JPH11211452A - Device and method for evaluating form error of structure, and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely evaluate a shape error regardless of the attitude of a structure by comparing the radius of a circular arc including three points of a structure with the radius of a circular arc including three points contained in the designed form information of the structure. SOLUTION: A three-dimensional form measuring machine 3 measures the positions (coordinate values) of a work 4 (structure) in contact points by moving a measuring probe 31 by control of a control computer 1 to sequentially bring it into contact with the surface of the outer form of the work 4. A measurement result processing computer 2 calculates the radius of a circular arc including three measurement points of the measurement values measured in a plurality of measuring points, and calculates the radius of a circular arc including three points contained in the designed form of the structure corresponding to the three measuring points. The calculated radius of the circular arc including the three points of the structure is compared with the radius of the circular arc including the three points contained in the designed form information of the structure, whereby the form error from the designed form in the three measuring points of the structure is evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaluation device and an evaluation method for evaluating a shape error of a structure such as a work, and a computer-readable storage medium.

[0002]

2. Description of the Related Art Conventionally, works (structures) having various shapes have been manufactured at a manufacturing site of, for example, an automobile, and the works are manufactured so as to satisfy a design shape and dimensions. That is an important issue.

In recent years, three-dimensional shapes have been measured.
Due to the development of so-called three-dimensional measuring machines, it is possible to accurately and easily measure the three-dimensional shape of a work that is complicatedly formed by press working or the like.

As a method of comparing and evaluating the measurement results at a plurality of positions actually measured by such a three-dimensional measuring device with a design shape (design data), a computer for evaluation uses a computer for evaluation at each measurement position. Generally, a normal line to the design shape is obtained, a distance between each measurement position in the normal direction and the design shape is calculated, and the calculated distance is used as an error amount.

[0005]

However, in the above-mentioned conventional example, it is a premise that the work is arranged at a predetermined position to accurately evaluate a machining error. That is, when performing the measurement by the three-dimensional measuring device, if the work is not arranged at a predetermined position for some reason and the posture of the work is displaced in the rotation direction or the axial direction, the above method is used. Since the measurement result itself by the three-dimensional measuring machine is not reliable, the result of comparison and evaluation with the design shape cannot be trusted.

Therefore, for example, Japanese Patent Application Laid-Open No. 6-109461 discloses that the shape of the edge of a work is estimated using the least squares method based on the measurement result of a three-dimensional measuring machine, and the posture of the work is determined from the estimation result. Although a method of obtaining a processing error of the work based on the determined posture is disclosed, the required calculation is considerably complicated, and the applicable shape of the work is limited.

It is an object of the present invention to provide an apparatus and method for evaluating a shape error of a structure that accurately evaluates a shape error regardless of the posture of the structure, and a storage medium readable by a computer.

[0008]

Means for Solving the Problems In order to achieve the above object, an apparatus for evaluating a shape error of a structure according to the present invention has the following features.

In other words, there is provided a shape error evaluation apparatus for evaluating a shape error of a structure having a three-dimensional shape from a design shape,
A measuring means for measuring the shape of the structure at a plurality of measuring points in a desired measuring direction, and an arc having three measuring points among the measured values at the plurality of measuring points measured by the measuring means. First calculating means for calculating a radius, second calculating means for calculating the radius of an arc including three points included in the design shape of the structure corresponding to the three measurement points, The radius of the arc including the three points of the structure calculated by the first calculation unit and the 3D shape included in the design shape information of the structure calculated by the second calculation unit
Evaluation means for evaluating a shape error from the design shape at three measurement points of the structure by comparing the radius of the arc including the point. Thus, the shape error is accurately evaluated regardless of the posture of the structure.

Alternatively, in order to achieve the above object, a method for evaluating a shape error of a structure according to the present invention has the following configuration.

That is, a shape error evaluation method for evaluating a shape error of a structure having a three-dimensional shape from a design shape,
The shape of the structure is measured at a plurality of measurement points in a desired measurement direction, and among the measurement values at the plurality of measurement points obtained by the measurement, the radius of an arc passing through three measurement points is calculated. Calculating a radius of an arc passing through three points included in the design shape of the structure corresponding to the three measurement points, and calculating a radius of the arc passing through the three points of the calculated structure; By comparing the radius of a circular arc passing through three points included in the design shape of the body, the shape error of the structure at the three measurement points with respect to the design shape is evaluated. Thus, the shape error is accurately evaluated regardless of the posture of the structure.

Further, the present invention is characterized in that a computer-readable storage medium for operating a computer is provided as an apparatus for implementing the above-described method for evaluating a shape error of a structure.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an apparatus for evaluating a shape error of a structure according to the present invention. In the present embodiment, as an example of the shape error,
A description will be given as an evaluation of a processing error generated when a member (work) constituting a vehicle such as an automobile is processed by press working or the like. First, the overall configuration of the three-dimensional shape evaluation system used in the present embodiment will be described with reference to FIGS.

FIG. 1 is an overall configuration diagram of a three-dimensional shape evaluation system to which the present invention can be applied. In the figure, 3 is
It is a three-dimensional shape measuring machine for measuring a three-dimensional shape. 1 is
The control computer controls the three-dimensional shape measuring machine 3. Reference numeral 2 denotes a measurement result processing computer that performs an evaluation process of the measurement result of the three-dimensional shape measuring machine 3 and the like. The measurement result processing computer 2 and the control computer 1 are connected via a general communication network, and are capable of bidirectional communication. 5 is a work 4 which is a structure.
Is the pedestal base.

In this embodiment, the three-dimensional shape measuring machine 3
Measurement points by the measurement result processing computer 2
The data of the set measurement points is downloaded to the control computer 2.

The measurement probe 31 provided on the arm of the three-dimensional shape measuring machine 3 has a structure movable in the XYZ space shown in FIG. The three-dimensional shape measuring machine 3 measures the position (coordinate value) at those contact points by moving the measurement probe 31 and sequentially contacting the surface of the external shape of the work 4.

In the present embodiment, a general one is used for the three-dimensional shape measuring machine 3, and a description of a method for measuring the three-dimensional shape is omitted. Further, the shape measuring method of the three-dimensional shape measuring machine may be a method of bringing a measurement probe into contact with an object or a method of measuring without contact.

FIG. 3 is a block diagram of a computer for processing measurement results to which the present invention can be applied.

In the figure, reference numeral 22 denotes a display such as a CRT,
Reference numeral 3 denotes a keyboard as input means; 24, a ROM for storing a boot program and the like; 25, a RAM for temporarily storing various processing results; 26, a hard disk drive (26) for storing a program for performing a processing error evaluation process described later; A storage device such as an HDD), and 27 is a control computer 1
And 28, a communication interface for communicating with external devices via a communication network, and a printer 28 for printing processing results and the like. Each of these components is connected to the internal bus 2
9, and the CPU 21 is connected to the storage device 26.
The whole of the three-dimensional shape evaluation system shown in FIG.

FIG. 2 is a diagram showing a method of supporting a work at the time of measuring a three-dimensional shape applicable to the present invention. As shown in the figure, the base 5 has a plurality of support legs 5 for supporting the work 4.
2 is provided, and a processing reference surface 53 of the support leg 52 is provided.
Supports the work 4.

At a predetermined position of the base 5, a positioning pin 51 is provided. At a predetermined position of the work 4, the work is placed on the base 5 so that the positioning pin 51 A hole into which the tip is inserted is provided.
Thereby, a robot or the like (not shown) can place the work 4 at a predetermined position on the base 5 as shown in FIG. However, strictly speaking, it is necessary to provide a certain margin for the diameter of the hole provided in the work 4 and the positioning pin 51, and there is an allowable range of processing error. Further, positioning pins 51 are provided in holes provided in the work 4.
May not be properly inserted, the work 4 may be floating from a predetermined position on the base 5 (FIG. 1).
2). Therefore, for such a reason, the posture of the work 4 may be shifted on the base 5. In this case, according to the method for measuring a three-dimensional shape according to the above-described conventional technique, the position of the work 4 is deviated from the reference position, so that the processing error of the work 4 cannot be accurately evaluated. On the other hand, according to the method described below in the present embodiment, it is possible to accurately evaluate the processing error of the work 4 even if the posture of the work 4 on the base 5 is shifted to some extent.

<Processing Error Evaluation Processing> The processing error evaluation processing of the workpiece according to the present embodiment will be described below with reference to a flowchart of software executed by the measurement result processing computer 2.

FIG. 11 is a flowchart of a processing error evaluation process for a workpiece according to an embodiment of the present invention.

Steps S1 and S2: Prior to the evaluation of the machining error, the operator uses a three-dimensional CAD from an engineering workstation (EWS) (not shown) or the like.
(Computer-aided design) Obtain design data of the work 4 which is data (step S1), and evaluate a machining error with respect to the shape of the work 4 displayed on the display 22 based on the design data (step S1). Direction) (step S2).

FIG. 4 is a diagram for explaining a processing error evaluation position (direction) as one embodiment of the present invention.
A desired evaluation direction is set, such as a direction, b direction, and c direction shown in FIG.

Steps S3 and S4: Next, the operator measures points (hereinafter referred to as points) to be measured by the three-dimensional shape measuring machine 3 on the workpiece 4 displayed as a cross-sectional shape in the evaluation direction portion set in step S2. , Measurement points) are designated by a measurement pitch as shown in FIG. 5 (step S3). At this time, it is preferable that the designated measurement pitch is narrowed as the curve of the cross-sectional shape bends smaller.

The CPU 21 creates a plurality of measurement points on the design data representing the cross section of the work 4 based on the measurement pitch set in step S3, as shown in FIG.

Step S5: The CPU 21 proceeds to step S5.
The data on the measurement points created in step 4 is downloaded to the control computer 1. And the CPU 21
Causes the three-dimensional shape measuring machine 3 to measure each measurement point based on the downloaded data. It is assumed that the work 4 to be evaluated has been placed on the base 5 by this time.

As shown in FIG. 7, the three-dimensional shape measuring machine 3 moves the measuring probe 31 and sequentially contacts the surface of the work 4 to measure the positions (coordinate values) at those contact points. Go.

After that, the control computer 1 notifies that the three-dimensional shape measuring machine 3 has completed the measurement at each measurement point.
The CPU 21 uploads the data of the measurement result for each of the measurement points into the measurement result processing computer 2.

Step S6: Based on the measurement result data obtained from the control computer 1 in step S5 and the design data obtained from EWS in step S1, the processing error of the work 4 in the evaluation direction set in step S2 is determined. Perform an evaluation.

<Evaluation Method> FIG. 9 is a view showing a state in which a measurement result and a design shape are superimposed and displayed as an embodiment of the present invention. For example, the direction a in FIG. 4 is set as an evaluation direction. Show the case. Even if the display is performed only in such a state, if the processing error is large, the error can be recognized because the measurement result (black point) does not fall on the design data (solid line). It is necessary to quantitatively calculate the processing error.

Therefore, in the present embodiment, the radius of the curve of the cross section of the design shape is compared with the actual radius of the curve of the workpiece 4 corresponding to the cross section of the design shape.
Evaluate machining errors. As a method of calculating the radius of the curve, the radius of curvature of an arc passing through three points is calculated. Therefore, for the curve of the design shape, the radius of curvature of an arc passing through three points out of the plurality of measurement points specified in step S3 is calculated, and the curve of the actual work 4 corresponds to the three measurement points. The radius of curvature of an arc passing through the three measurement result points is calculated.

FIG. 8 is a diagram for explaining a method for evaluating a processing error according to an embodiment of the present invention. As shown in the figure, in the present embodiment, as an example, three of P1, P2, and P3 are used.
The radius of curvature R of the arc passing through the point is calculated as follows.

[0035]

(Equation 1)

At this time, assuming that the intersection of La and Lb is C, the radius of curvature R has the relationship of R = P1C = P2C = P3C (where PnC represents a line segment). The radius R can be calculated from this relational expression.

It is needless to say that the three points used for calculating the radius of curvature of the circular arc can be calculated with higher accuracy by preferably selecting three consecutive points.

FIG. 10 is a diagram comparing the measurement results and the design shape with the calculated radius of curvature as one embodiment of the present invention, and plotted from an oblique straight line (a straight line with a slope of 1) in FIG. The farther the point is, the larger the processing error is.

<Comparison with Conventional Measurement Method> Next, the evaluation method according to the above-described embodiment and the conventional evaluation method will be compared with reference to FIG. 12 and FIG.

FIG. 12 shows, as an embodiment of the present invention, a work 4 as design data placed at a predetermined position on a base in a design ideal posture and a shift on the base. FIG. 4 is a diagram illustrating the actual posture of a placed work 4. As shown in the figure, the design data (solid line) and the measurement points (black dots) specified by the design data are shifted from the actual measurement results (white dots) corresponding to those measurement points. It can be seen that the posture of the work 4 at the time is not at the predetermined position as shown by the broken line.

In such a state, the evaluation results obtained by the evaluation method according to the present embodiment and the conventional evaluation method are compared.

FIG. 13 is a diagram showing a comparison result when the machining error of the work 4 is evaluated by the evaluation method according to the present embodiment and the conventional evaluation method in the state of FIG.

In the drawing, in the case of the conventional evaluation method, since the posture of the work 4 is shifted from a predetermined position, not only the actual processing error of the work 4 but also the influence of the shift of the posture of the work 4 is exerted on the evaluation result. It is understood that is included. That is, the tendency of the error value in the normal direction calculated for each measurement point shown in FIG.
Tend to be similar to the posture. On the other hand, in the case of the evaluation method according to the present embodiment, the error value of the radius of curvature calculated for each measurement point shown in FIG.

As can be seen from the above results, according to the evaluation method of the present embodiment, even if there is a slight deviation in the posture of the work 4, the radius of the curved surface of the cross section of the design shape and the radius of the curved surface of the work 4 By comparing with the above, the processing error of the work can be accurately evaluated. Therefore, even if the positioning accuracy of the work 4 on the base 5 is slightly roughened, no major problem occurs, and the lead time when the work 4 is placed on the base 5 can be shortened.

In FIGS. 1 and 2 of the above-described embodiment, an example in which the surface of the outer shape of the work 4 is measured by the three-dimensional shape measuring machine 3 is shown. It goes without saying that a processing error of the shape of the inner surface can be evaluated by the above-described method as long as the structure can measure the shape of the inner surface.

In the embodiment described above, software for realizing the operation of the flowchart of FIG.
It is needless to say that the present invention is also applicable to a case where the information is stored in a storage medium such as a floppy disk and the information of the storage medium is read into, for example, a personal computer to operate the computer as the measurement result processing computer 2 according to the present embodiment. .

[0047]

As described above, according to the present invention,
A structure error evaluation apparatus and method for accurately evaluating a shape error regardless of the posture of the structure, and a computer-readable storage medium are provided.

[0048]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a three-dimensional shape evaluation system to which the present invention can be applied.

FIG. 2 is a diagram illustrating a method of supporting a workpiece during three-dimensional shape measurement applicable to the present invention.

FIG. 3 is a block diagram of a measurement result processing computer to which the present invention can be applied.

FIG. 4 is a diagram illustrating an evaluation position (direction) of a processing error according to an embodiment of the present invention.

FIG. 5 is a diagram showing a state in which a measurement pitch is designated for a design shape according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a state in which measurement points are set for a design shape according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a state in which a work surface is measured by a probe of a three-dimensional measuring machine according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a processing error evaluation method as one embodiment of the present invention.

FIG. 9 is a diagram showing a state in which a measurement result and a design shape are superimposed and displayed as one embodiment of the present invention.

FIG. 10 is a diagram in which a measurement result and a design shape are compared by a calculated radius of curvature as one embodiment of the present invention.

FIG. 11 is a flowchart of processing for evaluating a processing error of a work as one embodiment of the present invention.

FIG. 12 shows a work 4 as design data placed at a predetermined position on a base in a design ideal posture as one embodiment of the present invention, and a work 4 placed on a base with a displacement. FIG. 4 is a diagram showing the actual posture of the work 4.

FIG. 13 is a diagram illustrating a comparison result when the processing error of the work 4 is evaluated by the evaluation method according to the present embodiment and the conventional evaluation method in the state of FIG.

[Explanation of symbols]

 1: control computer, 2: measurement result processing computer, 3: three-dimensional measuring machine, 4: work, 5: base, 21: CPU, 22: display, 23: keyboard, 24: ROM, 25: RAM, 26: storage device, 27: communication interface, 28: printer, 29: internal bus, 31: probe, 51: positioning pin, 52: support leg, 53: processing reference plane,

Claims (9)

[Claims] 1. A shape error evaluation device for evaluating a shape error of a structure having a three-dimensional shape from a design shape, wherein the shape of the structure is measured at a plurality of measurement points in a desired measurement direction. Measuring means; first calculating means for calculating the radius of an arc including three measuring points among the measured values at the plurality of measuring points measured by the measuring means; and corresponding to the three measuring points. However, a second calculation of the radius of an arc including three points included in the design shape of the structure is performed.
Calculating means, a radius of an arc including three points of the structure calculated by the first calculating means, and three points included in the design shape information of the structure calculated by the second calculating means. Evaluation means for evaluating a shape error of the structure at three measurement points with respect to the designed shape by comparing the radius with the radius of the circular arc. 2. The structure error evaluation according to claim 1, further comprising setting means for setting the plurality of measurement points to a smaller pitch as the shape of the structure is bent in a smaller manner. apparatus. 3. The apparatus according to claim 1, wherein the shape error is a processing error generated by processing the structure. 4. The apparatus according to claim 1, wherein the structure is a vehicle member formed by press working. 5. A shape error evaluation method for evaluating a shape error between a design shape of a structure having a three-dimensional shape and a design shape, wherein the shape of the structure is measured at a plurality of measurement points in a desired measurement direction. Calculating the radius of an arc passing through the three measurement points among the measurement values at the plurality of measurement points obtained by the measurement, and calculating the radius of the arc corresponding to the three measurement points, By calculating the radius of an arc passing through the three included points, and comparing the calculated radius of the arc passing through the three points of the structure with the radius of the arc passing through the three points included in the design shape of the structure And evaluating a shape error of the structure at three measurement points with respect to the design shape. 6. The method according to claim 5, wherein the plurality of measurement points have a smaller pitch as the shape of the structure bends smaller. 7. The shape of a structure according to claim 5, wherein the method for evaluating the shape error of the structure is used for evaluating a processing error caused by processing the structure as the shape error. Error evaluation method. 8. The method according to claim 5, wherein the method for evaluating a shape error of the structure is used for evaluating a vehicle member formed by press working as the structure. 9. A recording medium storing a program for a shape error evaluation process for evaluating a shape error between a design shape of a structure having a three-dimensional shape and a design shape. Measuring means for measuring the shape of the structure at a plurality of measuring points in a desired measuring direction, and three measuring points among the measured values at the plurality of measuring points measured by the measuring means. First calculating means for calculating a radius of an arc; and second calculating means for calculating a radius of an arc including three points included in the design shape of the structure corresponding to the three measurement points.
Calculating means, a radius of an arc including three points of the structure calculated by the first calculating means, and three points included in the design shape information of the structure calculated by the second calculating means. A computer-readable storage medium operable as evaluation means for evaluating a shape error between the design shape and three measurement points of the structure by comparing the radius with the radius of the arc.