Luenberger Observer for Battery Open-Circuit Voltage Estimation
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Solution Overview
Problem
Current methods for estimating the state of charge of a battery, particularly the open-circuit voltage (Voc), are inaccurate and complex, especially in non-ideal situations where initial conditions are unknown, leading to unreliable results and high computational demands.
Innovation Solution
A method utilizing a Luenberger observer structure to estimate the open-circuit voltage (Voc) based on linearized functions around work points dependent on temperature and state of charge measurements, allowing for precise estimation without prior knowledge of initial conditions, and minimizing processing resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If direct measurement methods are used to determine battery characteristics, then measurement simplicity is improved, but measurement precision deteriorates in non-ideal situations
Solution Approach 1:
The patent introduces an observer system as an intermediary that indirectly estimates the open-circuit voltage and state of charge through mathematical models and measurements of accessible parameters (terminal voltage, current, temperature), rather than directly measuring the inaccessible open-circuit voltage. This mediator enables precise determination of battery characteristics during operation without requiring ideal static conditions.
2Measurement precision
If complex calculation methods are used to estimate state of charge, then measurement precision is improved, but device complexity worsens
Solution Approach 1:
The patent implements a feedback mechanism where the observer continuously compares estimated values with actual measurements and adjusts the state of charge estimation accordingly. The correction term in the observer equation uses the difference between measured terminal voltage and modeled voltage to refine the open-circuit voltage estimate, achieving high precision through iterative feedback rather than complex batch calculations.
Solution Approach 2:
The patent transforms the complex problem of estimating open-circuit voltage by changing the approach from direct voltage measurement to estimating it through differential equations and observer dynamics. The method uses measurable parameters (terminal voltage, current, temperature) and transforms them through mathematical models to derive the inaccessible open-circuit voltage and state of charge with high precision.
3Measurement precision
If continuous monitoring is performed to maintain accuracy, then measurement precision is improved, but use of energy worsens
Solution Approach 1:
The patent employs periodic correction rather than continuous complex calculations. The observer updates the state of charge estimation at discrete time steps using the differential equation approach, performing calculations only when necessary to maintain accuracy. This periodic action maintains measurement precision while significantly reducing computational energy consumption compared to continuous monitoring methods.
Data Source
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AI summary
Method, and associated data processing device, for the calculation of an open-circuit voltage (10) of an energy accumulator (2), which comprises the following steps: i) establishing a mathematical model of the energy accumulator (2) according to a system of equations and a plurality of descriptive parameters, ii) obtaining the measurement of electric current (3) which is flowing through the energy accumulator (2), iii) verifying a null value of the electric current measurement obtained during a predetermined period of time, iv) obtaining the voltage measured at the terminals of the energy accumulator (21), v) calculating the estimated voltage at the terminals of the energy accumulator (22) by means of an observer (41), v) calculating the open-circuit voltage of the energy accumulator (10), such that a precise calculation is obtained in any type of situation, for example during driving, and without knowing the prior state of use of the battery.