Angle-Domain Cylinder Pressure Measurement System
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Solution Overview
Problem
Current cylinder pressure measurement systems process signals in the time-domain, leading to inaccurate engine control and high processing power/memory requirements, increasing costs and implementation complexity.
Innovation Solution
A system that converts analog cylinder pressure signals to digital signals in the angle-domain using angular position data, followed by time-domain filtering and sampling, allowing for accurate angle-domain pressure measurement and reduced processing needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog cylinder pressure signals are processed in the time-domain, then processing can be performed, but measurement accuracy deteriorates and processing power/memory requirements increase
Solution Approach 1:
The patent transforms the processing domain from time-domain to angle-domain by changing the reference parameter from time to engine angle. This is achieved by sampling the pressure signal at angles corresponding to piston position rather than at uniform time intervals, which directly addresses the measurement accuracy issue while reducing processing complexity
Solution Approach 2:
The patent introduces an angle-domain intermediary representation as a intermediate step between time-domain sampling and final pressure measurement. By converting time-domain samples to angle-domain samples using the relationship between crank angle and time, the system achieves accurate pressure measurements without requiring complex time-domain processing
2Ease of manufacture
If analog cylinder pressure signals are processed in the time-domain, then processing can be performed, but implementation cost increases
Solution Approach 1:
The patent simplifies implementation by changing the sampling parameter from time-based to angle-based. This allows the use of simpler processing algorithms that operate in the angle-domain, reducing the computational complexity and memory requirements while maintaining manufacturing feasibility
3Loss of information
If time-domain processing is used, then processing can be performed, but the correlation with engine operation deteriorates
Solution Approach 1:
The patent restores the correlation with engine operation by changing the processing parameter from time to engine angle. Since engine angle directly reflects piston position and combustion phase, processing in the angle-domain maintains direct correlation with engine operation events, improving information retention while enhancing processing efficiency
Data Source
AI summary
Techniques for measuring cylinder pressure include receiving an analog cylinder pressure signal indicative of pressure in a cylinder of an engine and an angular position signal indicative of an angular position of the engine. The analog cylinder pressure signal is converted to a digital cylinder pressure signal by (i) windowing the analog cylinder pressure signal in the angle-domain using the angular position signal and (ii) sampling the windowed analog cylinder pressure signal in the time-domain, and the digital cylinder pressure signal is filtered in the time-domain to obtain a filtered digital cylinder pressure signal. A measured pressure in the angle domain is obtained by sampling the filtered digital cylinder pressure signal using the angular position signal, and operation of the engine is controlled using the measured cylinder pressure.