Method and apparatus for optimizing work distribution

• US 6,249,715 B1
• Filed: 02/06/1998
• Issued: 06/19/2001
• Est. Priority Date: 03/18/1997
• Status: Expired due to Fees

• Current Assignee: Sumitomo Wiring Systems Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Wiring Systems Limited (Sumitomo Corporation)
• Inventors: Yuri, Hidetaka, Kurihara, Kiyokazu
• Primary Examiner(s): Gordon, Paul P.
• Application Number:
  US09/019,698
• Time in Patent Office: 1,229 Days
• Field of Search: 705/9, 705/8, 700/111, 700/100, 700/108, 700/95, 700/97, 702/182
• US Class Current: 700/111
• CPC Class Codes: G06Q 10/04 Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem" market predictions or forecasting for commercial activities G06Q30/0202
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

Method and apparatus for optimizing a work distribution, and in particular, to the optimization of work distribution along an assembly line or in a production process. A difficulty level is set for each task to be performed and a skill level is set for each respective worker. A time variation factor is set based upon the ranked work difficulty and the skill level of the workers. A compensation value is provided in accordance with the worker to whom an operation time of each element work is distributed, based upon a time variation factor. An assigned operation time per worker is maintained in equilibrium among respective workers by distributing each task in a preferential order, based on the compensated operation time.

Claims

1. A method for optimizing work distribution among multiple workers in handling a flow of production, said method comprising:

assigning a difficulty ranking to each task of a multiple-task assembly according to difficulty level;

assigning a skill ranking to each worker of the multiple workers for each task, according to the worker'"'"'s skill level in performing that task;

setting time variation factors corresponding to each task, each time variation factor being representative of at least an increase in operation time between different skill levels of the multiple workers performing the corresponding task;

compensating an operation time of each task assigned to a worker according to the time variation factor set for that task; and

maintaining an overall assigned operation time per worker in equilibrium among the multiple workers by distributing the tasks in a preferred order based on the compensated operation times.

2. The method according to claim 1, wherein said assigning a difficulty ranking includes collecting and analyzing Analytical Hierarchy Process data.

3. The method according to claim 1, wherein said assigning a skill ranking includes collecting and analyzing worker experience data and measured performance data.

4. The method according to claim 1, wherein said maintaining an overall assigned operation time per worker in equilibrium among the multiple workers by distributing the tasks in a preferred order based on the compensated operation times comprises:

shifting tasks among the multiple working areas to bring an overall assigned operation time for each worker to less than a predetermined threshold.

5. The method according to claim 4, wherein said predetermined threshold is approximately 90% of total man-hours of the multiple workers divided by a total number of the multiple workers.

6. The method according to claim 4, further comprising:

raising said predetermined threshold by a predetermined amount when shifting of tasks among the multiple working areas cannot bring the overall assigned operation time to less than the predetermined threshold.

7. The method according to claim 1, wherein said time variation factor increases in accordance with either one of a decrease in worker skill ranking or an increase in task difficulty ranking, and compounds with both of a decrease in worker skill ranking and an increase in task difficulty ranking.

8. The method according to claim 1, further comprising:

setting an overall assigned operation time per worker,

checking if actual measured operation time exceeds the overall assigned operation time by a predetermined tolerance; and

when said checking is true;

determining the excess time over the overall assigned operation time;

splitting a sub-task from the task assigned to the working area at a divisible point closest to half of said excess time; and

shifting the sub-task to an adjacent working area while maintaining the preferred order of tasks.

9. The method according to claim 1, in which at least one said task comprises a multiple element task grouped to be indivisible as a single task.

10. A method for optimizing work distribution in a flow of production including multiple tasks having a preferred order along a conveyor which transports products by multiple workers, said method comprising:

setting a normal operation time per working area according to a total of working man-hours of the multiple workers and a total number of the multiple workers;

assigning working areas, including working areas along the conveyor in a continuous manner in a reverse-flow direction to the conveyor;

classifying each task of the multiple tasks as one of;

divisible tasks, including at least two sub-tasks assignable among separate working areas; and

non-divisible tasks, including one or more sub-tasks which may only be assigned to a same working area;

classifying said indivisible tasks as one of;

prior handling indivisible tasks, to be performed before all of said divisible task; and

post handling indivisible tasks, to be performed after all of said divisible tasks;

distributing said prior handling indivisible tasks to said working areas in order from an earliest working area in the flow of production, an operation time of said prior handling indivisible tasks per worker being no greater than said normal operation time, and a preferred order of said prior handling indivisible tasks being maintained;

distributing said divisible tasks to said working areas and ordered after the prior handling indivisible tasks, an operation time of divisible tasks assigned to each working area being no greater than said normal operation time, and a preferred order of the divisible tasks being maintained; and

distributing said multiple tasks to said working areas in approximate equilibrium by, when assigned operation times at working areas along the conveyor vary from one other, shifting at least one task from one working area to an adjacent working area while maintaining the preferred order of tasks within said one working area and among said working areas.

11. The method according to claim 10, wherein said distributing said multiple tasks comprises:

distributing said divisible tasks to said working areas in approximate equilibrium by, when assigned operation times at working areas along the conveyor vary from one other, shifting at least one sub-task of said divisible tasks from one working area to an adjacent working area while maintaining the preferred order of sub-tasks within said one working area and among said working areas.

12. The method according to claim 10, wherein said distributing said multiple tasks comprises:

distributing said indivisible tasks to said working areas in approximate equilibrium by, when assigned operation times at working areas along the conveyor vary from one other, shifting at least one indivisible task from one working area to an adjacent working area while maintaining the preferred order of indivisible tasks within said one working area and among said working areas.

13. The method according to claim 10, further comprising:

distributing said post handling indivisible tasks to said working areas in reverse order from a last working area in said flow of production, an operation time of said post handling indivisible tasks per worker being no greater than said normal operation time, and the preferred order of said post handling indivisible tasks being maintained.

14. The method according to claim 10, wherein said shifting at least one task from one working area to an adjacent working area while maintaining the preferred order of tasks within said one working area and among said working areas comprises:

shifting tasks among the working areas to bring an overall assigned operation time for each working area to less than a predetermined threshold.

15. The method according to claim 14, further comprising:

raising said predetermined threshold by a predetermined amount when said shifting tasks among the working areas cannot bring the overall assigned operation time to less than the predetermined threshold.

16. The method according to claim 10, wherein said distributing said divisible tasks to working areas comprises:

distributing said divisible tasks to working areas along the conveyor in order such that when an assigned operation time of divisible tasks assigned to one working area has not yet reached said normal operation time, a sub-task from a subsequent divisible task in order is distributed to said one working area.

17. The method according to claim 10, wherein said distributing said divisible tasks to working areas comprises, when a last prior handling working area in which a prior handling indivisible task is distributed is less than said normal operation time:

distributing to said last working area at least one sub-task from a subsequent divisible task in order, such that an assigned operation time of indivisible and divisible tasks assigned to said last prior handling working area does not exceed said normal operation time.

18. The method according to claim 10, further comprising:

assigning a difficulty ranking to each task according to difficulty level;

assigning a skill ranking to each worker of the multiple workers for each task, according to the worker'"'"'s skill level in performing each task;

setting time variation factors corresponding to each task, each time variation factor being representative of at least an increase in operation time between different skill levels of the multiple workers performing the corresponding task; and

compensating an operation time of each task assigned to a worker according to the time variation factor set for that task;

wherein at least one of said distributing said prior handling indivisible tasks, said distributing said divisible tasks to working areas; and

said distributing said multiple tasks in approximate equilibrium employs the compensated operation times therein.

19. The method according to claim 18, wherein said distributing said multiple tasks in approximate equilibrium employs the compensated operation times therein, thereby distributing said multiple tasks in approximate equilibrium by, when assigned compensated operation times at working areas along the conveyor vary from one other, shifting at least one task from one working area to an adjacent working area while maintaining the preferred order of tasks within said one working area and among said working areas.

20. An apparatus for optimizing work distribution among multiple workers in handling a flow of production, said apparatus comprising:

a plurality of working areas at which workers perform tasks assigned thereto;

a product database storing difficulty rankings of each task of a multiple-task assembly according to difficulty level;

a worker database storing skill rankings of each worker of the multiple workers for each task, according to the worker'"'"'s skill level in performing that task;

a work distribution simulator storing variation factors corresponding to each task, each time variation factor being representative of at least an increase in operation time between different skill levels of the multiple workers performing the corresponding task;

said work distribution simulator compensating an operation time of each task assigned to a worker according to the time variation factor set for that task; and

said work distribution simulator maintaining an overall assigned operation time per worker in equilibrium among the multiple workers by distributing the tasks to said working areas in a preferred order based on the compensated operation times.

21. The apparatus according to claim 20, wherein said difficulty rankings are in accordance with Analytical Hierarchy Process data.

22. The apparatus according to claim 20, wherein said skill rankings are in accordance with worker experience data and measured performance data.

23. The apparatus according to claim 20, wherein said work distribution simulator shifts tasks among the plurality of working areas to bring an overall assigned operation time for each worker to less than a predetermined threshold.

24. The apparatus according to claim 23, wherein said predetermined threshold is approximately 90% of total man-hours of the multiple workers divided by a total number of the multiple workers.

25. The apparatus according to claim 23, wherein said work distribution simulator raises said predetermined threshold by a predetermined amount when shifting of tasks among the plurality of working areas cannot bring the overall assigned operation time to less than the predetermined threshold.

26. The apparatus according to claim 20, wherein said time variation factor increases in accordance with either one of a decrease in worker skill ranking or an increase in task difficulty ranking, and compounds with both of a decrease in worker skill ranking and an increase in task difficulty ranking.

27. The apparatus according to claim 20, said work distribution simulator further sets an overall assigned operation time per worker, checks if actual measured operation time exceeds the overall assigned operation time by a predetermined tolerance;

and when said checking is true, determines the excess time over the overall assigned operation time, splits a sub-task from the task assigned to the worker at a divisible point closest to half of said excess time, and shifts the sub-task to an adjacent worker while maintaining the preferred order of tasks.

28. The apparatus according to claim 20, in which at least one said task comprises a multiple element task grouped to be indivisible as a single task.

29. An apparatus for optimizing work distribution in a flow of production including multiple tasks having a preferred order along a conveyor which transports products by multiple workers, said apparatus comprising:

a plurality of working areas at which workers perform tasks assigned thereto, including working areas distributed along the conveyor in a continuous manner in an order of reverse-flow direction to the conveyor;

a work distribution simulator that sets a normal operation time per working area according to a total of working man-hours of the multiple workers and a total number of the multiple workers;

said work distribution simulator classifying each task of the multiple tasks as one of;

divisible tasks, including at least two sub-tasks assignable among separate working areas; and

non-divisible tasks, including one or more sub-tasks which may only be assigned to a same working area; and

classifying said indivisible tasks as one of;

prior handling indivisible tasks, to be performed before all of said divisible task; and

post handling indivisible tasks, to be performed after all of said divisible tasks;

said work distribution simulator distributing said prior handling indivisible tasks to said working areas in order from an earliest working area in the flow of production, an operation time of said prior handling indivisible tasks per worker being no greater than said normal operation time, and a preferred order of said prior handling indivisible tasks being maintained;

said work distribution simulator distributing said divisible tasks to said working areas and ordered after the prior handling indivisible tasks, an operation time of divisible tasks assigned to each working area being no greater than said normal operation time, and a preferred order of the divisible tasks being maintained; and

said work distribution simulator distributing said multiple tasks to said working areas in approximate equilibrium by, when assigned operation times at working areas vary from one other, shifting at least one task from one working area to an adjacent working area while maintaining the preferred order of tasks within said one working area and among said working areas.

30. The apparatus according to claim 29, wherein said work distribution simulator distributes said divisible tasks in approximate equilibrium by, when assigned operation times at working areas along the conveyor vary from one another, shifting at least one sub-task of said divisible tasks from one working area to an adjacent working area while maintaining the preferred order of sub-tasks within said one working area and among said working areas.

31. The apparatus according to claim 29, wherein said work distribution simulator distributes said indivisible tasks in approximate equilibrium by, when assigned operation times at working areas along the conveyor vary from one another, shifting at least one indivisible task from one working area to an adjacent working area while maintaining the preferred order of indivisible tasks within said one working area and among said working areas.

32. The apparatus according to claim 29, wherein said work distribution simulator distributes said post handling indivisible tasks in reverse order from a last worker in said flow of production, an operation time of said post handling indivisible tasks per worker being no greater than said normal operation time, and the preferred order of said post handling indivisible tasks being maintained.

33. The apparatus according to claim 29, wherein said work distribution simulator shifts tasks among the plurality of working areas to bring an overall assigned operation time for each working area to less than a predetermined threshold.

34. The apparatus according to claim 33, wherein said work distribution simulator raises said predetermined threshold by a predetermined amount when said shifting tasks among the plurality of working areas cannot bring the overall assigned operation time to less than the predetermined threshold.

35. The apparatus according to claim 29, wherein said work distribution simulator distributes said divisible tasks to working areas along the conveyor in order such that when an assigned operation time of divisible tasks assigned to one working area has not yet reached said normal operation time, a sub-task from a subsequent divisible task in order is distributed to said one working area.

36. The apparatus according to claim 29, wherein, when a last prior handling working area in which a prior handling indivisible task is distributed is less than said normal operation time, said work distribution simulator distributes to said last working area at least one sub-task from a subsequent divisible task in order, such that an assigned operation time of indivisible and divisible tasks assigned to said last prior handling working area does not exceed said normal operation time.

37. The apparatus according to claim 29, further comprising:

a product database storing difficulty rankings of each task according to difficulty level;

a worker database storing skill rankings of each worker of the multiple workers for each task, according to the worker'"'"'s skill level in performing that task;

said work distribution simulator storing variation factors corresponding to each task, each time variation factor being representative of at least an increase in operation time between different skill levels of worker performing the corresponding task; and

said work distribution simulator compensating an operation time of each task assigned to a worker according to the time variation factor set for that task,

wherein said work distribution simulator employs the compensated operation times in at least one of distributing said prior handling indivisible tasks, distributing said divisible tasks to working areas; and

distributing said multiple tasks in approximate equilibrium therein.

38. The apparatus according to claim 37, wherein said work distribution simulator employs the compensated operation times in distributing said multiple tasks in approximate equilibrium, thereby distributing said multiple tasks in approximate equilibrium by, when assigned compensated operation times at working areas along the conveyor vary from one other, shifting at least one task from one working area to an adjacent working area while maintaining the preferred order of tasks within said one working area and among said working areas.