JPH04273009A - Device and method for shape measurement - Google Patents

Abstract

PURPOSE:To eliminate a kinetic error of a drive system to relatively move a measured article from a measured value in the case when the shape of the measured article is measured by relatively moving a probe of a displacement measurement equipment against the measured article. CONSTITUTION:An angle of rotation of a rotary table 3 to rotate a male screw 2 is measured by a rotation angle sensor 12, vertical coordinate of a probe 4a is measured by a displacement sensor 13, a relative position error between the male screw 2 and the probe 4a is obtained on the basis of a measured values of these rotation angle sensor 12 and displacement sensor 13 in a computer 11, influence of the position error on the measured value of a displacement measurement equipment 4 is computed and the measured value of the displacement measurement equipment 4 is corrected by the computed influence. As a kinetic error of a drive system is eliminated from the measured value of the displacement measurement equipment 4, it is possible to grasp the correct shape of the measured article.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention measures the shape of a measured object by moving the probe of a displacement measuring device relative to the measured object, such as a thread groove roundness measuring device. In particular, the method and device for measuring the shape of the object to be measured can be accurately measured by eliminating the influence of motion errors in the drive system that moves the probe relative to the object to be measured on the measured values of the displacement measuring device. It has been made possible.

0002

[Prior Art] A shape measuring device such as a roundness measuring device moves the probe of a displacement measuring device relative to the object to be measured, and uses the measurement value of the displacement measuring device to determine the irregularities on the surface of the object to be measured. Generally, these shape measuring devices measure the shape of the object by recognizing it, and because it is necessary to measure surface irregularities over a relatively long distance with high precision, Measurements are taken by moving the probe of the displacement measuring device along a highly accurate slide.

[0003] In such a shape measuring device, in order to prevent unnecessary force from being applied to the slide that guides the relative movement, a configuration is adopted such as using a belt drive or driving the slide via a coupling. ing.

0004

[Problems to be Solved by the Invention] However, when a configuration like the above-mentioned shape measuring device is adopted, such as using a belt drive or driving through a coupling, the damping coefficient of the driving force transmission system is low and The disadvantage is that the rigidity is low and resonance phenomena are likely to occur.Also, even if the driven part and the drive source are rigidly coupled, periodic errors such as ripples in the drive source may occur. In the shape measuring apparatus as described above, periodic positional errors often occur in the relative positions of the object to be measured and the probe due to motion errors of the drive system.

[0005] Such positional errors have a particularly large effect on the measurement values of measuring instruments that measure the shape of slopes, such as thread groove roundness measuring instruments, and it is difficult to accurately measure the shape. had to remove the effects of such position errors.

[0006] In order to deal with such problems, focusing on the fact that position errors occur periodically, a method has been developed that removes components of the same frequency as the position errors by processing the measured values of the displacement measuring device with a notch filter. The shape of the object to be measured was recognized based on the removed value, but simply filtering the measured value would remove all components with the same frequency as the noise, so it would be difficult to identify the shape of the object being measured. The problem is that the truly necessary ingredients contained in the liquid are also lost.

[0007] The present invention was made by focusing on the unresolved problems of the conventional technology, and it is possible to measure an accurate shape by removing only the noise caused by the motion error of the drive system. The purpose of the present invention is to provide a method and apparatus that can perform the following steps.

[0008]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 measures the shape of the object by moving a probe of a displacement measuring device relative to the object. In the shape measuring method, the relative position of the probe with respect to the object to be measured is determined to determine the relative position error between the object and the probe, and the relative position error is determined based on the designed shape of the object to be measured. Calculating the influence on the detected value of the displacement measuring device, correcting the measured value of the displacement measuring device based on the calculated influence, and recognizing the shape of the object to be measured based on the corrected value. do.

Further, in order to achieve the above object, the invention according to claim 2 comprises a displacement measuring device and a relative moving means for moving a probe of the displacement measuring device relative to an object to be measured. In the shape measuring device, a relative position measuring means for measuring the relative position of the probe with respect to the object to be measured, and a relative position error between the object to be measured and the probe are calculated based on the relative position measured by the relative position measuring means. a position error calculation means; an influence calculation means for calculating the influence of the relative position error on the measured value of the displacement measuring device based on the designed shape of the object to be measured; and a correction means for correcting the measured value of the displacement measuring device based on the displacement measuring device.

0010

[Operation] In the invention as claimed in claim 1, the relative position error of the object to be measured and the probe is determined from the actual relative position of the probe of the displacement measuring device to the object to be measured, and is based on the designed shape of the object to be measured. The effect of the relative position error of the object to be measured and the probe on the measured value of the displacement measuring device is calculated, so when the measured value of the displacement measuring device is corrected based on that influence, the measured value can be calculated from the measured value. This means that noise components caused by relative position errors between the object and the probe have been removed.

Since the shape of the object to be measured is recognized based on the corrected value, an accurate shape can be measured in which the influence of the relative position error between the object and the probe is removed. Further, in the invention according to claim 2, the relative position measuring means measures the relative position of the probe with respect to the object to be measured, and based on the relative position, the position error calculating means calculates the relative position error of the object to be measured and the probe. Calculate.

[0012] The influence calculation means calculates the influence of the relative position error of the object to be measured and the probe on the measurement value of the displacement measuring device based on the designed shape of the object to be measured, and calculates the effect calculated. Since the correction means corrects the measured value of the displacement measuring device based on , the noise component resulting from the relative position error of the object to be measured and the probe is removed from the measured value of the displacement measuring device.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a thread groove roundness measuring instrument 1 to which the present invention is applied.First, the configuration of this embodiment will be explained with reference to FIG.

This roundness measuring device 1 is a device for measuring the roundness of the thread groove of a male thread 2 which is a triangular thread as an object to be measured. The probe 4a of the displacement measuring device 4, which measures the radial displacement of the flank of the thread groove of the male screw 2, is moved up and down while the probe 4a of the displacement measuring device 4 is fixed on the rotary table 3 and rotated as shown in FIG. The roundness of the thread groove is measured by recognizing the radial unevenness of the upper and lower flanks of the thread groove of the male screw 2.

The rotary table 3 is connected via a coupling 6 to a rotary drive source 5 composed of an electric motor or the like disposed below the rotary table 3, whereby the rotary drive force of the rotary drive source 5 is transmitted. Receive it and rotate.

On the other hand, the probe 4a of the displacement measuring device 4 is attached to the rotary table 3 while its tip is in contact with the thread groove of the male screw 2.
It moves while being guided by a slide 7 disposed parallel to the rotation axis of the slider, and the movement is performed by a feed screw mechanism 8.

The measured value of the displacement measuring device 4 is supplied to a computer 11 via a low-pass filter 9 for preventing aliasing and an A/D converter 10. Further, in this embodiment, a rotation angle sensor 12 for measuring the rotation angle of the rotary table 3 and a displacement sensor 13 for measuring the vertical position of the probe 4a are provided. Measured values are also supplied to computer 11 .

The computer 11 also includes a displacement measuring device 4 for measuring the radial displacement of the flank of the thread groove of the male screw 2.
The measured value δt supplied from the rotation angle sensor 12, the rotation angle θ of the rotary table 3 supplied from the rotation angle sensor 12, and the displacement sensor 1
Based on the vertical coordinate y of the probe 4a supplied from the probe 3, a predetermined calculation process is executed to determine the roundness of the thread groove of the male screw 2. Note that time will hereinafter be expressed as t.

Next, the operation of this embodiment will be explained. Now, the probe 4a is guided by the slide 7 and smoothly dy/
dt=Moves at a constant rate, d only depends on the rotational speed of the rotary table 3
It is assumed that there is a speed fluctuation of θ/dt=A cosωt. (A, ω: constant) Then, the rotary table 3 and the probe 4
between a and θE (t) = (A/ω) sin
ωt
...A positional synchronization error corresponding to (1) will occur.

As a result, as shown in FIG. 2, the male screw 2, which should normally be in the position indicated by the chain line at time t, is
It will be rotated by θE (t) extra and will be at the position indicated by the solid line, and the slope of the measured flank with respect to the horizontal plane will be reduced to 1/α (see the upper right corner of Figure 2), and the lead of the thread groove will be changed to L.
(See Figure 2), the measured value δt of the displacement measuring device 4
(t) is affected by the synchronization error mentioned above, (θE /2π)Lα=(α/2π)
This includes an error of L(A/ω) sin ω (2).

Therefore, the measured value δt (t
) By removing the above-mentioned error from , it is possible to recognize the accurate shape of the male thread 2 from which the influence of speed fluctuations of the rotary table 3 has been removed.

Since the frequency ω component is delayed by the low-pass filter 9 by a time Δt(ω) which is known from the filter characteristics, the true measured value δR of the flank after removing the influence of the speed fluctuation of the rotary table 3 (t) is δR (t) = δt (t) −
(αL/2π)θE (t-Δt)...(3)
becomes.

Incidentally, the flank inclination α can be determined from the designed shape of the male screw 2, and the positional synchronization error θE (t) between the rotary table 3 and the probe 4a can be determined by the rotation angle sensor 1.
The difference Δθ(
t), and the delay time Δt may be determined by using the delay of the most significant component of Δθ(t) determined as the position synchronization error.

Therefore, the true measured value δR (t) is
δR (t) = δt (t) − (α
It can be obtained as L/2π)Δθ(t−Δt) (4).

In addition, if there is periodic velocity fluctuation only in the velocity dy/dt of the probe 4a, the vertical coordinate y of the probe 4a measured by the displacement sensor 13 and the vertical coordinate of the probe 4a that should exist at the same time. Tokara probe 4
If we find the synchronization error Δy(t) at the position a and use the delay of the most significant component of the synchronization error Δy(t) at that position as Δt, the true measured value δR (t) is calculated as δR (t) = δt (t) −α
Δy(t−Δt)……(
5).

Furthermore, the rotary table 3 and the probe 4a
Even if there is a speed fluctuation in both, the total synchronization error ΔS(t) (=Δy(t
) +(L/2π)Δθ(t) ) can be approximated only by prominent frequency components ω, then the true measured value δR (t
) is δR (t) = δt (t
) −αΔS(t−Δt)
...It can be obtained as (6).

FIG. 3 is a graph showing an example of the effects of this embodiment. That is, the resonance frequency of the rotary table 3 and the drive system is 6.6Hz, and the cutoff frequency of the low-pass filter 9 is 25Hz.
Hz, when using a secondary filter with an attenuation constant ζ = 0.6, when the delay time Δt was set to 7 msec and the measured value of the displacement measuring device 4 was corrected, as shown in Figure 3, when no correction was made at all. (See FIG. 4), the influence of resonance of the rotary table 3 is removed, and the accurate shape of the male screw 2 can be grasped.

Moreover, this embodiment has the advantage that there is no risk of data necessary for grasping the shape being lost, unlike the conventional method in which filter processing is simply performed. In this embodiment, the rotary table 3, the rotary drive source 5, the coupling 6, and the feed screw mechanism 8 constitute a relative moving means, and the rotation angle sensor 12 and the displacement sensor 13 constitute a relative position measuring means. The process of calculating position synchronization errors Δθ(t) and Δy(t) in the computer 11 corresponds to the position error calculation means, and the computer 11
The processing based on the above equation (2) in corresponds to the influence calculation means, and the processing based on the above equation (4) and (5) in the computer 11
) and (6) correspond to the correction means.

[0029] In the above embodiment, the present invention was applied to a device for measuring the roundness of the thread groove of the male screw 2. It is applicable not only to a combination of a dynamic system and a rotational system but also to a combination of linear motion systems, for example.

Furthermore, in the above embodiment, the case where a triangular screw is used as the object to be measured has been explained, but the present invention is not limited to this. For example, even if the slope (
dδ/dy) is used as α, or δ
The same effect can be obtained by finding (Δθ, Δy) from the design values and using it as αΔS.

[0031]

[Effects of the Invention] As explained above, according to the present invention,
Find the positional error between the object to be measured and the probe, calculate the influence of that positional error on the measured value of the displacement measuring device, and
Since the measured value of the displacement measuring device is corrected using the calculated influence, it is possible to eliminate the influence of the movement error of the drive system on the measured value, and it is possible to grasp the accurate shape of the object to be measured. This has the effect that there is no risk of data loss.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of this embodiment.

FIG. 3 is a graph explaining the effects of this embodiment.

FIG. 4 is a graph showing measured values without correction.

[Explanation of symbols]

1 Roundness measuring device (shape measuring device) 2
Male thread (object to be measured) 3
Rotary table 4 Displacement measuring device 4a Probe 11 Computer 12 Rotation angle sensor 13 Displacement sensor

Claims (2)

[Claims] 1. A shape measuring method in which a probe of a displacement measuring device is moved relative to an object to be measured to measure the shape of the object, the method comprising measuring the relative position of the probe to the object to be measured and measuring the shape of the object. Determining the relative position error of the object to be measured and the probe, calculating the influence of the relative position error on the detected value of the displacement measuring device based on the designed shape of the object to be measured, and based on the calculated influence. A method for measuring a shape, comprising: correcting a measured value of the displacement measuring device, and recognizing the shape of the object based on the corrected value. 2. A shape measuring device comprising a displacement measuring device and relative moving means for moving a probe of the displacement measuring device relative to the object to be measured, wherein the relative position of the probe with respect to the object to be measured is determined. a relative position measuring means for measuring; a position error calculating means for calculating a relative position error between the object to be measured and the probe based on the relative position measured by the relative position measuring means; influence calculation means for calculating the influence of the relative position error on the measured value of the displacement measuring device based on the influence calculation means; and correction means for correcting the measured value of the displacement measuring device based on the influence calculated by the influence calculating means; A shape measuring device characterized by being provided with.