Method for optimizing a link schedule

• US 20040081162A1
• Filed: 10/29/2002
• Published: 04/29/2004
• Est. Priority Date: 10/29/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hodson, William R.
• Granted Patent: US 7,363,380 B2
• Time in Patent Office: Days
• US Class Current: 370/395.4
• CPC Class Codes: A01K 15/025 Toys specially adapted for animals
• CPC Class Codes: G06F 15/16 Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs coordinating program control therefor G06F9/52; in regulating and control system G05B
• CPC Class Codes: G06F 9/46 Multiprogramming arrangements
• CPC Class Codes: H04L 12/40 Bus networks
• CPC Class Codes: H04L 12/5601 Transfer mode dependent, e.g. ATM
• CPC Class Codes: H04L 2012/40208 characterized by the use of a particular bus standard
• CPC Class Codes: H04L 2012/4026 Bus for use in automation systems
• CPC Class Codes: H04L 47/24 Traffic characterised by specific attributes, e.g. priority or QoS
• CPC Class Codes: H04L 47/2475 for supporting traffic characterised by the type of applications
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]

Abstract

A method for improving a link schedule used in a communications network is disclosed. While the method applies generally to networks that operate on a scheduled communications basis, it is described in the context of a Foundation FIELDBUS. The method includes: scheduling sequences and their associated publications according to their relative priority, per application; minimizing delays between certain function blocks, and between certain function blocks and publications; and grouping certain publications. Accordingly, advantages such as latency reduction, schedule length reduction, and improved communications capacity are gained.

Claims

1. A method for creating a link schedule for a network that communicates in accordance to a periodically executed schedule, the method including the steps of:

identifying a plurality of function blocks requiring execution;

identifying each of the function blocks as a member of one or more groups;

prioritizing the groups such that each group has a priority relative to the other groups; and

scheduling each of the groups containing at least one unscheduled function block, one group at a time, in an order based on the priority of each group for communication on the network.

2. The method of claim 1 further including the step of:

identifying each non-back-calculation publication associated with each function block.

3. The method of claim 2 wherein the group scheduling further includes minimizing delays between one or more elements within each group.

4. The method of claim 3 wherein the group scheduling further includes minimizing delays between certain groups.

5. The method of claim 4 wherein the group scheduling further includes minimizing delays between:

a) the completion of execution of a primary connection output-producing function block and the initiation of execution of the function block directly inputting the primary connection output produced by the primary connection output producing function block;

b) the completion of execution of a non-back-calculation publication-producing function block, and the non-back-calculation publication produced by the non-back-calculation publication producing function block; and

c) the initiation of execution of a non-back-calculation publication-inputting function block, and the non-back-calculation publication input by the non-back-calculation inputting block.

6. The method of claim 5 wherein the delay minimizing is subject to:

a) a function block scheduling limitation prohibiting the execution times of two function blocks associated with one single-application processor device from overlapping; and

b) a publication scheduling limitation prohibiting the execution times of any two publications from at least partially overlapping such that each of the following is prohibited;

two non-back-calculation publications at least partially overlapping, two back-calculation publications at least partially overlapping, and a non-back-calculation publication at least partially overlapping with a back-calculation publication.

23. The method of claim 6 wherein the link schedule communicates on a mixed network that includes at least one FIELDBUS.

24. The method of claim 23 wherein the FIELDBUS is a FOUNDATION™

FIELDBUS.

7. A method for creating a link schedule for a network that communicates in accordance to a periodically executed schedule, the method including the steps of:

identifying a plurality of function blocks requiring execution;

identifying each of the function blocks as a member of one or more groups;

prioritizing the groups such that each group has a priority relative to the other group based on at least one of;

a group type associated with each respective group;

a period length associated with each respective group; and

scheduling each of the groups containing at least one unscheduled function block, one group at a time, in an order based on the priority of each group for communication on the network.

8. The method of claim 7 wherein the groups are further prioritized such that each group has a priority relative to the other group based on a group type that is within a period length associated with each respective group.

9. The method of claim 8 wherein the group prioritizing is based on a period length associated with each respective group and a group type associated with each respective group, wherein:

each of the period lengths that is relatively shorter has higher priority than each of the period lengths that is relatively longer;

each of the groups that is a monitoring type has a lower priority than each of the groups that is not a monitoring type; and

when a cascade type group and a control type group have period lengths of equal size, the control type group has a higher priority than the cascade type group.

10. The method of claim 9 wherein the group scheduling further includes scheduling each group containing at least one scheduled function block as early in the schedule as possible when all of the unscheduled blocks in the group are independent and that each respective unscheduled block in the independent group:

does not produce a primary connection output that is directly input by a function block having an execution time within the schedule;

does not produce a non-back-calculation publication directly input by a function block having an execution time within the schedule;

does not directly input a non-back-calculation publication produced by a function block having an execution time within the schedule; and

does not directly input a primary connection output produced by a function block having an execution time within the schedule.

11. The method of claim 10 wherein the early scheduling further includes adjusting the unscheduled blocks in each respective independent group within the schedule to minimize any delay between one or more elements within each respective independent group.

12. The method of claim 11 wherein the early scheduling further includes adjusting the independent unscheduled blocks in each respective independent group within the schedule to minimize any delay between:

a) the completion of execution of a primary connection output producing function block, and the initiation of execution of the function block directly inputting the primary connection output produced by the primary connection output producing function block;

b) the completion of execution of a non-back-calculation publication producing function block, and the non-back-calculation publication produced by the non-back-calculation publication producing function block; and

c) the initiation of execution of a non-back-calculation publication inputting function block, and the completion of the non-back-calculation publication input by the non-back-calculation inputting block.

21. The method of claim 12 wherein the link scheduled communicates on a mixed network that includes at least one FIELDBUS.

22. The method of claim 21 wherein the FIELDBUS is a FOUNDATION ™

FIELDBUS.

13. A method for creating a link schedule for a network that communicates in accordance to a periodically executed schedule, the method including the steps of:

identifying a plurality of function blocks requiring execution;

identifying each of the function blocks as a member of one or more groups;

prioritizing the groups such that each group has a priority relative to the other group based on at least one of;

a group type associated with each respective group;

a period length associated with each respective group;

scheduling each of the groups containing at least one unscheduled function block, one group at a time, in an order based on the priority of each group;

identifying any back-calculation publication associated with each respective function block requiring execution; and

assigning each respective back-calculation publication a publication time within the schedule, within a time window of eligibility associated with the respective back-calculation publication, such that at least a first potential publication gap is minimized, or alternatively a second potential publication gap is maximized.

14. The method of claim 13 wherein the groups are further prioritized such that each group has a priority relative to the other group based on a group type that is within a period length associated with each respective group.

15. The method of claim 14 wherein each group is a sequence and each sequence is a group of function blocks wherein an input associated with each function block is dependent on a primary connection output associated with an immediately-preceding function block, except for the function block beginning the sequence.

16. The method of claim 15 wherein each group is a sequence and each sequence is a single function block that does not input another function block'"'"'s primary connection output and does not produce a primary connection output that is input by another function block.

17. The method of claim 16 wherein each sequence is formed by one of:

identifying a function block that does not input another block'"'"'s primary connection output as the beginning block, and following a path of function blocks from the beginning block such that an input associated with each function block, except the beginning block, is dependent on a primary connection output associated with an immediately-preceding function block; and

determining if a function block is single, and does not input another function block'"'"'s primary connection output and does not produce a primary connection. output that is input by another function block.

18. The method of claim 17 wherein at least one of the identified beginning function blocks is an input class function block.

19. The method of claim 18 wherein the link schedule communicates on a mixed network that includes at least one FIELDBUS.

20. The method of claim 19 wherein the FIELDBUS is a FOUNDATION™

FIELDBUS.