Crankshaft Speed Analysis for IMEP Estimation
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Solution Overview
Problem
Internal combustion engines face challenges in accurately determining indicated mean effective pressure (IMEP) without pressure sensors in each cylinder, leading to potential misfires and torque imbalances, which can damage the engine and reduce performance and fuel economy.
Innovation Solution
A system and method that estimate IMEP by determining expected and measured crankshaft speed responses, using pre-determined expected response vectors and inverse matrix calculations to calculate coefficients, which are then used to estimate IMEP and adjust engine operating parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are installed in each cylinder to measure IMEP, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses crankshaft speed as an intermediary parameter to indirectly measure cylinder IMEP. Instead of directly measuring cylinder pressure with sensors, the system measures crankshaft speed fluctuations caused by combustion pressure variations. This intermediary measurement approach eliminates the need for expensive pressure sensors in each cylinder while maintaining measurement capability through the relationship between combustion pressure and crankshaft rotational dynamics
Solution Approach 2:
The patent replaces the mechanical pressure sensing system with an electrical/electronic measurement system. Instead of using mechanical pressure sensors installed in each cylinder, the system uses electrical sensors to measure crankshaft speed and processes this data through mathematical models and signal processing algorithms to derive IMEP values, thereby eliminating complex mechanical sensor installations
2Reliability
If pressure sensors are installed in each cylinder to detect misfires, then detection reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent creates a virtual copy of the pressure measurement function through computational modeling. Instead of physically installing pressure sensors in each cylinder, the system uses mathematical models and signal processing to create virtual pressure measurements from crankshaft speed data. This copying approach achieves misfire detection capability without the high manufacturing costs of physical sensor installation
Solution Approach 2:
The patent makes the crankshaft speed measurement system multi-functional. The same crankshaft speed measurements used for basic engine operation monitoring are also utilized for IMEP determination and misfire detection across all cylinders. This universal approach allows one measurement system to serve multiple diagnostic functions, eliminating the need for additional dedicated sensors and reducing overall system cost
3Productivity
If IMEP is not accurately determined, then fuel economy deteriorates, but adding pressure sensors increases device complexity
Solution Approach 1:
The patent implements a feedback control system where IMEP values derived from crankshaft speed measurements are used to adjust fuel injection and ignition timing. The system continuously monitors crankshaft speed, calculates IMEP for each cylinder, compares it to target values, and adjusts combustion parameters accordingly. This feedback loop enables accurate fuel management and optimal fuel economy without requiring complex pressure sensor systems
Solution Approach 2:
The patent changes the measurement parameter from direct cylinder pressure to crankshaft speed. By measuring crankshaft rotational speed and using mathematical relationships between combustion pressure and rotational dynamics, the system derives IMEP values. This parameter change allows accurate combustion measurement using simpler, less intrusive measurements that do not require complex sensor installations in each cylinder
Data Source
AI summary
A system for an engine includes first, second, third, and fourth modules. The first module determines an expected response of crankshaft speed due to combustion within a cylinder of the engine. The second module determines a value based on the expected response and a measured response of crankshaft speed due to combustion within the cylinder of the engine. The third module estimates an indicated mean effective pressure (IMEP) for the cylinder of the engine based on the value. The fourth module selectively adjusts an operating parameter of the engine based in the estimated IMEP.