Battery Current Sensor Offset Correction for Low Temperature Accuracy
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Solution Overview
Problem
In extremely low temperature environments, the correction accuracy of current sensor outputs in vehicle systems decreases due to temperature-dependent offset errors, leading to inaccurate battery charge and discharge current measurements.
Innovation Solution
A control system that switches between first and second correction controls based on the current sensor's temperature at startup, using a calculated offset error before shutdown for higher temperatures and a startup-determined error for lower temperatures, ensuring accurate correction of current sensor outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the output of the current sensor is corrected by using the learned value of the offset error (calculated based on the output just before stop) in extremely low temperature environments, then the correction process is simple and consistent, but the correction accuracy decreases because the offset error changes with temperature
Solution Approach 1:
The correction control is made dynamic by switching between first correction control (using learned offset error) and second correction control (using startup-determined offset error) based on the current sensor temperature. When temperature is above threshold, first correction control is used; when below threshold, second correction control is used. This dynamic adaptation resolves the contradiction by selecting the appropriate correction method based on operating conditions.
Solution Approach 2:
The correction parameter (offset error value) is changed based on temperature conditions. Instead of using a fixed learned offset error value, the system determines the offset error at startup when temperature is low, and uses this temperature-compensated value for correction. This parameter change approach maintains correction accuracy across different temperature environments.
2Ease of operation
If the vehicle system is started up in an extremely low temperature environment, then the current sensor temperature is considerably lower than steady temperature, but using the learned offset error (from steady temperature conditions) for correction leads to inaccurate correction
Solution Approach 1:
The system performs preliminary determination of the offset error at startup before normal operation begins. By determining the offset error at startup when the current sensor is still at low temperature, the system prepares the correct correction parameter in advance, ensuring accurate correction from the beginning of operation in cold environments.
Solution Approach 2:
The system uses feedback from temperature sensing to determine which correction control to apply. The temperature of the current sensor is monitored, and this feedback information is used to select the appropriate correction method, ensuring that the correction accuracy matches the operating temperature conditions.
Data Source
AI summary
A control system for a battery includes a current sensor and an electronic control unit. The electronic control unit is configured to calculate a first error and a second offset error of the current sensor respectively based on outputs of the current sensor just before a stop of the electronic control unit and at startup of the electronic control unit. The electronic control unit is configured to correct an output of the current sensor by using a first error when a temperature of the current sensor at startup of the electronic control unit is higher than or equal to a threshold temperature, and correct the output of the current sensor by using a second error when the temperature of the current sensor at startup of the electronic control unit is lower than the threshold temperature.