JP2012035399A - Correction matrix derivation device, error correction device, and machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an error of a processing position of a workpiece, and to correct each error small as a whole even if errors of different magnitudes occur in a plurality of places on the workpiece.SOLUTION: In the correction matrix derivation device 20, an operation part 26 performs first weighting factor reconfiguration re-configuring the weighting factor G of a first maximum alienation reference point selected on the basis of the coordinates after a first correction conversion by a temporary correction matrix by a given increment g1; and performs the second correction matrix calculation operation of a correction matrix which is the correction matrix for correction conversion of the reference coordinates of respective reference points 100a, and calculates the correction matrix in which a value obtained by adding a value obtained by multiplying the weighting factor G of the respective reference points 100a to a squared value of the distance between the coordinates after the correction conversion of the reference coordinates of the respective reference points 100a by the correction matrix and the corresponding measured coordinates for all the reference points 100a, becomes the minimum by the method of a least square.

Description

  The present invention relates to a correction matrix deriving device, an error correcting device, and a machine tool.

  2. Description of the Related Art Conventionally, in a machine tool, since a deviation occurs in the machining position of a workpiece due to various factors, correction of the deviation of the machining position has been performed. For example, Patent Document 1 below discloses a machine tool reference position correction apparatus for correcting such a shift in the machining position of a workpiece.

  The machine tool reference position correction apparatus disclosed in Patent Document 1 corrects a workpiece machining error caused by thermal deformation of a component of a machine tool. This reference position correction apparatus is fixed to a work support table of a machine tool, and is a machine tool that is rotated by being attached with a jig provided with a first reference hole and a second reference hole, and a work processing tool. And a touch sensor attached to the main shaft instead of the tool, and the position of both reference holes of the jig is detected using the touch sensor. Specifically, the touch sensor is moved in the horizontal axis direction to detect the center position of each reference hole in the horizontal axis direction, and the touch sensor is moved in the vertical axis direction to determine the center position of each reference hole in the vertical axis direction. The distance between the center positions of the respective reference holes is obtained from the detected center positions. Then, the distance between the center positions of the two reference holes when the component of the machine tool is at room temperature is measured in advance, and the distance between the center positions of the two reference holes at the room temperature is measured. The amount of change in the distance between the center positions is calculated. In this reference position correcting apparatus, the relative position between the spindle and the table is corrected by the calculated amount of change in the distance with the center position of the first reference hole as the reference position.

JP 2009-251621 A

  However, the reference position correction apparatus of the above-mentioned Patent Document 1 only corrects an error in the relative position between the spindle and the table caused by thermal deformation on the apparatus side, and deformation due to various factors occurs in the workpiece, If there is a deviation in the work position on the workpiece, the error in the machining position cannot be corrected, and if there are different machining position errors at multiple positions on the workpiece, It is not possible to perform a correction that reduces the error of the overall.

  The present invention has been made in order to solve the above-described problems, and the purpose of the present invention is to make it possible to correct an error in the machining position of the workpiece caused by deformation of the workpiece or displacement of the installation position, and on the workpiece. Even when errors of different sizes occur at a plurality of positions, it is possible to perform correction to reduce each error as a whole.

  In order to achieve the above object, the inventor of the present application measures actual coordinates (measurement coordinates) of a plurality of reference points on a workpiece whose coordinates on the reference coordinate axis are known, and each reference point is known on the reference coordinate axis. When the reference coordinate that is the coordinate of the correction is corrected and converted, the value of the square of the distance between the coordinate of each reference point after the correction conversion and the corresponding measurement coordinate is the sum of all the reference points is the minimum value. Thus, the inventors have come up with the idea of calculating a correction matrix capable of correcting and converting the reference coordinates of each reference point by the least square method, and correcting and converting a workpiece machining command using the correction matrix.

  According to this error correction technique, the machining command for the workpiece is corrected based on the distance (error) between the reference coordinate of the workpiece reference point and the measurement coordinate, resulting in deformation of the workpiece or displacement of the installation position. The error of the machining position of the workpiece to be corrected can be corrected. In this error correction, the workpiece processing command is corrected and converted by the correction matrix so that the sum of squares of the distance between the reference coordinate of each reference point after the correction conversion and the corresponding measurement coordinate is minimized. Therefore, even when errors having different sizes occur at a plurality of positions on the workpiece, the errors can be reduced as a whole.

  By the way, in the field of machining, it is often necessary to ensure that the error is less than or equal to an allowable value at each of the reference points on the measured workpiece. If a small number of reference points whose measurement coordinates are significantly displaced from the reference coordinates are included in the plurality of reference points, there is a possibility that correction cannot be performed so that the error of the reference points is less than the allowable value. .

  Specifically, in the error correction technique described above, even if a small number of reference points whose measurement coordinates are significantly displaced from the reference coordinates are included in the plurality of reference points, reference points other than the reference points are included. As a factor affecting the calculation of the correction matrix, the error of occupies a large specific gravity. For this reason, when the reference coordinates of all the reference points are corrected using the calculated correction matrix, errors of reference points other than the significantly displaced reference points are corrected to an allowable value or less, but the significantly displaced reference points. In some cases, the error is not sufficiently corrected, and an error larger than the allowable value may remain after the correction.

  Therefore, the inventor of the present application performs a correction matrix derivation device having the following configuration in order to perform correction to minimize the errors of all the reference points while minimizing the errors of the reference points that are significantly displaced. Invented an error correction device and a machine tool.

  That is, the correction matrix deriving device according to the present invention processes a workpiece by the tool by moving at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis. A correction matrix deriving device for deriving a correction matrix for converting the machining command so as to correct an error of a machining position that occurs during actual machining of a workpiece in a machine tool having a drive device that executes A measuring device that measures the actual coordinates of a plurality of reference points on the workpiece, each of which is given coordinates on a reference coordinate axis, and a reference coordinate that is a coordinate given to the plurality of reference points and the measuring device The correction matrix is calculated based on measured coordinates that are actual coordinates of the plurality of reference points. A calculation unit that performs a calculation for calculating the reference coordinates, and the calculation unit is a temporary correction matrix for correcting and converting the reference coordinates of the reference points, and the reference coordinates of the reference points are converted to the temporary coordinates. A temporary correction matrix is calculated by the method of least squares so that a value obtained by adding the squares of the distances between the coordinates after correction conversion by the correction matrix and the corresponding measurement coordinates becomes the minimum value. A first correction matrix calculation operation, a first correction conversion for correcting and converting the reference coordinates of each reference point by the temporary correction matrix calculated by the first correction matrix calculation operation, and an equal weight for each reference point A first weighting coefficient setting for setting each coefficient, and a distance between the coordinates after the first correction conversion of the reference coordinates among the reference points and the corresponding measurement coordinates A first selection for selecting a first maximum separation reference point that is the largest reference point, and a first weight for resetting the weight coefficient of the selected first maximum separation reference point to a value increased by a predetermined increment. A correction matrix for correcting and converting the reference coordinates of each reference point after resetting the coefficient and resetting the first weighting coefficient, wherein the reference coordinates of each reference point are corrected and converted by the correction matrix. A value obtained by multiplying the value of the square of the distance between the coordinate after the measurement and the corresponding measurement coordinate by the weighting factor set for each reference point and adding all the reference points is a minimum. A second correction matrix calculation operation for calculating such a correction matrix by the least square method is performed.

  In this correction matrix deriving device, the arithmetic unit resets the weight coefficient of the first maximum separation reference point to a value increased by a predetermined increment, and then corresponds to the coordinates after correction conversion of the reference coordinates of each reference point. The reference coordinates of each reference point so that the value obtained by multiplying the square value of the distance to the measurement coordinate by the weighting factor set for each reference point is the sum of all the reference points. Since the correction matrix that can be corrected and converted is calculated by the least square method, the reference coordinates of each reference point can be corrected and converted so that the sum of squares of the distance between the reference coordinates of each reference point and the measurement coordinates is minimized. As compared with the case of obtaining a correct correction matrix, a correction matrix can be calculated in which an error in the actual coordinates from the reference coordinates of the first maximum separation reference point among the reference points is greatly added. Accordingly, if the workpiece machining command is corrected and converted by the calculated correction matrix, the error of the reference point where the measurement coordinate is displaced from the reference coordinate to the maximum, that is, the reference point where the measurement coordinate is significantly displaced from the reference coordinate is minimized. Thus, it is possible to perform correction to reduce the error of all the reference points as a whole.

  In the correction matrix deriving device, the calculation unit includes: a second correction conversion that corrects and converts the reference coordinates of the reference points by the correction matrix calculated by the second correction matrix calculation calculation; A second selection for selecting a second maximum separation reference point that is a reference point having the longest distance between the coordinate after the second correction conversion of the reference coordinate and the corresponding measurement coordinate; and the second correction conversion Calculation of a post-correction separation distance that is a distance between the coordinates of each subsequent reference point and the corresponding measurement coordinate, and an average value of the post-correction separation distance that is an average value of the post-correction separation distance for each reference point And the post-correction separation distance for the second maximum separation reference point calculated with the second correction matrix calculation calculation this time is accompanied with the correction matrix calculation calculation of the previous time. The determination as to whether the first condition that the calculated maximum separation reference point is larger than the corrected separation distance is satisfied, and the average value of the corrected separation distance calculated with the second correction matrix calculation calculation this time is A determination is made as to whether a second condition that is greater than the corrected post-correction distance average value calculated with the previous correction matrix calculation operation is satisfied, and the first condition and the second condition When it is determined that both are satisfied, the correction matrix calculated in the previous correction matrix calculation operation is set as the final calculation result, and at least one of the first condition and the second condition is satisfied. If it is determined that the second weighting factor is not set, the second weighting factor resetting is performed to reset the weighting factor of the second maximum separation reference point to a value increased by a predetermined increment. A correction matrix for correcting and converting the reference coordinates of each reference point, between the coordinates after correction conversion of the reference coordinates of each reference point by the correction matrix and the corresponding measurement coordinates The next time the correction matrix is calculated by the method of least squares so that the value obtained by multiplying the value of the square of the distance by the weighting factor set for each reference point is the sum of all the reference points is minimized. A second correction matrix calculation calculation may be performed.

  In this configuration, with respect to the maximum separation reference point calculated by the calculation unit with the previous correction matrix calculation calculation, the corrected separation distance for the second maximum separation reference point calculated with the current second correction matrix calculation calculation is calculated. The corrected post-correction distance average value calculated with the current second correction matrix calculation calculation is greater than the post-correction separation distance average value calculated with the previous correction matrix calculation calculation. The second maximum separation reference point is selected by multiplying the square value of the corrected separation distance of the selected second maximum separation reference point by a weighting factor increased by a predetermined increment until Since the correction matrix calculation calculation is performed, the error of the reference point where the measurement coordinate is significantly displaced from the reference coordinate is reduced well, and the error of all the reference points is reduced well overall. It is possible to calculate the correction matrix that can perform Kusuru correction.

  In the correction matrix deriving device, the calculation unit includes: a second correction conversion that corrects and converts the reference coordinates of the reference points by the correction matrix calculated by the second correction matrix calculation calculation; A second selection for selecting a second maximum separation reference point that is a reference point having the longest distance between the coordinate after the second correction conversion of the reference coordinate and the corresponding measurement coordinate; and the second correction conversion Calculation of a post-correction separation distance that is a distance between the coordinates of each subsequent reference point and the corresponding measurement coordinate, and an average value of the post-correction separation distance that is an average value of the post-correction separation distance for each reference point And the post-correction separation distance for the second maximum separation reference point calculated with the second correction matrix calculation calculation this time is accompanied with the correction matrix calculation calculation of the previous time. The first condition that the calculated maximum separation reference point is larger than the post-correction separation distance, and the post-correction separation average value calculated in accordance with the second calculation calculation of the second correction matrix is the previous one. And whether the second condition of greater than the post-correction separation distance average value calculated with the correction matrix calculation calculation is satisfied, and the second maximum calculated with the current second correction matrix calculation calculation A third condition that the post-correction separation distance for the separation reference point is smaller than the post-correction separation distance for the maximum separation reference point calculated with the previous correction matrix calculation calculation; From the post-correction separation distance for the second maximum separation reference point calculated along with the second correction matrix calculation calculation, along with the current second correction matrix calculation calculation A value obtained by subtracting the average value of the post-correction separation distances from the post-correction separation distance for the maximum separation reference point calculated by the correction matrix calculation operation of the previous one is used. It is determined whether the fourth condition of being larger than the value obtained by subtracting the corrected post-correction distance average value calculated with the calculation operation is satisfied, and whether both the first condition and the second condition are satisfied Or, when it is determined that both the third condition and the fourth condition are satisfied, the correction matrix calculated in the previous correction matrix calculation calculation is used as the final calculation result, In this case, after resetting the weighting coefficient of the second maximum separation reference point to a value increased by a predetermined increment, and after resetting the second weighting coefficient, each reference point Correction conversion of the reference coordinates A correction matrix for correcting the reference coordinates of each reference point with a value of the square of the distance between the coordinates after the correction conversion of the reference coordinates by the correction matrix and the corresponding measurement coordinates. The next second correction matrix calculation calculation may be performed in which a correction matrix is calculated by the least square method so that a value obtained by adding the weighted coefficient multiplied by all the reference points is minimized.

  In this configuration, the second maximum separation reference point calculated with the current second correction matrix calculation calculation is compared with the post-correction separation distance with respect to the maximum separation reference point calculated with the previous correction matrix calculation calculation. Even if the post-correction separation distance is decreased, the difference between the post-correction separation average value and the post-correction separation distance for the maximum separation reference point is the second correction matrix this time as compared with the previous correction matrix calculation calculation. If the calculation calculation increases, the subsequent second correction matrix calculation calculation is not performed, and the correction matrix calculated in the previous correction matrix calculation calculation becomes the final calculation result. In other words, in this configuration, the error of the reference point (maximum separation reference point) whose measurement coordinate is significantly displaced from the reference coordinate is reduced, while the error of the maximum separation reference point is the average of the errors of all the reference points. It is possible to calculate a correction matrix that can be corrected so as to approach the value.

  In the correction matrix deriving device, the calculation unit derives a scaling factor that represents an expansion / contraction rate of the workpiece due to temperature prior to the first correction matrix calculation operation, and in the first correction matrix calculation operation, the scaling factor is calculated. The temporary correction matrix is calculated when the reference coordinates of the reference points are corrected and converted using the temporary correction matrix including the second correction matrix calculation operation, and the second correction matrix calculation operation includes calculating the temporary correction matrix. It is preferable to calculate the correction matrix when the reference coordinates of the reference point are corrected and converted.

  In this configuration, since the provisional correction matrix and the correction matrix are calculated by a calculation based on the least square method with an element of the scaling factor representing the expansion / contraction rate of the work due to temperature, an error caused by expansion / contraction due to the temperature of the work Can be obtained. For this reason, if the workpiece machining command is corrected and converted using the correction matrix, errors caused by expansion and contraction due to the workpiece temperature can be corrected.

  The error correction apparatus according to the present invention performs machining of a workpiece by the tool by moving at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis. An error correction device that is provided in a machine tool having a driving device and corrects a machining position error that occurs during actual machining of a workpiece, and is derived by the correction matrix deriving device and the correction matrix deriving device. A machining command correction conversion unit that corrects and converts the machining command using the correction matrix.

  In this error correction device, since the machining command correction conversion unit corrects and converts the workpiece machining command using the correction matrix derived by the correction matrix deriving device, the workpiece command is displaced to the maximum from the reference coordinates among the reference points of the workpiece. It is possible to perform correction to reduce the machining errors of the parts corresponding to all the reference points of the workpiece as a whole while minimizing the machining errors of the parts corresponding to the reference points.

  A machine tool according to the present invention is a machine tool for machining a workpiece, and moves at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis. Thus, according to the drive device for processing the workpiece with the tool, the error correction device, and the machining command corrected and converted by the error correction device, the drive device executes at least one of the workpiece and the tool. And a control device for processing the workpiece.

  In this machine tool, the control device causes the drive device to move at least one of the workpiece and the tool in accordance with the machining command corrected and converted by the error correction device, so that the workpiece is machined. Thus, it is possible to minimize the machining error of the part corresponding to all the reference points of the workpiece while minimizing the machining error of the part corresponding to the reference point displaced to the maximum from the reference coordinates.

  As described above, according to the present invention, the correction that minimizes the errors of all the reference points while minimizing the errors of the reference points in which the measurement coordinates are significantly displaced from the reference coordinates among the reference points of the workpiece. It can be performed.

1 is a schematic perspective view of a machine tool according to an embodiment of the present invention. It is a functional block diagram of the machine tool by one Embodiment of this invention. It is a flowchart which shows the process process of the workpiece | work by the machine tool of one Embodiment of this invention. It is a figure for demonstrating the method of the calibration in the machine tool of one Embodiment of this invention. It is a figure for demonstrating the measuring method of the reference | standard bar | burr at the time of deriving the scaling magnification in the machine tool of one Embodiment of this invention. It is a perspective view which shows the state of the reference | standard sphere arrange | positioned on a workpiece | work. It is a figure for demonstrating the measuring method of the measurement coordinate of the reference point in the machine tool of one Embodiment of this invention. It is a figure which shows the process until selection of the 1st largest separation | separation reference point among the flowcharts which show the calculation process of the correction matrix by the correction matrix derivation device of one embodiment of the present invention. It is a figure which shows the process after the 2nd correction matrix calculation calculation among the flowcharts which show the calculation process of the correction matrix by the correction matrix derivation device of one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, with reference to FIG.1 and FIG.2, the structure of the machine tool by one Embodiment of this invention is demonstrated.

  The machine tool according to the present embodiment is for machining a workpiece W that is a workpiece, and by moving the workpiece W and the tool 5 in accordance with a machining command represented by a movement vector on a reference coordinate axis, The workpiece W is processed by the tool 5.

  Specifically, the machine tool of this embodiment includes a drive device 2, a tool 5, an error correction device 6 (see FIG. 2), and a control device 7 (see FIG. 2).

  The drive device 2 is a device that executes machining of the workpiece W by the tool 5 by moving the workpiece W and the tool 5 for machining the workpiece W according to the machining command. The drive device 2 includes a workpiece drive device 3 and a tool drive device 4.

  The workpiece driving device 3 moves the workpiece W in the X-axis direction, which is the horizontal direction, according to the machining command. The work drive device 3 moves the work W placed on the table 3b in the X-axis direction by moving the table 3b in the X-axis direction on the bed 3a fixed on the installation surface. This work drive device 3 includes a servo motor (not shown) as a drive source for moving the table 3b in the X-axis direction.

  The tool driving device 4 moves the tool 5 in the horizontal direction in the Y-axis direction orthogonal to the X-axis direction and the Z-axis direction (vertical direction) orthogonal to both the X-axis and the Y-axis in accordance with the machining command. It is.

  Specifically, the tool driving device 4 includes a pair of columns 8, a cross rail 10, a horizontal movement device 12, a vertical movement device 14, and a main shaft device 16.

  The pair of columns 8 are separately provided on both sides of the bed 3a in the width direction (Y-axis direction) of the bed 3a.

  The cross rail 10 is disposed so as to extend in the Y-axis direction above the bed 3a, and is supported by a pair of columns 8 so as to be movable in the vertical direction. The cross rail 10 is moved up and down along the column 8 by a drive mechanism (not shown).

  The horizontal movement device 12 is supported by the cross rail 10 so as to be movable in the Y-axis direction (longitudinal direction of the cross rail 10). The horizontal movement device 12 includes a servo motor (not shown), and moves in the Y-axis direction along the cross rail 10 by the driving force of the servo motor.

  The vertical movement device 14 is mounted on the horizontal movement device 12. The vertical movement device 14 includes a servo motor (not shown), and is moved in the Z-axis direction with respect to the horizontal movement device 12 by the driving force of the servo motor.

  The spindle device 16 is supported by the vertical movement device 14. The spindle device 16 holds the tool 5 and rotates the tool 5 about an axis extending in the Z-axis direction. The workpiece W is cut by the tool 5 rotated by the spindle device 16.

  Then, the tool 5 is moved in the Y-axis direction and the Z-axis direction by the movement of the horizontal movement device 12 in the Y-axis direction and the movement of the vertical movement device 14 in the Z-axis direction. The tool 5 is moved relative to the workpiece W in accordance with the machining path by a combination of the movement in the Z-axis direction and the movement of the workpiece W in the X-axis direction by the workpiece driving device 3 so that the workpiece W is shaped into a predetermined shape. It is designed to be processed.

  The error correction device 6 is for correcting an error in the machining position that occurs during actual machining of the workpiece W. Specifically, the error correction device 6 includes a correction matrix derivation device 20 and a machining command correction conversion unit 22 as shown in FIG.

  The correction matrix deriving device 20 derives a correction matrix for correcting and converting a machining command so as to correct a machining position error that occurs during actual machining of the workpiece W. The error of the machining position that occurs during actual machining of the workpiece W is an error that occurs between the machining position on the workpiece W that is instructed by the machining command and the position on the workpiece W that is actually cut by the tool 5. Yes, it is caused by expansion / contraction of the workpiece W due to temperature, twisting of the workpiece W, gravity deformation of the workpiece W, misalignment of the installation position of the workpiece W, and the like.

  The correction matrix deriving device 20 includes a measurement device 24, a calculation unit 26, and a storage unit 28.

  The measuring device 24 measures the coordinates of the measurement object. The measuring device 24 measures the actual coordinates of a plurality of reference points 100a on the workpiece W to which the coordinates on the reference coordinate axis are respectively given. Specifically, the workpiece W is provided with a plurality of reference balls 100 as shown in FIG. The plurality of reference spheres 100 are provided so as to protrude from the upper surface of the flat workpiece W, and are disposed apart from each other. The center point of each reference sphere 100 is a reference point 100a. As shown in FIG. 2, the measurement device 24 includes a measurement probe 34, a coordinate acquisition unit 36, a coordinate calculation unit 38, and a coordinate storage unit 40.

  The measurement probe 34 (see FIG. 4) is a touch sensor having a linearly extending shaft portion 34a and a spherical sensor portion 34b provided at the tip (lower end) of the shaft portion 34a. The measurement probe 34 is attached to the spindle device 16 instead of the tool 5. At this time, the measurement probe 34 is held by the spindle device 16 in a posture extending in the Z-axis direction, and the spindle is aligned with the position of the axis (rotary axis) of the tool 5 held by the spindle device 16. It is held in the device 16. The measurement probe 34 is configured to send a signal to the coordinate acquisition unit 36 when the sensor unit 34b at the tip thereof contacts the object.

  The coordinate acquisition unit 36 receives movement coordinate data in the X-axis direction from the workpiece driving device 3, movement coordinate data in the Y-axis direction from the horizontal movement device 12 in the tool driving device 4, and vertical movement device 14 in the tool driving device 4. The movement coordinate data in the Z-axis direction is respectively obtained from the sensor probe 34b of the measurement probe 34. When the sensor unit 34b of the measurement probe 34 contacts the object and a signal is sent from the measurement probe 34, the sensor unit 34b at that time The coordinate of the contacted part is obtained from the data of each moving coordinate.

  The coordinate calculation unit 38, when the sensor unit 34b of the measurement probe 34 contacts the outer surface of each reference sphere 100 on the workpiece W from each direction of the XYZ axes, and the coordinate acquisition unit 36 acquires the coordinates of the contact portion, The coordinates of the reference point 100 a located at the center of each reference sphere 100 are calculated from the coordinates of the contact part acquired by the coordinate acquisition unit 36. A detailed process of deriving the coordinates of each reference point 100a on the workpiece W by the measurement probe 34, the coordinate acquisition unit 36, and the coordinate calculation unit 38 of the measurement device 24 will be described later.

  The coordinate storage unit 40 stores the coordinates of each reference point 100a calculated by the coordinate calculation unit 38. In addition, the coordinate acquisition part 36, the coordinate calculation part 38, and the coordinate memory | storage part 40 are integrated in the arithmetic unit provided in the machine tool.

  The computing unit 26 calculates a correction matrix based on the reference coordinates given to the plurality of reference points 100a on the workpiece W and the measurement coordinates that are actual coordinates of the plurality of reference points 100a measured by the measuring device 24. And other various calculations and judgments. The correction matrix is represented by an Euler angle and a translation vector, and how the reference coordinates of the plurality of reference points 100a are rotated in order to bring the reference coordinates of the reference points 100a on the workpiece W closer to the measurement coordinates. Indicates whether to translate. Detailed contents such as various calculations and determinations performed by the calculation unit 26 for calculating the correction matrix will be described later.

  The storage unit 28 includes a machining command (NC program) for the workpiece W, a correction value calculated by calibration, a scaling factor, reference coordinates of each reference point 100a on the workpiece W, and on the workpiece W measured by the measuring device 24. Measurement coordinates of each reference point 100a, provisional correction matrix data calculated by the first correction matrix calculation calculation, correction matrix data calculated by the second correction matrix calculation calculation, and processing command after correction conversion by the correction matrix Save other data.

  The machining command correction conversion unit 22 corrects and converts the machining command using the correction matrix derived by the calculation unit 26 of the correction matrix deriving device 20 and stored in the storage unit 28.

  The control device 7 controls the driving of the work driving device 3 and the driving of the tool driving device 4. The control device 7 causes the workpiece driving device 3 to move the workpiece W in accordance with the machining command corrected and converted by the machining command correction conversion unit 22 and causes the horizontal movement device 12 and the vertical movement device 14 of the tool driving device 4 to move the tool 5. To move the workpiece W.

  Next, a machining process of the workpiece W by the machine tool of this embodiment will be described.

  In the machine tool according to the present embodiment, when processing the workpiece W, calibration is first performed as shown in FIG. 3 (step S1). This calibration is performed using a reference jig 102 as shown in FIG. Specifically, the reference jig 102 has a base portion 102a installed on the table 3b of the machine tool, a leg portion 102b extending from the base portion 102a, and a sphere 102c provided at the tip of the leg portion 102b. . This calibration is performed by attaching the measurement probe 34 to the spindle device 16 and detecting the coordinates of a plurality of locations on the outer surface of the sphere 102 c with the measurement probe 34. Specifically, by driving the work driving device 3 and the tool driving device 4, the sensor portion 34b of the measurement probe 34 is brought into contact with a plurality of locations on the outer surface of the sphere 102c as indicated by arrows in FIG. Thereby, the coordinate acquisition part 36 acquires the coordinate of each location which the sensor part 34b contacted among the spherical bodies 102c. Then, the calculation unit 26 calculates a deviation between the coordinates acquired by the coordinate acquisition unit 36 and the original coordinates that the sensor unit 34b should contact with the sphere 102c, and calculates a correction value for correcting the deviation. Then, the machining command (NC program) of the workpiece W is corrected by the calculated correction value. The processing command after correction by this calibration is stored in the storage unit 28.

  Next, measurement of the reference bar 104 and calculation of the scaling factor m based on the measurement result are performed (step S2). As the reference bar 104, a bar having the shape shown in FIG. 5, which is not deformed such as twisting or distortion, is made of the same material as the workpiece W, and has a known length at room temperature. Data on the length of the reference bar 104 at normal temperature is stored in the storage unit 28. In the measurement of the reference bar 104, first, the reference bar 104 is set on the table 3b so as to extend in the Y-axis direction. Thereafter, the measurement probe 34 is moved by the tool driving device 4, and the coordinates of both ends of the reference bar 104 are respectively measured by the measuring device 24. Then, the calculation unit 26 calculates the actual length of the reference bar 104 from the coordinates of both ends of the reference bar 104 measured by the measuring device 24, and the calculated actual length is stored in the storage unit 28. By dividing by the length of the bar 104 at room temperature, the magnification of the actual length with respect to the length of the reference bar 104 at room temperature is calculated. This magnification is the scaling magnification m. The data of the calculated scaling factor m is stored in the storage unit 28.

  Next, the workpiece W is set on the table 3b, and the actual coordinates of each reference point 100a on the workpiece W are measured (step S3). When measuring the actual coordinates of the reference point 100a, the work probe 3 brings the measurement probe 34 closer to the reference sphere 100 from the direction of the arrow i shown in FIG. The coordinates of the contacted part are acquired by the coordinate acquisition unit 36. Next, the work probe 3 and the tool driver 4 bring the measurement probe 34 closer to the reference sphere 100 from the direction of the arrow ii opposite to the direction of the arrow i, and the sensor unit 34b contacts the reference sphere 100. The coordinates of the contacted part are acquired by the coordinate acquisition unit 36. The coordinate calculation unit 38 calculates the center coordinates between the coordinates of the two parts acquired in the X-axis direction. The calculated coordinates are stored in the coordinate storage unit 40.

  Thereafter, the contact part of the sensor unit 34b with respect to the reference sphere 100 in the i direction and the contact part of the sensor unit 34b with respect to the reference sphere 100 in the ii direction calculated by the coordinate calculation unit 38 by the work driving device 3 and the tool driving device 4. The sensor part 34b of the measurement probe 34 is disposed on one side of the reference sphere 100 on a straight line passing through the coordinates of the middle point and extending in the Y-axis direction, and the sensor part 34b is referenced from the direction of arrow iii in FIG. The coordinate acquisition unit 36 acquires the coordinates of the contacted part of the sphere 100. Next, the tool driving device 4 brings the measurement probe 34 into contact with the reference sphere 100 from the direction of the arrow iv opposite to the direction of the arrow iii, and the coordinates of the contacted part are acquired by the coordinate acquisition unit 36. Then, the coordinate calculation unit 38 calculates the coordinates of the center between the coordinates of the two parts acquired in the Y-axis direction. In this way, the coordinates of the center of the reference sphere 100 in the Y-axis direction are obtained. The calculated coordinates of the center of the reference sphere 100 in the Y-axis direction are stored in the coordinate storage unit 40.

  Next, one of the reference spheres 100 on a straight line that passes through the coordinates of the center in the Y-axis direction of the reference sphere 100 calculated by the coordinate calculation unit 38 and extends in the X-axis direction by the work driving device 3 and the tool driving device 4. The sensor part 34b of the measurement probe 34 is arranged on the side, the sensor part 34b is brought into contact with the reference sphere 100 from the direction of the arrow v, and the coordinates of the contacted part are acquired by the coordinate acquisition part 36. Thereafter, the tool driving device 4 causes the measurement probe 34 to approach the reference sphere 100 from the direction of the arrow vi opposite to the direction of the arrow v so that the sensor unit 34b contacts the reference sphere 100, and the coordinates of the contacted part. Is acquired by the coordinate acquisition unit 36. The coordinate calculation unit 38 calculates the center coordinates between the coordinates of the two parts acquired in the X-axis direction. In this way, the coordinates of the center of the reference sphere 100 in the X-axis direction are obtained. The calculated coordinates of the center of the reference sphere 100 in the X-axis direction are stored in the coordinate storage unit 40.

  Next, the workpiece driving device 3 and the tool driving device 4 are measured on a straight line that passes through the coordinates of the center in the X-axis direction and the Y-axis direction of the reference sphere 100 obtained as described above and extends in the Z-axis direction. The sensor unit 34b of the probe 34 is arranged on the upper side of the reference sphere 100, the sensor unit 34b is brought into contact with the reference sphere 100 from the upper side in the Z-axis direction, and the coordinates of the contacted part are acquired by the coordinate acquisition unit 36. . Then, from the coordinates of the contact part of the sensor unit 34b in the Z-axis direction acquired by the coordinate acquisition unit 36 and the radius data of the reference sphere 100 stored in the storage unit 28, the coordinate calculation unit 38 generates a reference sphere 100. The coordinates of the center in the Z-axis direction are calculated. The calculated coordinates of the center of the reference sphere 100 in the Z-axis direction are stored in the coordinate storage unit 40.

  As described above, the actual coordinates (measurement coordinates) of the center point (reference point 100a) of the reference sphere 100 in the X, Y, and Z axis directions are obtained. Note that the measurement coordinates of the center point of the reference sphere 100 obtained by the coordinate calculation unit 38 are stored in the storage unit 28 in addition to the coordinate storage unit 40. Then, the actual coordinates of the reference points are measured for all the reference points 100a (reference spheres 100), and the measured coordinate data of all the reference points 100a are stored in the storage unit 28. The

  Next, the correction matrix is calculated by the calculation unit 26 of the correction matrix deriving device 20 (step S4).

  The calculation of the correction matrix is performed based on the flowcharts shown in FIGS. Specifically, first, the calculation unit 26 performs initial value calculation (step S11 in FIG. 8).

  In this initial value calculation, the calculation unit 26 selects a combination of the minimum number of reference points 100a for which a correction matrix can be calculated. In the present embodiment, there are a total of n reference points 100a, and, for example, three reference points 100a are selected from the n reference points 100a as the minimum number of reference points 100a for which a correction matrix can be calculated. . Then, the calculation unit 26 obtains an initial value t0 [j] that forms a matrix for converting the reference coordinates of the selected reference point 100a (hereinafter referred to as a selection reference point) so as to approach the corresponding measurement coordinates. The initial value t0 [j] includes an Euler angle and a translation vector for converting the reference coordinates of the selected reference point so as to approach the corresponding measurement coordinates, and the scaling factor m obtained in step S2. included. Specifically, the initial value t0 [j] includes (t0 [0], t0 [1], t0 [2]) as the translation vector and (t0 [3], t0 as the Euler angles). [4], t0 [5]) and t0 [6] as the scaling magnification m.

  The Euler angle and the translation vector included in the initial value t0 [j] are, for example, when a plane is constituted by the reference coordinates of the selection reference point, the plane constituted by the reference coordinates is that of the selection reference point. Euler angles and translation vectors necessary for converting the reference coordinates so as to overlap a plane constituted by measurement coordinates, and at least one of the coordinates after conversion of the reference coordinates of each selected reference point Is an Euler angle and a translation vector that coincide with the measurement coordinates of the selected reference point.

  Next, the calculation unit 26 performs a first correction matrix calculation calculation for calculating a temporary correction matrix for correcting and converting the reference coordinates of each reference point 100a (step S13). At this time, the calculation unit 26 adds the square value of the distance between the coordinate after the reference coordinate of each reference point 100a is corrected and converted by the correction matrix and the corresponding measurement coordinate to all the reference points 100a. A temporary correction matrix that minimizes the calculated value is calculated by the method of least squares.

  Specifically, first, the measurement coordinates of the reference point 100a are Pi = (Xi, Yi, Zi), the reference coordinates of the reference point 100a are pi = (xi, yi, zi), and the measurement coordinates Pi and the reference coordinates pi Let Li be the distance between them, and let Fi be the square value of the distance Li between the measurement coordinates Pi and the reference coordinates pi. Here, i = 0, 1, 2,..., N−1.

  The calculation unit 26 obtains a solution t [j] that minimizes the value F = Σ (Fi) obtained by adding Fi to all the reference points 100a as a solution that satisfies the following nonlinear simultaneous equation (1). This solution t [j] is an element constituting the temporary correction matrix.

  ∂F / ∂t [j] = 0 (1)

  Since the nonlinear simultaneous equation (1) cannot be solved analytically, the calculation unit 26 solves the equation (1) using an asymptotic method. At this time, the initial value t0 [j] obtained by the initial value calculation is used as the solution t [j] to be used first. The calculation unit 26 corrects and converts the reference coordinates pi = (xi, yi, zi) of each reference point using a matrix composed of initial values t0 [j]. The coordinates (x, y, z) after this correction conversion are obtained by the following equations (2) to (4).

x = m * [{cos (a) * cos (c) -sin (a) * cos (b) * sin (c)} * xi- {cos (a) * sin (c) + sin (a) * cos (B) · cos (c)} × yi + {sin (a) · sin (b)} × zi + u] (2)
y = m × [{sin (a) · cos (c) + cos (a) · cos (b) · sin (c)} × xi + {− sin (a) · sin (c) + cos (a) · cos ( b) · cos (c)} × yi + {− cos (a) · sin (b)} × zi + v] (3)
z = m * {sin (b) * sin (c) * xi + sin (b) * cos (c) * yi + cos (b) * zi + w} (4)

  Here, u = t0 [0], v = t0 [1], w = t0 [2], a = t0 [3], b = t0 [4], c = t0 [5], m = t0 [6 ].

  And the calculating part 26 is between the measurement coordinate Pi = (Xi, Yi, Zi) corresponding to the coordinate (x, y, z) after correction | amendment conversion about each reference point 100a by the following formula | equation (5). A distance squared value E is calculated.

E = (x−Xi) ² + (y−Yi) ² + (z−Zi) ² (5)

  Further, as shown in the following equation (6), the calculation unit 26 calculates the square value E of the distance obtained by the above equation (5) to all the reference points 100a (i = 0 to n−1). A value F obtained by adding 100a) is calculated.

  F = ΣE (6)

  And the calculating part 26 calculates | requires dF [j] represented by the following formula | equation (7).

  dF [j] = Σ (∂E / ∂t [j]) = Σ (dE [j]) (7)

  Note that j = 0, 1, 2, 3, 4, and 5, and here, the initial values t0 [1] to t0 [5] are used as t [j]. That is, the calculation unit 26 obtains a value dF [j] obtained by adding all values obtained by partial differentiation of E with respect to the initial values t0 [1] to t0 [5].

  DE [j] is expressed by the following equation (8).

  dE [j] = 2 × {(x−Xi) · dX [j] + (y−Yi) · dY [j] + (z−Zi) · dZ [j]} (8)

  Note that dX [j], dY [j], and dZ [j] are the coordinate values of the coordinates (x, y, z) after correction conversion of each reference point 100a, respectively, t [j] It is a value obtained by partial differentiation with an initial value t0 [1] to t0 [5]). That is, dX [j] = ∂x / ∂t [j], dY [j] = ∂y / ∂t [j], and dZ [j] = ∂z / ∂t [j].

  And the calculating part 26 calculates | requires aa [j] [k] represented by the following formula | equation (9).

  aa [j] [k] = Σ (∂ (∂E / ∂t [j]) / ∂t [k]) = Σ (dEE [j] [k]) (9)

  Note that k = 0, 1, 2, 3, 4, and 5, and here, the initial values t0 [1] to t0 [5] are used as t [k]. That is, the calculation unit 26 adds the values aa [j] [k] obtained by adding all the partial differential values of the dF [j] with the initial values t0 [1] to t0 [5] according to the above equation (9). ].

  Here, dEE [j] [k] is expressed by the following formula (10).

  dEE [j] [k] = 2 × G × {dX [k] · dX [j] + (x−Xi) · dXX [j] [k] + dY [k] × dY [j] + (y−Yi DYY [j] [k] + dZ [k] dZ [j] + (z−Zi) dZZ [j] [k]} (10)

  DXX [j] [k] is a value obtained by partial differentiation of dX [j] by t [k], and dYY [j] [k] is obtained by partial differentiation of dY [j] by t [k]. DZZ [j] [k] is a value obtained by partial differentiation of dZ [j] with respect to t [k]. Here, the initial values t0 [1] to t0 [5] are used as t [k].

  Then, the calculation unit 26 solves the following linear simultaneous equations (11) asymptotically expanded ∂F / ∂t [j] = 0 to obtain an asymptotic solution t [j], that is, t [0] to t [5]. ].

  aa [j] [0] × t [0] + aa [j] [1] × t [1] +... + aa [j] [5] × t [5] = s [j] + dF [j] · (11)

  Note that s [j] is the total of constant parts generated by partial differentiation.

  When solving the linear simultaneous equations (11), dF [j] obtained by the equation (7) and aa [j] [k] obtained by the equation (9) are used.

  The calculation unit 26 performs the calculation for obtaining the asymptotic solution t [j] according to the equations (2) to (11), or the obtained asymptotic solution t [j] converges or the number of calculations Is performed until a predetermined number of preset times is reached. When the calculation unit 26 repeatedly performs the calculation, the asymptotic solution t [j] obtained by one calculation related to the equations (2) to (11) is used as an initial value in the next calculation. Repeat the above operation.

  Then, the calculation unit 26 determines whether or not the asymptotic solution t [j] has converged (step S15). At this time, the calculation unit 26 sets the convergence condition of the asymptotic solution t [j] that the value of dF [0] + dF [1] +... + DF [5] is lower than the set value. Specifically, the arithmetic unit 26 determines that the asymptotic solution t [j] has converged when the value of dF [0] + dF [1] +... + DF [5] falls below the set value. If the value of dF [0] + dF [1] +... + DF [5] is greater than or equal to the set value, it is determined that the asymptotic solution t [j] has not converged.

  If the calculation unit 26 determines that the asymptotic solution t [j] has not converged, the calculation unit 26 determines whether there are any other combinations of selection reference points to be selected in the initial value calculation (step). S17). Here, when the calculation unit 26 determines that there are no other combinations of selection reference points to be selected in the initial value calculation, it outputs an error display to a display (not shown). On the other hand, when the calculation unit 26 determines that there are other combinations of selection reference points to be selected in the initial value calculation, the calculation unit 26 selects a new selection reference point and performs the processing from step S11 again.

  Further, in the determination of step S15, when the calculation unit 26 determines that the asymptotic solution t [j] has converged, a matrix constituted by the converged asymptotic solution t [j] is used as a temporary correction matrix. The data is stored in the storage unit 28 (step S19).

  And the calculating part 26 performs correction | amendment conversion (1st correction | amendment conversion) of the reference | standard coordinate of each reference | standard point 100a using the temporary correction matrix (step S21).

  Thereafter, the calculation unit 26 calculates a post-correction separation distance that is a distance between the coordinates of each reference point 100a after the correction conversion using the temporary correction matrix in step S21 and the corresponding measurement coordinates, and each of the reference points. Calculation of the average distance after correction, which is the average value of the distance after correction 100a, is performed (step S22).

  Next, the computing unit 26 performs initial setting of the number of weighting coefficient assignment calculations N1 and N2, and initial setting of the weighting coefficient G (first weighting coefficient setting) (step S23). Here, the weighting factor G reflects the value of the square of the distance between the coordinate after the correction conversion of each reference point 100a and the corresponding measurement coordinate in the second correction matrix calculation calculation described later with what weight. A weighting factor G is individually prepared for each of the reference points 100a. Here, the calculation unit 26 initially sets the weighting coefficient G for each reference point 100a to an equal value (1.0). Note that the initial setting value of the weighting factor G can be changed to an arbitrary value larger than 1. Further, when the second correction matrix calculation calculation described later is repeatedly performed, the weight coefficient G of the maximum separation reference point selected corresponding to each calculation is reset, but the number N1 of weight coefficient addition calculations is set. , N2 corresponds to the number of times the weighting coefficient G is set. Here, the calculation unit 26 initially sets the weighting coefficient addition calculation times N1 and N2 to 1. N1 corresponds to the total number of times the weighting factor G is set, and N2 is a weight for resetting the weighting factor G when the asymptotic solution t [j] does not converge in the second correction matrix calculation calculation described later. This corresponds to the number of times the coefficient G is set.

  Next, the computing unit 26 is the first reference point having the largest distance between the coordinates after the reference coordinates are corrected and converted by the temporary correction matrix in step S21 and the corresponding measurement coordinates among the reference points 100a. The maximum separation reference point is selected (first selection) (step S25).

  Next, the computing unit 26 resets the weight coefficient G of the selected first maximum separation reference point to a value increased by a predetermined increase g1 set in advance (first weight coefficient reset) (step S26). . The increment g1 of the weighting factor G can be set to an arbitrary value in advance and is stored in the storage unit 28.

  Next, the calculation unit 26 performs a second correction matrix calculation calculation for calculating a correction matrix for correcting and converting the reference coordinates of each reference point 100a (step S27 in FIG. 9). At this time, the calculation unit 26 sets each reference point 100a to a square value of the distance between the coordinate after the reference coordinate of each reference point 100a is corrected and converted by the correction matrix and the corresponding measurement coordinate. A correction matrix is calculated by the method of least squares so that a value obtained by multiplying the weighted coefficient G by the sum of all the reference points 100a is minimized.

  Specifically, the calculation unit 26 performs basically the same calculation as the first correction matrix calculation calculation in the second correction matrix calculation calculation. However, in the first calculation of the second correction matrix, the initial value t0 [j] is used as the first solution when the nonlinear simultaneous equation ∂F / ∂t [j] = 0 is solved using the asymptotic method. Is used instead of the asymptotic solution t [j] constituting the provisional correction matrix.

  Then, in this second correction matrix calculation calculation, the calculation unit 26 calculates the value of E for each reference point 100a using the following equation (13) instead of the above equation (5).

E = G × {(x−Xi) ² + (y−Yi) ² + (z−Zi) ² } (13)

  Here, for the first maximum separation reference point, since the weighting coefficient G is increased in step S26, the value of E for the first maximum separation reference point is larger than the other reference points. The calculation unit 26 obtains an asymptotic solution t [j] constituting the correction matrix in the second correction matrix calculation calculation in the same manner as the first correction matrix calculation calculation except for the above. Accordingly, in the second correction matrix calculation calculation, a correction matrix in which the square value of the post-correction separation distance of the first maximum separation reference point is largely reflected as compared to the square value of the post-correction separation distance of the other reference points. Desired.

  Next, the calculation unit 26 determines whether or not the asymptotic solution t [j] obtained by the second correction matrix calculation calculation has converged (step S29). At this time, the calculation unit 26 performs convergence determination in the same manner as in step S15.

  Then, when the calculation unit 26 determines that the asymptotic solution t [j] obtained in the second correction matrix calculation calculation has not converged, the weighting coefficient addition calculation number N2 is set to a preset maximum value. It is determined whether or not it exceeds (step S31). Note that the maximum value of the weighting coefficient addition calculation number N2 can be set to an arbitrary number in advance and is stored in the storage unit 28.

  When the calculation unit 26 determines that the weighting coefficient addition calculation count N2 exceeds the preset maximum value, the calculation matrix data stored in the storage unit 28 at that time is used as the final calculation result. (Step S33). On the other hand, when the calculation unit 26 determines that the weighting coefficient application calculation number N2 does not exceed the preset maximum value, the calculation unit 26 thereafter increments the weighting coefficient application calculation number N1 and N2 and the first maximum separation criterion. After resetting the point weighting factor G (step S35), the convergence judgment of the asymptotic solution t [j] calculated by the next second correction matrix calculation calculation (step S27) and the second correction matrix calculation calculation is performed. (Step S29) is performed again.

  In addition, in the increment of the weight coefficient addition calculation times N1 and N2 in step S35, the calculation unit 26 increases the weight coefficient addition calculation times N1 and N2 by 1, respectively. In step S35, the calculation unit 26 increases the weighting coefficient G of the first maximum separation reference point by the increment g1. In the next second correction matrix calculation calculation, the calculation unit 26 calculates the asymptotic solution t [j] (correction matrix) by applying the weighting coefficient G reset in step S35 for the first maximum separation reference point. I do.

  If the calculation unit 26 determines in step S29 that the asymptotic solution t [j] obtained by the second correction matrix calculation calculation has converged, the calculation unit 26 determines a correction matrix composed of the asymptotic solution t [j]. Then, correction conversion (second correction conversion) of the reference coordinates of each reference point 100a is performed (step S37).

  Thereafter, the calculation unit 26 calculates a post-correction separation distance that is a distance between the coordinates of each reference point 100a after the correction conversion by the correction matrix in step S37 and the corresponding measurement coordinate, and each reference point 100a. The corrected post-correction distance average value, which is the average value of the post-correction separation distances, is calculated (step S38).

  Next, the calculation unit 26 has the largest distance (post-correction separation distance) between the coordinates after the reference coordinates are corrected and converted by the correction matrix in step S37 among the reference points 100a and the corresponding measurement coordinates. The second maximum separation reference point that is a point is selected (second selection) (step S39).

  Thereafter, the calculation unit 26 determines whether or not the weighting coefficient addition calculation count N1 exceeds a preset maximum value (step S40). It should be noted that the maximum value of the weighting coefficient addition calculation number N1 can be set to an arbitrary number in advance and is stored in the storage unit 28.

  If the calculation unit 26 determines that the number N1 of weighting coefficient addition calculations exceeds a preset maximum value, the calculation unit 26 next selects the second maximum separation selected in step S39 after the current second correction conversion. It is determined whether or not a condition that the corrected separation distance for the reference point is smaller than the corrected separation distance for the maximum separation reference point selected after the previous correction conversion is satisfied (step S41). In the determination of step S41 after the first calculation of the second correction matrix, the reference coordinates of the first maximum separation reference point are used as the separation distance after correction for the maximum separation reference point selected after the previous correction conversion. A post-correction separation distance between the coordinate corrected and converted by the temporary correction matrix and the corresponding measurement coordinate is used.

  If the calculation unit 26 determines that the condition is satisfied, the calculation unit 26 stores the matrix formed by the asymptotic solution t [j] calculated in step S27 in the storage unit 28 as a correction matrix (step S42). . At this time, if there is correction matrix (temporary correction matrix) data previously stored in the storage unit 28, the matrix data is updated to the newly stored correction matrix data. Thereafter, the calculation unit 26 sets the correction matrix data stored in the storage unit 28 as the final calculation result (step S33).

  On the other hand, when the calculation unit 26 determines in step S41 that the condition is not satisfied, the calculation unit 26 performs the process of step S33. That is, the correction matrix data stored in the storage unit 28 at that time is used as the final calculation result.

  In addition, when the calculation unit 26 determines in step S40 that the weighting coefficient addition calculation count N1 does not exceed the preset maximum value, next, both the following first condition and second condition are satisfied. It is determined whether or not both of the following third condition and fourth condition are satisfied (step S45).

  The first condition is that the maximum separation reference that the post-correction separation distance for the second maximum separation reference point calculated with the current second correction matrix calculation calculation is calculated with the previous correction matrix calculation calculation is calculated. This is a condition that the distance is larger than the corrected separation distance for the point. Further, the second condition is that the corrected post-correction distance average value (the corrected post-correction distance average value calculated in step S43) calculated in association with the current second correction matrix calculation calculation is the correction matrix one time before that. This is a condition that it is larger than the corrected post-correction distance average value calculated with the calculation operation. The third condition is that the post-correction separation distance for the second maximum separation reference point calculated with the second correction matrix calculation calculation this time is the maximum calculated with the correction matrix calculation calculation of the previous one. The condition is that the distance is smaller than the corrected separation distance for the separation reference point. Further, the fourth condition is that the corrected post-correction distance average value calculated along with the current second correction matrix calculation operation from the post-correction separation distance for the maximum separation reference point calculated along with the current second correction matrix calculation operation. After correction, the value obtained by subtracting is calculated from the post-correction separation distance for the maximum separation reference point calculated with the previous correction matrix calculation calculation, with the previous correction matrix calculation calculation. This is a condition that it is larger than the value obtained by subtracting the average distance.

  In the determination in step S45 associated with the first calculation of the second correction matrix, the first maximum separation reference point selected in step S25 is used as the maximum separation reference point selected after the previous correction conversion. As the post-correction separation distance and the post-correction separation distance average value calculated with the previous correction matrix calculation calculation, the post-correction separation distance calculated in step S22 with the first correction matrix calculation calculation and The average distance after correction is used.

  In the determination of step S45, when the calculation unit 26 determines that both the first condition and the second condition are satisfied, or that both the third condition and the fourth condition are satisfied, Then, the process of step S33 is performed. In other cases, the matrix constituted by the asymptotic solution t [j] calculated in step S27 is stored in the storage unit 28 as a correction matrix in the same manner as the process of step S42. (Step S47) and incrementing the weighting coefficient application calculation number N1 and resetting the weighting coefficient G of the second maximum separation reference point (seconding weighting coefficient resetting) (Step S49), Correction matrix calculation calculation is performed. That is, in this case, the calculation unit 26 repeatedly performs a cycle including steps S27, S29, S37, S38, S39, S40, S45, and S49.

  Note that in the increment of the weighting coefficient addition calculation number N1 in step S49, the calculation unit 26 increases the weighting coefficient addition calculation number N1 by one. In step S49, the calculation unit 26 increases only the weight coefficient G of the second maximum separation reference point selected in step S39 by the increment g1, and does not increase the weight coefficient G of the other reference points 100a.

  Then, in the next second correction matrix calculation calculation, the calculation unit 26 selects the second correction matrix calculation calculation described in step S27 instead of the first maximum separation reference point in the second maximum separation reference. The second maximum separation reference point selected in step S39, the value of E is calculated using the weighting factor G reset in step S49, and the other reference points For 100a, the value of E is calculated using each weighting factor G.

  In addition, in the second correction matrix calculation calculation in the next cycle, the calculation unit 26 uses the first as a solution used when solving the nonlinear simultaneous equation ∂F / ∂t [j] = 0 using the asymptotic method. The asymptotic solution t [j] constituting the correction matrix calculated by the second correction matrix calculation calculation of the previous cycle is used.

  Further, in the determination in step S41 of the next cycle, the calculation unit 26 uses the corrected separation distance for the second maximum separation reference point selected in step S39 of the previous cycle as the previous corrected separation distance.

  Then, after the calculation unit 26 calculates the correction matrix as described above, the machining command correction conversion unit 22 performs correction conversion of the machining command (NC program) using the calculated correction matrix (step S5).

  Thereafter, the control device 7 causes the workpiece driving device 3 to move the workpiece W according to the machining command corrected and converted by the machining command correction conversion unit 22 and causes the tool driving device 4 to move the tool 5 to move the workpiece W. Let it be processed.

  As described above, in the present embodiment, the calculation unit 26 resets the weight coefficient G of the maximum separation reference point to a value increased by a predetermined increment g1, and then corrects and converts the reference coordinates of each reference point 100a. A value obtained by multiplying the value of the square of the distance between the later coordinate and the corresponding measurement coordinate by the weighting coefficient G set for each reference point 100a and adding all the reference points 100a is the minimum. Since the correction matrix capable of correcting and converting the reference coordinates of each reference point 100a is calculated by the least square method, the sum of squares of the distances between the reference coordinates of each reference point and the measurement coordinates is simply minimized. Compared with the case where a correction matrix capable of correcting and converting the reference coordinates of each reference point is obtained, a correction matrix is calculated that greatly considers the error of the actual coordinates with respect to the reference coordinates of the maximum separated reference point among the reference points 100a. Rukoto can. Therefore, by correcting and converting the machining command for the workpiece W using the calculated correction matrix, the reference point where the measurement coordinate is displaced to the maximum from the reference coordinate, that is, the error of the reference point where the measurement coordinate is significantly displaced from the reference coordinate is minimized. Thus, it is possible to perform correction to reduce the error of all reference points as a whole.

  In the present embodiment, the calculation unit 26 calculates the maximum corrected separation distance for the second maximum separation reference point calculated along with the current second correction matrix calculation calculation as calculated along with the previous correction matrix calculation calculation. The post-correction separation calculated by the previous correction matrix calculation calculation is greater than the post-correction separation distance for the reference separation point, and the corrected post-correction separation average value calculated by the second correction matrix calculation calculation is calculated. The weighting factor G obtained by selecting the second maximum separation reference point and increasing the square value of the corrected separation distance of the selected second maximum separation reference point by a predetermined increment g1 until it becomes larger than the distance average value. In order to perform the second correction matrix calculation calculation performed by multiplying the error, the error of all the reference points is reduced as a whole while the error of the reference point where the measurement coordinates are significantly displaced from the reference coordinates is satisfactorily reduced. It is possible to calculate the correction matrix that can be corrected to reduce the good.

  Further, in the present embodiment, the second maximum separation calculated with the current second correction matrix calculation calculation compared to the post-correction separation distance for the maximum separation reference point calculated with the previous correction matrix calculation calculation. Even if the post-correction separation distance for the reference point is reduced, the difference between the corrected post-correction distance average value for the maximum separation reference point and the corrected post-correction distance average value is larger than that of the previous correction matrix calculation calculation. If the number of the two correction matrix calculation calculations increases, the second correction matrix calculation calculation for the subsequent rounds is not performed, and the correction matrix calculated in the previous correction matrix calculation calculation becomes the final calculation result. That is, in the present embodiment, the error of the reference point (maximum separation reference point) where the measurement coordinate is significantly displaced from the reference coordinate is reduced, and the error of the maximum separation reference point is the error of all the reference points. It is possible to calculate a correction matrix that can be corrected so as to approach the average value.

  In the present embodiment, the provisional correction matrix and the correction matrix are calculated by the least square method with an element of the scaling factor m representing the expansion / contraction rate of the workpiece W depending on the temperature. It is possible to obtain a correction matrix that takes into account errors due to the above. For this reason, the error due to the expansion and contraction due to the temperature of the workpiece W can be corrected by correcting and converting the machining command of the workpiece W by the correction matrix.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, the correction matrix deriving device and the error correcting device according to the present invention may be applied to a machine tool other than the machine tool as shown in the above embodiment.

  Moreover, the calculating part 26, the memory | storage part 28, and the process command correction | amendment conversion part 22 do not need to be integrated in the machine tool. For example, the calculation unit 26, the storage unit 28, and the machining command correction conversion unit 22 are incorporated in an external terminal such as a personal computer, and the machining command data obtained through calculation processing and correction conversion by the external terminal is stored in the machine tool. You may make it output to the control apparatus 7. FIG.

  In the determination in step S45, only determination is made as to whether both the first condition and the second condition are satisfied. If both the first condition and the second condition are satisfied, the process in step S33 is performed. In other cases, the next second correction matrix calculation may be performed through steps S47 and S49.

  Further, the method for deriving the scaling factor is not limited to the method shown in the above embodiment. For example, a detection device that detects the temperature of the workpiece W is installed in the machine tool, and a correlation between the temperature measured in advance and the scaling factor of the workpiece W is registered in the storage unit 28, and the detection device Based on the detected temperature of the workpiece W and the correlation, the calculation unit 26 may obtain the scaling factor of the workpiece W at the temperature.

4 Tool Driving Device 5 Tool 7 Control Device 20 Correction Matrix Deriving Device 22 Processing Command Correction Conversion Unit 24 Measuring Device 26 Computing Unit W Workpiece

Claims (6)

A machine tool including a drive device that performs machining of a workpiece by the tool by moving at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis. A correction matrix deriving device for deriving a correction matrix for converting the machining command so as to correct a machining position error that occurs during actual machining of the workpiece,
A measuring device for measuring the actual coordinates of each of a plurality of reference points on the workpiece given coordinates on the reference coordinate axes,
An operation for calculating the correction matrix is performed based on reference coordinates that are coordinates given to the plurality of reference points and measurement coordinates that are actual coordinates of the plurality of reference points measured by the measurement device. With an arithmetic unit,
The calculation unit is a temporary correction matrix for correcting and converting the reference coordinates of the reference points, and corresponds to the coordinates after the reference coordinates of the reference points are corrected and converted by the temporary correction matrix. A first correction matrix calculation operation for calculating a temporary correction matrix by a least-square method so that a value obtained by adding the squares of the distances to the measurement coordinates to the sum of all the reference points is minimized, and the first correction A first correction conversion for correcting and converting the reference coordinates of the reference points using the temporary correction matrix calculated by a matrix calculation calculation; a first weighting factor setting for setting equal weighting factors for the reference points; The first maximum separation reference that is the reference point having the longest distance between the coordinate after the first correction conversion of the reference coordinate among the reference points and the corresponding measurement coordinate. A first selection of selecting the first weighting factor, a first weighting factor resetting to reset the weighting factor of the selected first maximum separation reference point to a value increased by a predetermined increment, and a resetting of the first weighting factor Thereafter, a correction matrix for correcting and converting the reference coordinates of the reference points, and the measurement coordinates corresponding to the coordinates after the reference coordinates of the reference points are corrected and converted by the correction matrix. A correction matrix is calculated by the method of least squares so that a value obtained by multiplying the value of the square of the distance by the weighting factor set for each reference point and adding all the reference points is minimized. A correction matrix deriving device that performs a second correction matrix calculation calculation.   The calculation unit includes: a second correction conversion that corrects and converts the reference coordinates of the reference points by the correction matrix calculated by the second correction matrix calculation calculation; A second selection for selecting a second maximum separation reference point that is the reference point having the largest distance between the coordinate after the correction conversion and the corresponding measurement coordinate; and the reference point of the reference point after the second correction conversion. The calculation of the corrected separation distance that is the distance between the coordinate and the corresponding measurement coordinate, the calculation of the corrected separation distance average value that is the average value of the corrected separation distance for each reference point, and the current Correction for the maximum separation reference point calculated by the correction matrix calculation calculation of the previous time when the post-correction separation distance for the second maximum separation reference point calculated in association with the second correction matrix calculation calculation Determination of whether the first condition that the distance is larger than the separation distance is satisfied, and the correction matrix average calculated after the second correction matrix calculation calculation this time is the previous correction matrix calculation When it is determined whether the second condition that is larger than the corrected post-correction distance average value calculated along with the calculation is satisfied, and it is determined that both the first condition and the second condition are satisfied If the correction matrix calculated in the previous correction matrix calculation operation is the final calculation result, and it is determined that at least one of the first condition and the second condition is not satisfied, A second weighting factor reset for resetting the weighting factor of the second maximum separation reference point to a value increased by a predetermined increment, and after the resetting of the second weighting factor, the reference coordinates of each reference point are correction A correction matrix for converting each reference point to a square value of a distance between the coordinate after correction conversion of the reference coordinate of each reference point by the correction matrix and the corresponding measurement coordinate Performing a second correction matrix calculation operation for the next time to calculate a correction matrix by a least square method so that a value obtained by multiplying the set weighting factor by the sum of all the reference points is minimized. The correction matrix deriving device according to 1.   The calculation unit includes: a second correction conversion that corrects and converts the reference coordinates of the reference points by the correction matrix calculated by the second correction matrix calculation calculation; A second selection for selecting a second maximum separation reference point that is the reference point having the largest distance between the coordinate after the correction conversion and the corresponding measurement coordinate; and the reference point of the reference point after the second correction conversion. The calculation of the corrected separation distance that is the distance between the coordinate and the corresponding measurement coordinate, the calculation of the corrected separation distance average value that is the average value of the corrected separation distance for each reference point, and the current Correction for the maximum separation reference point calculated by the correction matrix calculation calculation of the previous time when the post-correction separation distance for the second maximum separation reference point calculated in association with the second correction matrix calculation calculation The first condition that the distance is larger than the separation distance, and the average value of the post-correction separation distance calculated with the second correction matrix calculation calculation this time is calculated with the correction matrix calculation calculation of the previous time. The determination as to whether the second condition of greater than the corrected post-correction distance average value is satisfied, and the post-correction separation distance for the second maximum separation reference point calculated in accordance with the current second correction matrix calculation calculation Is calculated to be smaller than the post-correction separation distance for the maximum separation reference point calculated with the previous correction matrix calculation operation, and with the current second correction matrix calculation operation The average post-correction distance calculated with the second calculation calculation of the second correction matrix is subtracted from the post-correction distance for the second maximum separation reference point. The post-correction separation distance calculated with the previous correction matrix calculation operation from the post-correction separation distance for the maximum separation reference point calculated with the previous correction matrix calculation operation. A determination is made as to whether a fourth condition that is greater than the value obtained by subtracting the average value is satisfied, and both the first condition and the second condition are satisfied, or the third condition and the fourth condition are satisfied. When it is determined that both of the conditions are satisfied, the correction matrix calculated in the previous correction matrix calculation calculation is used as the final calculation result. In other cases, the second maximum separation reference point is used. A second weighting factor resetting to reset the weighting factor to a value increased by a predetermined increment, and a correction for correcting and converting the reference coordinates of each reference point after the second weighting factor resetting Matrix, before The square value of the distance between the coordinate after the reference coordinate of each reference point is corrected and converted by the correction matrix and the corresponding measurement coordinate is multiplied by the weighting factor set for each reference point. The correction matrix deriving device according to claim 1, wherein a second correction matrix calculation operation is performed for calculating a correction matrix such that a value obtained by adding all of the reference points is minimized by a least square method.   Prior to the first correction matrix calculation calculation, the calculation unit derives a scaling factor that represents the expansion / contraction rate of the workpiece due to temperature. In the first correction matrix calculation calculation, the temporary correction matrix including the scaling factor is used. The temporary correction matrix is calculated when the reference coordinates of each reference point are corrected and converted. In the second correction matrix calculation calculation, the reference coordinates of each reference point are calculated using the correction matrix including the scaling factor. The correction matrix deriving device according to claim 1, wherein the correction matrix is calculated when correction conversion is performed. A machine tool including a driving device that performs machining of a workpiece by the tool by moving at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis An error correction device for correcting an error of a processing position that is provided and is generated during actual processing of a workpiece,
The correction matrix deriving device according to any one of claims 1 to 4,
An error correction apparatus comprising: a processing command correction conversion unit that corrects and converts the processing command using the correction matrix derived by the correction matrix deriving device. A machine tool for machining a workpiece,
A drive device that performs machining of the workpiece by the tool by moving at least one of the workpiece and a tool for machining the workpiece according to a machining command represented by a movement vector on a reference coordinate axis;
An error correction device according to claim 5;
A machine tool, comprising: a control device that causes the drive device to move at least one of the workpiece and the tool in accordance with a machining command corrected and converted by the error correction device to machine the workpiece.

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