Bus Controller Redundancy for ASIL D Safety
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Solution Overview
Problem
Current CAN bus configurations in vehicles typically reach only ASIL B safety level, falling short of the industry's goal to achieve ASIL D, which is necessary for premium automobiles to ensure safety in case of system failures.
Innovation Solution
A bus-based communication system is enhanced with a bus controller, first and second buffers, and a comparator, where the first buffer delays the bus input signal by a preset time, and the bus redundant controller receives this delayed signal to output a redundant signal, allowing the comparator to detect abnormalities and generate an interrupt signal when inconsistencies are found.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CAN bus configuration is used, then device complexity is low, but reliability reaches only ASIL B level
Solution Approach 1:
The system segments the communication path into multiple independent channels: a primary CAN bus controller and a redundant CAN bus controller operate in parallel. This segmentation allows the system to achieve higher reliability (ASIL D) by isolating faults to specific segments while maintaining overall system functionality through the alternative path.
Solution Approach 2:
The redundant controller and comparison mechanism are pre-configured and continuously monitoring before faults occur. The system performs preliminary redundancy preparation by maintaining a standby controller that can immediately take over if the primary controller fails, thus achieving high reliability without adding complex real-time decision-making logic.
2Reliability
If redundant controller and buffers are added, then reliability improves to ASIL D level, but device complexity increases
Solution Approach 1:
The system creates a complete copy of the CAN bus controller in the redundant controller, including all transmission and reception functionalities. This copying approach simplifies the overall system architecture by using identical modular units rather than designing complex error-correction mechanisms, thereby achieving high reliability through redundancy while keeping individual component complexity manageable.
Solution Approach 2:
The comparison unit continuously monitors and compares outputs from both the primary controller (via first buffer) and redundant controller (via second buffer). This feedback mechanism automatically detects discrepancies or failures and triggers appropriate responses, achieving high reliability through continuous verification without requiring complex manual intervention systems.
3Measurement precision
If buffers with preset time delay are introduced, then fault detection capability is enhanced, but loss of time increases
Solution Approach 1:
The system changes the time parameter by introducing configurable buffer delays that can be optimized for different operating conditions. The first buffer delays the primary controller output and the second buffer delays the redundant controller output by comparable amounts, allowing the comparison to occur at synchronized time points. This parameter adjustment enables accurate fault detection while minimizing unnecessary delays by optimizing buffer sizes for the specific application requirements.
Data Source
AI summary
The disclosure provides a bus-based communication system, which comprises a bus controller, a first buffer, a bus redundant controller, a second buffer and a comparator. The bus controller is configured to receive a bus input signal and send a bus output signal. The first buffer is connected with the bus controller in parallel to receive the bus input signal, and is configured to output the bus input signal after a preset time, wherein the preset time is two or more duty cycles of the bus controller. The bus redundant controller is connected to an output terminal of the first buffer and configured to receive a bus output signal delayed by at least T cycles output by the first buffer and output a bus redundant output signal.