Method and machine for determining a space coordinate of a measurement point on a measurement object

• US 20080033680A1
• Filed: 07/10/2007
• Published: 02/07/2008
• Est. Priority Date: 01/18/2005
• Status: Active Grant

• Current Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Inventors: Grupp, Guenter
• Granted Patent: US 7,610,162 B2
• Time in Patent Office: Days
• US Class Current: 702/95
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 5/008 using coordinate measuring machines

Abstract

A measurement point is approached with a probe head arranged on a displacement mechanism having at least two supports. An actual difference value between the displacement positions of a first and a second support is determined. A static difference value representing is provided and subtracted from the actual difference, in order to obtain a dynamic difference value representing a static difference between the first and the second displacement positions is subtracted from the actual difference value in order to obtain a dynamic difference value. The space coordinate of the measurement point is determined as a function of the dynamic difference value.

Claims

1. A method for determining at least one space coordinate of a measurement point on a measurement object, comprising the steps of:

approaching the measuring point with a probe head arranged on a displacement mechanism which comprises a first and a second movable support,

determining a first displacement position of the first support and determining a second displacement position of the second support,

determining an actual difference value between the first and the second displacement positions,

providing a static difference value which represents a static difference between the first and the second displacement positions,

subtracting the static difference value from the actual difference in order to obtain a dynamic difference value, and

determining the space coordinate of the measurement point as a function of the dynamic difference value.

2. The method of claim 1, wherein the space coordinate determined by using the dynamic difference value is subsequently corrected by using the static difference value.

3. The method of claim 1, wherein the supports are moved substantially parallel in a first space direction when approaching the measurement point, and wherein the probe head is moved in a second space direction transverse to the first space direction when approaching the measurement point, wherein the space coordinate is determined both in the first space direction and in the second space direction by using the dynamic difference value.

4. The method of claim 1, wherein the static difference value is determined by means of a calibration run and then permanently provided in a memory.

5. The method of claim 4, wherein the static difference value is determined by a calibration run executed without any measurement value corrections.

6. The method of claim 4, wherein the measurement point is approached by means of at least two drives, a first drive moving the first support and a second drive moving the second support, but the calibration run is carried out with only one of the drives.

7. The method of claim 1, wherein the first and the second displacement positions are determined by means of temperature-corrected measuring instruments.

8. The method of claim 1, wherein the measurement point is approached by means of at least two drives, a first drive moving the first support, a second drive moving the second support, and the two drives being actuated by a common regulator which receives the dynamic difference value as an input quantity.

9. The method of claim 8, wherein the first and second drives are switched off when the dynamic difference value exceeds a predefined threshold value.

10. The method of claim 8, wherein the common regulator comprises a position regulator and a synchronous regulator, which is subordinated to the position regulator, the dynamic difference value being supplied to the synchronous regulator as an input quantity.

11. The method of claim 8, wherein a drive current for the first and second drives is limited to a predefined maximum value.

12. The method of claim 11, wherein the predefined maximum value is approximately equal to the current value required for an acceleration of the supports.

13. The method of claim 8, wherein the common regulator controls the first and second drives so that drive currents of approximately the same level result in both drives.

14. A coordinate measuring machine for determining at least one space coordinate of a measurement point on a measurement object, comprising

a displacement mechanism having a first and a second movable support,

a probe head arranged on the displacement mechanism for approaching the measuring point,

a first and a second measuring instrument for determining a first displacement position of the first support and a second displacement position of the second support,

an actual difference formation unit for determining an actual difference value between the first and second displacement positions,

a memory for permanently storing and providing a static difference value representing a static difference between the first and second displacement positions, and

a calculation unit for determining the space coordinate of the measurement point, the calculation unit comprising a subtractor for subtracting the static difference value from the actual difference value in order to obtain a dynamic difference value, and configured to determine the space coordinate as a function of the dynamic difference value.

15. A computer program product comprising program code configured for carrying out a method, when executed on a processor of a coordinate measuring machine, comprising the following steps:

approaching the measuring point with a probe head arranged on a displacement mechanism which comprises a first and a second movable support,

determining a first displacement position of the first support and determining a second displacement position of the second support,

determining an actual difference value between the first and the second displacement positions,

receiving a static difference value which represents a static difference between the first and the second displacement positions,

subtracting the static difference value from the actual difference value in order to obtain a dynamic difference value, and

determining the space coordinate of the measurement point as a function of the dynamic difference value.