Vehicle Battery SOC Memory Rewrite Control
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Solution Overview
Problem
The frequent rewriting of state of charge (SOC) information in nonvolatile memory of electric vehicles leads to premature deterioration, as it is rewritten every time the vehicle stops, potentially exceeding the memory's rewrite limit, which can result in loss of critical SOC data.
Innovation Solution
A control device for electric vehicles that includes an SOC acquisition unit, a ΔSOC acquisition unit, and a rewriting unit, which rewrites the memory SOC only when the difference between the current and stored SOC exceeds a predetermined value, set based on vehicle speed, to reduce the number of rewrites and ensure reliable SOC storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOC information is rewritten every time the vehicle is stopped, then the SOC information is kept up-to-date, but the number of rewriting times increases and may exceed the upper limit of the nonvolatile memory
Solution Approach 1:
The patent changes the rewriting condition parameter from 'every vehicle stop' to 'when ΔSOC exceeds predetermined value'. This parameter change reduces the frequency of rewriting operations while ensuring SOC information remains reliable for control purposes.
Solution Approach 2:
Instead of rewriting SOC information at every opportunity (excessive action), the patent applies partial action by rewriting only when the difference ΔSOC exceeds a predetermined threshold. This partial action is sufficient to maintain control reliability while extending memory lifespan.
2Duration of action of moving object
If the predetermined value for rewriting is set high, then the number of rewriting times is reduced, but the accuracy of SOC information may be insufficient for various controls
Solution Approach 1:
The patent makes the predetermined value dynamic by adjusting it based on vehicle speed. At high speeds where SOC changes rapidly, a larger predetermined value is used to reduce rewriting frequency. At low speeds where SOC changes slowly, a smaller predetermined value maintains higher SOC information accuracy for control purposes.
Solution Approach 2:
The predetermined threshold value is changed according to vehicle operating conditions (speed). This parameter adaptation allows the system to balance between reducing rewriting frequency and maintaining sufficient SOC accuracy for various vehicle controls under different operating conditions.
Data Source
AI summary
An ECU includes a nonvolatile memory. An SOC acquisition unit acquires SOCc, which is a current SOC of a battery. A ΔSOC calculation unit calculates a difference ΔSOC (=|SOCm−SOCc|) between an SOCm (memory SOC) stored in the nonvolatile memory and the SOCc. A rewriting unit rewrites the SOCm stored in the nonvolatile memory to the SOCc, on the condition: ΔSOC>threshold value S1 during charging, ΔSOC>threshold value S2 during discharging, or ΔSOC>predetermined value α when an ignition switch is operated to switch from ON to OFF.