High-Voltage Contactor Control for False Sticking Detection
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Solution Overview
Problem
Existing in-vehicle control devices erroneously detect sticking failures in contactors due to transient short circuits caused by factors other than actual sticking, such as misalignment or thermal expansion, leading to unnecessary system shutdowns.
Innovation Solution
The in-vehicle control device includes a determination unit to assess contactor sticking likelihood, performs off control to prevent current conduction, vibration control to correct misalignment, and voltage equalization to manage capacitor discharge, ensuring efficient removal of transient short circuits without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sticking failure detection is performed by determining whether voltage of a smoothing capacitor has changed, then sticking failures can be detected, but transient short circuits are erroneously detected as sticking failures
Solution Approach 1:
The control unit performs preliminary actions by turning off the contactor before voltage measurement and turning it on again before measuring current. This preliminary action allows the system to establish a baseline state and compare subsequent measurements against it, enabling differentiation between transient short circuits and actual sticking failures.
Solution Approach 2:
The system uses feedback by comparing the current measurement with the previously stored current value. When the current does not change despite the contactor being turned on, this feedback indicates a potential sticking failure. The system also uses feedback from voltage measurements to determine when the contactor is properly off, creating a closed-loop verification process.
2Reliability
If the contactor is immediately turned off when sticking is detected, then safety can be ensured, but transient short circuits cannot be distinguished from actual sticking failures
Solution Approach 1:
Before immediately shutting down the system upon detecting a potential sticking failure, the control unit performs preliminary verification actions. It turns off the contactor, waits for a predetermined period, then turns it on again and measures current. This preliminary verification sequence allows the system to distinguish between transient conditions and actual failures, avoiding unnecessary shutdowns and maintaining vehicle availability while ensuring safety.
Solution Approach 2:
Instead of immediately taking the extreme action of shutting down the entire system, the control unit performs a partial verification sequence first. It isolates the contactor for testing while keeping other systems operational, and only initiates a full shutdown if the sticking failure is confirmed through multiple measurement cycles, thus balancing safety with productivity.
3Measurement precision
If multiple measurement cycles are performed to verify sticking failure, then false detections can be reduced, but the time required for detection increases
Solution Approach 1:
The control unit employs periodic action by performing measurement cycles at regular intervals with predetermined waiting periods. It turns off the contactor, waits for a specific duration, turns it on, measures current, then repeats the cycle. This periodic measurement approach allows the system to gather multiple data points over time to confirm sticking failure while maintaining a structured, efficient timeline that minimizes detection time.
Solution Approach 2:
The system performs preliminary measurements and comparisons before initiating full verification sequences. By quickly checking initial conditions and only proceeding with extended measurement cycles when necessary, the system reduces the average detection time while maintaining high verification accuracy.
Data Source
AI summary
An in-vehicle control device (10) includes a determination unit (11) that determines whether or not a target contactor (21) for connecting and disconnecting a high-voltage circuit of a battery (2) installed in a vehicle is likely to have sticking after the high-voltage circuit is used; and an off control unit (12) that performs an off control to prohibit current conduction to the target contactor (21) for a given period of time when the determination unit (11) determines that the target contactor (21) is likely to have sticking, whereby attempt to remove a transient short circuiting of the target contactor (21).