δz _ini ) can be obtained by the following equation 4.

Error due to geometric errors included in the initial position measurement value _{(δx ini, δy ini, δz} ini) since regarded as a mounting error of the target ball 12, .delta.x ₆ is a component number 3 of ε _6, δy _6, the .delta.z ₆ Update as shown in Equation 5 below.

Assuming that each measurement value is (x _Mi , y _Mi , z _Mi ), the expected value (x _Ei , y _Ei , z _Ei ) of each measurement value when the geometric error is corrected and controlled with the new correction parameters is as follows: 6 can be obtained.

Next, the calculation method of the prediction error vector, the current error vector, and the accuracy index value in S8 will be described.
First, each prediction error vector (δx _Ei , δy _Ei , δz _Ei ) can be calculated by the following equation 7, and each current error vector (δx _Mi , δy _Mi , δz _Mi ) can be calculated by the following equation 8, respectively.

Assuming that the accuracy index value is the maximum value of the norm of each error vector, the norm ve _Ei of the prediction error vector is the following equation 9, and the norm ve _Mi of the current error vector is the following equation 10, and the respective maximum values are obtained.

  If both maximum values are displayed on the screen display unit 28 in this way, both accuracy index values can be compared. Therefore, if the maximum value of the norm of the predicted error vector is larger than the maximum value of the norm of the current error vector, there is a high possibility that the geometric error identification value is inappropriate and there is a possibility of a measurement error. It will be an opportunity to start over. Conversely, if the maximum value of the norm of the predicted error vector is smaller than the maximum value of the norm of the current error vector, it is possible to predict how much the machine motion accuracy and machining accuracy will improve from the smaller amount. It is possible to easily evaluate the performance of error compensation.

The accuracy index value may be the maximum absolute value of each component of each error vector. In this case, the absolute value (vx _Ei , vy _Ei , vz _Ei ) of each component of the prediction error vector is given by the following equation 11, and the absolute value (vx _Mi , vy _Mi , vz _Mi ) of each component of the current error vector is The maximum value of each is obtained.

In addition, the shapes of the touch probe and the target sphere can be changed as appropriate, and the display mode of the accuracy index value can be changed as appropriate for the notification means. Further, when the accuracy index value exceeds the threshold value, it is also possible to perform voice notification using an alarm sound, synthesized voice, or the like.
Furthermore, in the above embodiment, an example is described in which the error compensation program automatically executes the process from the measurement of the initial position to the display of the accuracy index value, but the command value list, the correction parameter, It is also possible to display an expected value or the like on the screen display partway and to proceed by an input instruction from the operator.

  1 .. Bed 2. Spindle head 3. Table 4 Cradle 5 Trunnion 11 Touch probe 12 Target ball 21 Control unit 22 Data storage unit , 23 .. Measurement value acquisition unit, 24 .. Measurement command value generation unit, 25 .. Geometric error identification calculation unit, 26 .. Correction parameter calculation unit, 27 .. Accuracy index calculation unit, 28.

Claims (8)

Provided in a machine having three or more translation axes, one or more rotation axes, a rotatable main shaft, and a table;
An initial position measuring means for measuring an initial position in a three-dimensional space of a jig to be measured attached to the other by means of a position measuring sensor attached to one of the spindle and the table;
Command value calculation means for calculating a command value of the position measurement sensor and the jig to be measured when the rotation axis is calculated at a plurality of angles from the initial position measurement value;
Based on the command value, the position measurement sensor and the jig to be measured are positioned at a plurality of locations, and the measurement value acquisition means for measuring the position of the jig to be measured in a three-dimensional space by the position measurement sensor,
Geometric error identification means for identifying a geometric error related to the translation axis and / or the rotation axis based on the measurement value obtained by the measurement value acquisition means;
Correction parameter calculation means for calculating a correction parameter based on the geometric error identification value obtained by the geometric error identification means;
Control means for correcting and controlling the operation of the machine using the correction parameter, and an error compensation system comprising:
A corrected expected value calculation means for calculating an expected value of the measurement value at each measurement position when the correction control is executed;
An accuracy index value calculating means for calculating an accuracy index value of the geometric error identification value using at least the measured value and the predicted value;
An informing means for informing the accuracy index value;
A machine error compensation system comprising:   The corrected expected value calculation means uses the command values, the geometric error identification values, and the measurement values corresponding to the command values, and performs the correction control when the correction control is executed. The machine error compensation system according to claim 1, wherein an expected value of the measured value is calculated.   The corrected predicted value calculation means calculates an initial position error due to the geometric error at the initial position from the initial position measurement value and the geometric error identification value, and calculates the initial position error and each measurement position. A predicted value of the measurement value at each measurement position when the correction control is executed is calculated using a command value, the geometric error identification value, and the measurement value corresponding to each command value. The machine error compensation system according to claim 2.   4. The machine according to claim 3, wherein the corrected predicted value calculation unit calculates the initial position error and the predicted value of the measured value by performing homogeneous coordinate conversion. 5. Error compensation system.   5. The machine according to claim 1, wherein the accuracy index value calculating unit calculates a norm of a difference vector between the measured value and an expected value thereof and the command value as an accuracy index value. 6. Error compensation system.   The notification means notifies the accuracy index value when the accuracy index value calculated by the accuracy index value calculation means exceeds a preset threshold, and also notifies that the threshold has been exceeded. The machine error compensation system according to any one of claims 1 to 5. An error compensation method for identifying and correcting a geometric error in a machine having three or more translation axes, one or more rotation axes, a rotatable spindle, and a table,
An initial position measuring step for measuring an initial position of the jig to be measured in a three-dimensional space by attaching a position measuring sensor to one of the spindle and the table and a jig to be measured on the other; and
A command value calculating step for calculating a command value of the position measurement sensor and the jig to be measured when the rotation axis is calculated at a plurality of angles from the initial position measurement value;
Based on the command value, the position measurement sensor and the jig to be measured are positioned at a plurality of locations, and a measurement value acquisition step of measuring the position of the jig to be measured in a three-dimensional space by the position measurement sensor,
A geometric error identification step for identifying a geometric error related to the translation axis and / or the rotation axis based on the measurement value obtained by the measurement value acquisition step;
A correction parameter calculation step for calculating a correction parameter based on the geometric error identification value obtained by the geometric error identification step;
A corrected expected value calculation step for calculating an expected value of the measurement value at each measurement position when the operation of the machine is corrected and controlled using the correction parameter;
An accuracy index value calculating step of calculating an accuracy index value of the geometric error identification value using at least the measured value and the predicted value;
An informing step for informing the accuracy index value;
An error compensation method for a machine, characterized in that   A machine error compensation program for causing a computer to execute the machine error compensation method according to claim 7.

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