Cascaded Engine Control Loop for Cylinder Injection Stability
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Solution Overview
Problem
Internal combustion engine control systems face challenges in achieving stable and adjustable cylinder-specific control due to signal chain tolerances and non-linearities, leading to high operational costs and safety risks from malfunction.
Innovation Solution
A cascaded rotational speed control loop with an inner injection duration control loop, where a rotational speed controller calculates a target torque and injection duration, and an injection duration controller adjusts injector fueling, using a precontrol value to compensate for age-related changes and ensure continued operation by calculating a virtual injection beginning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotational speed control loop is used for internal combustion engine regulation, then the engine can be controlled, but signal chain tolerances and injection device tolerances cause different fuel amounts to be injected into individual cylinders, requiring filtering of the controlled variable to achieve stable control
Solution Approach 1:
The patent divides the engine control into cylinder-specific control loops, where each cylinder has its own injection duration control. This segmentation allows individual correction of injection amounts for each cylinder based on its actual performance, rather than using a single filtered control variable for the entire engine.
Solution Approach 2:
The patent implements feedback by measuring the actual injection duration for each cylinder and comparing it with the target injection duration. The difference is used to calculate a correcting variable that adjusts the control signal for that specific cylinder, creating a closed-loop control system that compensates for tolerances.
2Reliability
If filtering is applied to the controlled variable to achieve stable control loop, then control stability improves, but the system complexity increases and adjustment becomes costly
Solution Approach 1:
The patent extracts the control function from a centralized filtered control loop and distributes it to individual cylinder control loops. Each cylinder has its own simple control logic that compares target injection duration with actual injection duration, eliminating the need for complex filtering of aggregate control variables.
3Reliability
If protection against malfunction is implemented, then operational safety improves, but the system becomes more complex and harder to adjust
Solution Approach 1:
The patent implements self-service through automatic malfunction detection and fallback mechanisms. The system continuously monitors whether the actual injection duration can be captured, and automatically switches to using only the target injection duration if detection fails, without requiring external intervention or complex protection circuits.
4Measurement precision
If actual injection duration detection is used for closed-loop control, then control precision improves, but the system becomes vulnerable to detection failures and malfunctions
Solution Approach 1:
The patent prepares for potential detection failures by having a fallback control mode ready. When actual injection duration detection is available, it is used for precise control; when detection fails, the system automatically transitions to using only the target injection duration, ensuring continuous operation without interruption or malfunction.
Data Source
AI summary
A method for controlling an internal combustion engine having a common rail system together with individual accumulators. A rotational speed-control deviation (dn) is determined from a target rotational speed (nSL) that represents the set point for an outer control loop to control the rotational speed, as well as from an actual rotational speed (nIST). A target torque (MSL) is determined from the rotational speed-control deviation (dn) via a rotational speed controller as a master controller. A target injection duration (SD(SOLL)) is determined from the target torque (MSL). The target duration injection (SD(SOLL)) represents the set point for an inner control loop for controlling cylinder-specific injection duration. An injection duration deviation is determined from the target injection duration (SD(SOLL)) and from an actual injection duration. A correcting variable is determined from the injection duration deviation via an injection duration controller as a follow-up controller, and an injection duration is determined from the correcting variable and the target injection duration for activating the injectors.