Powertrain Delta Current Estimation for Micro-Hybrid Engine Stop
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Solution Overview
Problem
In micro-hybrid vehicles, automatic engine stops can lead to excessive current demands on the battery during engine stop/start events, potentially causing voltage drops and inhibiting optimal fuel economy due to the inability to accurately predict changes in current demand from electrical loads.
Innovation Solution
A controller is programmed to estimate changes in current demand based on operating conditions such as voltage, speed, and temperature of electrical loads, selectively turning the engine off or on to maintain a predetermined threshold, ensuring the battery voltage remains within safe limits and optimizing fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is automatically stopped to improve fuel economy, then fuel consumption is reduced, but current demand on the battery increases excessively causing voltage drops
Solution Approach 1:
The controller performs preliminary estimation of current demand changes before actually stopping the engine. By calculating the difference between current demands of components that will be off during engine stop versus components that will be on, the system predicts total current demand in advance, allowing proactive prevention of voltage drops before they occur.
Solution Approach 2:
The system continuously monitors operating conditions (voltage, speed, temperature) of electrical components and feeds this information back to the controller. Based on this feedback, the controller dynamically adjusts engine stop/start decisions to maintain battery voltage within safe limits while maximizing fuel economy benefits.
2Use of energy by moving object
If the engine is stopped during idle or coasting, then fuel economy improves, but accurate prediction of current demand changes is difficult
Solution Approach 1:
The controller calculates expected current demand changes in advance by comparing the sum of current demands of components that will be off during engine stop against components that will be on. This preliminary calculation provides accurate prediction of net current demand change before the engine stop event occurs.
Solution Approach 2:
The system estimates current demand based on dynamic operating parameters including voltage, speed, and temperature of electrical components. By continuously updating these parameters and using them to recalculate expected current demand, the system maintains prediction accuracy despite changing operating conditions during idle or coasting states.
Data Source
AI summary
A vehicle includes an engine, electrical loads, and at least one controller. While the engine is on, the controller calculates the change in current demand of the electrical loads expected from turning the engine off. The decision to command the engine off is then based on the expected change in current demand. Electrical loads that will change state from on to off when the engine is turned off will increase the expected change in current demand. Electrical loads that will change state from off to on when the engine is turned off will decrease the expected change in current demand. Operating conditions associated with the electrical loads, such as operating voltage, temperature, and speed, may affect the expected change in current demand.