Current Calibration Coefficient for Shunt Measurement Error Correction
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Solution Overview
Problem
Conventional current detection devices in electric vehicles, particularly those using shunts for current measurement, suffer from low precision due to errors in analog-to-digital conversion, which affect the accuracy of state of charge (SOC) calculations for battery packs.
Innovation Solution
A measurement device and method that includes a host computer and current source connected in series with a shunt, allowing for the calculation of a current calibration coefficient to improve the accuracy of current detection by calibrating the current values measured by the current detection device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a shunt is used for current measurement, then the implementation is simple and cost-effective, but the measurement precision deteriorates due to errors in analog-to-digital conversion
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual current measurement. A calibration coefficient is pre-calculated by comparing the shunt-based measurement with a reference standard, and this coefficient is then stored and applied to correct subsequent measurements, thereby improving precision without changing the simple shunt implementation
Solution Approach 2:
The patent changes the parameter of the measurement system by introducing a calibration coefficient that modifies the relationship between the measured voltage and the calculated current. This coefficient adjusts for systematic errors in the analog-to-digital conversion, transforming the measurement precision without altering the fundamental shunt-based architecture
2Measurement precision
If Hall Effect or fluxgate principles are used for current measurement, then the measurement precision is improved, but the cost increases and the device becomes more complex
Solution Approach 1:
The patent introduces an intermediary calibration coefficient that mediates between the simple shunt-based measurement system and the requirement for high precision. Instead of directly using complex Hall Effect or fluxgate sensors, the calibration coefficient acts as an intermediary that corrects the simpler system's errors, achieving comparable precision without the complexity
Solution Approach 2:
The patent creates a virtual reference standard through calibration against a known reference current, effectively copying the precision characteristics of sophisticated measurement systems into a correction algorithm that can be applied to the simpler shunt-based system
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
The proposed solution effectively reduces errors in current detection, enhancing the precision of SOC calculations and improving the overall accuracy of current measurement in electric vehicle battery packs.
Implementation Method 1
A shunt is actually a resistor with a very small resistance value. When a direct current flows through the shunt, a voltage drop is resulted. By measuring the voltage drop across the shunt, a current though the shunt can be obtained.
Implementation Method 2
a voltage analog-digital conversion unit for performing an analog-digital conversion on the voltage analog signal to obtain a voltage value
Data Source
AI summary
A measurement device includes: a host computer and a current source, wherein the host computer is configured to: control, when ambient temperature of a current detection device is at a preset temperature within an operation temperature range of a shunt of the current detection device, the current source to output a current with a preset current value to the current detection device; receive a calibrated current value sent by the current detection device; calculate a measurement error of the current detection device according to the preset current value and the calibrated current value; and instruct, when the measurement error is less than a preset current error, the current detection device to use the predetermined current calibration coefficient as a current calibration coefficient.