Marine Drive-by-Wire Isolated CAN Bus Segmentation
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Solution Overview
Problem
Marine propulsion drive-by-wire control systems face challenges with increased complexity and reliability issues due to long CAN bus lengths, propagation delays, and induced noise from electromagnetic interference, which complicate installation and communication across multiple engines and helms.
Innovation Solution
The implementation of isolation circuits and modules within the CAN bus network to isolate each ECU bus from spurious signals and reduce bus length by eliminating conductive jumpers, ensuring each bus is terminated at its ends, thereby simplifying installation and preventing noise propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single shared CAN bus is used to connect multiple ECUs and PCMs across multiple helms, then system complexity is reduced and installation is simplified, but reliability decreases due to propagation delays, electromagnetic interference, and noise propagation over long bus lengths
Solution Approach 1:
The system divides the communication network into multiple isolated CAN bus segments, with each helm having its own isolated bus connecting to isolated buses at each engine/PCM. This segmentation prevents noise propagation across the entire system while maintaining simplified local connections, resolving the contradiction between system simplicity and communication reliability over long distances
Solution Approach 2:
Isolation circuits are introduced as intermediary devices between different bus segments. These isolation circuits act as mediators that allow communication between helms and engines while blocking electromagnetic interference and noise propagation, thereby maintaining reliable communication without requiring a complex point-to-point wiring scheme
2Reliability
If isolation circuits are implemented between each ECU bus and PCM bus, then reliability improves by preventing noise propagation and reducing electromagnetic interference, but device complexity increases due to additional isolation modules and wired connections
Solution Approach 1:
The communication network is segmented into isolated bus segments at each helm and engine, with isolation circuits placed at strategic connection points. This segmentation approach provides reliable noise isolation without requiring isolation circuits between every single ECU and PCM connection, thereby reducing installation complexity while maintaining system reliability
Solution Approach 2:
Multiple isolation functions are combined into standardized isolation circuits that are integrated at bus connection points. By merging the isolation functionality into compact modules that handle multiple protection functions (noise filtering, galvanic isolation, signal transmission), the implementation complexity is reduced while maintaining high reliability
3Reliability
If redundant ECUs are provided at a second helm for controlling multiple marine engines, then system reliability improves through redundancy, but device complexity and installation difficulty increase
Solution Approach 1:
The redundant ECU system is organized into isolated bus segments, where each helm operates independently on its own isolated CAN bus segment. This segmentation allows redundancy to be implemented without creating complex interconnections between helms, as each helm's ECUs communicate with PCMs through isolated buses, simplifying the overall redundant system architecture
Data Source
AI summary
A marine propulsion drive-by-wire control system controls multiple marine engines, each one or more PCMs, propulsion control modules for controlling engine functions which may include steering or vessel vectoring. A helm has multiple ECUs, electronic control units, for controlling the multiple marine engines. A CAN, controller area network, bus connects the ECUs and PCMs with multiple PCM and ECU buses. The ECU buses are connected through respective isolation circuits isolating the respective ECU bus from spurious signals in another ECU bus.