OAT Sensor Diagnostic System Using IAT Signal Comparison
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Solution Overview
Problem
Traditional outside air temperature (OAT) systems are not onboard diagnostic (OBD) compliant, leading to inaccurate ambient temperature estimation and slower response times due to their location near the engine, which affects the performance of OAT-dependent vehicle systems.
Innovation Solution
An OAT diagnostic system that includes an ambient temperature monitoring module to compare OAT signals from an OAT sensor with intake air temperature (IAT) signals, generating difference signals to determine sensor faults and improve the accuracy and responsiveness of OAT information, making it OBD compliant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If OAT sensor is located near the engine, then response time is improved, but measurement accuracy deteriorates due to engine heat interference
Solution Approach 1:
The patent uses IAT sensor as an intermediary reference to indirectly assess OAT sensor accuracy. By comparing OAT sensor readings with IAT sensor readings (which are less affected by engine heat), the system can detect OAT sensor faults without relocating the sensor away from the engine for better accuracy.
Solution Approach 2:
The system implements a feedback mechanism where the OAT sensor output is continuously compared with the IAT sensor output. When the difference exceeds a threshold, the system generates a fault indication, allowing real-time monitoring and correction of measurement accuracy issues while maintaining the OAT sensor's optimal location for fast response.
2Reliability
If OAT system is made OBD compliant with diagnostic tests, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing OAT sensor system multi-functional by adding diagnostic capabilities that reuse existing sensors (OAT and IAT) and controllers. The same hardware infrastructure performs both temperature measurement and self-diagnosis, achieving OBD compliance without proportionally increasing device complexity.
Solution Approach 2:
The OAT sensor system performs self-diagnosis by comparing its own output with the IAT sensor output. The system monitors itself for faults and generates appropriate diagnostic codes, enabling the system to service and validate its own reliability without requiring external diagnostic equipment.
3Device complexity
If IAT-based estimates are used for OAT, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
Instead of completely replacing the OAT sensor with IAT-based estimates, the patent uses a partial approach: the OAT sensor remains in place and is periodically validated against the IAT sensor. This hybrid approach maintains measurement precision where possible while using the simpler IAT reference for diagnostic purposes, achieving a balance between precision and complexity.
Data Source
AI summary
An outside air temperature (OAT) diagnostic system includes an ambient temperature monitoring module that receives (i) an OAT signal from an OAT sensor and (ii) an intake air temperature (IAT) signal from an IAT sensor of an engine. The ambient temperature monitoring module compares the OAT signal to an IAT signal and generates a first difference signal. A performance reporting module determines whether the OAT sensor is exhibiting a fault and generates an OAT performance signal based on the first difference signal.