JPH07111339B2 - Measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention moves the coordinates of the measured object surface by moving the probe and the measured object relative to each other along the surface of the measured object while they are in contact with each other. Regarding the required measurement method. In particular, it can be used for a measuring method for highly accurately obtaining the coordinates and shape of the surface of a measured object having a three-dimensional curved surface.

[Background technology and its problems]

As a device for measuring the coordinates and the shape of the surface of the object to be measured, particularly the coordinates and the shape of the surface of the object to be measured having a three-dimensional curved surface, for example, as shown in FIG. Direction, that is, a pair of parallel springs 5 displaceable in the Z-axis direction with respect to the probe body 1, and a pair of parallel springs 6 and X displaceable in the Y-axis direction.
The stylus 2 is held via a pair of parallel springs 7 which can be displaced in the axial direction, and the displacement amount of each of the parallel springs 5, 6, 7 or the displacement amount of the stylus 2 in the X, Y and Z axial directions is different. A displacement detector 22 such as a dynamic transformer (however, the detectors in the Y- and Z-axis directions are omitted in FIG. 3) is provided with a probe 8 configured to detect, and the probe 8 is preset. There is known a so-called coordinate measuring machine that measures coordinates and a shape of an object to be measured while moving along the surface of the object to be measured according to a program.

When measuring the coordinates and shape of the surface of the object to be measured having a three-dimensional curved surface with this type of measuring machine, the probe body 1 is pushed into the object to be measured so that the stylus 2 is displaced with respect to the probe body 1. Then, the probe 8 is moved along the surface of the object to be measured.

If friction does not occur between the stylus 2 and the object to be measured, the displacement direction of the stylus 2, that is, the direction of the displacement vector acting on the stylus 2 is nothing but the normal direction of the surface of the object to be measured. Therefore, the contact position (Cx, Cy, Cz) on the surface of the object to be measured that comes into contact with the stylus 2 is the origin of the center position of the stylus 2. It is represented by. Where r is the radius of stylus 2, Px, Py,
Pz is the axial displacement of the stylus 2 relative to the probe body 1, and e is Is.

Therefore, if the axial displacement (coordinates) of the probe 8 (probe body 1) is Mx, My, Mz, the contact coordinates (Tx, Ty, Tz) when viewed from the coordinates of the entire measuring machine are: Can be expressed as

However, such an idea holds only when friction does not occur between the surface of the object to be measured and the surface of the stylus 2, and in reality, the direction of the displacement vector acting on the stylus 2 due to the influence of friction is Since it deviates from the direction normal to the surface of the object to be measured, a measurement error occurs.

Therefore, as a method of removing the influence of friction, for example, it is possible to measure while applying vibration to the stylus, or to bring the probe into contact with the surface of the object to be measured from a direction orthogonal to it, but in any method, When the measurement surface of the object to be measured is a three-dimensional curved surface, highly accurate measurement cannot be performed.

[Object of the Invention]

Here, an object of the present invention is to eliminate the error caused by the friction generated between the probe and the object to be measured, and to measure the coordinates of the surface of the object to be measured having a three-dimensional curved surface with high accuracy. To provide.

[Means and Actions for Solving Problems]

Therefore, the configuration of the present invention, the probe and the object to be measured, which holds the spherical stylus in the probe body displaceably in the three-dimensional direction, in a state in which the stylus is in contact with the object to be measured and displaced with respect to the probe body. The relative displacement of the probe body, the relative displacement of the probe body, the displacement of the stylus with respect to the probe body, and the distance from the origin of the stylus to the contact point in contact with the surface of the measurement object in the measurement direction In the measurement method for obtaining the contact coordinates on the surface, the origin coordinate value of the current stylus and the origin coordinate values of the stylus before that are (x ₁ , y ₁ , z ₁ ), (x ₀ , y ₀ , z ₀ ), Displace the stylus with respect to the main unit in each axial direction (P
x, Py, Pz), each axial component Nx, Ny, Nz of the normal direction vector of the DUT surface is Substituting each axis component Nx, Ny, Nz into the following equation, Tx = Mx + Px− (r / e ′) Nx Ty = My + Py− (r / e ′) Ny Tz = Mz + Pz− (r / e ′ ) Nz (However, Mx, My, Mz; Relative displacement of probe body in each axial direction r; Stylus radius The feature is that contact point coordinates Tx, Ty, Tz are obtained.

Therefore, the measuring method of the present invention will be specifically described.

In the present invention, the stylus of the probe is pressed against the surface of the object to be measured, and while the displacement between the stylus and the probe body occurs, the probe and the object to be measured are moved relative to the surface of the object to be measured. To do. In such a measurement, a frictional force is generated between the stylus of the probe and the object to be measured, which causes the direction of the displacement vector acting on the stylus to deviate from the direction normal to the surface of the object to be measured. If equation (2) is used as it is, an error will occur. Since the frictional force is generated in the direction opposite to the relative movement direction between the probe and the object to be measured, the displacement vector acting on the stylus shifts in the relative movement direction. In the present invention, the displacement vector acting on the stylus is obtained by projecting a vector projected from the origin of the stylus on the surface orthogonal to the relative movement direction in the state where it does not contact the object to be measured, and this vector is the normal line to the surface of the object to be measured. By using it as a direction vector, the influence of the frictional force generated in the counter-moving direction of the probe is eliminated, and highly accurate measurement is achieved.

That is, even when a frictional force is generated, the above equation (2) can be applied mutatis mutandis if the normal direction of the surface of the object to be measured can be obtained to some extent. Now, assuming that the normal vector of the surface of the measured object is Nx, Ny, Nz, the contact coordinates (Tx, Ty, Tz) of the measured object in contact with the probe are It is represented by. However, e'is Is. If Nx, Ny, and Nz are determined so that e ′ = 1, the above equation (3) becomes Can be simplified as follows.

The present invention is premised on such an idea, and how to obtain Nx, Ny, and Nz will be described below.

Now, as shown in FIG. 1, the current center position of the stylus 2 is 0 (x ₁ , y ₁ , z ₁ ) and the probe origin, that is, the center of the stylus 2 when the stylus 2 is not in contact with the object to be measured. The position is C, and the center position of the stylus 2 before an appropriate sampling time is 0 '(x ₀ , y ₀ , z ₀ ). At this time, the vector connecting the center positions 0 and 0 ' Is Can be expressed as

Next, straight line from probe origin C Let Q be the perpendicular leg that is dropped vertically to the vector ▲
▼ is on a plane perpendicular to the scanning direction. That is, it is nothing but the direction of the normal to the surface of the object to be measured.

The vector ▲ ▼ can be expressed as ▲ ▼ ＝ (Nx, Ny, Nz) …… (5) ＝ ▲ ▼ ＋ ▲ ▼.

Here, the vector ▲ ▼ is ▲ ▼ = (Px, Py, Pz) (6). The vector ▲ ▼ is Is. On the right side of equation (7) If only the coefficient of is calculated, from equations (4) and (6), Becomes

Therefore, from the above equations (5), (6), (7) and (8), Is expressed as

Therefore, the coordinates of the center position 0,0 'of the stylus 2 (x ₁ , y ₁ , z
₁ ) (x ₀ , y ₀ , z ₀ ) and the displacement amount (Px, Py, Pz) of the stylus 2 with respect to the probe body 1 in each axial direction,
Since Nx, Ny, and Nz are obtained from the equations (9A), (9B), and (9C), by substituting these into the equation (3), the coordinates of the surface of the object to be measured can be obtained with high accuracy.

Furthermore, by obtaining the coordinates of a plurality of points on the surface of the object to be measured, the shape of the surface of the object to be measured can also be obtained with high accuracy from these coordinate points.

〔Example〕

Hereinafter, a measuring device to which the measuring method of the present invention is applied will be described with reference to FIG.

In the figure, 21x, 21y and 21z are displacement detectors for detecting the displacement amount of the probe 8 in each axial direction relative to the measuring machine main body,
22x, 22y, and 22z are displacement detectors that detect the amount of displacement of the stylus 2 with respect to the probe body 1 in each axial direction. The signals from the displacement detectors 21x, 21y, 21z are converted into digital signals by the A / D conversion circuit 23 and then input to the addition circuit 24.
Also, the signals from the displacement detectors 22x, 22y, 22z are
After being converted into a digital signal by the / D conversion circuit 25, it is input to the adder circuit 24 and the arithmetic circuit 26.

The adding circuit 24, at each preset sampling interval,
Displacement amount of the probe 8 given from the A / D conversion circuit 23 (Mx,
(My, Mz) and the displacement amount (Px, Py, Pz) of the stylus 2 given through the A / D conversion circuit 25 are added, and this sum (coordinate value of the center position of the stylus 2) is updated and stored in the storage circuit 27. And to the arithmetic circuit 26.

The arithmetic circuit 26 updates the coordinate value (x ₀ , y ₀ , z ₀ ) before one sampling updated and stored in the storage circuit 27 and the current coordinate value (x ₁ , y ₁ , z ₁ ) given from the adder circuit 24. ) And the stylus 2 displacement amount (Px, Py, Pz) based on equations (9A) to (9C), (Nx, Ny, Nz) is calculated, and this is substituted into equation (3) to obtain the contact coordinates ( Tx, Ty, Tz) is then sent to the comparison circuit 28.

The comparison circuit 28 uses the contact coordinates (Tx, Ty,
Tz) is outside the allowable range Host computer
While sending an alarm signal to 31, the contact coordinates (Tx, Ty, Tz) are displayed on the display 30 through the counting circuit 29.

The host computer 31 drives the motors 34x, 34y, 34z of the respective axes of the measuring machine main body through the control circuit 32 and the drive circuit 33 according to a preset program. And
When the alarm signal from the comparison circuit 28 is given, each motor 34
Stop driving x, 34y, 34z.

Next, the operation of this device will be described. Host computer
When each of the motors 34x, 34y, 34z is driven by the drive command from 31, the probe 8 is moved in the X, Y, Z-axis directions while being in contact with the surface of the object to be measured by the drive.
Then, the displacement amount of the probe 8 in the X, Y, and Z axis directions (Mx, M
y, Mz) are respectively detected by the displacement detectors 21x, 21y, 21z, and then input to the adder circuit 24 via the A / D conversion circuit 23.
At the same time, after the displacement amount (Px, Py, Pz) of the stylus 2 with respect to the probe body 1 is detected by the displacement detectors 22x, 22y, 22z, the addition circuit 24 and the arithmetic circuit 2 are passed through the A / D conversion circuit 25.
Input to 6.

Then, the adder circuit 24 causes the displacement amount (Mx, My, M) of the probe 8 given from the A / D conversion circuit 23 to be provided at each sampling interval.
z) and the displacement amount (Px, Py, Pz) of the stylus 2 given through the A / D conversion circuit 25 are added, and the sum (center position coordinate value of the stylus 2) is updated and stored in the storage circuit 27,
And it gives to the arithmetic circuit 26.

The arithmetic circuit 26 updates the coordinate value (x ₀ , y ₀ , z ₀ ) before one sampling updated and stored in the storage circuit 27 and the current coordinate value (x ₁ , y ₁ , z ₁ ) given from the adder circuit 24. ) And the stylus 2 displacement (Px, Py, Pz) based on the equations (8A) to (8C), (Nx, Ny, Nz) is obtained, and this is further calculated based on the equation (3). , Ty, Tz) and then sends it to the comparison circuit 28.

The comparator circuit 28 sends an alarm signal to the host computer 31 when the contact coordinates (Tx, Ty, Tz) from the arithmetic circuit 26 with respect to the target value given from the host computer 31 are out of the allowable range, while the contact point The coordinates (Tx, Ty, Tz) are displayed on the display 30 through the counting circuit 29.

Therefore, the probe 8 is attached to these contact coordinates (Tx, Ty, Tz).
Since the error due to the friction with the measured object has been eliminated,
The coordinates of the surface of the object to be measured can be measured with high accuracy.

Although the probe 8 is moved while being in contact with the surface of the object to be measured in the above-described embodiment, the object to be measured may be moved with respect to the probe 8 on the contrary. It is sufficient that at least one of the probe 8 and the object to be measured can move with respect to the other.

Further, when obtaining the relative movement direction between the probe 8 and the object to be measured, the center position coordinate of the stylus 2 is not always 0.
It may not be (x ₁ , y ₁ , z ₁ ), 0 '(x ₀ , y ₀ , z ₀ ), but may be a coordinate position representing a position in place of it. Also, 0'is 0
It is not limited to the coordinates of the measurement point one sampling before, but the point is that the coordinates of the point before the current measurement point for obtaining the direction component may be used. in short, Anything that can be used instead of

Further, in the case of scanning measurement drive, the relative movement direction between the probe 8 and the object to be measured is calculated using the command coordinate position data of two or several points related to the preliminarily programmed relative movement direction, and this direction component is calculated. You may use it.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a measuring method which eliminates an error caused by friction between a probe and a measured object and can measure the coordinates of the measured object surface having a three-dimensional curved surface with high accuracy. .

[Brief description of drawings]

FIG. 1 is a diagram showing the measuring principle of the present invention, and FIG. 2 is a block diagram showing an embodiment of a measuring apparatus to which the method of the present invention is applied.
FIG. 3 is a diagram showing the structure of the probe. 1 ... Probe body, 2 ... Stylus, 8 ... Probe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Abiko Kenji, 165 Sakado, Takatsu-ku, Kawasaki City, Kanagawa Mito Works Ltd. Microcode Headquarters (56) Reference JP-A-56-7008 (JP, A) JP-A-SHO 60-233512 (JP, A)

Claims (1)

[Claims] 1. A probe having a spherical stylus movably held in a probe body in a three-dimensional direction and an object to be measured, the object being measured in a state where the stylus is in contact with the object to be measured and displaced with respect to the probe body. Move relative to the surface of
The relative displacement of the probe body, the displacement of the stylus with respect to the probe body, and the distance in the measurement direction from the origin of the stylus to the contact point that contacts the surface of the object to be measured, in the measuring method for obtaining the contact coordinates of the surface of the object to be measured, The coordinates of the origin of the stylus and the coordinates of the origin of the stylus before that are (x ₁ , y ₁ , z ₁ ), (x ₀ , y ₀ , z ₀ ), and the displacement of the stylus with respect to the probe body in each axial direction ( P
x, Py, Pz), each axial component Nx, Ny, Nz of the normal direction vector of the DUT surface is Substituting each axis component Nx, Ny, Nz into the following equation, Tx = Mx + Px− (r / e ′) Nx Ty = My + Py− (r / e ′) Ny Tz = Mz + Pz− (r / e ′ ) Nz (However, Mx, My, Mz; Relative displacement of probe body in each axial direction r; Stylus radius A measuring method characterized by obtaining contact point coordinates Tx, Ty, Tz.