Luenberger Observer for Air Mass Flow Correction
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Solution Overview
Problem
Mass air flow sensors (MAF) provide unstable measurements of air flow rate through a throttle valve, especially under transient conditions and low engine loads, due to fluid dynamics and sensor placement, leading to inaccurate air-fuel ratio calculations.
Innovation Solution
A Luenberger observer is used to correct air mass flow rate measurements by combining signals from a MAF sensor and an outflow model of the throttle valve, with low-pass filtering and error calculation to stabilize and improve the accuracy of air flow rate measurements across all operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a MAF sensor is used to measure air flow rate through the throttle valve, then the air mass flow rate can be determined for fuel injection calculation, but the measurement becomes unstable under transient conditions and low engine loads due to fluid dynamics and sensor placement
Solution Approach 1:
The patent introduces a Luenberger observer as an intermediary system that processes both the MAF sensor signal and the outflow model calculation. This observer acts as a mediator that combines the direct sensor measurement with the model-based estimation to produce a corrected, stable air flow rate signal that eliminates the instability issues of the raw MAF measurement while maintaining accuracy across all operating conditions.
Solution Approach 2:
The Luenberger observer implements feedback by continuously comparing the MAF sensor measurement with the outflow model calculation and using the difference (error signal) to correct the final air flow rate measurement. This feedback mechanism allows the system to compensate for the instability of the MAF sensor in real-time, particularly under transient conditions and low engine loads where the original measurement fails.
2Measurement precision
If the MAF sensor signal is heavily filtered to reduce electrical noise, then stationary condition readings improve, but transient condition measurements become incorrect and affect air trapped calculation
Solution Approach 1:
The system dynamically adapts the filtering characteristics based on operating conditions. The Luenberger observer combines the filtered MAF signal with the outflow model in a way that maintains appropriate response characteristics across different engine states. This dynamic approach allows the system to achieve both stationary stability and transient responsiveness without the trade-off inherent in fixed filtering approaches.
Solution Approach 2:
The patent changes the parameters used for air flow rate determination based on operating conditions. Rather than using a fixed filtered signal, the system switches between and combines different signal processing approaches (raw MAF, filtered MAF, outflow model) depending on the engine state, thereby optimizing both stationary accuracy and transient response characteristics.
3Device complexity
If the outflow model uses average pressure values ignoring cylinder pumping peaks, then the model is simple to implement, but strong discrepancies occur between calculated and real flow rates under high pressure ratios
Solution Approach 1:
The Luenberger observer serves as an intermediary that reconciles the simple outflow model with the need for accurate flow rate calculation. By combining the model output with the MAF sensor signal through the observer framework, the system compensates for the model's simplifications (using average pressures) and achieves accurate flow rate determination even under high pressure ratios where the model alone would fail.
Data Source
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AI summary
Method for correcting a measurement of an air flow rate passing through a throttle valve (TV) of an Otto cycle internal combustion engine (E), carried out by means of a mass air flow sensor (MAF), the engine (E) comprising an intake manifold (IM) on which is arranged: the throttle valve (TV), the mass air flow sensor (MAF), upstream of the throttle valve, a first pressure sensor (PU) and a second pressure sensor (PD) arranged respectively upstream and downstream of the throttle valve (TV), a temperature sensor (TU) arranged upstream of the throttle valve (TV), wherein the mass air flow sensor (MAP) is arranged between said temperature sensor (TU) and the throttle valve (TV), the method comprising the implementation, by means of a processing unit (ECU), of a Luemberger observer (OBS) to calculate a signal (xk) representative of the mass air flow rate passing through the throttle valve, wherein the observer is configured to simultaneously acquire at the input a first signal (eyk), a function of a second signal (x̃k) generated by the mass air flow sensor (MAP) and a third signal (ϕthrk), calculated by means of a throttle valve outflow model, representative of said mass air flow passing through the throttle valve.