Vehicle Controller Battery Current Thresholds for Autostop
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Solution Overview
Problem
Existing hybrid vehicle systems face challenges in optimizing engine autostart/autostop functions to improve fuel economy while ensuring drivability, safety, and comfort, particularly in managing battery power during engine stops and starts at varying speeds and current demands.
Innovation Solution
A controller-programmed strategy that permits engine autostopping based on vehicle speed and battery current thresholds, with load shedding and delayed autostarting during aggressive braking or steering events to manage current demands and ensure efficient energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If engine autostopping is permitted at higher speeds and varying current demands, then fuel economy is improved, but drivability and safety may deteriorate
Solution Approach 1:
The patent applies dynamics by making the autostop/autostart control strategy adaptive to varying vehicle conditions. The controller dynamically adjusts autostop permission based on real-time monitoring of vehicle speed, battery current demand, and brake actuation parameters. This dynamic adjustment allows the system to permit autostopping under favorable conditions (improving fuel economy) while automatically inhibiting it when conditions suggest potential drivability or safety issues may arise.
Solution Approach 2:
The system changes operational parameters (vehicle speed threshold, battery current threshold, brake actuation parameter) to optimize the balance between fuel economy and drivability/safety. By monitoring these parameters and adjusting control decisions based on their values, the system can expand autostop conditions to improve fuel consumption while maintaining reliability through parameter-based safety checks.
2Use of energy by moving object
If engine autostopping is expanded to more conditions, then fuel economy improves, but battery power management complexity increases
Solution Approach 1:
The control strategy is segmented into distinct operational modes and decision points. The controller evaluates specific conditions (vehicle speed below threshold, battery current below threshold, brake actuation parameter checks) in a structured sequence. This segmentation of the control logic into discrete, manageable conditions simplifies the overall management complexity while enabling expanded autostop conditions for improved fuel economy.
Solution Approach 2:
The system employs feedback mechanisms where the controller continuously monitors vehicle speed, battery current demand, and brake actuation parameters, then adjusts autostop/autostart decisions based on this feedback. This closed-loop control approach manages battery power efficiently by responding to actual system states, reducing the complexity of predicting and managing all possible scenarios in advance.
3Reliability
If delayed autostarting is implemented during aggressive braking, then battery current demand is managed, but engine response time increases
Solution Approach 1:
The system applies preliminary anti-action by proactively delaying autostart during aggressive braking events before the engine would naturally restart. The controller predicts that aggressive braking (detected through brake actuation parameters) will cause high battery current demand, and pre-emptively delays autostart to prevent exceeding battery capabilities. This preliminary intervention manages battery current while the delay in engine response is temporary and condition-specific.
Data Source
AI summary
A vehicle includes an engine and a controller configured to autostop and autostart the engine. Engine autostops are conditioned on a vehicle speed condition. In addition, engine autostops are conditioned on a battery current threshold that changes as the speed of the vehicle changes.