USE OF INCLINOMETERS TO IMPROVE RELOCATION OF A PORTABLE ARTICULATED ARM COORDINATE MEASURING MACHINE

• US 20110178763A1
• Filed: 01/14/2011
• Published: 07/21/2011
• Est. Priority Date: 01/20/2010
• Status: Abandoned Application

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E., Parker, David H.
• Application Number:
  US13/006,458
• Publication Number:
  US 20110178763A1
• Time in Patent Office: Days
• US Class Current: 702/152
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 21/047 Accessories, e.g. for positioning, for tool-setting, for measuring probes
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor
• CPC Class Codes: G05B 19/401 characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes G05B19/19 takes precedence
• CPC Class Codes: G05B 19/406 characterised by monitoring or safety G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/24067 Processor stores variables, events and date in eeprom, for external monitor
• CPC Class Codes: G05B 2219/37193 Multicoordinate measuring system, machine, cmm
• CPC Class Codes: G05B 2219/40233 Portable robot
• CPC Class Codes: G05B 2219/40596 Encoder in each joint
• CPC Class Codes: G05B 2219/45061 Measuring robot

Abstract

A method of relocating a portable articulated arm coordinate measuring machine (AACMM) from a first location to a second location, wherein the AACMM has, at the first location, a first origin point and a first frame of reference and, at the second location, a second origin point and a second frame of reference, the method including the steps of: measuring an amount of tilt of the portable AACMM along two perpendicular directions, each of which are approximately perpendicular to a gravity vector, with the portable AACMM in each of the first and second locations; measuring a first target and a second target with the portable AACMM in the first location to obtain, in the first frame of reference, a first set of x, y, and z coordinates and a second set of x, y, and z coordinates; measuring the first target and the second target with the portable AACMM in the second location to obtain, in the second frame of reference, a third set of x, y, and z coordinates and a fourth set of x, y, and z coordinates; and finding x, y, and z coordinates of the second origin point with respect to the first frame of reference, wherein the x, y, and z coordinates of the second origin point are found using the first, second, third, and fourth sets of x, y, and z coordinates but without using additional x, y, and z coordinates of a third target measured with the AACMM at the first location and at the second location.

Claims

1. A method of relocating a portable articulated arm coordinate measuring machine (AACMM) from a first location to a second location, wherein the AACMM has, at the first location, a first origin point and a first frame of reference and, at the second location, a second origin point and a second frame of reference, the method comprising the steps of:

measuring, with the portable AACMM in the first location, an amount of tilt of the portable AACMM along a first set of two perpendicular directions, each direction approximately perpendicular to a gravity vector;

measuring, with the portable AACMM in the second location, an amount of tilt of the portable AACMM along a second set of two perpendicular directions, each direction approximately perpendicular to the gravity vector;

measuring a first target and a second target with the portable AACMM in the first location to obtain, in the first frame of reference, a first set of x, y, and z coordinates and a second set of x, y, and z coordinates;

measuring the first target and the second target with the portable AACMM in the second location to obtain, in the second frame of reference, a third set of x, y, and z coordinates and a fourth set of x, y, and z coordinates; and

finding x, y and z coordinates of the second origin point with respect to the first frame of reference, wherein the x, y, and z coordinates of the second origin point are found using the first, second, third, and fourth sets of x, y, and z coordinates but without using additional x, y, and z coordinates of a third target measured with the AACMM at the first location and at the second location.

2. The method of claim 1, further comprising the step of:

identifying a first gravity frame of reference of the AACMM in the first location as that frame of reference resulting from application of the measured amount of tilt along the first set of two perpendicular directions to rotate x, y, and z axes of the first frame of reference into transformed x, y, and z axes of the first gravity frame of reference in such a way that the transformed z axis of the first gravity frame of reference is aligned with the gravity vector.

3. The method of claim 2, further comprising the step of:

identifying a second gravity frame of reference of the AACMM in the second location as that frame of reference resulting from application of the measured amount of tilt along the second set of two perpendicular directions to rotate x, y, and z axes of the second frame of reference into transformed x, y, and z axes of the second gravity frame of reference in such a way that the transformed z axis of the second gravity frame of reference is aligned with the gravity vector.

4. The method of claim 3, further comprising the step of:

determining a yaw angle of the portable AACMM in the second location, wherein the determined yaw angle comprises an amount of rotation about the transformed z axis of the second gravity frame of reference to make the transformed x and y axes of the second gravity frame of reference parallel to the transformed x and y axes of the first gravity frame of reference.

5. The method of claim 3, further comprising the steps of:

converting the first set of x, y, and z coordinates into a first set of transformed x, y, and z coordinates in the first gravity frame of reference;

converting the second set of x, y, and z coordinates into a second set of transformed x, y, and z coordinates in the first gravity frame of reference;

converting the third set of x, y, and z coordinates into a third set of transformed x, y, and z coordinates in the second gravity frame of reference; and

converting the fourth set of x, y, and z coordinates into a fourth set of transformed x, y, and z coordinates in the second gravity frame of reference.

6. The method of claim 5, further comprising the step of:

calculating the z coordinate of the second origin point in the first frame of reference using the transformed z coordinates from the first set of transformed x, y, and z coordinates and the third set of transformed x, y, and z coordinates.

7. The method of claim 6, further comprising the step of:

calculating the z coordinate of the second origin point in the first frame of reference using the transformed z coordinates from the second set of transformed x, y, and z coordinates and the fourth set of transformed x, y, and z coordinates.

8. The method of claim 7, further comprising the step of:

calculating the z coordinate of the second origin point in the first frame of reference by taking an average of the z coordinate calculated in claim 6 and the z coordinate calculated in claim 7.

9. The method of claim 5, further comprising the step of:

finding the x and y coordinates of the second origin point in the first frame of reference by solving two equations simultaneously, wherein the first equation includes transformed x and y coordinates from the first and third sets of transformed x, y, and z coordinates and the second equation includes transformed x and y coordinates from the second and fourth sets of transformed x, y, and z coordinates.

10. The method of claim 4, further comprising the step of:

transforming coordinate data collected by the AACMM in the first location and the second location into a common global frame of reference.

11. A computer program product comprising a storage medium having computer-readable program code embodied thereon, which when executed by a computer causes the computer to implement a method of relocating a portable articulated arm coordinate measuring machine (AACMM) from a first location to a second location, wherein the AACMM has, at the first location, a first origin point and a first frame of reference and, at the second location, a second origin point and a second frame of reference, the method including the steps of:

measuring, with the portable AACMM in the first location, an amount of tilt of the portable AACMM along a first set of two perpendicular directions, each direction approximately perpendicular to a gravity vector;

measuring, with the portable AACMM in the second location, an amount of tilt of the portable AACMM along a second set of two perpendicular directions, each direction approximately perpendicular to the gravity vector;

identifying a first gravity frame of reference of the AACMM in the first location as that frame of reference resulting from application of the measured amount of tilt along the first set of two perpendicular directions to rotate x, y, and z axes of the first frame of reference into transformed x, y, and z axes of the first gravity frame of reference in such a way that the transformed z axis of the first gravity frame of reference is aligned with the gravity vector;

identifying a second gravity frame of reference of the AACMM in the second location as that frame of reference resulting from application of the measured amount of tilt along the second set of two perpendicular directions to rotate x, y, and z axes of the second frame of reference into transformed x, y, and z axes of the second gravity frame of reference in such a way that the transformed z axis of the second gravity frame of reference is aligned with the gravity vector;

measuring a first target and a second target with the portable AACMM in the first location to obtain, in the first frame of reference, a first set of x, y, and z coordinates and a second set of x, y, and z coordinates;

measuring the first target and the second target with the portable AACMM in the second location to obtain, in the second frame of reference, a third set of x, y, and z coordinates and a fourth set of x, y, and z coordinates;

finding x, y and z coordinates of the second origin point with respect to the first frame of reference, wherein the x, y, and z coordinates of the second origin point are found using the first, second, third, and fourth sets of x, y, and z coordinates but without using additional x, y, and z coordinates of a third target measured with the AACMM at the first location and at the second location; and

determining a yaw angle of the portable AACMM in the second location, wherein the determined yaw angle comprises an amount of rotation about the transformed z axis of the second gravity frame of reference to make the transformed x and y axes of the second gravity frame of reference parallel to the transformed x and y axes of the first gravity frame of reference.

12. The computer program product of claim 11, in which the method further comprises the step of:

calculating the z coordinate of the second origin point in the first frame of reference using the transformed z coordinates from the first set of transformed x, y, and z coordinates and the third set of transformed x, y, and z coordinates.

13. The computer program product of claim 12, in which the method further comprises the step of:

calculating the z coordinate of the second origin point in the first frame of reference using the transformed z coordinates from the second set of transformed x, y, and z coordinates and the fourth set of transformed x, y, and z coordinates.

14. The computer program product of claim 13, in which the method further comprises the step of:

calculating the z coordinate of the second origin point in the first frame of reference by taking an average of the z coordinate calculated in claim 12 and the z coordinate calculated in claim 13.

15. The computer program product of claim 11, in which the method further comprises the step of:

finding the x and y coordinates of the second origin point in the first frame of reference by solving two equations simultaneously, wherein the first equation includes transformed x and y coordinates from the first and third sets of transformed x, y, and z coordinates and the second equation includes transformed x and y coordinates from the second and fourth sets of transformed x, y, and z coordinates.

16. The computer program product of claim 11, in which the method further comprises the step of:

transforming coordinate data collected by the AACMM in the first location and the second location into a common global frame of reference.