Asynchronous Fly-By-Wire Bus Layout for Redundant CAN Control
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Solution Overview
Problem
Modern aircraft fly-by-wire systems face challenges in minimizing wiring and associated costs while maintaining redundancy and data integrity, leading to increased complexity and potential electrical faults.
Innovation Solution
Aircraft fly-by-wire systems utilize a bus arrangement with unique subsets of CAN buses and actuation control modules, ensuring redundancy without triplicate connections, and employ asynchronous intermodule bus arrangements for efficient data communication and processing, reducing the need for physical electrical connections and minimizing wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy is increased to ensure fail-operational status, then reliability is improved, but device complexity increases due to more wiring and interfaces
Solution Approach 1:
The system segments the communication architecture into multiple independent CAN buses (CAN_HIGHEST_PRIORITY, CAN_HIGHER_PRIORITY, CAN_HIGHER_STILL_PRIORITY, CAN_LOWEST_PRIORITY) with different functional assignments. Flight control modules and actuation control modules are distributed across these segments, allowing redundancy without requiring complete triplicate connections between all components. Each segment handles specific priority levels of data traffic, enabling partial redundancy while reducing overall wiring complexity.
Solution Approach 2:
The CAN bus network acts as an intermediary communication medium between flight control modules and actuation control modules. Instead of direct point-to-point wiring between all redundant components, the CAN bus provides a standardized communication interface that mediates data exchange. This intermediary approach allows multiple modules to share common communication pathways while maintaining logical redundancy, significantly reducing the physical wiring required compared to direct interconnected redundant systems.
2Reliability
If data integrity is increased through redundant communication paths, then reliability is improved, but the amount of wiring and costs increase
Solution Approach 1:
The system dynamically routes communication traffic across different CAN bus priority levels based on data importance and system state. During normal operation, data flows through optimized paths; during fault conditions, the system dynamically switches to alternative redundant paths. This dynamic routing capability allows the system to maintain data integrity through multiple potential paths without requiring all redundant wiring to be actively connected and managed simultaneously, reducing the effective wiring burden while preserving data integrity capabilities.
Solution Approach 2:
The system changes communication parameters such as message priority levels, transmission frequencies, and bus selection based on operational conditions. By adjusting these parameters dynamically, the system can achieve high data integrity through software-controlled communication strategies rather than relying solely on physical redundant wiring. This parameter-based control allows the same physical infrastructure to provide different levels of redundancy and data integrity as needed.
Data Source
AI summary
Aircraft fly-by-wire systems and related vehicle electrical systems are provided. In one embodiment, an electrical system suitable for use with a control surface of a vehicle, such as an aircraft, is provided. The electrical system includes an asynchronous intermodule bus arrangement, a first vehicle control module, and a second vehicle control module. Each vehicle control module includes a respective interface arrangement to obtain and exchange data from different sensing arrangements with a first frequency, and a respective processing system to obtain the sensed data and determine actuator commands based on the sensed data with a lower frequency.