Adaptive Battery SOC Threshold Control for Hybrid Vehicles
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Solution Overview
Problem
Hybrid electric vehicles face challenges in efficiently managing their traction battery state of charge, particularly in transitioning between charge depleting and charge sustaining modes, which affects the number of all-electric miles driven and user satisfaction.
Innovation Solution
A vehicle controller is configured to maintain the traction battery's state of charge within specific thresholds by selectively expanding or contracting the SOC range based on operating conditions, allowing the vehicle to operate in either mode for extended periods while preventing the SOC from falling below a minimum threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle maintains a strict SOC threshold to prevent battery depletion, then battery reliability is improved, but the number of all-electric miles driven is reduced
Solution Approach 1:
The patent applies dynamics by making the SOC threshold adaptive rather than fixed. The controller dynamically adjusts the SOC threshold based on driving cycle detection: using a first threshold during detected drive cycles and a second (lower) threshold during idle periods. This dynamic adjustment allows the vehicle to maximize all-electric miles during actual driving while preventing battery depletion during charging opportunities, thus resolving the contradiction between reliability and duration.
Solution Approach 2:
The patent changes the SOC threshold parameter based on operating conditions. By detecting whether the vehicle is in a drive cycle or idle period, the controller switches between two different SOC threshold values. This parameter change strategy allows flexible optimization: higher threshold during driving to ensure reliability, lower threshold during idle to extend all-electric range, effectively resolving the technical contradiction.
2Productivity
If the vehicle operates in deplete mode to maximize all-electric miles, then productivity is improved, but battery state of charge falls below safe levels
Solution Approach 1:
The patent implements feedback by continuously monitoring SOC levels and comparing them against dynamically adjusted thresholds. The controller detects the current operating mode (drive cycle vs. idle) and adjusts the SOC threshold accordingly. This feedback mechanism ensures that the vehicle operates in deplete mode to maximize productivity when SOC is above the threshold, while automatically preventing unsafe battery levels by switching to sustain mode when the threshold is approached, thus resolving the contradiction between productivity and reliability.
3Reliability
If the SOC range is fixed to ensure battery safety, then reliability is improved, but adaptability to different driving conditions deteriorates
Solution Approach 1:
The patent makes the SOC range dynamic by implementing two different threshold levels based on detected driving conditions. During drive cycles, the controller uses a first SOC threshold that allows more aggressive deplete mode operation for adaptability. During idle periods, it switches to a second, lower threshold to ensure battery safety. This dynamic adaptation to different operating conditions resolves the contradiction between reliability and adaptability.
Data Source
AI summary
A vehicle includes a traction battery, and a controller configured to, responsive to a transition from deplete mode to sustain mode during a first drive cycle, maintain a state of charge (SOC) of the battery within a range defined by a first maximum threshold, and responsive to initiation of a next drive cycle in the sustain mode, maintain the SOC within a range defined by a second maximum threshold greater than the first.