Sensor Unit Addressing for Passenger Protection Systems
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Solution Overview
Problem
Existing passenger protection systems, such as those using airbags and seatbelts, face challenges in determining whether a failure in sensor units is due to an open-failure or sensor-failure, especially when bus switches are not used, making it difficult to specify the location of the issue.
Innovation Solution
A communication device with an ECU and sensor units connected in a daisy chain form, where sensor units transmit set addresses and characteristic information, and an ECU with a memory unit and failure check unit to store and compare this information, allowing for the identification of failing sensor units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bus switches are used to connect sensor units to ECU, then the sensor units can be independently controlled and initialized, but the chip size becomes large and voltage drops occur at end-stage sensor units
Solution Approach 1:
The patent removes bus switches from the sensor units entirely, extracting the switching function from individual sensor units. Instead, a single switch is placed in the main power supply line before the daisy-chain connection, eliminating the need for multiple bus switches while maintaining power control capability.
Solution Approach 2:
The patent merges the power supply control for all sensor units into a single switch located in the main power line. This consolidates multiple independent switching operations into one centralized control point, simplifying the overall system architecture.
2Ease of operation
If bus switches are used in sensor units, then individual sensor units can be initialized in sequence, but bus switches generate noise when impedance mismatch occurs
Solution Approach 1:
The patent extracts the switching function from individual sensor units and places it in a centralized location in the main power line. This removes the noise-generating bus switches from proximity to sensitive sensor components, eliminating the impedance mismatch issue that causes noise.
3Reliability
If sensor units are connected in daisy chain form without bus switches, then chip size is reduced and noise is minimized, but it becomes difficult to determine whether failure is due to open-failure or sensor-failure
Solution Approach 1:
The patent implements a feedback mechanism where each sensor unit transmits its identification information and operational status back to the ECU. The ECU monitors these feedback signals to determine whether a failure is due to open-circuit or sensor malfunction, enabling accurate failure diagnosis without bus switches.
Solution Approach 2:
The patent introduces communication signals as an intermediary between sensor units and ECU. These signals carry diagnostic information that mediates the failure detection process, allowing the ECU to distinguish between different failure types even without direct switching control of individual sensors.
4Adaptability or versatility
If multiple bus switches are used in sensor units, then individual sensor units can be independently addressed, but the impedance of bus switches causes voltage drops
Solution Approach 1:
The patent extracts the addressing and selection function from multiple distributed bus switches and implements it through software-based addressing in the ECU combined with a single centralized switch. This maintains individual addressing capability while eliminating the voltage drops caused by multiple switch impedances.
Data Source
AI summary
In each sensor unit, when a sensor control unit cannot detect current flowing to an output side, its address is set to the same address as a sensor unit of the last stage. In an ECU, if the set address and characteristic information of each sensor unit are not stored in a memory unit when the set addresses and the characteristic information of all the sensor units are received by an ECU control unit, the received set addresses and the characteristic information are stored. A failure check unit checks received characteristic information received by the ECU control unit with characteristic information stored in the memory unit. If one characteristic information is in disagreement, a sensor unit having such characteristic information is determined to be failing. If plural characteristic information are in disagreement, a sensor unit having characteristic information and closest to the ECU is determined to be failing.