Self-Tuning Engine Control via Cylinder Pressure Feedback
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Solution Overview
Problem
Traditional combustion control systems for internal combustion engines face inaccuracies due to production variations, component wear, and cylinder-to-cylinder differences, particularly in diesel engines, where thermodynamic properties change during expansion, leading to errors in pressure estimation and synchronization.
Innovation Solution
A method to accurately peg a pressure transducer's voltage offset and correct phasing errors by calculating the ratio of specific heats and polytropic exponents, using measured voltage signals and cylinder volumes during specific crank angle windows, to improve engine control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional control systems use baseline engine conditions and standard sensing variables, then the control system is simple and easy to operate, but measurement precision deteriorates due to production variations, component wear, and cylinder-to-cylinder differences
Solution Approach 1:
The patent implements feedback control by continuously measuring actual cylinder pressure and comparing it with estimated motoring pressure to calculate pressure ratio. This feedback loop enables real-time adjustment of ignition timing, EGR rate, and fuel rate to compensate for production variations, component wear, and cylinder-to-cylinder differences, thereby maintaining measurement precision without complicating operation
Solution Approach 2:
The system performs self-calibration by automatically determining voltage offset and polytropic exponent values during engine operation. The controller uses measured pressure data and crankshaft position to self-determine compensation parameters, eliminating the need for manual calibration procedures while maintaining high measurement precision
2Device complexity
If pressure transducer voltage offset is not accurately determined, then the control system is simpler, but measurement precision deteriorates due to errors in pressure estimation
Solution Approach 1:
The controller automatically determines voltage offset values during engine operation by analyzing pressure transducer signals at specific crankshaft positions. The system self-calibrates by comparing measured pressure with estimated motoring pressure and adjusting voltage offset accordingly, eliminating manual calibration complexity while achieving high measurement precision
Solution Approach 2:
The system performs preliminary voltage offset determination during engine operation before using the pressure data for control decisions. By pre-calculating accurate voltage offset values based on measured pressure signals and crankshaft position, the system ensures high measurement precision is established before the main control function executes
3Device complexity
If polytropic constant is assumed constant during compression stroke, then calculations are simpler, but measurement precision deteriorates due to thermodynamic property changes during expansion
Solution Approach 1:
The patent transitions from a static polytropic constant assumption to a dynamic model where the polytropic exponent varies with crankshaft position and thermodynamic state. The controller calculates real-time polytropic exponents for compression and expansion strokes separately, adapting the model to actual thermodynamic conditions and maintaining high measurement precision despite increased calculation complexity
Solution Approach 2:
The system changes the polytropic parameter from a fixed constant to a variable that depends on crankshaft position and thermodynamic state. By calculating different polytropic exponents for compression and expansion phases and adjusting them based on actual operating conditions, the system maintains accurate motoring pressure estimation while accounting for thermodynamic property changes
4Device complexity
If cylinder volume is not accurately synchronized with pressure signal, then the control system is simpler, but measurement precision deteriorates due to phasing errors
Solution Approach 1:
The controller uses feedback from crankshaft position sensors and pressure transducers to continuously synchronize cylinder volume calculations with pressure signal phase. By comparing actual pressure signal timing with expected timing based on crankshaft position, the system adjusts volume calculations in real-time to maintain accurate phasing, eliminating synchronization errors without excessive complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of combustion-related parameter calculations, reducing errors caused by heat transfer losses and synchronization issues, thereby improving engine control precision.
Implementation Method 1
Cylinder pressure within the Matekunas disclosure is determined via a pressure sensing transducer that produces a voltage that is linearly related to pressure
Implementation Method 2
It is assumed that prior to start of combustion the cylinder contents follow a polytropic process so that: PVn=constant
Data Source
AI summary
The present invention relates to: self-tuning engine control algorithms using inputs from transducers that measure pressure in the engine cylinders, and from an engine crankshaft rotational position sensor; methods of processing the input signals to “self-tune” or learn accurate values for a) pressure transducer voltage offset, b) crank position encoder error and c) engine compression ratio; improved pressure-ratio-based algorithms for calculating cylinder heat release fraction as a function of crank angle.