Engine Speed Determination Using Firing Fraction for Cylinder Deactivation
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Solution Overview
Problem
Cylinder deactivation in internal combustion engines causes significant variation in engine speed, leading to undesired variations in target actuator values, which is challenging for engine control systems to manage effectively.
Innovation Solution
A system comprising a firing fraction module, an engine speed module, and an actuator control module that determines the engine speed based on a target firing fraction and filters crankshaft position signals to minimize speed variation while maintaining responsive actuator adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cylinders are deactivated to improve fuel economy, then fuel economy improves, but engine speed variation increases causing undesired variation in target actuator values
Solution Approach 1:
A firing fraction calculation module is introduced as an intermediary between the cylinder deactivation system and the engine speed determination system. This module calculates the firing fraction (ratio of active cylinders to total cylinders) and uses it to adjust the engine speed calculation, effectively mediating the impact of cylinder deactivation on engine speed stability and preventing undesired variations in target actuator values
2Measurement precision
If engine speed is determined using traditional methods, then engine speed is measured, but significant variation occurs when cylinders are deactivated
Solution Approach 1:
The system changes the parameter used for engine speed determination by incorporating the firing fraction into the calculation. Instead of using a fixed relationship between crankshaft position and engine speed, the system dynamically adjusts the calculation based on the actual firing fraction, thereby maintaining measurement precision while compensating for stability variations caused by cylinder deactivation
3Ease of operation
If target actuator values are adjusted based on engine speed, then actuator control is achieved, but undesired variation occurs due to engine speed fluctuation
Solution Approach 1:
The system implements a feedback mechanism where the calculated firing fraction is continuously used to adjust the engine speed determination, which in turn feeds back to the actuator control module. This closed-loop feedback ensures that target actuator values are adjusted based on the corrected engine speed that accounts for cylinder deactivation, thereby maintaining actuator control ease while reducing undesired variations
Data Source
AI summary
A system according to the principles of the present disclosure includes a firing fraction module, an engine speed module, and an actuator control module. The firing fraction module determines a target firing fraction corresponding to a target number of activated cylinders out of a first number of cylinders in a firing order of an engine. The first number is a denominator of the target firing fraction. The engine speed module determines a plurality of periods based on a crankshaft position signal, with each of the periods corresponding to a predetermined amount of crankshaft rotation. The engine speed module determines the speed of the engine based on the plurality of periods and the target firing fraction. The actuator control module controls an actuator of at least one of the engine and a torque converter based on the engine speed.