Method and apparatus for palletizing packages of random size and weight

• US 5,908,283 A
• Filed: 11/26/1996
• Issued: 06/01/1999
• Est. Priority Date: 11/26/1996
• Status: Expired due to Term

• Current Assignee: United Parcel Service Of America Incorporated (United Parcel Service Incorporated)
• Original Assignee: United Parcel Service Of America Incorporated (United Parcel Service Incorporated)
• Inventors: Janik, Jaroslav, Jackson, Peter Douglas, Penkar, Rajan Chandrakant, Lecko, John H., Snyder, Joseph P. Jr., Huang, Pao-Ter, Cai, Christopher Chunsheng
• Primary Examiner(s): Young, Karen M.
• Assistant Examiner(s): MORSE, GREGORY ALLAN
• Application Number:
  US08/756,675
• Time in Patent Office: 917 Days
• Field of Search: 414/799, 414/902, 901/2, 901/6, 901/8, 901/49, 198/502.2, 198/370.01
• US Class Current: 414/801
• CPC Class Codes: B65G 47/90 Devices for picking-up and depositing articles or materials
• CPC Class Codes: B65G 47/905 Control arrangements
• CPC Class Codes: B65G 47/91 incorporating pneumatic, e.g. suction, grippers
• CPC Class Codes: B65G 61/00 Use of pick-up or transfer devices or of manipulators for stacking or de-stacking articles not otherwise provided for
• CPC Class Codes: G06Q 10/043 Optimisation of two dimensional placement, e.g. cutting of clothes or wood
• CPC Class Codes: Y10S 414/116 including control for pattern of group

Abstract

A method and apparatus for palletizing rectangular packages received in random size and weight. A "corner"-based modeling system is used to assist in evaluating possible placements of packages accumulated on a line conveyor, and a placement evaluation process is used to select a "best" package placement based on heuristic analysis. Statistically-based measurement and comparison is used to assist in the evaluation process.

Claims

1. A method for accepting a plurality of parallelepiped packages of random size and shape and selecting one of said packages on an accumulator for placement at a different location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of said plurality of packages received in step "a";

c) accumulating said packages in side-justified alignment on an accumulator in the order which they were received; and

d) selecting individual packages from said accumulator for placement at said designated location, said selection based on the assistance of data received through step "b".

2. The method as claimed in claim 1, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

3. The method as claimed in claim 1, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

4. The method as claimed in claim 1, wherein in step "c" said packages are aligned in side-justified line contact.

5. A method for accepting a plurality of parallelepiped packages of random size and shape and selecting one of said packages on an accumulator for placement at a different designation location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package of said plurality of packages received in step "a";

c) accumulating said packages on a one-way accumulator in side-justified line contact in the order which they were received; and

d) selecting and removing packages in non-sequential order from said accumulator.

6. The method as claimed in claim 5, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

7. The method as claimed in claim 5, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

8. A method for accepting a plurality of parallelepiped packages of random size and shape and selecting one of said packages on an accumulator for placement at a different designation location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package of said plurality of packages received in step "a";

c) accumulating said packages on a one-way accumulator in side-justified line contact in the order which they were received;

d) selecting packages in non-sequential order from said accumulator; and

e) ejecting a nonselected package from the downstream end of said one-way accumulator after a preselected number of selections in step "d" has been made.

9. The method as claimed in claim 8, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

10. The method as claimed in claim 8, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

11. A method for stacking packages at a stacking destination with a gripping apparatus having a finite package access range including said stacking destination, said method comprising the steps of:

a) placing a plurality of packages in line contact on an accumulator conveyor including a direct pick-up buffer section within the access range of said gripping apparatus and a pre-buffer section outside of the access range of said gripping apparatus that said plurality of packages in line contact includes at least one package in said direct pick-up buffer section and at lest one package in said pre-buffer section;

b) identifying a pair of packages which would tend to stack well together under at least one predetermined stacking principle, the first designated package of said pair being within a plurality of packages in said direct pick-up buffer section and the second designated package of said pair being in said pre-buffer section;

c) removing at least one package within said direct pick-up buffer section such that said designated package within said pre-buffer section is moved into said access range of said gripping apparatus; and

d) stacking both of said designated packages together at said stacking destination according to said predetermined stacking principle.

12. The method as claimed in claim 11, wherein said second designated package is moved into said direct pick-up buffer section in step "c" while said first designated package is within said direct pick-up buffer section.

13. The method as claimed in claim 11, wherein said second designated package is moved into said direct pick-up buffer section in step "c" while said first designated package is at said stacking destination.

14. The method as claimed in claim 11, wherein said predetermined stacking principle defined in step "d" is a principle based upon the assumption that two packages of the same height stacked side-by-side is preferable.

15. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each of said packages in said plurality of packages received in step "a";

c) accumulating said packages in line contact in the order they were received;

d) determining a plurality of parallelepiped corner sites at said designated stack location, each of said parallelepiped corner sites defined at their bottom by upwardly directed direct support surfaces capable of package support;

e) defining at least one potential package placement within at least one of said corner sites; and

f) placing the package at said potential package placement selected in step "d".

16. The method for stacking packages as claimed in claim 15, wherein in step "c", a list of package neighbors is developed for each corner.

17. The method as claimed in claim 16, wherein said neighbor list is developed by including packages within a predetermined distance range relative to said corner.

18. The method for stacking packages as claimed in claim 16, wherein in step "c", a front neighbor list, a back neighbor list, a left neighbor list, and a right neighbor list is developed for each corner.

19. The method as claimed in claim 15, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

20. The method as claimed in claim 15, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

21. The method for stacking packages as claimed in claim 15, wherein said plurality of parallelepiped corner sites are each at least partially defined by supporting surfaces existing at said designated stack location.

22. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package in said plurality of packages received in step "a";

c) accumulating said packages on an accumulator in line contact in the order in which they were received;

d) identifying one of said packages on said accumulator;

e) establishing a plurality of potential package placements at said stack location capable of receiving said identified package; and

f) placing a selected package at said one of said potential package placements.

23. The stacking method as claimed in claim 22, wherein further package placement locations are determined by shifting the package position to different location within the outside boundary of the designated stack location.

24. The stacking method as claimed in claim 23, wherein in step "e", the establishment of said package placement positions includes defining a package placement configured such that if placed the selected package side surface would be aligned with the side surface of a previously-stacked package.

25. The stacking method as claimed in claim 23, wherein in step "e", the establishment of said package placement positions includes defining a package placement configured such that if placed the selected package side surface would overhang the side surface of a previously-stacked package by a distance proportional to a dimension of said selected package.

26. The stacking method as claimed in claim 23, wherein in step "e", the establishment of said package placement positions includes defining a package placement configured such that if placed the selected package side surface would overlap the side surface of a previously-stacked package by a distance proportional to a dimension of said selected package.

27. The stacking method as claimed in claim 22, wherein in step "e", the establishment of said package placement positions includes defining a package placement configured such that if placed the selected package side surface would be aligned with and "flush" with the outside boundary of the designated stack location.

28. The stacking method as claimed in claim 27, wherein further package placement locations are determined by shifting the package position within the outside boundary of the designated stack location after said package placement has so been made "flush".

29. The method as claimed in claim 22, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

30. The method as claimed in claim 22, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

31. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package in said plurality of packages received in step "a";

c) accumulating said packages on an accumulator in line contact in the order they were received;

d) identifying one of said packages on said accumulator and one package placement position at said stack location capable of receiving said identified package;

e) at least partially evaluating the stability of said selected package at said placement position by use of preselected stability criteria, and

f) giving preference to placing said package at said package placement position based upon said stability criteria.

32. The method as claimed in claim 31, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

33. The method as claimed in claim 31, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

34. A method for accepting at least one parallelepiped package of random size and shape and stacking said package together at a designated stack location, said method comprising the steps of:

a) receiving at least one parallelepiped package;

b) determining at least one outside length dimension of said unstacked parallelepiped package received in step "a";

c) identifying at one package placement position at said stack location capable of receiving said identified package;

d) at least partially evaluating the stability of said unstacked identified package at said placement position by determining the percentage of support the package bottom surface would receive if placed at said position, and applying said percentage against a threshold, and

e) placing said package at said package placement position only if said threshold is reached.

35. The method as claimed in claim 34, wherein step "b" is accomplished by actually measuring said outside dimension after said package is received.

36. The method as claimed in claim 34, wherein step "b" is accomplished by identifying said package and referencing a dimensional reading assigned to said package prior to its receipt.

37. The method of stacking packages as claimed in claim 34, wherein said designated stack location is a pallet and in said step "d" a determination is made of the support said package would receive if placed atop a bare pallet surface configured to accept a plurality of packages thereon.

38. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package in said plurality of packages received in step "a";

c) accumulating said packages on an accumulator in line contact in the order which they were received;

d) identifying one of said packages and one package placement position at said stack location capable of receiving said identified package;

e) at least partially evaluating the stability of said unstacked identified package at said placement position by determining the percentage of support the package bottom surface would receive if placed at said position, and applying said percentage against a threshold, and

e) placing said package at said package placement position only if said threshold is reached.

39. The method as claimed in claim 38, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

40. The method as claimed in claim 38, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

41. The method of stacking packages as claimed in claim 38, wherein in said step "d" a determination is made of the support said package would receive if placed atop a previously stacked package.

42. A method for accepting at least one parallelepiped package of random size and shape and stacking said package together at a designated stack location, said method comprising the steps of:

a) receiving at least one parallelepiped package;

b) determining at least one outside length dimension of said unstacked parallelepiped package received in step "a";

c) identifying at least one common package placement position at said stack location capable of receiving said identified package;

d) at least partially evaluating the stability of said unstacked identified package at said placement position by determining the effective support surface available to the package bottom surface if placed at said position, said effective support surface defined by an effective support surface boundary, and comparing said effective support surface to a defined gravity center region assigned to said unstacked identified package, said gravity center region defined as a region on the bottom surface of said package through which the gravity center force vector of said unstacked package is likely to pass, and

e) placing said package at said package placement position only if said gravity center region falls within said effective support surface boundary.

43. The method as claimed in claim 42, wherein step "b" is accomplished by actually measuring said outside dimension after said package is received.

44. The method as claimed in claim 42, wherein step "b" is accomplished by identifying said package and referencing a dimensional reading assigned to said package prior to its receipt.

45. The stacking method as claimed in claim 42, wherein said effective support surface boundary determined in step "d" is at least partially defined by solid package support extending below said package bottom surface through at least one layer of packages therebelow.

46. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package in said plurality of packages received in step "a";

c) accumulating said packages on an accumulator;

d) identifying one of said packages on said accumulator and one package placement position at said stack location capable of receiving said identified package;

e) at least partially evaluating the stability of said unstacked identified package at said placement position by determining the effective support surface available to the package bottom surface if placed at said position, said effective support surface defined by an effective support surface boundary, and comparing said effective support surface to a defined gravity center region assigned to said unstacked identified package, said gravity center region defined as a region on the bottom surface of said package through which the gravity center force vector of said unstacked package is likely to pass, and

f) giving preference to placing said package at said package placement position if said effective support surface sufficiently overlaps said gravity support region.

47. The method as claimed in claim 46, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

48. The method as claimed in claim 46, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

49. The stacking method as claimed in claim 46, wherein said effective support surface boundary determined in step "e" is at least partially defined by solid package support extending below said package bottom surface through at least one layer of packages therebelow.

50. A method of accessing the stability of an selected package if placed in a particular stacked package placement atop one or more previously placed packages, comprising the steps of:

a) determining the percentage of direct package support the package would have if placed at said package placement, and making a determination of instability if a threshold is not met;

b) determining the effective support surface available to the package bottom surface if placed at said package placement, said effective support surface defined by an effective support surface boundary, and comparing said effective support surface to a defined gravity center region assigned to said unstacked identified package, said gravity center region defined as a region on the bottom surface of said package through which the gravity center force vector of said unstacked package is likely to pass;

c) checking side support available to the package if placed at said package placement;

d) making a determination of instability if predetermined thresholds are not met in either of steps "b" and "c";

e) checking support surface distribution on said bottom surface of said package if placed at said package placement, and making a determination of stability if a predetermined threshold is met; and

f) stacking the package only if a determination of stability is made for said package if placed at said package placement.

51. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) determining at least one common outside length dimension of each package in said plurality of packages received in step "a";

c) accumulating said packages on an accumulator;

d) identifying one of said packages on said accumulator and one package placement position at said stack location capable of receiving said identified package and being atop at least one previously-stacked package;

e) at least partially evaluating the stability of said selected package at said placement position by;

1) determining the percentage of direct package support the package would have if placed at said package placement, and making a determination of instability if a threshold is not met;

2) determining the effective support surface available to the package bottom surface if placed at said package placement, said effective support surface defined by an effective support surface boundary, and comparing said effective support surface to an defined gravity center region assigned to said unstacked identified package, said estimated gravity center region defined as a region on the bottom surface of said package through which the gravity center force vector of said unstacked package is likely to pass;

3) checking side support available to the package if placed at said package placement;

4) making a determination of instability if predetermined thresholds are not met in either of steps "2" and "3"; and

5) checking support surface distribution on said bottom surface of said package if placed at said package placement, and making a determination of stability if a predetermined threshold is met; and

f) stacking the package only if a determination of stability is made for said package if placed at said package placement.

52. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) measuring at least one common outside length dimension of each package in said plurality of packages;

c) accumulating said packages on an accumulator in side-justified line contact;

d) identifying at least one package on said accumulator, and also identifying within said designated stack location a plurality of package placements corresponding to said identified package;

e) assigning a performance index to each of said package placements by use of predetermined stacking performance criteria;

f) identifying the package placement assigned the highest performance index in step "e"; and

g) stacking the package associated with the package placement identified in step "f" at said package placement identified in step "f".

53. The method as claimed in claim 52, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

54. The method as claimed in claim 52, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

55. The method as claimed in claim 52, wherein said performance index includes the use of a tapering index, which penalizes package placements which result in a tapering stack.

56. The method as claimed in claim 52, wherein said performance index includes the use of a level index, which gives preference to package placements which result in stacked packages having upper surfaces at approximately the same level.

57. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location, said method comprising the steps of:

a) receiving said packages in a random manner;

b) measuring at least one common outside length dimension of each package of said plurality of packages;

c) accumulating said packages on an accumulator in side-justified line contact;

d) identifying at least one package on said accumulator, and also identifying within said designated stack location a plurality of package placements corresponding to said identified package;

e) evaluating the stability of said package placements;

f) assigning a performance index to each of said stabile package placements by use of predetermined stacking performance criteria;

g) identifying the stabile package placement assigned the highest performance index in step "f"; and

h) stacking the package associated with the package placement identified in step "g" at said package placement identified in step "g".

58. The method as claimed in claim 57, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

59. The method as claimed in claim 57, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

60. The method as claimed in claim 57, wherein said performance index includes the use of a tapering index, which penalizes package placements which result in a tapering stack.

61. The method as claimed in claim 57, wherein said performance index includes the use of a level index, which gives preference to package placements which result in stacked packages having upper surfaces at approximately the same level.

62. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking said packages together at a designated stack location and for transferring one parallelepiped package from a first location to a second location with a interfering stack of parallelepiped packages intersecting a direct path intermediate said first and second locations, said method comprising the steps of:

a) receiving said packages in a random manner;

b) measuring at least one common outside length dimension of each package of said plurality of packages;

c) accumulating said packages in the order in which they were measured;

d) identifying one of said packages on said accumulator and identifying within said designated stack location a package placement capable of receiving said identified package;

e) transferring said identified package along a placement path from said accumulator to said package placement position at said stack, said path lying substantially in a vertical plane and also including a plurality of intermediate via positions being a selected distance above interference positions determined to cause interference between the package and other packages already in place at said stack location.

63. The method as claimed in claim 62, wherein in step "e", said path is concave downwardly to approximate a minimum distance path in said vertical plane.

64. The method as claimed in claim 62, wherein step "b" is accomplished by actually measuring the outside dimension of each package after it is received.

65. The method as claimed in claim 62, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

66. The method as claimed in claim 62, wherein forward package collision searching is conducted to determine at least some of said via positions.

67. The method as claimed in claim 62, wherein backward package collision searching is conducted to determine at least some of said via positions.

68. A time-efficient method for transferring a parallelepiped package from a first location to a second location with a interfering stack of parallelepiped packages intersecting a direct path intermediate said first and second locations, said method comprising the steps of:

a) determining the packages of said stack of said interfering parallelepiped packages which intersect a vertical plane passing through the geometric center of said packages at their first and second locations;

b) determining a plurality of via positions which correspond to positions which would allow the transferring package to just vertically clear said interfering packages;

c) transferring said package along a placement path from said accumulator to said package placement position at said stack, said path lying substantially in a vertical plane and also including at least one of said via positions.

69. The method as claimed in claim 68, wherein in step "e", said path is concave downwardly to approximate a minimum distance path in said vertical plane.

70. The method as claimed in claim 68, wherein said step of determining said common outside length of said plurality of packages is accomplished by actually measuring said outside dimension.

71. The method as claimed in claim 68, wherein step "b" is accomplished by referencing a dimensional reading assigned to each of said packages prior to their receipt.

72. The method as claimed in claim 68, wherein forward package collision searching is conducted to determine at least some of said via positions.

73. The method as claimed in claim 68, wherein backward package collision searching is conducted to determine at least some of said via positions.

74. A method for accepting a plurality of parallelepiped packages of random size and shape and stacking a first and subsequently a second package at a designated stack location, said method comprising the steps of:

accumulating said first and said second packages on an accumulator conveyor in line contact;

instructing a gripper mechanism to pick up said first package from said accumulator conveyor for placement at said designated stack location; and

evaluating the placement of said second package at said designated stack location while said gripper mechanism is on its way to pick up said first package from said accumulator conveyor.

75. A method for selecting individual packages from an accumulated package line comprised of plurality of packages in line contact along their lengths, said accumulated package line including at its opposing ends first and second end packages defining corresponding first and second outwardly opposing surfaces, the actual distance between said outwardly opposing surfaces defining said overall actual length of said accumulated package line, said accumulated package line also including at least one intermediate package located between said end packages, said method comprising the steps of:

a) determining one common dimension of a plurality of packages as a "nominal length" of each of said packages;

b) subsequent to step "a", accumulating said accumulated package line as a plurality of packages in line contact such that said common actual dimensions of said packages combine to comprise the actual line length of said accumulated package line;

c) measuring the actual line length of said accumulated package line by measuring the distance between said first and second outwardly opposing surfaces;

d) determining the difference between said actual accumulated package line length and the summation of the nominal line lengths of all the packages in the line as an "actual line error";

e) assigning a portion of said actual line error to said intermediate package within said line; and

f) instructing a gripper to move to pick up said intermediate package, said instructions at least partially based on said nominal length measurements and said portion of said actual line error assigned to said intermediate package.

76. The method as claimed in claim 75, wherein said the measurement of said actual line length of said accumulated package line is done by urging said first opposing surface of said first package against a reference stop surface of known location and by measuring the distance of said second opposing surface of said second package relative to said reference stop surface.

77. The method as claimed in claim 76, wherein the portion of said actual line error assigned to said intermediate package is directly dependent upon the number of packages between said reference stop surface and said intermediate package.

78. The method as claimed in claim 75, wherein said method is conducted upon an accumulated package line having said intermediate package in direct contact with at least one of said end packages.

79. The method as claimed in claim 75, wherein said method is conducted upon an accumulated package line having said intermediate package not being in direct contact with either of said end packages, instead having at least one package between the intermediate package and each of the end packages.

80. A method for selecting individual packages from an accumulated package line comprised of plurality of packages in line contact along their lengths, said accumulated package line including at its opposing ends first and second end packages defining corresponding first and second outwardly opposing surfaces, the actual distance between said outwardly opposing surfaces defining said overall actual length of said accumulated package line, said accumulated package line also including at least one intermediate package located between said end packages, said method comprising the steps of:

a) determining one common dimension of a plurality of packages as a "nominal length" of each of said packages;

b) subsequent to step "a", accumulating said accumulated package line as a plurality of packages in line contact such that said common dimensions of said packages combine to comprise the actual line length of said accumulated package line;

c) measuring the actual line length of said accumulated package line by measuring the distance between said first and second outwardly opposing surfaces;

d) determining the difference between said actual accumulated package line length and the summation of the nominal line lengths of all the packages in the line as "actual line error";

e) assigning a portion of said actual line error to said intermediate package within said line;

f) instructing a gripper to move to pick up said intermediate package, said instructions at least partially dependent upon based on said nominal length measurements and said portion of said actual line error assigned to said intermediate package;

g) accumulating another package to create a modified accumulated package line;

h) measuring the actual line length of said modified accumulated package line;

i) determining the difference between said actual modified accumulated package line length and the summation of the nominal line lengths of all the packages in the modified accumulated package line as a second "actual line error";

j) determining a weighted actual line error dependent upon said original actual line error determined in step "d" and said second actual line error determined in step "i"; and

k) instructing a gripper to move to pick up another intermediate package, said instructions at least partially dependent upon based on said nominal length measurements and said portion of said weighted actual line error assigned to said intermediate package.