Coordinate measuring machine and method of measuring therein

• US 5,434,803 A
• Filed: 03/23/1993
• Issued: 07/18/1995
• Est. Priority Date: 03/26/1992
• Status: Expired due to Term

• Current Assignee: Tokyo Seimitsu Company Limited
• Original Assignee: Tokyo Seimitsu Company Limited
• Inventors: Yoshida, Hitoshi
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): Wachsman, Hal D.
• Application Number:
  US08/035,585
• Time in Patent Office: 847 Days
• Field of Search: 364/560, 364/559, 364/474.05, 364/474.03, 364/474.25, 364/474.37, 33/502-504, 73/1 J
• US Class Current: 702/168
• CPC Class Codes: G01B 21/04 by measuring coordinates of points

Abstract

A coordinate measuring machine and the method of measuring therein wherein the instruction of the geometic shape is prevented from mistaking and the geometic shape of the workpiece is measured without interrupting the joystick operation. The measuring direction of the probe and the measured value of workpiece are taken in the data receiving part. The geometic shape calculation part calculates the errors of each geometic shape based on the measured value from the data receiving part and the formula which was input previously and represents the geometic shape such as "a straight line or circle". And, the geometic shape recognition part compares respective shape errors such as "a straight line and circle" which are calculated in geometic shape calculation part and recognizes the geometic shape having the lowest shape errors. Further, the optimal geometic shape is recognized again based on the geometic shape having the lowest recognized shape errors and the measuring direction of the probe which is input from said data receiving part. Therefore, the step for inputting the geometic shape of the workpiece by the key can be removed before measuring. Moreover, the geometic shape can be recognized in a short time, because the geometic shape of workpiece can be automatically set based on the characteristic such as "a point, straight line or circle" whenever the definite measured point of the geometic shape of the workpiece is obtained.

Claims

1. A coordinate measuring machine wherein a measuring element is brought into contact with a workpiece which is placed on a table to measure the shape of the workpiece, comprising:

a data receiving device recording at least one measured value and a measuring direction of the measuring element when the measuring element is brought into contact with a workpiece;

a shape error calculating device receiving the at least one measured value from the data receiving device and having stored therein a plurality of formulae representing a corresponding plurality of geometric shapes, the shape error calculating device calculating shape errors based on the plurality of formulae and the at least one measured value from the data receiving device;

a geometric shape determining device for determining a geometric shape of the workpiece based on the number of measured values and amount of shape errors from the plurality of formulae, the geometric shape determining device determining the geometric shape to be a point when the number of measured values is one, the geometric shape determining device comparing the shape errors calculated by said shape error calculating device for at least two geometric shapes when the number of measured values is more than one to determine a temporary geometric shape having the least shape error and determining an optimal geometric shape based on the temporary geometric shape and the measuring direction of the measuring element recorded by the data receiving device when the number of measured values is more than one; and

a data display device displaying one of the temporary and optimal geometric shapes.

2. The coordinate measuring machine of claim 1, wherein said shape error calculating device calculates shape errors based on the straightness of a straight line, the roundness of a circle, the elliptical shape error of an ellipse, the sphericity of a sphere, the flatness of a plane, the cylindricity of a cylinder, and the conical shape error of a cone.

3. The coordinate measuring machine of claim 1, wherein:

when a first measured value is recorded by the data receiving device, the first measured value is set as a first distinctive point and the geometric shape determining device determines the temporary geometric shape to be a point;

when a second measured value is recorded by the data receiving device, the second measured value is set as a second distinctive point, and the geometric shape determining device determines the optimal geometric shape to be a line when a distance, L1, between said first and second distinctive points is greater than a first predetermined distance;

when a third measured value is recorded by the data receiving device, the third measured value is set as a third distinctive point and the geometric shape determining device determines the optimal geometric shape to be a plane when an angle, Θ

1, between a line passing through said first and second distinctive points and a line passing through said first and third distinctive points is greater than a first predetermined angle, an area formed by a first triangle connecting said first, second, and third distinctive points is greater than a predetermined area, and an angle Θ

2, between a normal line of said first triangle and the moving direction of said measuring element during recording of said third measured value is smaller than a second predetermined angle;

when a third measured value is recorded by said data receiving device, the third measured value is set as a third distinctive point, and the geometric shape determining device determines the optimal geometric shape to be a circle when an angle Θ

1, between a line passing through said first and second distinctive points and a line passing through said first and third distinctive points is greater than a first predetermined angle, an area formed by a first triangle connecting said first, second, and third distinctive points is greater than a predetermined area, and an angle, Θ

2 between a normal line of said first triangle and the moving direction of said measuring element during the recording of said third measured value is larger than said second predetermined angle;

when the geometric shape has been determined to be a circle, and a fourth measured value is recorded by said data receiving device the fourth measured value is set as a fourth distinctive point, and the geometric shape determining device determines the optimal geometric shape to be a sphere when a distance, L2, between said fourth distinctive point and the plane of a circle passing through said first, second and third distinctive points is larger than a second predetermined distance;

when the geometric shape has been determined to be a circle, and a fourth measured value is recorded by said data receiving device, the fourth measured value is set as a fourth distinctive point, and the geometric shape determining device determines the optimal geometric shape to be an ellipse when said distance, L2, between said fourth distinctive point and a circle passing through said first, second, and third distinctive points is smaller than said second predetermined distance and a distance, L3, between said fourth distinctive point and the circumference of a circle passing through said first, second and third distinctive points is larger than a third predetermined distance;

when the geometric shape has been determined to be a plane, and a fourth measured value is recorded by said data receiving device, the fourth measured value is set as a fourth distinctive point and the geometric shape determining device determines the optimal geometric shape to be a sphere when a distance, L4, between and said fourth distinctive point and a plane passing through said first, second and third distinctive points is larger than a fourth predetermined distance;

when the geometric shape has been determined to be a sphere, and a fifth measured value is recorded by said data receiving device, the fifth measured value is set as a fifth distinctive point and the geometric shape determining device determines the optimal geometric shape to be a cylinder when a distance, L5, between said fifth distinctive point and a surface of a sphere passing through said first, second, third and fourth distinctive points is larger than a fifth predetermined distance;

when the geometric shape has been determined to be an ellipse, and a fifth measured value is recorded by said data receiving device, the fifth measured value is set as a fifth distinctive point and the geometric shape determining device determines the optimal geometric shape to be a cylinder when a distance, L6, between said fifth distinctive point and the plane of an ellipse passing through said first, second, third, and fourth distinctive points is larger than a sixth predetermined distance; and

when the geometric shape has been determined to be a cylinder, and a sixth measured value is recorded by said data receiving device, the sixth measured value is set as a sixth distinctive point and the geometric shape determining device determines the optimal geometric shape to be a cone when a distance, L7, between said sixth distinctive point and the surface of a cylinder passing through said first, second, third, fourth, and fifth distinctive points is larger than a seventh predetermined distance.

4. The coordinate measuring machine of claim 3 wherein said first predetermined distance is 10 μ

m.

5. The coordinate measuring machine of claim 3 wherein said first predetermined angle is 1°

and the predetermined area is 0.0001 mm².

6. The coordinate measuring machine of claim 3 wherein said second predetermined angle is 60°

.

7. The coordinate measuring machine of claim 3 wherein said second predetermined distance is one tenth of a radius of a circle passing through said first, second, and third distinctive points.

8. The coordinate measuring machine of claim 7 wherein said third predetermined distance is one tenth of a radius of a circle passing through said first, second, and third distinctive points.

9. The coordinate measuring machine of claim 3 wherein said fifth predetermined distance is one tenth of a radius of a sphere passing through said first, second, third, and fourth distinctive points.

10. The coordinate measuring machine of claim 3 wherein said seventh predetermined distance is one tenth of a radius of a cylinder passing through said first, second, third, fourth and fifth distinctive points.

11. A method of determining a shape of a workpiece in a coordinate measuring machine having a data receiving device with a measuring element that contacts a surface of the workpiece to determine the shape, of the workpiece, the method comprising the steps of:

recording with a data receiving device at least one measured value and a measuring direction of the measuring element when the measuring element contacts the surface of the workpiece;

calculating shape errors with a shape error calculating device based on a plurality of formulae that each represent at least one geometric shape and the at least one recorded measured value from the data receiving device;

comparing the calculated shape errors with a geometric shape determining device;

determining a temporary geometric shape having the least shape error with said geometric shape determining device;

determining an optimal geometric shape based on the temporary geometric shape and the recorded measuring direction with said geometric shape determining device; and

displaying one of the temporary and optimal geometric shapes on a data output part.

12. The method of claim 11 further comprising the steps of:

determining the temporary geometric shape with said geometric shape determining device to be a point when the number of measured values is one; and

comparing the calculated shape errors of at least two geometric shapes with said geometric shape determining device when the number of measured values is more than one.

13. The method of claim 11, further comprising the steps of:

determining the temporary geometric shape to be a point and setting a first measured value as a first distinctive point with said geometric shape determining device when the number of measured values is one;

determining the optimal geometric shape to be a straight line and setting a second measured value as a second distinctive point with said geometric shape determining device when the second measured value is input after the first measured value and a distance, L1, between said first and second distinctive points is greater than a first predetermined distance;

determining the optimal geometric shape to be a plane and setting a third measured value as a third distinctive point with said geometric shape determining device when the third measured value is input after the second measured value and an angle, Θ

1, between a line passing through said first and second distinctive points and a line passing through said first and third distinctive points is greater than a first predetermined angle, an area formed by a triangle connecting said first, second, and third distinctive points is greater than a predetermined area, and an angle, Θ

2, between a normal line of said triangle and the measuring direction of said measuring element during the recording of said third measured value is smaller than a second predetermined angle;

determining the optimal geometric shape to be a circle and setting the third measured value as the third distinctive point with said geometric shape determining device when the third measured value is input after the second measured value and an angle, Θ

1, between a line passing through said first and second distinctive points and a line passing through said first and third distinctive points is greater than a first predetermined angle, an area formed by a triangle connecting said first, second, and third distinctive points is greater than a predetermined area, and an angle, Θ

2, between a normal line of said triangle and the measuring direction of said measuring element during the recording of said third measured value is larger than said second predetermined angle;

determining the optimal geometric shape to be a sphere and setting a fourth measured value as the fourth distinctive point with said geometric shape determining device when the fourth measured value is input after the third measured value and the geometric shape was previously determined to be a circle and a distance, L2, between said fourth distinctive point and the plane of a circle passing through said first, second, and third distinctive points is larger than a second predetermined distance;

determining the optimal geometric shape to be an ellipse and setting the fourth measured value as the fourth distinctive point with said geometric shape determining device when the fourth measured value is input after the third measured value and the geometric shape was previously determined to be a circle, and said distance, L2, between said fourth distinctive point and the plane of a circle passing through said first, second, and third distinctive points is smaller than said second predetermined distance and a distance, L3, between said fourth distinctive point and the circumference of the circle passing through said first, second, and third distinctive points is larger than a third predetermined distance;

determining the optimal geometric shape to be a sphere and setting the fourth measured value as the fourth distinctive point with said geometric shape determining device when a fourth measured value is input after the third measured value and the geometric shape was previously determined to be a plane and a distance, L4, between said fourth distinctive point and a plane passing through said first, second, and third distinctive points is larger than a fourth predetermined distance;

determining the optimal geometric shape to be a cylinder and setting a fifth measured value as the fifth distinctive point with said geometric shape determining device when the fifth measured value is input after the fourth measured value and the geometric shape was previously determined to be a sphere and a distance, L5, between said fifth distinctive point and the surface of a sphere passing through said first, second, third and fourth distinctive points is larger than a fifth predetermined distance;

determining the optimal geometric shape to be a cylinder and setting the fifth measured value as the fifth distinctive point with said geometric shape determining device when the fifth measured value is input after the fourth measured value and the geometric shape was previously determined to be an ellipse and a distance, L6, between said fifth distinctive point and a plane of an ellipse passing through said first, second, third, and fourth distinctive points is larger than a sixth predetermined distance; and

determining the optimal geometric shape to be a cone and setting a sixth measured value as a sixth distinctive point with said geometric shape determining device when the sixth measured value is input after the fifth measured value and the geometric shape was previously determined to be a cylinder and a distance, L7, between said sixth distinctive point and a surface of a cylinder passing through said first, second, third, fourth and fifth distinctive points is larger than a seventh predetermined distance.

14. A method of determining a shape of a workpiece in a coordinate measuring machine having a data receiving device with a measuring element that contacts a surface of the workpiece to determine the shape of the workpiece, the method comprising the steps of:

recording at least one measured value and a measuring direction of the measuring element when the measuring element contacts the surface of the workpiece;

calculating shape errors based on a plurality of formulae representing plural geometric shapes and the at least one recorded measured value;

comparing the calculated shape errors;

determining a temporary geometric shape having the least shape error;

determining an optimal geometric shape based on the temporary geometric shape and the recorded measuring direction;

automatically setting the geometric shape of the workpiece in accordance with the optimal geometric shape; and

displaying one of the temporary and optimal geometric shapes.

15. A method of determining a shape of a workpiece in a coordinate measuring machine having a data receiving device with a measuring element, the method comprising the steps of:

contacting a surface of the workpiece with the measuring element;

recording at least one measured value and a measuring direction of the measuring element when the measuring element contacts the surface of the workpiece;

calculating shape errors based on a plurality of formulae representing plural geometric shapes and the at least one recorded measured value;

comparing the calculated shape errors;

determining a temporary geometric shape having the least shape error; and

determining an optimal geometric shape in accordance with the temporary geometric shape and the recorded measuring direction, wherein the shape of the workpiece is automatically set in accordance with the optimal geometric shape by the coordinate measuring machine.