Traffic management system and method for materials handling using traffic balancing and traffic density

• US 6,647,316 B2
• Filed: 02/22/2001
• Issued: 11/11/2003
• Est. Priority Date: 02/22/2001
• Status: Expired due to Term

• Current Assignee: Murata Machinery Limited (Muratec)
• Original Assignee: PRI Automation, Inc. (Azenta, Inc.)
• Inventors: Mariano, Thomas, Gaskins, Robert, Schnackertz, Ted, Levassuer, David, Liu, Jing Wen, Bahri, Namdar
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): Butler, Michael E.
• Application Number:
  US09/790,476
• Publication Number:
  US 20020138172A1
• Time in Patent Office: 992 Days
• Field of Search: 700/217, 700/213, 700/226, 700/228, 700/229
• US Class Current: 700/217
• CPC Class Codes: G06Q 10/047 Optimisation of routes or paths, e.g. travelling salesman problem

Abstract

A traffic management system for an automatic material handling system (AMHS) divides time into a series of discrete time periods and analyzes a plurality of move requests that are to be executed within a particular time period is disclosed. The traffic management system receives a plurality of move requests from the AMHS and determines how many move requests are to be executed and selects which move requests in particular will be executed in the next time period. The traffic management system prioritizes the selected move requests by analyzing each source node and destination node contained in a move request in conjunction with other node traffic data. The traffic management system analyzes this data to ensure that a move request is not executed if a material transport vehicle would be dispatched to a node having a node traffic balance value that exceeds a predetermined value and a node traffic density value that exceeds a predetermined value.

Claims

1. A method for prioritizing vehicle movements in an automatic material handling system, the method comprising:

providing an ordered list of move requests, the ordered list including a source node and a destination node associated with each move request;

calculating a traffic balance value for each source node and for each destination node for each move request;

calculating a traffic density value for each source node and for each destination node for each move request;

calculating a free car limit value for each source node and for each destination node for each move request;

searching said ordered list of move requests for a first move request having an associated source node and destination node each having said traffic balance value equal to a first traffic balance value and said traffic density value equal to a first traffic density value; and

assigning said first move request a first priority value.

2. The method of claim 1 wherein said first traffic balance value is 0.

3. The method of claim 1 wherein said first traffic density value is 2.

4. The method of claim 1 further comprising the steps of:

searching said ordered list of move requests for a second move request having an associated source node and destination node having said traffic balance value equal to a second traffic balance value and said traffic density value equal to a second traffic density value; and

assigning said second move request a second priority value.

5. The method of claim 4 wherein said second traffic balance value is between −

2 and 2.

6. The method of claim 5 wherein said second traffic balance value is between −

1 and 2.

7. The method of claim 1 further comprising the steps of:

searching said ordered list of move requests for a third move request having a source node having said free car limit value equal to a first free car limit value; and

assigning said third move request a third priority value.

8. The method of claim 7 wherein said second traffic density value is less than 3.

9. The method of claim 7 wherein said free car limit value is 1.

10. A method for prioritizing vehicle movements in an automatic material handling system, the method comprising:

providing an ordered list of move requests, the ordered list including a source node and a destination node associated with each move request;

calculating a traffic balance value for each source node and for each destination node for each move request;

calculating a traffic density value for each source node and for each destination node for each move request;

calculating a free car limit value for each source node and for each destination node for each move request;

searching said ordered list of move requests for a first move request having an associated source node and destination node each having said traffic balance value equal to a first traffic balance value and said traffic density value equal to a first traffic density value;

assigning said first move request a first priority value;

searching said ordered list of move requests for a second move request having an associated source node and destination node having said traffic balance value equal a second traffic balance value and said traffic density value equal to a second traffic density value;

assigning said second move request a second priority value;

searching said ordered list of move requests for a third move request having a source node having said free car limit value equal to a first free car limit value; and

assigning said third move request a third priority value.

11. The method of claim 10 wherein said first traffic balance value is 0.

12. The method of claim 10 wherein said first traffic density value is 2.

13. The method of claim 10 wherein said second traffic balance value is between −

2 and 2.

14. The method of claim 13 wherein said second traffic balance value is between −

1 and 2.

15. The method of claim 10 wherein said second traffic density value is less than 3.

16. The method of claim 10 wherein said free car limit value is 1.