Vehicle Switch State Diagnosis via AC Voltage Comparison
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Solution Overview
Problem
Existing vehicle electrical systems face challenges in reliably determining the switching state of a controllable switch between the generator and energy storage unit, leading to incorrect assessments of switch closure or opening, which can result in unstable voltage and power supply issues.
Innovation Solution
The system includes a comparison device that detects the AC voltage component at a specific connection of the switch and compares it with a predetermined comparison voltage potential, allowing for accurate diagnosis of the switch's state by measuring voltage potential deviations, thereby distinguishing between correct and incorrect switch states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching state is determined by measuring current or voltage across the switch, then the measurement method is simple, but the diagnosis reliability is low because 0A current or 0V cannot distinguish between switch open and switch closed without error
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring the voltage at the first connection point of the switch relative to electrical ground, rather than measuring directly across the switch. This intermediary measurement point allows differentiation between switch states because the voltage at this point reflects the AC voltage component from the generator when the switch is open, but not when closed. The comparison device then compares this measured voltage with a predetermined threshold to reliably determine the switching state.
2Reliability
If the switch state is monitored using current measurement, then the detection method is straightforward, but it cannot differentiate between controlled and uncontrolled switch opening
Solution Approach 1:
The patent uses the voltage at the first connection point as an intermediary indicator that reflects the switch state. When the switch is open, the AC voltage component from the generator appears at this point; when closed, it does not. This intermediary voltage signal enables the comparison device to distinguish between controlled opening (when generator voltage is present) and normal closed state (when generator voltage is absent), providing reliable state differentiation.
Solution Approach 2:
The system implements feedback by continuously monitoring the voltage at the first connection point and comparing it with the predetermined threshold. The comparison device provides feedback about the switch state by detecting whether the measured voltage exceeds the threshold, enabling real-time differentiation between switch open and closed states, and between controlled and uncontrolled opening.
Data Source
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Figure 4b
AI summary
An on-board power system for a vehicle has a switch (SW), a comparison device and a detection device and is capable of reliably detecting a state in which the switch is opened in an uncontrolled fashion or incorrectly has a high impedance. The switch connects the battery (BAT) to the system load (L) and to the generator (G) when the power demand in the on-board power system increases. The comparison device (VE) compares the alternating voltage component in the on-board power system with a predefined potential.