Crank Angle Sensor Signal Processing for MFB50 Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Internal combustion engines with spontaneous mixture ignition face challenges in accurately and efficiently estimating the crank angle at which 50% of the fuel mass is burnt, due to the high cost and limited reliability of pressure sensors typically used for this purpose.
Innovation Solution
A method utilizing a phonic wheel with equally spaced teeth, coupled with a sensor and control unit, estimates the 50% Mass Fraction Burnt (MFB50) combustion index by compensating for manufacturing tolerances and performing frequency analysis to calculate the crank angle, without requiring additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are used to directly measure cylinder pressure for determining MFB50, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent uses existing crank angle sensor signals as an intermediary to indirectly determine MFB50, rather than directly measuring cylinder pressure. The control unit processes crank angle signals through frequency analysis and phase angle calculations to derive combustion information, eliminating the need for expensive pressure sensors while maintaining measurement capability
Solution Approach 2:
The patent creates a virtual representation of pressure-based combustion information by processing crank angle signals. The control unit generates MFB50 estimates that replicate the information normally obtained from pressure sensors, using mathematical transformations of existing sensor data to produce equivalent combustion metrics
2Measurement precision
If pressure sensors are installed for MFB50 determination, then measurement accuracy is improved, but reliability decreases due to limited time reliability
Solution Approach 1:
The patent makes the existing crank angle sensor serve multiple functions by having the control unit process its signals to determine both crank position and combustion parameters. The same sensor that tracks engine rotation now also provides data for MFB50 calculation, eliminating the need for separate unreliable pressure sensors
Solution Approach 2:
The patent replaces the mechanical pressure sensing system with an electronic signal processing system. Instead of using physical pressure sensors that degrade over time, the control unit uses electronic processing of crank angle signals to derive combustion information, improving long-term reliability
3Measurement precision
If conventional methods are used for MFB50 estimation, then measurement precision is improved, but productivity decreases due to excessive calculation power requirements
Solution Approach 1:
The patent applies partial action by using only the necessary frequency analysis components needed for MFB50 determination. Rather than performing complete pressure curve analysis, the control unit focuses on detecting specific frequency components and phase angles in crank angle signals, achieving adequate precision with reduced computational effort
Solution Approach 2:
The patent changes the measurement parameters from direct pressure values to crank angle signal characteristics. By transforming the problem from pressure-based to angle-based measurement and using frequency domain analysis, the system achieves comparable precision with more efficient calculations suitable for embedded control units
4Measurement precision
If additional components are installed for MFB50 measurement, then measurement precision is improved, but ease of manufacture decreases
Solution Approach 1:
The patent makes the existing crank angle sensor universal by having it perform both its primary function of tracking engine rotation and the secondary function of providing data for combustion analysis. The control unit processes the same sensor signals for multiple purposes, eliminating the need for additional dedicated measurement components
Data Source
AI summary
A method for determining the angular speed of a drive shaft of an internal combustion engine at each tooth event of a phonic wheel presenting a number N of teeth includes detecting the angular amplitude for each tooth; detecting the time of each tooth; and determining the raw angular speed of each tooth according to the corresponding angular amplitude and time. For each tooth a compensation value is determined which represents the difference between the actual angular amplitude of the tooth and the theoretic angular amplitude of the tooth; and determining the angular speed of each tooth by correcting the raw angular speed based on the corresponding compensation value.