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MILCAN Adapting COTS CANbus to Military Vetronics

MILCAN Adapting COTS CANbus to Military Vetronics. Steven T. Majoewsky. Introduction Development Organization Progress Determinism Status. MILCAN. MILCAN Introduction. Who we are Why we are What are the Goals. Who we are Subgroup of IHSDBUG Formed in 1998

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MILCAN Adapting COTS CANbus to Military Vetronics

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  1. MILCAN Adapting COTS CANbus to Military Vetronics Steven T. Majoewsky

  2. Introduction Development Organization Progress Determinism Status MILCAN

  3. MILCANIntroduction Who we are Why we are What are the Goals

  4. Who we are Subgroup of IHSDBUG Formed in 1998 Both industry and government representation United Kingdom Canada Sweden United States Germany MILCAN Introduction

  5. MILCANIntroduction Why we are: Apply low-cost CAN technology to military vehicles Address timing and latency issues Establish guidelines for common usage Component suppliers Vehicle manufacturers Countries

  6. Why we are: “More is better, but the Northern Alliance is using Russian equipment as well as equipment purchased on the black market. There is British equipment as well as U.S. equipment. The interoperability is…………well, rather a sticky wicket.” . Lt. Col. Tim Eads, ret. MILCAN Introduction

  7. What are the Goals Create message structure & connectivity guidelines for using CANbus in military ground combat vehicles Use off-the-shelf hardware Make Interoperability Easier MILCAN Introduction

  8. Goals continued Provide for real-time deterministic data transfer Use SAE J1939 and ISO 1198 to max extent Easily bridgeable MILCANIntroduction

  9. Built upon J1939 and ISO 11898 Military Vehicles - Roots in Automotive CAN applications Militarized hardware MILCAN Development

  10. Create Simplified message ID structure Fits within J1939 Create protocol for optional deterministic message transfer Create guideline documents MILCANDevelopment

  11. MILCAN Organization 3 documents produced Physical layer Data Link layer Application layer

  12. MILCAN Organization Physical layer Opto-coupled Very large currents in vehicles Large ground-bounce In-cable power Polarity of connectorization important EMI/EMC considerations Shielded bus Military connectors

  13. MILCAN Organization

  14. MILCAN Organization

  15. MILCAN Progress Data Link layer 29-bit addressing MILCAN A Bit 25 used as Protocol Type Bit J1939/ISO11898 sets to 0 MILCAN sets to 1 11-bit addressing MILCAN B Based on CANopen

  16. MILCAN Progress Data Link layer Multi-Frame Messages Primary/Sub Type specifies which messages have multiple frames 1st byte of payload is sequence number Sequence numbers range from 1 to 249 J1939 compatibility Sequence number 250 signals end of message

  17. MILCAN Progress Application layer Simple, Flexible message identifier scheme Easy to implement hardware filtering Support multiple instances of same device Instance specification in payload byte Separate function identity from physical address Hand controller as example

  18. MILCAN Progress 28 26 25 24 23 16 15 8 7 0 Primary Type Sub Type Source Address Priority 1 0 MILCAN Frame Identifier

  19. MILCANProgress Typical Primary Types Motion Control Fire Control Defensive Aid Suite Battle Management System

  20. MILCANDeterminism Support for both real-time deterministic messages and random event-driven messages simultaneously

  21. MILCAN Determinism High priority “sync” message establish timing on bus Sync message payload contains rotating time slot number Real-time deterministic messages assigned higher priority Transmitted in response to proper time slot number sync message Non-real-time messages fit into gaps

  22. MILCANDeterminism One bus “sync generator” at any given time Simple sync claim arbitration process can establish one of many possible nodes as sync generator If one sync generator fails, another will take over

  23. MILCANDeterminism Timing Concerns Jitter Drift

  24. MILCANDeterminism Timing Solution Allow time reserve Remember, this is COTS application

  25. MILCAN Determinism Sync message rate determines Primary Time Unit (PTU) Sync message payload contains time slot value Number of time slot values defines slowest deterministic repetition rate

  26. MILCAN Determinism Message Priorities 0 Protocol Operation Messages (sync) 1 HRT 1 1 PTU --4 SRT 1 8 PTU 2 HRT 2 8 PTU --5 SRT 2 64 PTU 3 HRT 3 64 PTU --6 SRT 3 512 PTU 7 Non Real Time messages use any available space

  27. MILCAN Status 3 Documents produced MILCAN Physical Layer MILCAN Data Link Layer MILCAN Application Layer Message Type table being refined Over-the-Bus Identifier Modification under consideration

  28. Established international dialog and understanding among suppliers, system integrators and users As military usage increases, information is shared Reduces duplication and incompatibilities MILCANStatus

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