Engine Air Charge Control via Intake Manifold Pressure
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Solution Overview
Problem
Conventional control methods for internal combustion engines with variable valve lift systems struggle to accurately adjust air charge due to non-linear error dynamics and fluctuations in intake manifold pressure, leading to unstable and imprecise control of the throttle valve.
Innovation Solution
A control method based on differential equations that account for setpoint and actual intake manifold pressures, using a transfer function to model the throttle valve's dynamic behavior and filter the setpoint intake manifold pressure to stabilize the system, allowing for precise calculation of the setpoint mass flow through the throttle valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control methods are used with variable valve lift systems, then the system can operate with basic throttle control, but the air charge control becomes inaccurate due to non-linear error dynamics and pressure fluctuations
Solution Approach 1:
The patent changes the control parameter from direct charge control to indirect pressure control. By controlling the intake manifold pressure as an intermediate parameter, the system achieves more accurate air charge control while accounting for non-linear dynamics. The differential equation-based controller adapts to varying operating conditions by continuously adjusting based on pressure deviations, thereby improving measurement precision without requiring fundamentally new hardware.
Solution Approach 2:
The patent introduces intake manifold pressure as an intermediary variable between the throttle valve and the cylinder charge. Instead of directly controlling charge based on valve position, the system first controls the intermediate pressure field in the intake manifold. This intermediary approach linearizes the control problem and provides a more stable basis for feedback control, resolving the accuracy issue while maintaining reasonable system complexity.
2Speed
If the setpoint intake manifold pressure is used directly for control, then the response to load changes is fast, but the system becomes unstable due to noisy sensor signals and pressure fluctuations
Solution Approach 1:
The patent applies filtering to the setpoint intake manifold pressure signal before it enters the control loop. This beforehand cushioning of the signal removes high-frequency noise and abrupt fluctuations that would cause instability. By pre-processing the reference signal to match the actual system dynamics capabilities, the controller responds smoothly to genuine load changes while ignoring spurious noise, thereby maintaining both speed and stability.
Solution Approach 2:
The patent implements a feedback mechanism that continuously compares the actual intake manifold pressure with the filtered setpoint pressure. The differential equation-based controller uses this feedback to generate corrective throttle valve adjustments. The feedback loop naturally dampens oscillations and compensates for disturbances, providing the stability needed to handle noisy sensor signals while maintaining responsive control through the differential equation structure.
3Adaptability or versatility
If high dynamic camshaft adjustments are made, then the valve timing can be optimized for different operating conditions, but the conventional control approach fails to maintain stable air charge
Solution Approach 1:
The patent explicitly accounts for dynamic valve timing changes in the control model. The differential equation controller incorporates the time-varying nature of camshaft adjustments and their effect on intake manifold pressure dynamics. By modeling the system as dynamic rather than static, the controller can adapt its behavior to match the changing valve timing, maintaining reliable air charge control across varying operating conditions while preserving the benefits of high dynamic camshaft adjustment capability.
Data Source
AI summary
A method for operating an internal combustion engine based on a control of a supplied fresh air quantity, the method comprising the following steps: implementing an adjustment of a throttle valve for the control of the supplied fresh air quantity as a function of a setpoint mass flow via the throttle valve; determining the setpoint mass flow via the throttle valve according to a differential equation, which is a function of a control deviation ascertained as a function of a setpoint intake manifold pressure and an actual intake manifold pressure.