Engine Controller Cylinder Pressure Estimation Torsional Vibration
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Solution Overview
Problem
Existing methods for estimating cylinder internal pressure in internal combustion engines are inaccurate due to torsional vibration in the crankshaft, which is not adequately accounted for in current technologies, and require complex calculations and expensive sensors.
Innovation Solution
A controller and control method that calculates crank angle speed and acceleration, determines torsional vibration torque with a natural angular frequency, and estimates cylinder internal pressure using an equation of motion for the crankshaft system, simplifying the calculation by considering torsional vibration without solving complex inertia systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the crankshaft is treated as a rigid body to simplify calculations, then the calculation complexity is reduced, but the measurement precision of combustion condition deteriorates due to unaccounted torsional vibration
Solution Approach 1:
The crankshaft is segmented into multiple rotational bodies (first rotational body and second rotational body) connected by a elastic element representing the crankshaft's flexible nature. This segmentation allows the system to model torsional vibration while maintaining manageable calculation complexity through modular structure.
Solution Approach 2:
An elastic element is introduced as an intermediary between the first and second rotational bodies to represent the crankshaft's flexibility. This intermediary component enables the system to account for torsional vibration effects without requiring complex direct modeling of the crankshaft's elastic deformation.
2Measurement precision
If a cylinder internal pressure sensor is used to measure combustion condition accurately, then the measurement precision is improved, but the device cost increases significantly
Solution Approach 1:
Instead of directly measuring cylinder internal pressure with expensive sensors, the system creates a computational model (copy) of the pressure-torque relationship. The combustion condition is inferred by calculating combustion gas pressure torque from crankshaft vibration characteristics, providing an accurate indirect measurement without physical pressure sensors in the cylinders.
Solution Approach 2:
The mechanical measurement system (cylinder internal pressure sensor) is replaced with a computational mechanics approach. The system uses equations of motion and torque calculations based on crankshaft dynamics to substitute for direct mechanical pressure measurement, reducing hardware cost while maintaining measurement accuracy.
3Measurement precision
If a complex equation of motion with multiple inertia systems is solved to account for torsional vibration, then the measurement precision is improved, but the calculation complexity and time increase significantly
Solution Approach 1:
The elastic element representing crankshaft flexibility is extracted and isolated from the complex multi-body inertia system. By separating the flexible component, the system reduces the complexity of the equations of motion while retaining the essential torsional vibration characteristics needed for accurate combustion torque calculation.
Solution Approach 2:
The system transitions from a static rigid-body model to a dynamic model that incorporates time-varying elastic deformation. The elastic element's dynamic behavior captures torsional vibration effects, enabling accurate real-time combustion measurement without requiring solution of complex static equilibrium equations for multiple inertia systems.
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 improves the accuracy of cylinder internal pressure estimation by accounting for torsional vibration, reducing the need for expensive sensors and simplifying calculations, leading to more precise fuel consumption and emission control.
Implementation Method 1
a specific crank angle sensor which is fixed to a nonrotation member and detects the detected unit
Implementation Method 2
an angle information calculator that detects a crank angle based on an output signal of the specific crank angle sensor, and calculates a crank angle speed which is a time change rate of the crank angle, and a crank angle acceleration which is a time change rate of the crank angle speed
Implementation Method 3
a torsional torque calculator that calculates a maximum value of a torsional vibration torque which is a vibration component of a torsional torque produced by torsion of the crankshaft, based on the crank angle acceleration in a combustion period
Implementation Method 4
calculates a value which has an amplitude of the maximum value of the torsional vibration torque and vibrates with a preliminarily set natural angular frequency of the torsional vibration
Implementation Method 5
a cylinder internal pressure estimator that calculates a combustion gas pressure torque produced by combustion, by use of an equation of motion of a rotation system of the crankshaft containing piston, connecting rod, and crank
Implementation Method 6
estimates a cylinder internal pressure of a combustion cylinder, based on the combustion gas pressure torque and the crank angle
Data Source
AI summary
To provide a controller and a control method for an internal combustion engine capable of estimating the cylinder internal pressure of the combustion cylinder accurately in consideration of the torsional vibration of the crankshaft. A controller for an internal combustion engine includes a torsional torque calculator that calculates a value which has an amplitude of the maximum value of torsional vibration torque calculated based on a crank angle acceleration in the combustion period, and vibrates with a preliminarily set natural angular frequency, as a torsional vibration torque in the combustion period; and a cylinder internal pressure estimator that calculates a combustion gas pressure torque, by use of the equation of motion of the rotation system of the crankshaft, based on the crank angle, the crank angle acceleration, and the torsional vibration torque, and estimates the cylinder internal pressure of the combustion cylinder based on the combustion gas pressure torque.