System for handling defects produced during the automated assembly of palletized elements

• US 6,035,243 A
• Filed: 10/22/1993
• Issued: 03/07/2000
• Est. Priority Date: 10/22/1993
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Galuga, Marta A., Glaspy, Jay A. Jr.
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Garland, Steven R.
• Application Number:
  US08/139,664
• Time in Patent Office: 2,328 Days
• Field of Search: 29/428-431, 29/563, 29/564, 29/568, 29/564.1, 700/95, 700/96, 700/108-117, 700/213, 700/217, 700/245, 700/247, 700/257
• US Class Current: 700/110
• CPC Class Codes: G05B 19/41805 characterised by assembly
• CPC Class Codes: G05B 19/41875 characterised by quality surveillance of production
• CPC Class Codes: G05B 2219/31028 Selecting workpieces from one or more containers by robot with vision
• CPC Class Codes: G05B 2219/31042 Enter pallet configuration, geometry, number of parts
• CPC Class Codes: G05B 2219/31296 Identification, pallet object data and program code for station
• CPC Class Codes: G05B 2219/32182 If state of tool, product deviates from standard, adjust system, feedback
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

The present invention is a method and apparatus for utilizing the characteristics of a pallet, or tray, used to supply workpieces to an automated, flexible assembly station or workcell. Once the characteristics are described and stored in memory, they may be used to uniquely identify workpieces which are determined to be defective during the automatic assembly operations. The defect information may then be stored in a cell controller which controls one or more workcells for later recall, in order to determine what, if any, further processing should be conducted on the defective workpieces and to prevent further processing thereof.

Claims

1. A flexible, workpiece assembly system for automatically performing operations on a plurality of similar workpieces located on a pallet, comprising:

a workcell for performing operations to modify at least one of said plurality of similar workpieces present on the pallet;

a cell controller in communication with said workcell, for controlling the operation of said workcell in response to a set of preprogrammed requirements;

means, located at said workcell, for detecting a defect in the assembly of the plurality of similar workpieces and generating an error message indicative of the defect, the error message including a first signal identifying, by location on the pallet, one of the plurality of workpieces detected as having a defect and a second signal, associated with said first signal, to indicate a nature of the defect detected therefor; and

a bus for communicating the error message to said cell controller, so that said cell controller may initiate an appropriate response.

2. The system of claim 1, wherein said first signal includes:

an area designator identifying an area on the pallet that contains the defective workpiece;

a row designator identifying a row on the pallet in which the workpiece lies; and

a column designator identifying a column on the pallet in which the workpiece lies.

3. The system of claim 1, wherein said cell controller includes a random access memory, and the system further includes means for storing a pallet ID, a workpiece location and a defect code for the defective workpiece in the cell controller memory, in response to said first and second signals, so as to prevent further use of the defective workpiece.

4. The system of claim 1, further including means, responsive to the error message, for identifying a defective workpiece and removing the defective workpiece from the pallet before further processing thereof.

5. The system of claim 1, further including means, responsive to said error message, for identifying a defective workpiece on the pallet so that the defective workpiece may be reworked before subsequent processing of the workpiece remaining on the pallet.

6. The system of claim 1, wherein the workcell comprises:

a robot controller; and

a robot, responsive to signals generated by said robot controller, for performing mechanical assembly operations to modify a workpiece present on the pallet.

7. The system of claim 6, wherein said defect detecting means comprises a vision system, attached to said robot, for detecting the presence of a workpiece on the pallet.

8. The system of claim 6, wherein said defect detecting means comprises a force sensor, integrally connected to the robot, for determining whether the force necessary to accomplish the workpiece assembly is within a predefined range.

9. A method of controlling a flexible, workpiece assembly system having a workcell which includes a robot controller and a robot, responsive to the robot controller, for assembling a plurality of similar workpieces present on a pallet presented to the workcell, comprising the steps of:

defining locations for the plurality of workpieces on the pallet presented to the workcell;

in response to a set of preprogrammed requirements provided to a cell controller, communicating from the cell controller to the workcell a plurality of commands for controlling the operation of the workcell so as to assemble the workpieces on the pallet;

detecting, at the workcell, a defect during the assembly of one of the workpieces present on the pallet and generating an error message indicative of a location of the defective one of the workpieces and a nature of the defect; and

communicating the error message to the cell controller over a bus.

10. The method of claim 9, further including the steps of:

determining whether the defect identified during assembly is a correctable defect; and

if so

automatically instituting an action to correct the defect;

otherwise

requesting, via the error message communicated to the cell controller, operator intervention to rectify the defect.

11. The method of claim 10, wherein the step of automatically instituting an action to correct the defect, includes the steps of:

generating commands to adjust the operating characteristics of the robot so as to avoid further defects during execution of the preprogrammed requirements; and

recording the occurrence of a correctable defect so as to maintain a record of such defects, wherein the record further identifies the workpiece on which the defect was noted by recording a pallet ID, and a row and column in which the workpiece is located on the pallet.

12. The method of claim 9, further including the steps of:

determining whether the defect identified during assembly is a fatal defect which cannot be corrected by the robot;

if a fatal defect, indicating that operator intervention is required at the workcell; and

recording, in memory, the presence of a defective workpiece on the pallet so as to maintain a record of such defects, wherein the record further identifies the workpiece on which the defect was noted by recording a pallet ID, and a row and column in which the workpiece is located.

13. The method of claim 9, further including the steps of:

determining whether the defect identified during assembly is a defect which cannot be corrected by the robot; and

if so

tagging the workpiece for which the defect was detected so as to identify the workpiece for subsequent correction of the defect.

14. The method of claim 13, wherein the step of tagging the workpiece includes:

generating, in a memory, a record which identifies the workpiece by recording a pallet ID for the pallet, and a row and column in which the workpiece is located thereon; and

indicating, within the memory record, that the workpiece has been identified as defective.

15. The method of claim 9, further including the steps of:

recording, in response to the error message, the presence of a potentially defective workpiece on the pallet so as to maintain a record of such defects, wherein the error message provides sufficient data to produce a record which identifies the workpiece on which the defect was noted by recording a pallet ID, and a row and column in which the workpiece is located.

16. A method of controlling a flexible, workpiece assembly system having a workcell which includes a robot controller and a robot, responsive to the robot controller, for assembling the workpieces, comprising the steps of:

defining locations for a plurality of workpieces on a pallet presented to the workcell;

in response to a set of preprogrammed requirements provided to a cell controller, communicating from the cell controller to the workcell a plurality of commands for controlling the operation of the workcell so as to assemble the workpieces on the pallet;

detecting, at the workcell, a defect during the assembly of a workpiece on the pallet and generating an error message indicative of the defect;

communicating the error message to the cell controller;

determining whether the defect identified during assembly is a correctable defect, and if so

automatically instituting an action to correct the defect by generating commands to adjust the operating characteristics of the robot so as to avoid further defects during execution of the preprogrammed requirements, and recording the occurrence of a correctable defect so as to maintain a record of such defects, wherein the record further identifies the workpiece on which the defect was noted by recording a pallet ID, and a pallet row and column location for the workpiece location,

otherwise requesting, via the error message communicated to the cell controller, operator intervention to rectify the defect;

tracking the total number of occurrences of correctable defects; and

indicating that operator intervention is required when the number of occurrences of correctable defects exceeds a predefined threshold level.

17. A method of controlling a flexible, workpiece assembly system having a workcell which includes a robot controller and a robot, responsive to the robot controller, for assembling the workpieces, comprising the steps of:

(1) defining locations for a plurality of workpieces on a pallet presented to the workcell;

(2) in response to a set of preprogrammed requirements provided to a cell controller, communicating from the cell controller to the workcell a plurality of commands for controlling the operation of the workcell so as to assemble the workpieces on the pallet;

(3) detecting, at the workcell, a defect during the assembly of a workpiece on the pallet and generating an error message indicative of the defect;

(4) communicating the error message to the cell controller

(5) interrogating the error message to determine if the error reported from the workcell is correctable; and

if so

(a) determining whether the correctable error may be corrected automatically or requires operator intervention, and if automatic correction is possible,

(b) effectuating automatic correction of the reported error, otherwise

(c) signaling an operator to manually adjust the robot;

otherwise

(6) determining whether the uncorrectable error is a fatal error; and

if so

(a) stopping the process and signaling for operator intervention before subsequent assembly operations are conducted at the workcell, otherwise

(b) identifying the defective workpiece on the pallet so that the defective workpiece may be prevented from further assembly processing.

18. The method of claim 17, wherein the step of identifying the defective workpiece includes the steps of:

storing, in cell controller memory, process error data derived from the error message which comprises a pallet identifier, a workpiece location, and a defect code for each defective workpiece;

retrieving, from the cell controller memory, the process error data associated with a particular pallet identifier; and

preventing, in response to the process error data retrieved, further use of the defective workpiece.

19. The method of claim 18, further including the step of removing defective workpieces identified by the process error data from the pallet.

20. The method of claim 18, further including the steps of:

retrieving the process error data for a particular pallet from the cell controller memory; and

reworking the defective workpieces identified by the process error data before subsequent processing of the pallet.

21. The method of claim 20, further including the step of displaying, on a user-interface screen, a graphical illustration of the pallet and the location of defective workpieces thereon to visually facilitate the manual selection of the defective workpieces.