Menu driven system for controlling automated assembly of palletized elements

• US 5,475,797 A
• Filed: 10/22/1993
• Issued: 12/12/1995
• 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: Glaspy, Jay A. Jr., Galuga, Marta A.
• Primary Examiner(s): Davis, George B.
• Application Number:
  US08/139,657
• Time in Patent Office: 781 Days
• Field of Search: 395/85, 395/80, 395/99, 395/88, 395/94, 395/82, 901/4, 901/41, 318/567, 318/568.13, 318/568.23, 318/568.25
• US Class Current: 700/247
• CPC Class Codes: G05B 19/41805 characterised by assembly
• CPC Class Codes: G05B 19/4182 manipulators and conveyor only
• CPC Class Codes: G05B 2219/31031 Assembly, manipulator cell
• CPC Class Codes: G05B 2219/31042 Enter pallet configuration, geometry, number of parts
• CPC Class Codes: G05B 2219/32228 Repair, rework of manufactured article
• CPC Class Codes: G05B 2219/36503 Adapt program to real coordinates, software orientation
• CPC Class Codes: G05B 2219/37002 Absence, detect absence, presence or correct position of workpiece
• CPC Class Codes: G05B 2219/37068 Setting reference coordinate frame
• CPC Class Codes: G05B 2219/37572 Camera, tv, vision
• CPC Class Codes: G05B 2219/50073 Signature analysis, store forces during test, compare with real ones during assemby
• 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 defining the critical 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.

Claims

1. A method of controlling a system for performing assembly operations on a plurality of workpieces residing on a pallet at a workcell, wherein the workcell includes a robot controller and a robot adapted to respond to commands received from the robot controller to assemble the workpieces comprising the steps of:

defining a location for each of the plurality of workpieces on the pallet, including defining a geometric structure of the pallet including

displaying, on a user-interface electrically interconnected to the workcell, a series of prompts to which an operator responds to characterize critical parameters of the pallet,

storing, in a memory, all values that the operator enters in response to the prompts, and

calculating, as a function of the values entered for the critical parameters, a nominal location for each of the plurality of workpieces residing on the pallet; and

communicating from a cell controller to the workcell, said cell controller having a set of preprogrammed requirements stored in a memory therein, said preprogrammed requirements for controlling an operation of the workcell, so as to cause the workcell to assemble the plurality of workpieces residing on the pallet.

2. The method of claim 1, wherein the step of defining the location of workpieces on the pallet further includes the step of teaching, by the operator manually directing the robot, a reference location for the pallet, said reference location being used by the robot controller to determine actual workpiece locations as a function of the reference location and the nominal location for each of the plurality of workpieces.

3. The method of claim 1, wherein the step of defining the location of workpieces on the pallet further includes the step of manually entering coordinates of a reference location for the pallet, said reference location being used by the robot controller to determine actual workpiece locations as a function of the reference location and the nominal location for each of the plurality of workpieces.

4. The method of claim 1, further including the step of adjusting the nominal location for each of the plurality of workpieces residing on the pallet as a function of a frame error value which represents positioning inaccuracies within the workcell.

5. The method of claim 4, wherein the frame error value is determined automatically by the robot controller using a method including the steps of:

moving the robot to simulate a production situation, and upon arriving at an extreme workpiece location on the pallet, storing an actual robot position in memory; and

calculating the frame error value as a function of the difference between the actual robot position at an extreme workpiece location and a corresponding nominal location for one of the plurality of workpieces residing on the pallet.

6. The method of claim 4, wherein the frame error value is entered manually via the user interface.

7. The method of claim 4, wherein the step of adjusting the nominal location for each of the plurality of workpieces residing on the pallet as a function of a frame error value comprises the steps of:

teaching coordinates of at least two additional reference locations using the robot, to thereby determine the coordinates of at least three reference locations;

storing the coordinates of the three reference locations in the memory; and

automatically deriving the frame error value as a function of the coordinates of the three reference locations stored in the memory.

8. The method of claim 1, wherein the step of defining the location of workpieces on the pallet includes the steps of:

retrieving, from a storage memory, a set of critical parameter values which characterize the pallet;

displaying, on a user-interface, the critical parameter values for the pallet while prompting the operator to make changes to those parameters which are incorrect;

storing all corrections made by the operator to the critical parameter values to establish a set of updated parameter values;

calculating, as a function of the updated parameter values, the nominal location for each of the plurality of workpieces residing on the pallet.