JPH04252911A - Three-dimensional measuring apparatus - Google Patents

Abstract

PURPOSE:To correctly correct a probe diameter and accurately measure a model shape. CONSTITUTION:When a probe 10 comes into contact with a model 7, a touch signal is output from a touch sensor 5. Robot positions for moving the probe 10 are measured by position measuring devices 1a, 1b,...1N. The probe center coordinate is calculated by calculators 2, 3 from the robot positions when the touch signals were output. A virtual plane calculator 4 calculates a virtual plane which is approximate to a plane including a point which is being measured. A probe diameter correcting device 6 shifts the calculated center coordinate of the probe along a perpendicular direction to the virtual plane by a radius of the probe toward the virtual plane, making the shifted coordinate a model surface coordinate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a three-dimensional measuring machine,
This allows the model shape to be measured with high accuracy.

0002

2. Description of the Related Art First, the outline of a conventional three-dimensional measuring machine will be explained with reference to FIG. The member 8X of the three-dimensional robot 8 moves in the X direction, the member 8Y moves in the Y direction, and the ram 8Z moves in the Z direction.
Move in the axial direction. A touch sensor 5 and a spherical probe 10 are attached to the ram 8Z. The touch sensor 5 outputs a touch signal when the probe 10 contacts the measurement model 7. The three-dimensional robot 8 is also equipped with axis position measuring devices 1a, 1b, and 1c to detect the position of the robot 8. To measure the model shape, probe 10
is brought into contact with the measurement model 7, and each axis position measuring device 1a, 1b
, 1c.

Next, the calculation section for determining the model shape is
This will be explained with reference to FIG. However, in FIG. 4, a case will be described in which the three-dimensional robot has an N axis. Each axis position detector 1a, 1b, . . . , 1N is formed of an optical scale or the like, and measures the position of each axis. The machine position calculator 2 is
Based on the data of each axis position measuring device 1a, 1b, ..., 1N,
The coordinate position of the touch sensor 5 is determined. When the probe 10 contacts the measurement model 7, the touch sensor 5 outputs a touch signal. The touch position calculator 3 calculates the center coordinates of the probe 10 from the coordinate position output from the machine position calculator 2 at the time the touch signal is output. The probe diameter corrector 6 corrects the calculated center coordinates of the probe 10 by shifting them toward the model by the radius of the probe 10, and calculates the corrected coordinates as model surface coordinates.

0004

[Problems to be Solved by the Invention] However, conventional three-dimensional measuring instruments have the following problems. That is, FIG. 5(a)
As shown in the figure, the probe 10 at the tip of the touch sensor 5 is brought into contact with the model surface 9, but even though the coordinates that are actually desired are point A on the model surface 9, the touch position calculator 3 The obtained coordinates are the coordinates of the probe center B. Therefore, point A on the model surface must be found by correcting the probe diameter r in a direction perpendicular to the model surface from point B. However, since coordinate measuring machines generally handle unknown shapes, the direction perpendicular to the model surface is not determined, and as shown in FIG. 5(b), the probe 10 comes into contact with the surface. Correction is performed with the immediately preceding probe direction as the perpendicular direction. Therefore, if the approach is not made perpendicular to the plane as shown in FIG. 5(b), a shifted point A will be obtained instead of the actual point A on the model.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a three-dimensional measuring machine that can accurately correct the probe diameter and measure the shape of a model with high precision.

[0006]

[Means for Solving the Problems] The configuration of the present invention that achieves the above object is a three-dimensional measuring machine that measures the shape of a model by bringing a spherical probe provided at the tip of a three-dimensional robot into contact with the model, contact detection means for detecting that the probe has contacted the model; position measurement means for measuring the position of each axis of the three-dimensional robot; and each axis of the three-dimensional robot at the time when it is detected that the probe has contacted the model. A position calculation means that calculates the center coordinates of the probe at that time from the position, and a virtual virtual device that approximates the surface including the current measurement point from multiple measurement points that have already been measured near the point currently being measured. The virtual surface calculation means for calculating the surface and the calculated center coordinates of the probe are moved toward the virtual surface by the radial length of the probe along the perpendicular direction perpendicular to the virtual surface, and the moved coordinates are It is characterized by having a probe diameter correction means that uses the coordinates of the probe surface.

[0007]

[Operation] The virtual surface calculator uses the currently measured point and several points in its vicinity among the already measured probe diameter center positions (
(minimum 2 points). A virtual surface (generally a flat surface is acceptable, but also includes a curved surface) is determined, and the perpendicular direction of the virtual surface at the measurement point is determined. As a result, the perpendicular direction can be determined more accurately regardless of the approach direction of the touch sensor, and measurement accuracy can be improved.

[0008]

[Examples] Examples of the present invention will be described below. Note that the same reference numerals are given to parts that perform the same functions as those in the prior art. Figure 1
shows an example of the present invention. Each axis position measuring device 1 shown in the figure
a, 1b, . . . , 1N are position sensors such as optical scales, and detect the position of the touch sensor 5. The machine position calculator 2 determines the position of the touch sensor 5 on the machine based on the position information from each axis position measuring device 1a, 1b, . . . , 1N. The touch position calculator 3 uses the coordinates from the mechanical position calculator 2 and the touch signal from the touch sensor 5 to determine the center coordinates of the probe 10 when the touch sensor 5 contacts the model.

As shown in FIG. 2, the virtual surface calculator 4 selects the point E currently being measured from the nearby measurement points C and D that have already been measured.
A virtual plane P is calculated in the vicinity of , and the perpendicular direction T at the measurement point is calculated.
seek. Along this surface perpendicular direction T, the probe diameter corrector 6 performs probe diameter correction to find measurement points on the model surface. Calculation is performed so that the surface approximates the actual surface including the virtual surface P and the point E.

[0010] Although this is a virtual surface, if there are three measurement points, a plane can be obtained, and if there are more points than that, a curved surface containing each point can be determined by three-dimensional interpolation. can do. The present invention does not specify these aspects.

Although the present invention cannot be applied if there are no measurement points nearby, the measurement points are generally placed to such an extent that points on the model surface can be interpolated on a plane, so there is no particular problem in practice.

The machine position calculator 2, touch position calculator 3, virtual surface calculator 4, and probe diameter corrector 6 are generally implemented as software on a device using a microcomputer.

[0013]

According to the present invention, when measuring an unknown shape, the perpendicular direction near the measurement point can be determined with high precision regardless of the approach direction of the probe of the touch sensor, and therefore the probe diameter can be corrected with high precision. Accuracy can be improved.

[Brief explanation of the drawing]

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

FIG. 2 is an explanatory diagram showing a method for determining a perpendicular direction.

FIG. 3 is a perspective view showing a coordinate measuring machine.

FIG. 4 is a block diagram showing a prior art.

FIG. 5 is an explanatory diagram showing a problem in the prior art.

[Explanation of symbols]

1a, 1b, 1c, 1N Axis position measuring device 2 Machine position calculator 3 Touch position calculator 4 Virtual surface calculator 5 Touch sensor 6 Probe diameter corrector 7 Measurement model 8 Robot 9 Model surface 10 Probe

Claims (1)

[Claims] 1. A three-dimensional measuring machine that measures the shape of a model by bringing a spherical probe provided at the tip of a three-dimensional robot into contact with the model, comprising a contact detection means for detecting that the probe has contacted the model. , a position measuring means for measuring the position of each axis of the three-dimensional robot, and a position for calculating the center coordinates of the probe at that time from the position of each axis of the three-dimensional robot at the time when contact of the probe with the model is detected. a calculation means; a virtual surface calculation means for calculating a virtual virtual surface that approximates the surface including the current measurement point from a plurality of measurement points that have already been measured in the vicinity of the point currently being measured; and a probe diameter correction means for moving the center coordinates of the probe to the virtual surface side by the radius length of the probe along the perpendicular direction perpendicular to the virtual surface, and making the moved coordinates the coordinates of the probe surface. A three-dimensional measuring machine characterized by: