Turbocharger Control Using Virtual Speed Sensor for Overspeed Protection
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Solution Overview
Problem
Existing turbocharger control methods are suboptimal due to factors like turbulent air flow, sensor inaccuracy, lag in actuator response, and sensitivity to engine conditions, leading to inefficiencies and potential wear in wastegate components.
Innovation Solution
A virtual turbocharger speed sensor (VRTSS) is used to model engine airflow and calculate turbocharger speed, enabling a control model to optimize wastegate position and maintain target boost pressure, while preventing overspeed and minimizing wastegate movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a basic control loop is used to monitor boost pressure and adjust wastegate position, then the system can maintain target boost pressure, but the control is suboptimal due to lag in actuator response and sensitivity to engine conditions
Solution Approach 1:
The control system performs preliminary action by predicting future turbocharger speed and boost pressure using a kinetic energy model before the actual state occurs. The model calculates predicted values based on current turbocharger speed, kinetic energy, and engine operating conditions, allowing the controller to proactively adjust wastegate position before lag causes deviation from target boost pressure.
Solution Approach 2:
The system implements feedback by continuously monitoring actual turbocharger speed (via virtual sensor), actual boost pressure, and engine operating conditions, then comparing these with predicted values to calculate correction signals. This closed-loop feedback mechanism compensates for actuator lag and maintains accurate boost pressure control despite delays in wastegate response.
2Reliability
If a physical governor is applied to reduce turbocharger speed, then overspeed can be prevented, but sudden changes in turbocharger speed lead to low cycle fatigue
Solution Approach 1:
The patent replaces the mechanical governor system with a virtual turbocharger speed sensor and kinetic energy-based control system. The virtual sensor calculates turbocharger speed from engine airpath sensors and a model of the engine air path, eliminating the need for direct mechanical speed sensing and governor mechanisms. This substitution allows for smoother, more gradual speed control that prevents overspeed while avoiding the sudden changes that cause low cycle fatigue.
3Reliability
If the wastegate is frequently adjusted for fine control, then boost pressure can be maintained, but excess movement of the wastegate can prematurely age the wastegate
Solution Approach 1:
The control system performs preliminary calculation of the optimal wastegate position using the kinetic energy model and predicted turbocharger speed, determining the necessary adjustment before actuation. This allows for more deliberate, less frequent adjustments compared to reactive control, reducing unnecessary wastegate movement while maintaining accurate boost pressure control.
Solution Approach 2:
The system uses feedback from the virtual turbocharger speed sensor and actual boost pressure measurements to determine when wastegate adjustment is truly necessary. By continuously monitoring the relationship between predicted and actual values, the controller can maintain boost pressure with minimal wastegate movement, only actuating when correction is needed rather than making continuous fine adjustments.
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 and efficiency of turbocharger speed control, reduces wastegate wear, and maintains target boost pressure by predicting future turbocharger speed and adjusting wastegate position accordingly.
Implementation Method 1
a turbine in the engine exhaust air flow to power a compressor
Implementation Method 2
the compressor being upstream of the intake manifold... to compress air to be provided to the intake manifold
Data Source
AI summary
Systems and methods for controlling turbocharger operation by maintaining a virtual turbocharger speed calculation using airflow parameters in the context of an engine. An example uses a turbocharger speed estimator, an energy observer, and an energy controller. Optimization of turbocharger speed control, including avoidance of overspeed, while reducing wastegate actuation, can be achieved using a predictive control algorithm.