Method of generating an error map for calibration of a robot or multi-axis machining center

• US 6,535,794 B1
• Filed: 05/03/1995
• Issued: 03/18/2003
• Est. Priority Date: 02/23/1993
• Status: Expired due to Term

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Raab, Simon
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): Rao, Sheela
• Application Number:
  US08/434,010
• Time in Patent Office: 2,876 Days
• Field of Search: 364/474.03, 364/474.05, 364/167.01, 364/191, 395/80, 395/88, 395/89, 395/99
• US Class Current: 700/262
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G01B 21/04 by measuring coordinates of points
• CPC Class Codes: G01B 5/008 using coordinate measuring machines
• 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 19/4207 in which a model is traced or scanned and corresponding data recorded
• CPC Class Codes: G05B 2219/37193 Multicoordinate measuring system, machine, cmm
• CPC Class Codes: G05B 2219/39028 Relative to base calibrated 6-DOF device, cmm connected between wrist and base
• CPC Class Codes: G05B 2219/40233 Portable robot
• CPC Class Codes: G05B 2219/41176 Compensation control, position error with data from lookup memory
• CPC Class Codes: G05B 2219/45061 Measuring robot

Abstract

A novel, portable coordinate measuring machine comprises a multijointed (preferably six joints) manually positionable measuring arm for accurately and easily measuring a volume, which in a preferred embodiment, comprises a sphere ranging from six to eight feet in diameter and a measuring accuracy of 2 Sigma +/−0.005 inch. In addition to the measuring arm, the present invention employs a controller (or serial box) which acts as the electronic interface between the arm and a host computer. The coordinate measuring machine of this invention is particularly useful in a novel method of generating an error map and thus correcting and/or programming the tool path for multi-axis machining centers, particularly robots.

Claims

1. A method for generating an error map for multi-axis devices in order to improve the repeatability and/or precision of multi-axis devices comprising the steps of:

(1) attaching the measurement arm of a passive three dimensional coordinate measuring machine (CMM) having multiple degrees of freedom to a multi-axis device and operating the CMM through a selected 3-dimensional path or operation which emulates the desired proselected programmed path or operation of the multi-axis device;

(2) developing 3-dimensional data of at least one of (a) position and (b) orientation from step (1) and storing said data, said data defining the actual path or operation of the multi-axis device;

(3) comparing the actual path or operation to the desired preselected programmed path or operation;

(4) generating an error map comparing the actual path or operation to the desired preselected programmed path or operation; and

(5) using said error map to improve the repeatability and/or precision of the multi-axis device;

wherein said CMM includes 6 degrees of freedom, said CMM comprises;

a movable arm having opposed first and second ends, said arm including a plurality of joints with each joint corresponding to a degree of freedom such that said arm is movable within a selected volume, each of said joints comprising a rotational transfer housing for housing a position transducer, said transducer producing a position signal;

a support base attached to said first end of said movable arm;

a probe attached to said second end of said movable arm; and

an electronic circuit for receiving said position signals from said transducer and providing a digital coordinate corresponding to the position of said probe in a selected volume.

2. The method of claim 1 wherein:

said multi-axis device comprises a device having at least 3 axes and the data developed in step (2) comprises position or orientation data.

3. The method of claim 1 wherein:

said multi-axis device comprises a device having at least 5 axes and the data developed in step (2) comprises position and orientation data.

4. The method of claim 1 wherein:

said multi-axis device comprises a machining device.

5. The method of claim 1 wherein:

said multi-axis device comprises a robot.

6. The method of claim 1 wherein:

said operation is selected from the group consisting of welding, sanding, cutting, machining, polishing, grinding, painting and cleaning.

7. The method of claim 1 wherein:

a mechanical linkage is used to attach said CMM to said multi-axis device.