JP2010145211A - Three-dimensional measurement machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional measurement machine capable of shortening the time required in calculating a correction parameter and improving measurement accuracy. <P>SOLUTION: The three-dimensional measurement machine includes a probe 21 including a measurement element 211A, a drive mechanism, and a correction parameter calculation device. The correction parameter calculation device includes: a restraint means 6 restraining translational displacement of the measurement element 211A without restraining rotational displacement of the measurement element 211A; a reference position setting part setting a position in which the moving amount of the probe 21 is zero as a reference position; and a measurement point information acquisition part moving the probe 21 to a plurality of measurement points in a state in which the measurement element 211A is restrained at the reference position by the restraint means 6 and acquiring a moving amount of the probe 21 from the reference position in each measurement point and a moving amount of the drive mechanism, wherein a correction parameter for correcting a coordinate system of the probe 21 is calculated on the basis of information obtained by the measurement point information acquisition part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coordinate measuring machine.

Conventionally, the probe is configured to be movable within a certain range, and includes a rod-like stylus having a spherical probe contacting the object to be measured at the tip, and the base end of the probe is held and driven. A coordinate measuring machine including a drive mechanism is known (for example, see Patent Document 1).
The probe used in the coordinate measuring machine includes a touch trigger probe that outputs a trigger signal when it comes into contact with an object to be measured, and a movable amount within a certain range. And a measurement probe that outputs (the amount of movement of) is known. In the following description, this measurement probe is simply referred to as a probe.
In the surface shape measuring apparatus (coordinate measuring machine) described in Patent Document 1, the movement amount of the probe and the movement amount of the drive mechanism are acquired in a state where the probe is pushed into the object to be measured, and the obtained movement amounts are synthesized. By doing so, the position (measurement value) of the probe is detected. Further, the surface shape measuring device measures the surface shape of the object to be measured based on the detected measurement value.

Here, the coordinate measuring machine acquires the movement amount of the probe based on the orthogonal coordinate system defined for the probe, and acquires the movement amount of the drive mechanism based on the orthogonal coordinate system defined for the drive mechanism.
Specifically, if the movement amount of the probe acquired by the coordinate measuring machine is (x _p , y _p , z _p ) and the movement amount of the drive mechanism is (x _m , y _m , z _m ), The measured value (x, y, z) is calculated by the following equation (1).

For this reason, when the coordinate system of a probe and a drive mechanism does not correspond, an error will arise in a measured value.
In addition, as a factor of mismatch of each coordinate system, for example, when there is an error between the scale for acquiring the moving amount of the probe and the scale for acquiring the moving amount of the driving mechanism, or in the driving mechanism There are cases where the orientation of each coordinate system does not match due to attachment errors when the probe is attached and held, or when there is spatial distortion between the three coordinate axes constituting each coordinate system and they are not orthogonal. It is done.

Therefore, in order to reduce the measurement error based on the mismatch of each coordinate system and improve the measurement accuracy, it is desirable that the coordinate measuring machine corrects the coordinate system of the probe. Here, as a correction for matching each coordinate system, a correction method using affine transformation is known.
Specifically, for example, when the transformation matrix (correction parameter) of affine transformation is A (A _{11 to} A ₃₃ ) and correction is performed so that the coordinate system of the probe matches the coordinate system of the drive mechanism, the movement of the probe after correction is performed. The quantity (x _p ′, y _p ′, z _p ′) is calculated by the following equation (2).

  Accordingly, the corrected measurement values (x ′, y ′, z ′) are calculated by the following equation (3).

Here, as a method of calculating the correction parameter, for example, a method of calculating the correction parameter based on a measurement value calculated by measuring a reference gauge having a known shape is known (for example, a patent Reference 2).
In the method described in Patent Document 2, an equation for defining the shape of the reference gauge based on a plurality of measurement values calculated by measuring the reference gauge at a plurality of measurement points, and an equation for calculating a correction parameter The correction parameter is calculated by finding the solution of the simultaneous equations in which. For this reason, it is necessary to measure the reference gauge at a large number of measurement points, and there is a problem that it takes time to calculate the correction parameter.

Further, as another method for calculating the correction parameter, for example, the correction parameter is calculated based on a measurement value calculated by moving the probe with the measuring element being pressed into the concave portion of the jig and performing measurement. A method is known (see, for example, Patent Document 3).
Specifically, in the method described in Patent Document 3, the correction parameter is set using a jig having a conical recess formed by arranging three spheres on a plane so as to be positioned at the apex of an equilateral triangle. Calculated.

Here, since the position of the probe is constrained by the concave portion of the jig, the amount of movement of the probe when the probe is moved and the amount of movement of the drive mechanism are the same in the opposite directions. Amount. Therefore, in the method described in Patent Document 3, the correction parameter is calculated without using the reference gauge by using this condition.
Further, since the position of the measuring element is constrained by the concave portion of the jig, the time required for calculating the correction parameter can be shortened as compared with the method described in Patent Document 2 using the reference gauge.

JP 2008-89578 A JP 2004-521343 A JP-A-2-284216

However, in the method described in Patent Document 3, since the position of the measuring element is constrained by being pushed into a conical recess formed in the jig, the plane direction of the jig (the direction orthogonal to the axial direction of the probe) ) And a direction away from the jig (a direction from the tip of the probe toward the base end), even if the probe is moved and measured, there is a problem that an effective measurement value cannot be obtained.
That is, in the method described in Patent Document 3, the coordinate measuring machine cannot obtain an effective measurement value within a sufficient range in the measurement space, and therefore cannot calculate an appropriate correction parameter, thereby measuring accuracy. There is a problem that there is a limit to improving it.
In particular, with a three-dimensional measuring machine, measurement is often performed with the probe being pushed into the object to be measured in a direction perpendicular to the axial direction of the probe. However, it is a very big problem that an effective measurement value cannot be obtained.

  An object of the present invention is to provide a three-dimensional measuring machine capable of reducing the time required for calculating correction parameters and improving measurement accuracy.

  According to the present invention, there is provided a three-dimensional measuring machine that is configured to be movable within a certain range and includes a probe having a spherical probe that comes into contact with an object to be measured, and a drive mechanism that holds and drives the probe. A correction parameter calculation device for calculating a correction parameter for correcting the coordinate system of the probe, wherein the correction parameter calculation device is configured to measure the measurement without constraining rotational displacement about the center of the probe. In a state where the restraining means for restraining the translational displacement of the child, the reference position setting unit for setting the position where the movement amount of the probe becomes 0 as the reference position, and the measuring member being restrained to the reference position by the restraining means The probe is moved to a plurality of measurement points in the measurement space, and the amount of movement of the probe from the reference position at each measurement point, and the movement of the drive mechanism A measurement point information acquisition unit for acquiring the correction parameter, and the correction parameter is calculated based on the movement amount of the probe and the movement amount of the drive mechanism acquired by the measurement point information acquisition unit. To do.

According to such a configuration, the correction parameter calculation device restrains the translational displacement of the tracing stylus without restraining the rotational displacement about the center of the tracing stylus (hereinafter referred to as the rotational displacement of the tracing stylus). The probe is moved to the measurement point in all directions while the probe is restricted to the reference position by the means and the restriction means, and the amount of movement of the probe from the reference position and the amount of movement of the drive mechanism at each measurement point are obtained. Since the measurement point information acquisition unit that performs measurement is provided, an effective measurement value can be obtained within a sufficient range.
Therefore, the correction parameter calculation device can reduce the time required for calculating the correction parameter, and can calculate an appropriate correction parameter. In addition, since an appropriate correction parameter can be calculated by the correction parameter calculation apparatus, the coordinate measuring machine can improve measurement accuracy.

Here, when measuring an object to be measured with a three-dimensional measuring machine, the object to be measured is measured in a state where the probe is pushed into the object to be measured. At this time, the probe does not undergo any displacement other than the displacement caused by the reaction force in the normal direction on the contact surface with the object to be measured and the displacement caused by the friction force on the contact surface. There is no displacement constraint. For this reason, if the measurement value is calculated by moving and measuring the probe while restraining the rotational displacement of the probe, an error occurs in the amount of movement of the probe, and an appropriate correction parameter cannot be calculated. There's a problem.
According to the present invention, the restraining means restrains the translational displacement of the measuring element without constraining the rotational displacement of the measuring element, so that the correction parameter calculating device can calculate an appropriate correction parameter.

  In the present invention, the restraining means includes two pressing members that are disposed to face each other with the measuring element sandwiched therebetween, and that press the measuring element along the facing direction. Two columnar portions each having an axial direction that is orthogonal to the direction and parallel to each other and projecting toward the measuring element are provided, and each columnar portion in one of the pressing members, and the other It is preferable that the columnar portions of the pressing member are provided so that axial directions thereof are orthogonal to each other and abut against the measuring element.

  According to such a configuration, the restraining means can bring each columnar portion into contact with the measuring element by pressing the measuring element with the two pressing members. Here, each columnar part in one pressing member and each columnar part in the other pressing member are provided so that the axial directions thereof are orthogonal to each other. Can be restrained. In addition, since each columnar portion is in contact with the measuring element by the pressing force of the pressing member, the restraining means adjusts the pressing force of each pressing member so as not to constrain the rotational displacement of the measuring element. Translational displacement can be constrained.

In the present invention, it is preferable that each of the columnar portions is formed in a columnar shape and is provided to be rotatable around a central axis.
According to such a configuration, each columnar part can rotate in accordance with the rotational displacement of the probe, so that the restraining means restrains the translational displacement of the probe without restricting the rotational displacement of the probe. be able to.

  In the present invention, the restraining means includes at least four pressing members that press the measuring element toward the center of the measuring element, and each pressing member includes a spherical abutting member that contacts the measuring element, It is preferable that the contact member includes a support member that rotatably supports the center of the contact member as a center of rotation.

  According to such a configuration, the restraining means can bring the contact member into contact with the measuring element by pressing the measuring element with at least four pressing members. Here, since each pressing member presses the measuring element toward the center of the measuring element, the restraining means can constrain the translational displacement of the measuring element with a simple configuration. Further, since the contact member is supported by the support member so as to be rotatable about the center of the contact member, the restraining means can restrain the translational displacement without restricting the rotational displacement of the measuring element. it can.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
[Schematic configuration of CMM]
FIG. 1 is a block diagram showing a schematic configuration of a coordinate measuring machine 1 according to the first embodiment of the present invention.
As shown in FIG. 1, the coordinate measuring machine 1 instructs the motion controller 3 via a coordinate measuring machine body 2, a motion controller 3 that executes drive control of the coordinate measuring machine body 2, an operation lever, and the like. And a host computer 5 for giving a predetermined command to the motion controller 3 and executing a calculation process.

FIG. 2 is an overall schematic diagram showing the coordinate measuring machine main body 2. In FIG. 2, the upper direction is defined as the + Z-axis direction, and two axes orthogonal to the Z-axis are described as the X-axis and the Y-axis, respectively. The same applies to the following drawings.
As shown in FIG. 2, the coordinate measuring machine main body 2 holds a probe 21 having a probe 211 </ b> A for measuring the workpiece W and a drive for driving the probe 21 while holding the proximal end side of the probe 21. A mechanism 22 and a surface plate 23 on which the drive mechanism 22 is erected are provided.
The drive mechanism 22 includes a slide mechanism 24 that holds the proximal end side of the probe 21 and allows the probe 21 to move, and a drive unit 25 that drives the probe 21 by driving the slide mechanism 24.

  The slide mechanism 24 extends from both ends of the surface plate 23 in the X-axis direction in the + Z-axis direction and is supported by the two columns 241 provided to be slidable along the Y-axis direction. A beam 242 extending along the direction, a slider 243 formed in a cylindrical shape extending along the Z-axis direction and slidably movable along the X-axis direction on the beam 242, and the inside of the slider 243 And a ram 244 provided to be slidable in the slider 243 along the Z-axis direction. Therefore, the drive mechanism 22 includes a plurality of drive shafts that drive the probe 21 in the X, Y, and Z axis directions. The ram 244 holds the proximal end side of the probe 21 at the end on the −Z axis direction side. A plurality of types of probes are prepared as the probe 21 and can be selected from these probes and held by the ram 244.

  As shown in FIGS. 1 and 2, the drive unit 25 supports the column 241 on the −X axis direction side among the columns 241, and drives the Y axis drive unit 251Y along the Y axis direction. An X-axis drive unit 251X (not shown in FIG. 2) that slides on the beam 242 to drive the slider 243 along the X-axis direction, and slides inside the slider 243 to drive the ram 244 along the Z-axis direction. A Z-axis drive unit 251Z (not shown in FIG. 2).

  As shown in FIG. 1, the X-axis drive unit 251X, the Y-axis drive unit 251Y, and the Z-axis drive unit 251Z have Xs for detecting the positions of the slider 243, the columns 241 and the ram 244 in the respective axial directions. An axis scale sensor 252X, a Y axis scale sensor 252Y, and a Z axis scale sensor 252Z are provided. Each scale sensor 252 is a position sensor that outputs a pulse signal corresponding to the amount of movement of the slider 243, each column 241, and the ram 244.

FIG. 3 is an enlarged schematic diagram of the probe 21.
As shown in FIG. 3, the probe 21 includes a stylus 211 having a probe 211 </ b> A on the distal end side, and a support mechanism 212 that supports the proximal end side of the stylus 211.
The support mechanism 212 supports the stylus 211 so as to be positioned at a predetermined position by urging the stylus 211 in the X, Y, and Z axis directions, and when an external force is applied to the probe 211A, that is, the probe 211A is When abutting against the workpiece W, the stylus 211 can be moved in the X, Y, and Z axis directions within a certain range. As shown in FIG. 1, the support mechanism 212 includes an X-axis probe sensor 213X, a Y-axis probe sensor 213Y, and a Z-axis probe sensor 213Z for detecting the position of each stylus 211 in each axial direction. Each probe sensor 213 is a position sensor that outputs a pulse signal corresponding to the amount of movement of the stylus 211 in each axial direction, like each scale sensor 252.

FIG. 4 is a schematic diagram showing the relationship between the probe 21 and the probe sensor 213X. In FIG. 4, the relative movement direction of the probe 21 and the object to be measured W is indicated by an arrow D.
Specifically, as shown in FIG. 4, the support mechanism 212 includes an urging member 212A, and positions the stylus 211 at a predetermined position. Each probe sensor 213 detects the position of the stylus 211 in each axial direction by detecting the position of the proximal end of the stylus 211.
For example, as shown in FIG. 4A, when no external force is applied to the probe 211A, that is, when the probe 211A is not in contact with the workpiece W, the probe detected by the probe sensor 213X. The amount of movement 21 in the X-axis direction is zero.
Then, as shown in FIG. 4B, when the probe 21 is moved in the X-axis direction and an external force is applied to the probe 211A, that is, when the probe 211A comes into contact with the workpiece W, The amount of movement of the probe 21 detected by the sensor 213X in the X-axis direction is the amount of movement corresponding to the amount of movement of the probe 211A.

As shown in FIG. 1, the motion controller 3 outputs from the operation control unit 4 or a drive control unit 31 that controls the drive unit 25 in response to a command from the host computer 5, each scale sensor 252, and each probe sensor 213. And a counter unit 32 that counts pulse signals to be transmitted.
The counter unit 32 counts the pulse signal output from each scale sensor 252 and measures the movement amount of the slide mechanism 24, and counts the pulse signal output from each probe sensor 213 to count the probe 21. A probe counter 322 for measuring the amount of movement. The movement amount of the slide mechanism 24 and the movement amount of the probe 21 measured by the scale counter 321 and the probe counter 322 are output to the host computer 5.

  The host computer 5 includes a CPU (Central Processing Unit), a memory, and the like, and controls the coordinate measuring machine main body 2 by giving a predetermined command to the motion controller 3, and includes a command unit 51, A movement amount acquisition unit 52, a measurement value calculation unit 53, a correction parameter calculation unit 54, and a storage unit 55 that stores data used by the host computer 5 are provided.

The command unit 51 gives a predetermined command to the drive control unit 31 of the motion controller 3 to drive the slide mechanism 24 of the coordinate measuring machine main body 2. Specifically, the command unit 51 outputs a position command value for driving the measuring element 211A. Note that the contour data of the workpiece W is stored in the storage unit 55.
The movement amount acquisition unit 52 acquires the movement amount (x _p , y _p , z _p ) of the probe 21 and the movement amount (x _m , y _m , z _m ) of the drive mechanism 22 measured by the counter unit 32. To do. Here, the movement amount acquisition unit 52 acquires the movement amount of the probe 21 based on the orthogonal coordinate system defined for the probe 21 (see FIG. 3), and based on the orthogonal coordinate system defined for the drive mechanism 22. Then, the movement amount of the drive mechanism 22 is acquired (see FIG. 2).

The measurement value calculation unit 53 calculates the measurement value, that is, the position of the probe 211A based on the movement amount of the probe 21 acquired by the movement amount acquisition unit 52 and the movement amount of the drive mechanism 22. Note that the amount of movement of the drive mechanism 22 is adjusted to indicate the position of the probe 211A when no movement of the stylus 211 occurs in the support mechanism 212, that is, when the amount of movement of the probe 21 is zero. .
Specifically, the measurement value calculation unit 53 combines the movement amount of the probe 21 acquired by the movement amount acquisition unit 52 and the movement amount of the drive mechanism 22 as shown in the following formula (4). Then, the measured value (x, y, z) is calculated.

Here, the measurement value calculation unit 53 corrects the coordinate system of the probe 21 by correcting the coordinate system of the probe 21 so as to coincide with the coordinate system of the drive mechanism 22. Specifically, if the correction parameter for correcting the coordinate system of the probe 21 is A (A _{11 to} A ₃₃ ), the movement amount (x _p ′, y _p ′, z _p ′) of the probe 21 after correction. Is calculated by the following equation (5). The correction parameter A is calculated by a correction parameter calculation unit 54 described in detail later and stored in the storage unit 55.

  Therefore, the measurement value calculation unit 53 calculates the corrected measurement value (x ′, y ′, z ′) by the following equation (6).

  The correction parameter calculation unit 54 calculates the correction parameter A, and includes a reference position setting unit 541 and a measurement point information acquisition unit 542.

FIG. 5 is a schematic diagram showing a state in which the measuring element 211 </ b> A is restrained by the restraining means 6.
As shown in FIG. 5, the correction parameter calculation unit 54 calculates the correction parameter A in a state where the measuring element 211A is restrained by the restraining means 6 installed on the surface plate 23 (see FIG. 2).
The restraining means 6 is disposed so as to face the measuring element 211A, and has two prismatic pressing members 61A and 61B that press the measuring element 211A along the opposing direction (the arrow direction in FIG. 5), Plate members 62A, 62B attached to the surface of the member 61A, 61B on the measuring element 211A side, and a pedestal 63 that supports the pressing members 61A, 61B so as to be slidable along the opposing direction.

  Each of the plate-like members 62A and 62B is formed in a rectangular plate shape having a plane orthogonal to the facing direction, and is attached to each of the pressing members 61A and 61B so that the longitudinal directions are orthogonal to each other. In addition, on the surface of each plate-like member 62A, 62B on the side of the probe 211A, two columnar portions 621A, 621B formed in a column shape having an axial direction in the longitudinal direction are provided, and each columnar portion 621A, 621B is Projecting toward the probe 211A.

  That is, the columnar portions 621A and 621B are provided on the pressing members 61A and 61B, and have axial directions that are orthogonal to the facing direction and parallel to each other. Each columnar portion 621A in one pressing member 61A and each columnar portion 621B in the other pressing member 61B are provided so that the axial directions thereof are approximately orthogonal to each other. The restraining means 6 restrains the translational displacement of the measuring element 211A by pressing the measuring element 211A with the pressing members 61A and 61B to bring the columnar portions 621A and 621B into contact with the measuring element 211A. Moreover, the pressing force of each pressing member 61A, 61B is adjusted to such an extent that the translational displacement of the measuring element 211A is constrained without restricting the rotational displacement of the measuring element 211A.

FIG. 6 is a schematic diagram showing the relationship between the probe 21 and the probe sensor 213X in a state where the translational displacement of the probe 211A is constrained. In FIG. 6, the relative movement direction of the probe 21 and the jigs J1 and J2 is indicated by an arrow D.
Here, as shown in FIG. 6A, the probe 21 is moved in a state in which the rotational displacement of the measuring element 211A is constrained and the measuring element 211A is constrained by the jig J1 that constrains the translational displacement of the measuring element 211A. In this case, the position of the base end portion of the stylus 211 is also moved by the same amount as the measuring element 211A. Therefore, the amount of movement of the probe 21 in the X-axis direction detected by the probe sensor 213X is compared with the case where the probe 211A moves by the same distance by contacting the object to be measured W (see FIG. 4A). And get bigger.

In contrast, as shown in FIG. 6B, the probe 21A is restrained by the jig J2 that restrains the translational displacement of the probe 211A without restricting the rotational displacement of the probe 211A. When the probe is moved, the amount of movement of the probe 21 detected by the probe sensor 213X in the X-axis direction is substantially the same as when the probe 211A is moved by the same distance by contacting the object to be measured W. Become.
In this embodiment, the pressing force of each pressing member 61A, 61B is adjusted to such an extent that the translational displacement of the probe 211A is restricted without restricting the rotational displacement of the probe 211A. The amount of movement of the probe 21 is substantially the same as when the probe 211A is moved by the same distance by coming into contact with the workpiece W.

  The reference position setting unit 541 sets a position where the amount of movement of the probe 21 becomes 0 as a reference position in a state where the probe 211A is restricted by the restraining means 6. Specifically, the reference position setting unit 541 causes the movement amount acquisition unit 52 to acquire the movement amount of the probe 21 while moving the probe 21 by causing the command unit 51 to output a position command value, so that the movement amount of the probe 21 is changed. The position that becomes 0 is detected. Then, when the reference position setting unit 541 detects a position where the movement amount of the probe 21 is 0, the reference position setting unit 541 sets the position as the reference position.

  The measurement point information acquisition unit 542 moves the probe 21 to a plurality of measurement points in the measurement space in a state where the probe 211A is restrained by the restraining means 6, and the amount of movement of the probe 21 from the reference position at each measurement point, And the movement amount of the drive mechanism 22 is acquired. Specifically, the measurement point information acquisition unit 542 moves the probe 21 to each measurement point by causing the command unit 51 to output a position command value, and causes the movement amount acquisition unit 52 to move the probe 21 from the reference position. And the movement amount of the drive mechanism 22 is acquired.

Then, the correction parameter calculation unit 54 calculates the correction parameter A based on the movement amount of the probe 21 and the movement amount of the drive mechanism 22 acquired by the measurement point information acquisition unit 542.
In other words, in the present embodiment, the correction parameter calculation device includes the restraining means 6 and the correction parameter calculation unit 54.

[Calculation method of correction parameters]
FIG. 7 is a flowchart showing a method for calculating the correction parameter A by the correction parameter calculation unit 54.
The user of the coordinate measuring machine 1 starts calculation of the correction parameter A in a state where the probe 211A is restrained by the restraining means 6.
When the calculation of the correction parameter A is started, the reference position setting unit 541 sets a position where the movement amount of the probe 21 becomes 0 in a state where the measuring element 211A is restrained by the restraining means 6 as a reference position (step ST1).

  When the reference position is set by the reference position setting unit 541, the measurement point information acquisition unit 542 moves the probe 21 to a plurality of measurement points in the measurement space in a state where the measuring element 211A is constrained by the restraining means 6. Then, the movement amount of the probe 21 from the reference position and the movement amount of the drive mechanism 22 at each measurement point are acquired (step ST2).

  Here, since the position of the probe 211A is constrained by the restraining means 6, the amount of movement of the probe 21 when the probe 21 is moved and the amount of movement of the drive mechanism 22 are the same in the opposite directions. This is the amount of movement. Therefore, when the coordinate systems of the probe 21 and the drive mechanism 22 match, as shown in the following formula (7), the movement amount of the drive mechanism 22 and the movement amount of the probe 21 are synthesized. When the measurement value is calculated, the measurement value becomes zero.

  On the other hand, when the coordinate systems of the probe 21 and the drive mechanism 22 do not match, the measured value does not become 0, so that the measured value becomes 0 as shown in the following equation (8). Then, the correction parameter A may be calculated.

  Moreover, the following formula (9) can be obtained by transforming the formula (8).

In Equation (9) described above, there are nine unknowns of the correction parameter A. Therefore, the amount of movement of the probe 21 and the amount of movement of the drive mechanism 22 at a sufficient number of measurement points at which these unknowns can be calculated. If acquired by the measurement point information acquisition unit 542, the correction parameter A can be calculated by the least square method or the like.
For example, if the number of measurement points measured by the measurement point information acquisition unit 542 is n, the simultaneous equations can be expressed by the following equation (10).

In the formula (10) described above, displacement of the probe 21, and the moving amount X _p of the drive mechanism 22, if simplified at the X _m, it is possible to obtain the following equation (11).

  Then, if the above-described equation (11) is modified so that the left side becomes the correction parameter A, the following equation (12) can be obtained.

Therefore, when the movement amount of the probe 21 from the reference position and the movement amount of the drive mechanism 22 are acquired by the measurement point information acquisition unit 542, the correction parameter calculation unit 54, as shown in the above equation (12). The correction parameter A is calculated based on the movement amount of the probe 21 and the movement amount of the drive mechanism 22 acquired by the measurement point information acquisition unit 542 (step ST3).
Then, the correction parameter calculation unit 54 stores the calculated correction parameter A in the storage unit 55.

According to this embodiment, there are the following effects.
(1) The correction parameter calculation apparatus moves the probe 21 to the measurement point in any direction from the reference position at each measurement point in a state in which the probe 211A is restricted to the reference position by the restriction means 6 and the restriction means 6. Since the measurement point information acquisition unit 542 for acquiring the movement amount of the probe 21 and the movement amount of the drive mechanism 22 is provided, an effective measurement value can be obtained within a sufficient range. Therefore, the correction parameter calculation apparatus can reduce the time required for calculating the correction parameter A and can calculate an appropriate correction parameter A. Further, since the appropriate correction parameter A can be calculated by the correction parameter calculation device, the coordinate measuring machine 1 can improve the measurement accuracy.

(2) Since the restraining means 6 restrains the translational displacement of the measuring element 211A without restricting the rotational displacement of the measuring element 211A, the correction parameter calculating device can calculate an appropriate correction parameter A.
(3) The restraining means 6 includes two pressing members 61A and 61B. Since the pressing members 61A and 61B are provided with the columnar portions 621A and 621B, the restraining means 6 is measured with a simple configuration. The translational displacement of the child 211A can be constrained. Further, the restraining means 6 can restrain the translational displacement of the measuring element 211A without adjusting the rotational displacement of the measuring element 211A by adjusting the pressing force of each of the pressing members 61A and 61B.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 8 is a schematic diagram showing a state in which the probe 211A is restrained by the restraining means 6A according to the second embodiment of the present invention.
In the following description, parts that have already been described are assigned the same reference numerals and description thereof is omitted.
In the first embodiment, the columnar portions 621A and 621B are fixed to the pressing members 61A and 61B.
On the other hand, in this embodiment, as shown in FIG. 8, each columnar portion 622A, 622B is formed in a columnar shape and is provided on each pressing member 61A, 61B (not shown) so as to be rotatable around the central axis. Is different.

In this embodiment as well, the same operations and effects as those of the first embodiment can be achieved, and the following operations and effects can be achieved.
That is, since each columnar part 622A, 622B can rotate according to the rotational displacement of the measuring element 211A, the restraining means 6A restrains the translational displacement of the measuring element 211A without restricting the rotational displacement of the measuring element 211A. can do.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.
FIG. 9 is a schematic diagram showing a state in which the probe 211A is restrained by the restraining means 6B according to the third embodiment of the present invention.
In the first embodiment, the restraining means 6 includes two pressing members 61A and 61B, and the measuring member 211A is brought into contact with the columnar portions 621A and 621B provided on the pressing members 61A and 61B. The translational displacement of the probe 211A was constrained without constraining the rotational displacement of 211A.
On the other hand, in the present embodiment, the restraining means 6B includes four pressing members 64 as shown in FIG. 9, and causes the contact members 641 provided on the respective pressing members 64 to contact the measuring element 211A. This is different in that the translational displacement of the probe 211A is restricted without restricting the rotational displacement of the probe 211A.

Specifically, the restraining means 6B includes four pressing members 64 that press the measuring element 211A toward the center of the measuring element 211A.
Each pressing member 64 includes a spherical abutting member 641 that abuts against the probe 211A, and a support member 642 that supports the abutting member 641 rotatably about the center of the abutting member 641.

In this embodiment as well, the same operations and effects as those of the first embodiment can be achieved, and the following operations and effects can be achieved.
That is, the restraining means 6B includes four pressing members 64, and each pressing member 64 includes each contact member 641. Therefore, the restraining means 6B restrains the translational displacement of the probe 211A with a simple configuration. be able to. Further, since the contact member 641 is supported by the support member 642 so as to be rotatable about the center of the contact member 641 as a rotation center, the restraining means 6B does not restrain the rotational displacement of the probe 211A. The translational displacement of 211A can be constrained.

Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope in which the object of the present invention can be achieved are included in the present invention.
For example, in each of the embodiments described above, the correction parameter calculation device includes the restraining means 6, 6A, and 6B, but may include other restraining means. In short, the correction parameter calculation device only needs to include a restraining unit that restrains the translational displacement of the probe 211A without restricting the rotational displacement of the probe.

In each of the above-described embodiments, the reference position setting unit 541 sets the position where the amount of movement of the probe 21 becomes 0 in a state where the measuring element 211A is constrained by the restraining means 6, 6A, 6B as the reference position. The reference position may be set in a state where no external force is applied to the probe, and the probe may be restrained by the restraining means without changing the amount of movement of the probe.
In the third embodiment, the restraining means 6B includes the four pressing members 64, but may include five or more pressing members.

The block diagram which shows schematic structure of the coordinate measuring machine which concerns on 1st Embodiment of this invention. The whole schematic diagram which shows the coordinate measuring machine main body in the said embodiment. The enlarged schematic diagram of the probe in the said embodiment. The schematic diagram which shows the relationship between the probe in the said embodiment, and a probe sensor. The schematic diagram which shows the state which restrained the measuring element with the restraining means in the said embodiment. The schematic diagram which shows the relationship between the probe in the state which restrained the translational displacement of the measuring element in the said embodiment, and a probe sensor. The flowchart which shows the calculation method of the correction parameter by the correction parameter calculation part in the said embodiment. The schematic diagram which shows the state which restrained the measuring element with the restraining means which concerns on 2nd Embodiment of this invention. The schematic diagram which shows the state which restrained the measuring element with the restraining means which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Three-dimensional measuring machine 6, 6A, 6B ... Restriction means (correction parameter calculation apparatus)
21 ... Probe 22 ... Drive mechanism 54 ... Correction parameter calculation unit (correction parameter calculation device)
61A, 61B ... Pressing member 64 ... Pressing member 211A ... Measurement element 541 ... Reference position setting unit 542 ... Measurement point information acquisition unit 621A, 621B ... Columnar portion 622A, 622B ... Columnar portion 641 ... Abutting member 642 ... Support member

Claims (4)

A three-dimensional measuring machine that is configured to be movable within a certain range and includes a probe having a spherical probe that contacts a measurement object, and a drive mechanism that holds and drives the probe,
A correction parameter calculation device for calculating a correction parameter for correcting the coordinate system of the probe;
The correction parameter calculation device includes:
Constraint means for constraining the translational displacement of the probe without constraining rotational displacement about the center of the probe as a rotation center;
A reference position setting unit that sets a position where the amount of movement of the probe is 0 as a reference position;
The amount of movement of the probe from the reference position at each measurement point by moving the probe to a plurality of measurement points in a measurement space in a state where the probe is constrained to the reference position by the constraint means, and A measurement point information acquisition unit for acquiring the movement amount of the drive mechanism,
A three-dimensional measuring machine characterized in that the correction parameter is calculated based on a movement amount of the probe and a movement amount of the drive mechanism acquired by the measurement point information acquisition unit. The three-dimensional measuring machine according to claim 1,
The restraining means is
Provided with two pressing members arranged to face each other across the measuring element and pressing the measuring element along the facing direction;
Each of the pressing members is provided with two columnar portions that are orthogonal to the facing direction and have an axial direction parallel to each other and are formed in a columnar shape protruding toward the measuring element,
The three-dimensional measuring machine characterized in that each columnar portion in one of the pressing members and each columnar portion in the other pressing member are provided so that their axial directions are orthogonal to each other and abut against the measuring element. . The three-dimensional measuring machine according to claim 2,
Each of the columnar portions is formed in a columnar shape, and is provided so as to be rotatable around a central axis. The three-dimensional measuring machine according to claim 1,
The restraining means is
Comprising at least four pressing members that press the measuring element toward the center of the measuring element;
Each pressing member is
A spherical abutting member that abuts against the measuring element;
A three-dimensional measuring machine comprising: a support member that rotatably supports the contact member with a center of the contact member as a rotation center.

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