Electro-optical systems for control of robots, manipulator arms and co-ordinate measuring machines

• US 4,453,085 A
• Filed: 05/11/1981
• Issued: 06/05/1984
• Est. Priority Date: 05/11/1981
• Status: Expired due to Term

• Current Assignee: LMI Technologies Inc.
• Original Assignee: Diffracto, Ltd. (LMI Technologies Inc.)
• Inventors: Pryor, Timothy R.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US06/262,492
• Time in Patent Office: 1,121 Days
• Field of Search: 356/399, 356/400, 356/401, 250/201, 250/202, 250/203, 250/561, 250/548, 250/557
• US Class Current: 250/203.1
• CPC Class Codes: A01B 69/008 automatic
• CPC Class Codes: B23P 19/10 Aligning parts to be fitted together
• CPC Class Codes: B25J 13/088 with position, velocity or acceleration sensors
• CPC Class Codes: B25J 18/002 comprising beam bending compensation means
• CPC Class Codes: B25J 19/021 Optical sensing devices
• CPC Class Codes: B25J 19/022 using lasers
• CPC Class Codes: B25J 9/1684 Tracking a line or surface by means of sensors
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G05B 19/39 using a combination of the means covered by at least two of the preceding groups G05B19/21, G05B19/27 and G05B19/33
• CPC Class Codes: G05B 2219/36417 Programmed coarse position, fine position by alignment, follow line, path adaptive
• CPC Class Codes: G05B 2219/36439 Guide arm in path by slaving arm to projected path, beam riding
• CPC Class Codes: G05B 2219/37572 Camera, tv, vision
• CPC Class Codes: G05B 2219/45083 Manipulators, robot

Abstract

Method and apparatus for accurate positioning of a moveable member such as a robot arm or the like. An encoder or other position sensing means on the robot is used to control positioning of the robot into a desired position. However, because of inaccuracies such as those built up by utilizing a plurality of position sensors or those occasioned by bending, etc., the robot arm, gripper or the like may be substantially out of position. In the present invention, an electro-optical system, having a reference point external of the robot, is used to determine if the arm, gripper or the like is actually in its desired position. If it is determined to be out of its desired position, a control signal is generated to effect movement of the arm or gripper or the like so that it is actually in its desired position.

Claims

1. A method for correcting position data of a machine having a member moveable in at least two co-ordinate axes, said machine comprising encoder means for providing rough position data to indicate the rough position of said member in each of said axes, said method comprising the steps of:

moving said moveable member to a position data correction location;

electro-optically determining the actual position of said member in at least one axis relative to a reference point external to said machine;

generating a signal representative of the electro-optically determined actual position of said member in the determined axis;

utilizing said signal to correct the rough position data in said encoder means for the determined axis; and

further moving said member to a precise desired position in the determined axis as indicated by said corrected position data.

2. A method for correcting position data of a machine as claimed in claim 1 wherein said electro-optically determining step includes the steps of generating a source of light as the reference point.

3. A method for correcting position data of a machine as claimed in claim 2 wherein the generated source of light is a projected laser light beam and wherein said electro-optically determining step includes the detecting of the location of the projected beam on a detector relative to the determined axis.

4. A method for correcting position data of a machine as claimed in claim 2 wherein the source of light is at a known location, and wherein the electro-optically determining step includes the imaging with a lens of the reference light source onto a detector.

5. A method for correcting position data of a machine as claimed in claim 4 wherein the detector is a photo detector array.

6. An apparatus for inspecting objects comprising:

a moving means for moving one or more electro-optical sensors along one or more axes of the object;

encoder means for determining the rough position of said sensor in each of the axes;

a reference point located external to said moving means;

electro-optic means for determining the actual position of said sensor in at least one axis relative to said reference point and for generating a signal representative of the electro-optically determined actual position to correct the encoder means determined rough position such that said sensor is subsequently accurately moved to a desired precise position in the determined axis by said moving means according to the corrected position indicated by said encoder means.

7. An apparatus for inspecting objects as claimed in claim 6 wherein there are at least two of said electro-optical sensors such that a plurality of features of the object are inspected.

8. A method of accurately positioning an element moveably mounted on a device having a means for moving said element, means for sensing the rough position of said element relative to the mounting, and control means responsive to said rough position sensing means for moving said element to a desired rough position in space;

the method comprising the steps of;

utilizing said member position sensing means to actuate said control means to move said moveable element to the desired rough position past a reference point external to said device;

determining by use of an electro-optical means the actual position of said moveable element in space relative to said reference point as said member is moved to said desired rough position, said electro-optical means comprising light source means, light detector means, and means responsive to the output signal of said light detector means for determining the actual position in space of said moveable element realtive to said external reference point;

determining relative to said reference point, any difference between the actual position in space of said element as determined by said electro-optical means and the rough position in space determined by said position sensing means; and

subsequently utilizing any determined difference in position to further actuate said control means to move said moveable element from the desired rough position to the desired actual position.

9. A method according to claim 8 wherein said device comprises a robot and wherein said moveable element comprises a portion thereof.

10. An apparatus for accurately positioning a moveable element comprising:

a device having said element moveably mounted thereon and including means for moving said element, means for sensing the rough position of said element relative to its mounting, and control means responsive to said position sensing means for moving said element to a desired rough position in space;

electro-optical means for determining the actual position of said moveable element in space relative to a reference point external to said device, said electro-optical means comprising light source means, light detector means, and means responsive to the output signal of said light detector means for determining the actual position in space of said moveable element relative to said external reference point;

means for determining, relative to said reference point, any difference between the actual position in space of said element as determined by said electro-optical means and the rough position in space as determined by said sensing means; and

means for subsequently utilizing any such determined difference in position to further actuate said control means to further move said moveable element from the desired rough position to the desired actual position.

11. Apparatus according to claim 10 wherein said device comprises a robot and wherein said moveable element comprises a portion thereof.