Barometric Pressure Inference Using Manifold Pressure Ratios
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Solution Overview
Problem
Existing methods for estimating barometric pressure (BP) in vehicle engines, which rely on manifold absolute pressure (MAP) sensors and pressure drops across the throttle, are inaccurate at throttle angles below a threshold, leading to less precise engine control.
Innovation Solution
A method that estimates BP by using a ratio of current manifold pressure to reference manifold pressure at different altitudes, adjusting engine operating conditions such as air charge, air-fuel ratio, and spark timing, and correcting MAP sensor offsets to ensure accurate BP estimation at any throttle angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If BP is inferred from MAP sensor output and pressure drop across the intake system, then vehicle cost is reduced, but measurement precision deteriorates at throttle angles below threshold
Solution Approach 1:
The patent changes the estimation parameters based on throttle angle conditions. When throttle angle is above threshold, it uses MAP sensor output plus pressure drop calculation. When throttle angle is below threshold, it switches to using the ratio relationship between current MAP and reference MAP at different altitudes. This dynamic parameter change resolves the contradiction by adapting the estimation method to operating conditions.
Solution Approach 2:
The patent creates a reference MAP model at known reference barometric pressure and reference altitude that copies the expected manifold pressure behavior. By comparing current MAP readings against this reference model, the system can infer actual barometric pressure even at low throttle angles where direct calculation fails, thus maintaining measurement precision without adding hardware cost.
2Device complexity
If BP is estimated using MAP sensor and pressure drop method, then device complexity is reduced, but reliability deteriorates during partial throttle operation
Solution Approach 1:
The patent implements a dynamic estimation system that automatically switches between two different BP estimation methods based on real-time throttle angle feedback. The system monitors throttle angle and dynamically selects the appropriate calculation method: pressure drop method for high throttle angles, ratio-based method for low throttle angles. This dynamic adaptation ensures reliable engine control across all operating conditions while maintaining simple device configuration.
Solution Approach 2:
The patent introduces a reference MAP model as an intermediary element that mediates between the simple pressure drop method and the need for accurate BP estimation at low throttle angles. This reference model acts as a bridge, allowing the system to use the simple pressure drop method when valid while compensating for its limitations through the ratio relationship with reference conditions, thus maintaining reliability without increasing device complexity.
3Measurement precision
If a dedicated BP sensor is installed, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing MAP sensor multi-functional by using it for both its primary function (measuring manifold pressure for engine control) and a secondary function (inferring barometric pressure through the ratio method). This universal usage eliminates the need for a dedicated BP sensor while maintaining measurement precision, as the MAP sensor data is processed through the ratio relationship with reference conditions to extract BP information.
Solution Approach 2:
The patent enables the MAP sensor to serve itself by using its own readings in conjunction with a reference MAP model to generate barometric pressure information. The system processes the MAP sensor data through the ratio calculation method, allowing the existing sensor to provide both engine control data and environmental BP information without requiring additional hardware, thus reducing device complexity while maintaining precision.
Data Source
AI summary
Methods and systems are provided for estimating barometric pressure based on a reference barometric pressure and manifold pressures at two different altitudes. In one example, a method may include adjusting an operating condition of the engine based on barometric pressure during engine operation at throttle angles less than a threshold, the barometric pressure based on a current manifold pressure relative to a reference manifold pressure at a current throttle angle and reference barometric pressure. Further, the method may include adjusting a manifold pressure sensor output based on an offset of the manifold pressure sensor.