Fail-Safe Mode Segmentation for EV Battery Protection
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Solution Overview
Problem
In electrified vehicles, when a sensor fails, the state of the electric power storage device cannot be detected, leading to potential progression of abnormalities in the device during fail-safe mode, as existing systems do not adequately restrict usage to prevent further damage.
Innovation Solution
The vehicle includes an electronic control unit that detects sensor failures and sets the fail-safe mode to a more restrictive second mode when an abnormality is detected, limiting the usage of the electric power storage device to prevent further damage, even if the sensor fails after the mode is established.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the vehicle transitions to a single fail-safe mode when sensor failure occurs, then the control system is simple and easy to implement, but the electric power storage device cannot be adequately protected when abnormalities are detected
Solution Approach 1:
The fail-safe mode is segmented into two distinct modes: a first fail-safe mode for when no abnormality is detected, and a second fail-safe mode for when abnormality is detected. This segmentation allows the system to provide appropriate protection levels based on the actual state of the electric power storage device, resolving the contradiction between system simplicity and adequate protection.
Solution Approach 2:
The system performs preliminary detection of abnormality signs in the electric power storage device before sensor failure occurs. This preliminary action allows the system to record the abnormality state and use this information to determine the appropriate fail-safe mode even after the sensor fails, ensuring continued protection without requiring complex real-time monitoring during fail-safe operation.
2Productivity
If the vehicle continues normal operation after sensor failure, then productivity is maintained, but the abnormality of the electric power storage device progresses unchecked
Solution Approach 1:
The system performs preliminary detection and recording of abnormality signs before sensor failure occurs. This allows the system to maintain vehicle operation in a fail-safe mode while preventing abnormality progression through restrictive control based on the pre-recorded abnormality information.
Solution Approach 2:
The system uses feedback from the preliminary abnormality detection to continuously adjust the level of restriction in the fail-safe mode. When abnormality is detected, the system transitions to a more restrictive second fail-safe mode that prevents further abnormality progression while still allowing limited vehicle operation.
3Reliability
If the vehicle waits for predetermined time after sensor failure before transitioning to fail-safe mode, then false transitions are avoided, but protection of the electric power storage device is delayed
Solution Approach 1:
The system performs preliminary detection of abnormality signs before sensor failure and records this information in advance. This preliminary action eliminates the need for waiting time after sensor failure, as the system can immediately transition to the appropriate fail-safe mode based on the pre-recorded abnormality state, thus avoiding both false transitions and protection delays.
Data Source
AI summary
An electrified vehicle includes an electric power storage device, a drive device, a sensor, and an electronic control unit. The electronic control unit causes transition of a traveling mode to an FS mode when a FS traveling condition is established. The electronic control unit detects a sign of an abnormality of an assembled battery using a detection value of a sensor when a sensor unit is normal. When the FS traveling condition is established and the sign of the abnormality of the assembled battery is not detected, the electronic control unit sets the FS mode to a predetermined first FS mode. When the FS traveling condition is established and the sign of the abnormality of the assembled battery is detected, the electronic control unit sets the FS mode to a second FS mode different from the predetermined first FS mode.