Variable Resolution Sampling for Engine Combustion Control
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Solution Overview
Problem
Cylinder pressure monitoring systems in production engines are expensive and unreliable, limiting their applicability to high-power density and efficiency applications, and require multiple sensors for engine control, which increases complexity and cost.
Innovation Solution
An engine control unit (ECU) processes high-frequency in-cylinder pressure measurements at varying sampling rates, eliminating the need for additional sensors like mass-air-flow, NOx, and knock sensors by calculating combustion metrics in real-time, such as peak pressure, adiabatic heat release rate, and combustion stability, to control ignition timing and fueling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cylinder pressure monitoring systems are implemented in production engines, then combustion control capability is improved, but system cost and complexity increase
Solution Approach 1:
The patent combines multiple sensor functions (mass-air-flow, NOx, knock sensors) into the ECU by using cylinder pressure measurements to calculate all necessary combustion metrics. This integration eliminates the need for separate sensors and reduces overall system complexity while maintaining combustion control capability.
Solution Approach 2:
The cylinder pressure sensor serves multiple functions: measuring mass-air-flow, detecting knock events, monitoring NOx-related combustion quality, and calculating combustion metrics. This multi-functionality reduces the number of components needed while improving measurement precision for combustion control.
2Measurement precision
If multiple sensors are used for engine control, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The cylinder pressure sensor is designed to perform multiple measurement functions simultaneously - determining mass-air-flow from pressure traces, detecting knock through high-frequency analysis, monitoring combustion quality indicators, and calculating combustion metrics. This single multi-functional sensor replaces what would traditionally require multiple separate sensors.
Solution Approach 2:
The system analyzes cylinder pressure signals at different frequency ranges and processing resolutions to extract different types of information. By changing the analysis parameters (frequency bands, sampling rates, calculation methods), the same pressure sensor provides diverse measurement capabilities equivalent to multiple specialized sensors.
3Measurement precision
If high-frequency pressure sampling is performed throughout the entire crank angle range, then measurement precision is improved, but computation demand increases
Solution Approach 1:
The patent divides the crank angle range into different sampling windows with different resolution requirements. High-frequency sampling is applied only during critical combustion phases (power stroke), while lower-frequency sampling is used during less critical phases (intake, compression, exhaust strokes). This segmentation maintains measurement precision where needed while reducing overall computation demand.
Solution Approach 2:
The sampling frequency is dynamically adjusted based on the engine cycle phase and operational conditions. The system increases sampling rates during combustion events requiring precise measurement and reduces rates during other phases, optimizing the balance between measurement precision and computational resource utilization.
Data Source
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AI summary
A system for controlling an internal combustion engine has an in-cylinder pressure sensor, a crank angle sensor and a controller coupled to receive inputs from the pressure sensor and crank angle sensor. The controller is configured to convert the cylinder pressure input into a combustion metric indicative of the combustion occurring in the measured cylinder and control fuel input and timing into the engine based on the combustion metric. The controller samples the in-cylinder pressure sensor at a high frequency during critical combustion events and at a lower frequency during the non-critical cylinder conditions.