JPH0352801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape measuring method, particularly a shape measuring method using magnetic force.

With the diversification and complexity of product shapes and the advancement of product processing and assembly technology, the importance of shape measurement for free-form surfaces is increasing, and in particular, it is possible to easily and efficiently measure the normal direction and displacement of free-form surfaces. It is desired to develop a method for measuring this.

Generally, the method of measuring a free surface is to bring a contact into contact with the object to be measured, but this method easily scratches the surface to be measured, is directional, and does not introduce errors due to friction. For certain reasons, accuracy is low and continuity cannot be achieved.

Therefore, a non-contact method is preferable for this type of shape measurement; for example, there is a method of calculating the normal direction of a point on a curved surface from the coordinate values of three points near the normal.
This method has the disadvantage of being impractical because it requires measurement and calculation of a large number of points. It is also possible to arrange three displacement gauges at the vertices of an equilateral triangle, or use a sensor in which two displacement gauges are movable in one force direction such as the Z direction, but from the viewpoint of ensuring accuracy, the sensor The disadvantage is that the head of the device cannot be made small, making the device large, and local changes in curvature cannot be measured. In addition, there is an optical type that uses a lens, mirror, and light receiving element, but there is a problem in that the reflectance changes slightly depending on the irregularities of the object to be measured, resulting in large errors.

The present invention was created through repeated research and experiments in order to solve the problems of the conventional shape measurement method as described above, and its purpose is to detect the normal direction of a three-dimensional free-form surface, Simultaneous detection of the distance and angle to a curved surface, detection of the inclination direction and angle of a straight surface, or even the detection of the center and direction of a hole can be easily and continuously performed.The sensor structure is extremely simple, and the Yansa head can be made compact. The object of the present invention is to provide a shape measuring method of this type that can also follow local curvature changes.

To achieve this objective, the present invention focuses on the fact that the stress acting on the discontinuous interface between different magnetic materials has only a component perpendicular to the surface, and is oriented from the side with higher magnetic permeability to the side with lower magnetic permeability, This is used to measure the shape using a magnetic force method, that is,
The feature is that a magnet is brought close to a surface to be measured made of a ferromagnetic material, and shape detection is performed by measuring the displacement caused by the magnet being attracted in the normal direction of the surface to be measured. .

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 show examples of sensors obtained by applying the shape measuring method according to the present invention, in which 1 is an object to be measured, and at least a surface 1 to be measured is shown.
1 is made of a ferromagnetic material such as iron. 2 is a magnet, and although a permanent magnet is used in the illustrated example, it is of course possible to use an electromagnet. In terms of angle measurement accuracy, the magnet 2 should have a cross-sectional area that does not create a moment at the tip of the sensor.
It is preferable to use a needle-like shape or a shape close to this instead of a disk-like shape as shown in the figure. It is desirable that the magnetic flux density be as high as possible from the viewpoint of sensitivity.

Reference numeral 3 denotes a support body that supports the magnet 2 and makes it face the surface to be measured 11 in a non-contact manner, and transmits the displacement of the magnet to a displacement meter to be described later. A rigid structure consisting of a vertical beam 31 that is about to rise is used, and a magnet 2 is attached to the tip of the vertical beam 31 by any method such as gluing, and the horizontal beam 30 is fixed to a support 6 such as an arm. It's summery. The embodiment shown in FIG. 3 is a flexible support, that is, a support with a structure that supports the magnet within a certain range, but allows the magnet to move freely within that range. A magnet 2 is attached, an enlarged portion 10 is provided in the middle of a vertical beam 31, and this is supported by a static pressure type or other air bearing 9 so as to be able to swing, translate, and rotate.

4 is a means for measuring the displacement caused by the magnet 2 being attracted in the normal direction of the surface to be measured 11, and is a means for measuring the displacement caused by the attraction of the magnet 2 in the normal direction of the surface to be measured 11, and can be a contact type or non-contact type such as a strain gauge, a piezoelectric element, a photoelectric element, an eddy current, a differential transformer, etc. You can use elements of type.

In this embodiment, a three-component force meter or something equivalent is used as the displacement measuring means, and in FIGS. , 5c, and 5d are attached to detect the inclination, and a plurality of contact displacement meters 6a, 6b, 7a, and 7b are also arranged on the cross beam 30, and these are used to detect displacement in the axial direction. In the embodiment shown in FIG. 3, non-contact or contact type displacement gauges 5, 6, and 7 are arranged on the vertical beam 31' behind the air bearing 9.

Therefore, in the present invention, the magnet 2 is attached to the support 3 and the magnet 2 is brought close to the surface to be measured 11. When the surface to be measured 11 is made of a ferromagnetic material, as mentioned earlier, the stress acting on the discontinuous interface between different magnetic materials has only a component perpendicular to the surface, and the stress is distributed from the side with higher magnetic permeability to the side with lower magnetic permeability. Since the magnet 2 is oriented toward the surface 11, the magnet 2 is always attracted in the normal direction of the surface 11 to be measured. Therefore, by measuring the displacement of the magnet 2 due to this attraction, the distance and inclination from the curved surface can be simultaneously detected using a single thin sensor structure.

That is, in the embodiments of FIGS. 1 and 2,
If Z is the distance between the surface to be measured 11 and the tip of the magnet 2, Z' is the axial displacement of the sensor axis, that is, the support 3, and θ ₁ and θ ₂ are the inclinations from the normal of the support 3, then Z The tensile force Pz′ in the ′ direction is measured by displacement meters 5a to 5d,
The forces Pθ ₁ and Pθ ₂ in the θ ₁ and θ ₂ directions are respectively
a, 6b, 7a, 7b.

The magnitude of 〓 that magnet 2 receives from the curved surface is Z and θ ₁ ,
It is a function of θ ₂ , and if θ ₁ and θ ₂ are held constant, Z can be found from the absolute value of 〓. For θ and θ, the components of 〓 are given by (Pz, Pθ ₁ , Pθ ₂ ),
Since the direction of the attraction force 〓 coincides with the normal direction, the inclinations θ ₁ and θ ₂ of the sensor axis can be determined from the following equations.

θ ₁ = tan ^-1 (Pθ ₁ /Pz), θ ₂ = tan ^-1 (Pθ ₂ /Pz) Figure 4 shows the experimental setup for examining the basic characteristics of the measurement method according to the present invention. 1
A rotary table 13 is placed on the rotary table 2, the object 1 to be measured is fixed to the rotary table 13, and a support body 3 to which a magnet 2 is attached is fixed by a support base 8.

In this experimental device, the vertical beam 31 and the horizontal beam 30
A 5 mm square aluminum material is used, a hole is drilled in the appropriate place, a circular hole load cell is attached, and a 2 mm thick, 8 mm diameter, residual magnetic flux density is attached to the tip of the vertical beam 31 via an iron holder 14 with a diameter of 9 mm. Equipped with a 10 kilogauss rare earth permanent magnet. The length from the rear beam to the tip of the magnet is 89.5mm.

Figure 5 shows the results of measuring the relationship between displacement Z and Z-axis output with θ=0 for an object to be measured with a thickness of 15 mm and material S45C. It can be seen that the distance from the surface to be measured can be measured.

Figure 6 takes Z′ as a parameter, and the inclination angles θ ₁ and θ ₁
This is the result of measuring the relationship between the shaft outputs, and this sixth
From the figure, the tilt angle can be measured by the output in the θ direction,
It can be seen that the smaller Z' is, the better the sensitivity is. The effect of own weight could be ignored because the weight of the sensor head was small at 2 gf.

In Figure 7, based on Pz' and Pθ ₁ measured at Z' = 1 mm, the actual inclination angle θ ₁ is plotted on the horizontal axis, and the inclination angle tan ^-1 (Pθ ₁ /Pz') measured by the sensor is plotted as a point. In the figure, the solid line is the theoretical value of tan ⁻¹ (Pθ ₁ /Pz′)=θ ₁ . It can be seen from FIG. 7 that the inclination angle of the surface to be measured can be measured while keeping Z at an arbitrary value.

Figure 8 shows the data obtained by measuring the influence of the plate thickness of the object to be measured, and Figures 9 and 10 show the data when the plate thickness is constant (15
mmt), the sensor characteristics due to changes in material were measured. These figures 8 to 10
From the figure, the experimental sensor has a plate thickness of approximately 0.9 mm.
If the properties are above, constant properties can be maintained regardless of the material, and this can be said to be a convenient property when applied to welding by a 5-axis laser processing machine, robot, stud welding, etc.

Since the present invention has the above characteristics,
It is possible to detect the normal direction of a curved surface made of ferromagnetic material, and simultaneously detect the distance and inclination from the curved surface.
It is possible to measure corners and corners, as well as detect the center and direction of holes.

Next, specific examples of the present invention will be shown.

Example 1 The shape of a curved surface was measured using the experimental apparatus shown in FIG. In the experiment, the relative movement between the surface to be measured and the magnet was obtained by moving the X-axis scale of the XY table at a constant pitch. At this time, the Y-axis and the rotation angle were adjusted so that Pz' was constant and Pθ was oriented toward O, that is, the normal direction.

FIG. 11 shows the measurement results for the R35 concave surface, and FIG. 12 shows the measurement errors. 1st
In Figure 2, the deviation from the set value Z ₀ = 1 mm is ΔZ
=Z-Z ₀ , the deviation from the normal direction is set as Δθ with the clockwise direction being positive, and ΔZ is determined according to the arc length S along the measurement surface.
We looked at the changes in Δθ. Good results were obtained even though the magnet was relatively large with a diameter of 8 mm.
The measurement accuracy is reduced by using a magnet, and the sensitivity of the 3-component force meter is reduced (the prototype sensor reduces strain below 50μstrain).
This can be easily improved by increasing the curvature, and it can be fully applied even when the curvature is large. Even in its current state, it is effective as a sensor when it is necessary to form a certain angle with a curved surface and maintain a certain distance (especially in the normal direction).

Figure 13 shows the corner of the RO according to the present invention, and Figure 14 shows the corner of the RO.
This shows the results of measuring each RO corner, and shows that corners and corners can be easily detected.

Example 2 The position and direction of the central axis of a hole were measured according to the present invention. Figure 15 shows the measurement method and principle.
1', and the magnet 2 is inserted into the ellipse 11' via the support 3. Since the magnet 2 is attracted in the normal direction of the hole curved surface, θ corresponding to the amount of eccentricity
If there is an axial output and the sensor axis is tilted, moving by Z in the axial direction will change the θ-axis output. Therefore, if the θ-axis output is set to 0, the center of the hole can be easily detected. 1st
Figure 6 shows the relationship between eccentricity and output, and it can be seen that the narrower the oval width dimension, the better the sensitivity.

The direction of the hole was detected according to the present invention.

Figure 16 shows the measurement method and results. Magnet 2 is inserted into a hole of b = 10 mm to the required depth (Z = -7.5 mm) through support 3, and magnet 2 is moved in this state. do. As a result, the θ-axis output changes, so the inclination of the hole from the central axis can be immediately detected.

When using the shape measuring method of the present invention as explained above, since it is a non-contact method, there is no need to worry about scratching the surface to be measured or errors caused by friction, and it is possible to continuously measure surfaces including the normal direction of curved surfaces and straight surfaces. It is possible to simultaneously detect the distance and inclination from the hole surface, etc., yet only one beam is sufficient, and the sensor head can be made small, making the sensor structure extremely simple and compact. It is possible to freely respond to changes in

The measurement method of the present invention uses the probe of a three-dimensional measuring machine, as well as processing machines and robots such as multi-axis laser processing machines, welding robots, and assembly robots that need to move with their wrists pointing in the normal direction and keeping a constant distance. It can be applied to a wide range of applications such as sensors in certain cases.

[Brief explanation of drawings]

FIG. 1 is a front view showing one embodiment of a sensor obtained by applying the magnetic shape measuring method according to the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a plan view showing another embodiment. , FIG. 4 is a perspective view of a measurement experiment apparatus using the sensors shown in FIGS. 1 and 2, FIG. 5 is a graph showing the relationship between displacement from the surface to be measured and output in the present invention, and FIG. A graph showing the relationship between the inclination from the linear direction and the output, FIG. 7 is a graph showing the inclination angle measurement results according to the present invention, and FIG. 8 is a graph showing the relationship between the thickness of the object to be measured and the maximum value of the output. 9 and 10 are graphs showing the relationship between the material of the object to be measured and the displacement characteristics of the magnet, FIG. 11 is a diagram showing the measurement results of a free-form surface according to the present invention, and FIG. A graph showing the measurement error, FIG. 13 is a diagram showing the corner measurement results according to the present invention, FIG. 14 is a diagram showing the corner measurement results according to the present invention, and FIG. 15 a,
b is an explanatory diagram showing the method of measuring the position and direction of the center axis of a hole according to the present invention, FIG. 16 is a graph showing the relationship between eccentricity and output when detecting a hole according to the present invention, and FIG. 3 is a graph showing the results of detecting the direction of a hole according to the present invention. 1...Object to be measured, 2...Magnet, 3...Support,
4... Means for measuring displacement, 11... Surface to be measured.

Claims (1)

[Claims] 1 Shape detection is performed by bringing a magnet close to a surface to be measured made of ferromagnetic material and measuring the displacement of the magnet due to attraction of the magnet in the normal direction of the surface to be measured. A magnetic shape measurement method characterized by: 2. The magnetic shape measuring method according to claim 1, wherein the displacement of the magnet is measured using a three-component force meter or similar means. 3. The magnetic shape measuring method according to claim 1, which uses a permanent magnet as the magnet. 4. The magnetic shape measuring method according to claim 1, which uses an electromagnet as the magnet.