Air Bag Safing Circuit Microcomputer Integration
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Solution Overview
Problem
The existing air bag systems require two microcomputers for the safing system, increasing costs due to the expense of microcomputers and complexity in electronic control, making it challenging to implement crash determination and self-diagnosis functions effectively.
Innovation Solution
The air bag system integrates a single microcomputer for crash determination and a hardware-based processing circuit for safing determination, with fault diagnosis functions transferred from the sub-microcomputer to the main microcomputer, allowing for the use of an inexpensive integrated circuit for safing processing, reducing circuitry and microcomputer count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two microcomputers are used for the safing system (main microcomputer and sub-microcomputer), then the reliability of crash determination is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent divides the safing system into two independent channels: a main crash determination line using a microcomputer for complex processing, and a safing line using a dedicated hardware circuit for simple acceleration threshold comparison. This segmentation allows each component to be optimized for its specific function, reducing overall system complexity while maintaining dual-channel reliability
Solution Approach 2:
The patent extracts the fault diagnosis function from the sub-microcomputer and transfers it to the main microcomputer. This eliminates the need for the second microcomputer while preserving the safing function, as the main microcomputer can monitor both channels and detect faults in the hardware circuit
2Reliability
If two microcomputers are used for the safing system, then the safety against erroneous activation is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive sub-microcomputer with a inexpensive hardware circuit that performs only the essential safing function of comparing acceleration values against a threshold. This substitution dramatically reduces manufacturing cost while maintaining the safety function, as the hardware circuit is simpler and cheaper to produce than a full microcomputer
3Device complexity
If fault diagnosis function is transferred to the main microcomputer, then the number of microcomputers is reduced, but the processing load on the main microcomputer increases
Solution Approach 1:
The main microcomputer performs self-diagnosis by monitoring its own operations and comparing results with the hardware circuit's output. This self-service approach allows the system to detect faults without requiring additional diagnostic hardware, maintaining simplicity while enabling the main microcomputer to handle both crash determination and fault diagnosis functions
Data Source
AI summary
To achieve an air bag system in which a safing determination processing circuit can be implemented on one integrated circuit, the air bag system, which is equipped with first and second sensors (101, 103) for detecting a vehicle crash, and which outputs a signal for expanding an air bag when it is determined that a vehicle crash has occurred based on the outputs of the first and second sensors, comprises: a processing unit (3) for processing an output signal of the first sensor (101) by software; and a processing circuit (2) for processing an output signal of the second sensor (103) by hardware, wherein the processing unit (3) includes a non-activation fault diagnosis section (33) which, based on the output signal of the second sensor (103), detects a failure that can lead to non-activation of the air bag, and the processing circuit (2) includes an erroneous-activation fault diagnosis section (240) which, based on the output signal of the second sensor (103), detects a failure that can lead to erroneous activation of the air bag.