Coordinated Variable Valve Timing and Electronic Throttle Control
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Solution Overview
Problem
Internal combustion engines face delays in delivering requested engine torque due to the inherent intake manifold filling delay, which affects fuel economy and engine performance when coordinating variable valve timing (VVT) and electronic throttle control (ETC) during transient periods.
Innovation Solution
The techniques decouple the scheduling of ETC and VVT by determining a target intake manifold absolute pressure (MAP) and valve position based on engine torque requests, volumetric efficiency, and actual MAP, using closed-loop feedback to command the throttle and valve actuators, thereby minimizing pumping losses and delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If VVT and ETC are coordinated during transient periods, then engine torque delivery is improved, but intake manifold filling delay causes torque delivery delay and reduced fuel economy
Solution Approach 1:
The system performs preliminary action by predicting future MAP values and calculating target valve positions in advance based on current operating conditions and driver torque requests. This allows the VVT system to proactively adjust valve timing before the intake manifold filling delay would otherwise cause torque delivery lag, effectively compensating for the inherent system lag.
Solution Approach 2:
The system implements feedback control by continuously monitoring actual MAP, comparing it with target MAP, and adjusting valve positions accordingly. The control algorithm uses feedback from current engine state (RPM, throttle position, actual MAP) to dynamically calculate optimal valve timing, ensuring accurate torque delivery while compensating for intake manifold filling delays.
2Measurement precision
If complex manifold dynamic modeling is used to address intake manifold filling delay, then torque delivery accuracy is improved, but system complexity increases
Solution Approach 1:
The system changes parameters by using simplified lookup tables and empirical correlations instead of complex manifold dynamic models. It transforms the control approach from solving complex differential equations to using pre-calibrated maps that relate RPM, throttle position, and desired torque to optimal valve positions, maintaining accuracy while dramatically reducing computational complexity.
Solution Approach 2:
The system replaces complex, computationally expensive manifold dynamic models with simpler, lighter computational structures (lookup tables and empirical formulas). These simplified models consume fewer computational resources and can be executed rapidly on embedded controllers, effectively trading model complexity for real-time performance.
Data Source
AI summary
A method can include determining, at a controller for an engine, the controller having one or more processors, a desired air-per-cylinder (APC) for the engine based on an engine torque request. The method can include determining, at the controller, a target intake manifold absolute pressure (MAP) based on a volumetric efficiency of the engine for electronic throttle control (ETC), wherein the volumetric efficiency for ETC is based on the desired APC and an actual MAP. The method can include commanding, by the controller, a throttle of the engine to deliver the target MAP. The method can include determining, at the controller, a target position for an intake valve of the engine based on a volumetric efficiency of the engine for variable valve timing (VVT), engine speed, and the actual MAP. The method can also include commanding, by the controller, the intake valve to the target position.