Time synchronized playback and control of dissimilar data files

• US 20060004862A1
• Filed: 06/08/2004
• Published: 01/05/2006
• Est. Priority Date: 06/08/2004
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Fisher, David Leonard, Bryan, James Luis
• Granted Patent: US 7,412,371 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09B 19/00 Teaching not covered by other main groups of this subclass teaching or practice apparatus for gun-aiming or gun-laying F41G3/26

Abstract

A system, and a corresponding method, provides time synchronized playback and control of dissimilar data in a simulation architecture. The system includes a master site including a controller, and agents, implemented by the controller, where the controller directs the agents to control simulation data logging and playback; simulation sites, including: one or more simulation computers, where simulation events occur, a computer, where the agents control the simulation site to record the simulation data, and a local log that stores the simulation data as events, where the agents control the test computer to replay the events; a time reference system including a master site time stamp, local time stamp pair for each of the simulation sites, each of the local time stamps related to a master time stamp, and one or more time normalization factors. The time normalization factors relate times recorded for each of the events to an earliest recorded event and to a time of initiation of a replay command. In the system, a corrected event time, dtEvent, and a corrected system time, dtSystem, are established. Events are then injected for replay into the simulation architecture when the dtEvent and the dtSystem are equal.

Claims

1. A method for time synchronizing playback of dissimilar data files, comprising:

logging a first data set at a first local site, wherein logging includes recording a time of each event in the first data set;

logging a second data set at a second local site, wherein logging includes recording a time of each event in the second data set;

logging a nth data set at a nth local site, wherein logging includes recording a time of each event in the nth data set, and wherein the first data set, second data set and nth data set relate to a simulation;

establishing a first master time stamp at a master site and a corresponding first local time stamp at the first local site, the first master time stamp related to a computer system clock at the master site and to a computer system clock at the first local site, wherein the first master time stamp of the master site corresponds to a time when the first local time stamp of the first local site was established;

establishing a second master time stamp at the master site and a corresponding second local time stamp at the second local site, the second master time stamprelated to the computer system clock at the master site and to a computer system clock at the second local site, wherein the second master time stamp of the master site corresponds to a time when the second local time stamp of the second local site was established;

establishing a nth master time stamp at the master site and a corresponding nth local time stamp at the nth local site, the nth master time stamp related to the computer system clock at the master site and to a computer system clock at the nth site, wherein the nth master time stamp of the master site corresponds to a time when the nth local time stamp of the nth local site was produced;

recording the first, the second and the nth master and local time stamps;

issuing a play command to commence a replay of the simulation;

correcting for differences and errors in among all the local site'"'"'s computer system clocks, wherein corrections are produced by comparison of a master time stamp and a local site'"'"'s local time stamp, wherein the correction is used to correct that local site'"'"'s system time.

normalizing the local site'"'"'s corrected system time referenced to the time when the play command is issued, wherein the normalization creates a time differential dtSystem;

normalizing the recorded time of each event in the data sets relative to a time of a first event in the data set, wherein the normalization creates time differentials, dtEvent;

normalizing for differences in logging start times among all local sites, wherein all local sites corrected logging start times are compared to determine the first local site to start logging;

comparing when all other local sites started logging and determining a correction to each local site'"'"'s dtEvent based on the logging start time differences;

advancing dtSystem as play time advances;

pausing dtSystem when play is paused; and

injecting logged event data, wherein the logged event data are injected when dtEvent equals dtSystem.

2. The method of claim 1, further comprising scaling dtSystem to change the speed of replaying the simulation.

3. The method of claim 1, wherein events are scanned in reverse order to replay the simulation backwards.

4. The method of claim 1, wherein the master site commands the first, second, and nth local sites to go to a specific dtSystem, wherein event data with a dtEvent equal to the specific dtSystem is injected into the simulation architecture.

5. The method of claim 1, wherein the local computer clock times are provided by a geo-positioning satellite clock.

6. The method of claim 1, further comprising correcting for variations in the local computer clock times between the first, second, and nth local sites.

7. The method of claim 6, wherein the master site comprises a time server, and wherein the time server provides the corrections for variations in the local computer clock times.

8. A system that provides time synchronized playback and control of dissimilar data in a simulation architecture, comprising:

a master site, comprising;

a controller, and

agents, implemented by the controller, wherein the controller directs the agents to control simulation data logging and playback;

simulation sites, comprising;

one or more simulation computers, wherein simulation events occur,

a computer, wherein the agents control the simulation site to record the simulation data, and

a local log that stores the simulation data as events, wherein the agents control the test computer to replay the events; and

a time reference system comprising;

a master site time stamp for each of the simulation sites,

a local time stamp for each of the simulation sites, each local time stamp related to the master site time stamp, and

one or more time normalization factors, wherein the time normalization factors relate times recorded for each of the events to an earliest recorded event and to a time of initiation of a replay command, wherein a corrected event time, dtEvent, and a corrected system time, dtSystem, are established, and wherein events are injected for replay into the simulation architecture when the dtEvent and the dtSystem are equal.

9. The system of claim 8, further comprising means for scaling dtSystem to change the speed of replaying the simulation.

10. The system of claim 8, wherein events are scanned in reverse order to replay the simulation backwards.

11. The system of claim 8, further comprising means for commanding the simulation sites to go to a specific dtSystem, wherein event data with a dtEvent equal to the specific dtSystem is injected into the simulation architecture.

12. The system of claim 8, wherein the master site and the simulation sites receive local computer clock times provided by a geo-positioning satellite clock.

13. The system of claim 12, further comprising means for correcting for variations in the local computer clock times among the simulation sites.

14. The system of claim 13, wherein the master site further comprises a time server, and wherein the time server provides the corrections for variations in the local computer clock times.

15. The system of claim 8, wherein the master time stamps and each corresponding local time stamps are related by a network delay, the network delay comprising a one-way time required to transfer signals between the master site and a local site.

16. A method, executed in a system comprising a plurality of nodes, for synchronizing time-referenced data, the time-referenced data recorded at two or more of the nodes, the method comprising:

establishing a master node and one or more local nodes from the plurality of nodes;

establishing master time stamps at the master node;

providing a master time stamp to each of the local nodes;

establishing local time stamps at each of the local nodes, wherein the local time stamps are related to a master time stamp;

commencing data recording at one or more of the local nodes;

recording a local time the data is recorded, whereby the time-referenced data are established; and

normalizing the recorded times among the local sites and the master site.

17. The method of claim 16, wherein normalizing the recorded times, comprises:

determining an earliest recorded data entry among the local sites; and

establishing a time correction for each of the subsequently recorded data entries relative to the earliest recorded data entry.

18. The method of claim 16, further comprising correcting for variations in local clock times among the local sites.

19. The method of claim 18, wherein the master site comprises a time server, and wherein the time server provides the corrections for variations in the local clock times.

20. A system for synchronizing time-related data recorded at a plurality of nodes in a network, comprising:

means for establishing a master node and one or more local nodes from the plurality of nodes;

means for establishing master time stamps at the master node;

means for providing a master time stamp to each of the local nodes;

means for establishing local time stamps at each of the local nodes, wherein the local time stamps are related to a master time stamp;

means for commencing data recording at one or more of the local nodes;

means for recording a local time the data is recorded, whereby the time-referenced data are established; and

means for normalizing the recorded times among the local sites and the master site.

21. The system of claim 20, wherein the means for normalizing the recorded times, comprises:

means for determining an earliest recorded data entry among the local sites; and

means for establishing a time correction for each of the subsequently recorded data entries relative to the earliest recorded data entry.

22. The system of claim 20, further means for comprising correcting for variations in local clock times among the local sites.

23. The system of claim 22, wherein the master site comprises a time server, and wherein the time server provides the corrections for variations in the local clock times.