Electronic Control Device for Engine EGR Rate Estimation
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Solution Overview
Problem
High EGR rate combustion systems face challenges in maintaining accurate EGR control, leading to unstable combustion, misfire, and knock issues due to excessive EGR rates, while lower EGR rates fail to effectively reduce knock, necessitating precise EGR control to prevent combustion failures.
Innovation Solution
An electronic control device that estimates intake pipe pressure and EGR rate using an air flow sensor and EGR valve opening, and corrects the EGR rate estimation based on intake pipe pressure sensor data to maintain high EGR control accuracy, employing a Kalman filter for state estimation and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the EGR rate is excessively increased to reduce pump loss and knocking, then the knock reduction effect is improved, but unstable combustion and misfire occur
Solution Approach 1:
The patent implements a feedback control mechanism where the EGR rate is continuously estimated based on intake pipe pressure measurements and fed back to the control system. The state estimation unit uses the measured intake pipe pressure to correct the estimated EGR rate, creating a closed-loop control system that automatically adjusts the EGR valve opening to maintain the EGR rate within the optimal range, preventing both excessive EGR (which causes misfire) and insufficient EGR (which fails to reduce knock).
Solution Approach 2:
The patent dynamically changes the control parameters (EGR valve opening, fuel injection amount, ignition timing) based on the estimated EGR rate and intake pipe pressure. By continuously monitoring and adjusting these parameters in real-time, the system adapts to varying engine operating conditions and maintains precise EGR control, resolving the contradiction between knock reduction and combustion stability.
2Reliability
If the EGR rate is lower than the control target value to maintain stable combustion, then misfire is prevented, but sufficient knock reduction effect cannot be obtained
Solution Approach 1:
The feedback control mechanism ensures that the EGR rate is continuously monitored and adjusted to match the target value. The state estimation unit calculates the estimated EGR rate based on intake pipe pressure and compares it with the target EGR rate, then adjusts the EGR valve opening accordingly. This closed-loop control enables the system to maintain stable combustion while achieving sufficient knock reduction by keeping the EGR rate precisely at the optimal level.
Solution Approach 2:
The patent replaces direct mechanical measurement of EGR rate with a mathematical estimation system based on intake pipe pressure measurements. Instead of using complex mechanical sensors to directly measure EGR flow, the system uses pressure sensors and computational algorithms (state estimation unit) to indirectly but accurately determine the EGR rate, enabling more precise and responsive control.
3Reliability
If high EGR control accuracy is required to prevent knock and misfire, then combustion stability is improved, but the complexity of the control system increases
Solution Approach 1:
The patent introduces an intermediary measurement approach by using intake pipe pressure as a proxy variable to estimate the EGR rate. Instead of directly measuring EGR flow with complex sensors, the system uses the readily available intake pipe pressure measurement as an intermediary parameter that correlates with EGR rate. This intermediary approach simplifies the control system while maintaining high EGR control accuracy through the state estimation unit's computational algorithms.
4Measurement precision
If the intake pipe pressure sensor is positioned downstream of the throttle valve to measure actual intake pressure, then measurement accuracy is improved, but the complexity of system configuration increases
Solution Approach 1:
The patent makes the intake pipe pressure sensor serve multiple functions: it measures the actual intake pipe pressure for accurate EGR rate estimation, and simultaneously provides data for diagnosing EGR system abnormalities. By positioning the sensor downstream of the throttle valve, it captures the true intake conditions affecting combustion while enabling comprehensive system monitoring and control, resolving the contradiction between measurement accuracy and system complexity.
Data Source
AI summary
Provided is an electronic control device that controls an engine including an EGR system that includes an EGR pipe and an EGR valve disposed in the EGR pipe, an air flow sensor provided in an intake pipe, a throttle valve on a downstream side of the air flow sensor, and an intake pipe pressure sensor that detects an intake pipe pressure. The electronic control device includes a state estimation unit that estimates the intake pipe pressure and an EGR rate based on at least a detection value from the air flow sensor and an EGR valve opening, and an estimation value correction unit that corrects an EGR rate estimation value from the state estimation unit based on a detection value from the intake pipe pressure sensor and an intake pipe pressure estimation value from the state estimation unit.