Air-Fuel Ratio Control via Asymmetric Sensor Deviation Conversion
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Solution Overview
Problem
Existing air-fuel ratio control systems for internal combustion engines face challenges in accurately controlling the air-fuel ratio due to the asymmetric output characteristic of oxygen concentration sensors, leading to inefficiencies in adjusting the exhaust gas air-fuel ratio to a target value.
Innovation Solution
An air-fuel ratio control apparatus that includes an air-fuel ratio sensor with a nonlinear output characteristic, an output deviation converter that converts deviations to predetermined values, a control input calculator to calculate feedback control inputs, and an air-fuel ratio controller to manage the fuel injection quantity, ensuring the output deviation is zero and compensating for sensor asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear air-fuel ratio sensor is used to detect exhaust gas air-fuel ratio, then the measurement is simple and direct, but the sensor cannot accurately detect the air-fuel ratio when the mixture is rich or lean due to its linear output characteristic
Solution Approach 1:
The patent combines a linear air-fuel ratio sensor and an oxygen concentration sensor into a hybrid detection system. The linear sensor provides basic air-fuel ratio measurement while the oxygen concentration sensor provides additional information about the exhaust gas composition. By merging these two sensors, the system achieves more accurate air-fuel ratio detection across all operating conditions (rich, stoichiometric, and lean mixtures) without requiring a single complex sensor type.
2Measurement precision
If an oxygen concentration sensor with inversion type output characteristic is used, then the sensor can detect air-fuel ratio changes dramatically around theoretical air-fuel ratio, but the asymmetric output characteristic causes difficulty in accurately controlling air-fuel ratio when rich or lean
Solution Approach 1:
The patent changes the parameter used for control by introducing a rich/lean determination flag that indicates whether the air-fuel ratio is rich or lean. Based on this flag and the output deviation of the oxygen concentration sensor, the system dynamically adjusts the control input. When the mixture is rich, the system applies one control strategy, and when lean, it applies another strategy. This parameter change enables accurate control despite the asymmetric output characteristic of the oxygen concentration sensor.
Solution Approach 2:
The patent implements dynamic control by adjusting the control input based on real-time determination of rich/lean conditions. The control system continuously monitors the output deviation of the oxygen concentration sensor and updates the control strategy accordingly. This dynamic adaptation allows the system to maintain optimal control accuracy across varying operating conditions, overcoming the limitations of the sensor's fixed inversion type output characteristic.
3Speed
If larger amount of correction is used for regions where output deviation is large, then the exhaust gas air-fuel ratio is quickly adjusted to target air-fuel ratio, but the control system becomes more complex requiring multiple regions and reference values
Solution Approach 1:
The patent segments the control strategy into distinct regions based on the output deviation of the oxygen concentration sensor. The detection range is divided into a first region (rich condition) and a second region (lean condition), with each region having its own control characteristics. This segmentation allows the system to apply appropriate control corrections for each operating condition without requiring an overly complex unified control algorithm.
Data Source
AI summary
An air-fuel ratio control apparatus for an internal combustion engine includes an air-fuel ratio sensor having an output characteristic which is nonlinear with respect to the air-fuel ratio of exhaust gas. An output deviation converter is configured to convert an output deviation to a first predetermined value if an output value of the air-fuel ratio sensor is on a richer side of a predetermined target value and to a second predetermined value if the output value is on a leaner side of the target value. A control input calculator is configured to calculate a control input to feedback-control the output value of the air-fuel ratio sensor such that the output deviation converted by the output deviation converter is to be zero. An air-fuel ratio controller is configured to control the air-fuel ratio of exhaust gas using the control input calculated by the control input calculator.