BEV Relay Sticking Detection Through Capacitor Voltage Tracking
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Solution Overview
Problem
Determining the sticking of a second relay in a battery electric vehicle is challenging due to its configuration, which affects the efficient operation of the vehicle.
Innovation Solution
A control device for a battery electric vehicle that includes a motor, drive circuit, energy storage device, first and second capacitors, and relays, which controls the relays and capacitors to determine relay sticking by monitoring voltage changes on specific lines, allowing for precise detection of relay abnormalities without torque output from the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second relay is controlled to turn off and the drive circuit and first relay are controlled to change the voltage of the first capacitor, then relay sticking can be detected, but the system requires complex control coordination of multiple components
Solution Approach 1:
The control device performs preliminary actions by controlling the first relay and drive circuit to change the first capacitor's voltage state before detecting relay sticking. This preliminary voltage change creates the necessary condition for accurate detection, allowing the system to detect second relay sticking by monitoring voltage changes on the connection line that result from the controlled voltage changes in the first capacitor.
2Measurement precision
If voltage changes are monitored on the connection line to detect second relay sticking, then detection accuracy is improved, but the system requires additional monitoring points and control steps
Solution Approach 1:
The first capacitor and connection line serve as intermediaries in the detection process. By controlling the first relay to change the first capacitor's voltage and monitoring the resulting voltage changes on the connection line, the system indirectly detects second relay sticking without requiring direct measurement at the relay contacts. This intermediary approach simplifies the detection mechanism while maintaining accuracy.
3Reliability
If the control device coordinates multiple relays and capacitors to detect relay abnormalities, then detection reliability is improved, but the control process becomes more complex
Solution Approach 1:
The control device implements periodic detection cycles where it systematically controls the first relay to change the first capacitor's voltage state, monitors the connection line voltage, and determines relay sticking status. This periodic action pattern creates a reliable detection routine that can be repeatedly executed to ensure accurate fault detection while maintaining organized control flow.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate determination of second relay sticking, ensuring reliable vehicle operation by identifying and addressing relay faults effectively.
Implementation Method 1
a first capacitor (34) attached to the power line (32)
Implementation Method 2
a voltage converter (40) including a second capacitor (40c) and configured to supply electric power from a charging line (44) to a connection line (46) after converting a voltage of the electric power
Implementation Method 3
a first relay (SMR) attached to the power line (32)
Data Source
AI summary
A control device for a battery electric vehicle is used in a battery electric vehicle, and is configured to control a drive circuit, a voltage converter, and first and second relays. In the case where the control device controls, with the second relay controlled to turn off, the drive circuit and the first relay such that the voltage of the first capacitor changes, the control device determines that the second relay is stuck when the voltage on the connection line at a position closer to the voltage converter than the second relay changes following the voltage of the first capacitor. Sticking of the second relay can thus be determined.