Oxygen Sensor Ambient Pressure Estimation
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Solution Overview
Problem
Existing engine systems face reduced accuracy in ambient pressure estimation due to reliance on models that may have errors and are bounded by specific operating conditions, leading to suboptimal engine control, especially when a dedicated ambient pressure sensor is not available or is degraded.
Innovation Solution
Utilizing an existing exhaust or intake oxygen sensor to estimate ambient pressure by leveraging its pressure dependency, where the sensor operates as a pressure sensor during unfueled conditions, allowing for accurate ambient pressure determination through pumping current analysis and humidity correction, thereby reducing the need for a dedicated ambient pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated ambient pressure sensor is used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The oxygen sensor is made multi-functional by enabling it to perform both its traditional oxygen concentration measurement function and a new ambient pressure measurement function. The control system selectively operates the sensor in different modes (oxygen sensing mode during fueled operation, pressure sensing mode during non-fueled operation) to achieve multiple measurement objectives with a single device, thereby reducing system complexity and cost while maintaining measurement precision.
2Device complexity
If ambient pressure is modeled based on engine operating conditions, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces the computational modeling approach (software-based estimation) with a direct physical measurement approach using the oxygen sensor's inherent pressure-dependent electrical characteristics. By utilizing the sensor's pumping current response to ambient pressure during non-fueled operation, the system achieves direct measurement rather than indirect estimation, significantly improving measurement precision while keeping the hardware simple.
3Device complexity
If the oxygen sensor is used for both oxygen sensing and pressure sensing, then device complexity is reduced, but reliability deteriorates due to dual-function operation
Solution Approach 1:
The system dynamically switches the oxygen sensor between different operating modes based on real-time engine conditions. During fueled operation, the sensor operates in oxygen sensing mode with appropriate reference voltage. During non-fueled operation when exposed to ambient air, the sensor switches to pressure sensing mode. This dynamic mode switching ensures each measurement function operates under optimal conditions, maintaining reliability while achieving multi-functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more accurate and cost-effective method for ambient pressure estimation, enhancing engine control across a wider range of operating conditions and confirming the accuracy of other pressure sources, thus improving powertrain performance.
Implementation Method 1
an oxygen sensor to: when propelling a hybrid vehicle using engine torque, estimate combustion air-fuel ratio via the oxygen sensor; and when propelling the hybrid vehicle using motor torque, estimate an ambient intake air pressure via the oxygen sensor
Implementation Method 2
the reference voltage may be a first, lower reference voltage. The controller may include instructions for estimating the ambient humidity based on a difference in output of the oxygen sensor upon modulation of the reference voltage between the lower voltage and an upper voltage where water molecules do dissociate at the oxygen sensor
Implementation Method 3
the output of the oxygen sensor while operating at the lower reference voltage may be corrected based on an ambient humidity estimate. Then, based on an offset between the corrected oxygen sensor pumping current relative to a reference pumping current, and further based on a pressure dependency of the sensor, the ambient pressure may be determined
Data Source
AI summary
Methods and systems are provided for leveraging the pressure dependency of an oxygen sensor for estimating an engine ambient pressure. An intake or exhaust oxygen sensor is used for ambient pressure estimation by applying a reference voltage to the sensor while the engine is being pulled-down in a hybrid vehicle, and correcting an output of the sensor for dilution effects due to ambient humidity. The estimated ambient pressure is used to correct or confirm pressure estimated by other sources, such as other pressure sensors or a pressure model, as well as to tune the performance of the engine.