JPS60107511A - Measuring method of straightness - Google Patents

Abstract

PURPOSE:To grasp a straightness shape in detail by installing three detectors which measure the distance from an object of measurement on a detector mount base at equal intervals, obtaining a measured value for every movement distance, and obtaining the straightness shape from data obtained by specific arithmetic. CONSTITUTION:Three displacement detectors A, B, and C are arranged on the detector mount base 3, and measured values are obtained at intervals of movement distance l/2 while the detectors are moved as shown by an arrow. Consequently, straightness errors are calculated at measurement objective points (ai) (i=2, 3, 4...) from one measurement data group of data obtained at the measurement objective points (ai) (i=0, 1, 2...). Similarly, straightness errors are obtained at measurement objective points (bi) (i=2, 3, 4...) from one measurement data group at measurement objective points (bi) (i=0, 1, 2...). The straightness shape of the object 1 of measurement is grasped in detail from the straightness errors at couples of measurement objective points.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a practical method for simultaneously measuring the straightness of an object to be measured, the straightness of a moving guide surface, and pitching during movement.

In recent years, with the increasing demand for higher precision in machine tools, the straightness control of guide surfaces (sliding surfaces) has become an important issue, and it is desirable to make its measurement easier. It is rare. The conventional method of measuring straightness is
Methods using a reference bar such as a straight edge, a piano wire as a reference straight line, or an autocollimator are known, and recently a method using an independent optical coordinate system using laser light has also been developed.

However, all of these methods require considerable preparation and skill for measurement work, are inefficient, and are susceptible to adverse effects from various noises, making them difficult to put to practical use in the field. Many problems remain.

As a new method for measuring the straightness of a vine that solves these problems, three displacement detectors are moved along the object to be measured.
The present inventors have reported a method of simultaneously measuring the straightness of the object to be measured and the straightness of the moving guide surface of the position detector from the measured values by these displacement detectors. (% patent application No. 57-1675611' - Straightness measurement method)
61), as shown in FIG. Three displacement detectors A and B measure the distance to object 1.

C at equal intervals in the moving direction of the detector mount 3! Install it with.

Then, while moving the detector mounting base 3 in the direction of the arrow in the figure, the distance υ from the surface of the object to be measured 1 is measured every movement distance l that is equal to the distance e between the displacement detectors A, B, and C. DKA respectively.

DKB', DKO (K = 0, 1, 2, -
). At this time, using the representative points for each distance e, the straightness of the measuring object 1, the straightness of the guide surface 2, and the pitching of the detector mount 3 are determined as YK, Xic, and 0K, respectively.
K=0.1,2. ...).

Incidentally, the pitching of the detector mount 3 is considered with the displacement detector A as a reference.

Here, as shown in FIG. 2, the straightness tA of the guide surface 2 at the measurement start position! ' e Measured values of B and C't DOA
r poBI I) oo and the measured value fi at the th measurement position? D.K.A.

DKB, DKO,K + If the measured value at the i-th position is DK+iA+DK+iB I DK+i0, then 1
From the figure, the linear equation tll (21 (31) holds true.

DKA-YK XK = DOA ・・・・・・・・・
...(1) DKB Yx+x XK l"θK =
I) 013 yIX o −(21DKOYK+2
K2(1-f)1<=DOOYt

2DKB-2+DoB-DKO+DOO=XK+2YK
+I YK+2-2 Y, +Y, - person...(4)
Also, in the +11 formula, +1. By substituting YK+□ and YK+2 obtained by setting → to +2 into equation (4), the following equation (5) is obtained.

XK+2=26XK+I XK 2DK+IA+DK+
2 people + 2DKBDKO + DGA 2'D6B + I)o□
+Xo+2Y, Yt ・= (5) Furthermore, equation (2), (
Using YK+2 obtained from equation 5) and equation (1), the following equation (
61, (71 are obtained.

yK+2=XK+2+DK+2A DOA”・(6
) That is, K=0.1, 2. Measured values of displacement detectors A, B, and C at positions DKA r DKB + DK
Using O, the straightness curve Y of the measuring object 1, the straightness curve X of the guide surface 2, and the pitching of the detector mount 3 are calculated sequentially from the above equations (5), (6), and (7). Therefore, θ can be calculated.

In this way, according to the present method, the rise and fall of the detector mount 3 when the detector mount 3 moves along the guide surface (
This makes it possible to perform highly accurate measurements that take into account not only the influence of longitudinal fluctuations (pitching) in the longitudinal direction, but also the effects of pitching in the longitudinal direction.

In this example, the case where the object to be measured 1 is stationary and the detector mount 3 is moved is explained, but conversely, the detector mount 3 is moved.
The above (5) also applies when the measurement object 1 is moving and the object 1 is stationary.
Equations (6) and (7) can be applied.

Next, a specific calculation method will be explained. As seen from the above equations (5), (6) and (7), using XK (K=2, 3, 4...) obtained from equation (5), Y
K is calculated, and pitching θK is determined from these values. Therefore, a specific application method of this formula (51) will be explained.

In Equation (5), is the straightness error at the measurement start position, and DOA + DOBr I)oo are both displacement measurement values at the measurement start position. Therefore, if the initial setting value of each displacement detector A, B, and C is 0, then
= DQA=DOB=DOO=0.

Under this assumption, K=0.1, 2. ..., XK+2 for n is as follows.

Xt= 2X, -0-2-DIA+D2A+O-0+2
Y, -Y.

M=2X, -X, -2・D2A+D3A +2・'D
I B DI O+2YI Y2Xn+2=2Xn+1
-Xn-2・Dn+1 person 10Dn+2 people+2・DnB-D
o.

+2Y'+ Yz However, Xl, Y, , Y, are expressed by formula (5) and (6
) cannot be fitted into the recurrence formula of the equation.In order to fit the straightness curve X, these values must be estimated in some way or their influence must be removed There is a need to.

Therefore, (in formula 51, X1=α, 2Y, -Y,
=β, the following equation (8) holds true.

Straightness error (true value) at XKSKth position CKs
Straightness error (calculated value) at the Kth position Also, this CK
is the measured value DNA by equation (5) assuming α = β = 0.
IDKI31 This is the value calculated from DKO.

Here, if we consider the straightness error as ``the deviation from the virtual straight line that minimizes the root mean square value of the error at each measurement point,'' then we can calculate the straightness error using equation (8) above. can be set using the following steps.

(1) Set CK for K=2 + 3 + 4 + ・= + 1.

(it) (Find α and β that minimize the root mean square value of XK expressed by the at formula.

Now, β can be calculated relatively easily using the least squares method using the following formula +9
1 (Can be determined in II.

However, = Σ', r, = Σ - r, = Σ 4° K = 2 - 2K - 2 δ1 = Σ (K - CK), δ,; Σ (K''・cK)K
-2 to -2 (it+) (α, β and (1
) Calculate XK from CK using equation (8).

This k becomes the straightness error as a deviation from the virtual straight line such that the root mean square value of the error at each measurement point is minimized.

On the other hand, the straightness curve of the object to be measured 1 can be determined by substituting xK into equation (6), and the pitching of the detector mount 3 can be determined by substituting YK and XK into equation (7).

As can be seen from the above explanation, the method explained based on FIG.
Due to the limitations of the calculation method, there is a drawback that only values (straightness errors) at discrete points for each distance wlj, e can be determined. That is, in order to grasp the detailed straightness shape of the measurement object 1 or the guide surface 2, three displacement detectors A, B,
It is necessary to reduce the mounting interval e of C and perform measurements and calculations in fine steps. However, reducing the mounting interval e tends to be constrained by the dimensions of the detector, the dimensions of the detector mounting base 30, etc., and it is difficult to reduce e sufficiently.

SUMMARY OF THE INVENTION An object of the present invention is to provide a straightness measuring method that eliminates the above-mentioned drawbacks and makes it possible to grasp straightness in detail.

The configuration of the present invention to achieve such an object is such that one of the detector mount and the object to be measured measures the distance between the object and the detector mount, which moves along a guide surface.
The three detectors are installed at equal intervals e in the movement direction, and the measured values of the three detectors at the measurement start position are obtained. A I DQB + Doo, move the detector mount or the object to be measured every interval e to obtain the measured value of the detector each time, and calculate the measured value at the Kth measurement position as DKA r DKB. r DKO, the guide surface straightness error at the measurement start position is M, that at the first position is Xl, the straightness error of the object to be measured at the first position is Yl, and that at the second position is Y2 and K+
Straightness error of the guide surface at the second position XK +2
Xx+z=2+Xx+I XK 21Dx+xA+D
x-+-z people+2"DKn-DKQ+2-Y, -Y2, and the value of XK+2 calculated for K=0, 1, 2,... is the value of X and Yl are calculated as follows.

The straightness of the guide surface is estimated and calculated by correcting it with a value related to Yl, and +□ is added to the straightness YK+2 of the object to be measured at this position and the amount of longitudinal vibration θ due to movement, respectively, by YK. 10Q = XK+2+DK+2 In the method of measuring straightness calculated by a person, the measured value of the detector is obtained for each moving distance e/N of the detector mount or the object to be measured, and thereby DKA, DKB
+DKO (K=0', '1, 2-), and each data group 1 (from -,
The present invention is characterized in that it includes N sets of guide surface straightness XK and straightness YK of the object to be measured, and determines the overall detailed straightness shape from these N sets of straightness shapes XK and yK.

A straightness measuring method according to an embodiment of the present invention will be explained below with reference to FIG. FIG. 2(a) is a diagram showing the measurement method according to the present invention, and the same numbers as in FIG. 1 indicate the same items. Note that for simplicity, the guide surface 2 has been omitted. In FIG. 2(a), al(1==Q l 1
+2+...) is a set of measurement object point sequences on the measurement object 1, set at equal intervals of 6f and 1'r. bi(i)
=o, 1.2.

...) is another set of measurement target point sequences, which are similarly set at equal intervals e. The separation between ai and bi is set to e/2 as shown in Figure 11.

As shown in the figure, there are 3 displacement detectors A and B on the detector mount 3.
, C are placed, and while moving in the direction of the arrow in the figure, a measured value is obtained for each moving distance %. Measurement target point sequence a1 (1=(1
, 1, 2, . . . ) by applying the method of 167561/1987 to a set of measurement data for the measurement target points ae (i=2.3, 4, . . . ). ) can be used to account for straightness errors. Similarly, measurement target point sequence b
From one set of measurement data group for i (i=0, '1, 2...), the measurement target point bi (i=2.3.4...)
Straightness error can be reduced.

Thus, as shown in FIG. 2(b), the detailed straightness shape of the measurement object 1 can be grasped from the straightness errors at these two sets of measurement object points.

The method for synthesizing straightness errors at two sets of measurement points is as follows:
For example, from the straightness error at the measurement target point ai, the positions corresponding to the start and end points of the measurement target point bi (the first and last points for which the straightness error is calculated, for example b and bn) A possible method is to calculate the straightness error at point bi by converting the straightness error at the start point and end point of bi to a value within the range. In addition, in FIG. 2(a), the case of two sets of measurement object point sequences ai + bi was explained, but the measurement object point sequence ai of the 7'CN set set in the middle of trouble, ai, Similar measurement and calculation processing is possible for b s + Ci... Of course, in this case, it is sufficient to obtain N sets of measurement data for each moving distance and apply the method of Japanese Patent Application No. 167561/1983 to the N sets of data sets.

As described above, according to the present invention, it is possible to grasp the straightness shape of the object 1 to be measured in detail with a fine pinch.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the prior art. FIGS. 2(a) and 2(b) are explanatory diagrams for explaining the present invention in detail. In the drawings, 1 is an object to be measured, 3 is a detector mounting base, and A, B', and C are displacement detectors. Patent applicant: Mitsubishi Heavy Industries, Ltd. Patent attorney: Shibu Mitsuishi (and one other person)

Claims (1)

[Scope of Claims] Three detectors for measuring the distance to the object to be measured are installed on the detector mount, in which one of the detector mount and the object to be measured moves along a guide surface. They are installed at equal intervals l in the movement direction, and the measured values of the three detectors at the measurement start position are respectively DOA + DOB t I)oo,
The detector mount or the object to be measured is moved every interval e to obtain the measured value of the detector each time, and the measured value at the Kth measurement position is DKA. Set DKB I DKO, enter the guide surface straightness error t-Xo at the measurement start position, that at the 1st position, and set the straightness error of the object to be measured at the 1st position as Y2. Taking it to the right, the straightness error XK+2 of the guide surface at the K+2nd position is XK+2°2°XK+I XK 2
6Dx+1 person+DK-1-2 people+2ΦKB-DKO+2
Calculated by 1Xゞη, K'=o, 1, 2. ,
Xl and Yl are obtained by calculating the value of XK+2 calculated for ... so that the square of the straightness error and the average value are minimized. The straightness of the guide surface is estimated and calculated by correcting it with a value related to Y2, and the straightness of the measurement object at this position YK+2 and the amount of vertical vibration in the longitudinal direction due to movement θ
+2 to each YK+2 = XK+2 10DK+
2 In the straightness measurement method calculated by A, the measured value of the detector is obtained for each travel distance G bag of the detector mounting base or the object to be measured, and thereby DKA r D
Obtain N sets of data groups consisting of KB + DKO (K = O,, 1, 2・-), and each data group! (from , N sets of guide surface straightness XK and straightness of measurement object YK
A straightness measuring method characterized in that the overall detailed straightness shape is determined from these N sets of straightness shapes XK and YK.