Fly-By-Wire Bus Segmentation for Fault-Resilient VTOL Control
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Solution Overview
Problem
Traditional fly-by-wire systems in VTOL aircraft require extensive redundancy for fault resiliency, leading to increased wiring and weight, which is undesirable for smaller aircraft like air taxis, and may result in inadequate failure modes and reduced availability of flight control components.
Innovation Solution
A fly-by-wire electrical system with a dual triplex bus arrangement using Controller Area Network (CAN) buses, where each flight control module is connected to a unique subset of buses, reducing physical electrical connections and maintaining independent communication paths to ensure high availability and data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fully redundant wiring is implemented in fly-by-wire systems, then fault resiliency and operational availability are improved, but the amount of wiring, weight, and device complexity increase significantly
Solution Approach 1:
The bus system is segmented into multiple distinct bus pairs (first pair, second pair, third pair) where each control module connects to a unique subset of buses. This segmentation allows the system to maintain redundancy while reducing the total wiring complexity compared to fully redundant configurations, as each segment serves a specific control module with dedicated fault isolation.
Solution Approach 2:
Each control module is assigned a unique local configuration of bus connections rather than uniform full redundancy. The first control module connects to the first and second bus pairs, the second control module connects to the second and third bus pairs, and the third control module connects to the first and third bus pairs. This local quality differentiation optimizes the balance between redundancy and wiring complexity for each specific control module.
2Reliability
If fully redundant wiring is implemented in fly-by-wire systems, then fault resiliency is improved, but weight increases due to additional wiring and components
Solution Approach 1:
The wiring system is divided into segmented bus pairs with selective connections to control modules. This segmentation reduces the total weight compared to fully redundant wiring by eliminating unnecessary wiring paths while maintaining sufficient fault resiliency through the unique subset connections of each control module to different bus pairs.
3Reliability
If redundant control modules are connected to common bus pairs, then fault resiliency is improved, but the risk of common cause electrical failures increases
Solution Approach 1:
Control modules are connected to segmented and distinct bus pairs rather than common shared buses. The first control module uses first and second bus pairs, the second control module uses second and third bus pairs, and the third control module uses first and third bus pairs. This segmentation isolates electrical failures to specific bus pairs, preventing common cause failures from affecting all control modules simultaneously.
Solution Approach 2:
Each control module has an asymmetric and unique connection pattern to bus pairs rather than symmetric identical connections. This asymmetric configuration ensures that no single bus pair failure can disable multiple control modules, as each module relies on a different combination of bus pairs for redundancy.
Data Source
AI summary
Aircraft fly-by-wire systems and related vehicle electrical systems are provided. A vehicle electrical system includes a bus arrangement having a plurality of buses, a first control module coupled to a first subset of the buses, a second control module coupled to a second subset of the buses, and a third control module coupled to a third subset of the buses. The first subset includes a first bus, a second bus, a third bus, and a fourth bus, the second subset includes the third bus, the fourth bus, a fifth bus, and a sixth bus, and the third subset includes the first bus, the second bus, the fifth bus and the sixth bus.