Active Battery Excitation for Accurate Parameter Estimation
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Solution Overview
Problem
Existing methods for estimating traction battery parameters in hybrid-electric and electric vehicles are inaccurate due to variations in battery impedance parameters over time and temperature, leading to errors in state of charge and power capability calculations.
Innovation Solution
A powertrain control system that actively excites the traction battery by modifying its power demand to ensure frequency components within specific ranges exceed predetermined magnitudes, allowing for accurate estimation of battery parameters based on variability and age, without affecting vehicle acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If battery parameters are estimated using prior art schemes without active excitation, then the estimation process is simple and does not affect vehicle acceleration, but the estimation accuracy deteriorates due to variations in battery impedance parameters over time and temperature
Solution Approach 1:
The patent applies electrical vibration (excitation) to the battery system by modulating the battery power demand with specific frequency components. This electrical excitation causes the battery to operate through varying impedance conditions, enabling accurate parameter estimation through frequency domain analysis without mechanical vibration
Solution Approach 2:
The patent implements periodic excitation by adding sinusoidal frequency components to the battery power demand signal. This periodic modulation creates controlled variations in battery operating conditions, allowing the estimation system to extract accurate impedance parameters through spectral analysis of the periodic responses
2Measurement precision
If active excitation is applied to improve parameter estimation accuracy, then estimation precision improves, but vehicle acceleration may be affected
Solution Approach 1:
The patent dynamically adjusts the excitation strategy based on current vehicle operating conditions. The controller monitors vehicle acceleration requirements and adaptively modulates the excitation signal, applying frequency components only when they will not compromise acceleration performance, thus achieving accurate estimation without sacrificing vehicle dynamics
Solution Approach 2:
The patent applies partial excitation by selectively adding frequency components to the battery power demand only in frequency ranges that do not interfere with vehicle acceleration. Instead of full excitation across all frequencies, the system applies excitation only where it provides estimation value without affecting propulsion performance
3Measurement precision
If excitation frequency components are added to battery power demand, then parameter estimation accuracy improves, but energy consumption increases
Solution Approach 1:
The patent optimizes excitation parameters by selecting specific frequency ranges and magnitudes that maximize estimation accuracy while minimizing energy consumption. The controller adjusts excitation amplitude and frequency based on battery impedance characteristics, applying the minimum necessary excitation energy to achieve accurate parameter identification
Data Source
AI summary
Hybrid-electric and pure electric vehicles include a traction battery. During vehicle operation, impedance parameters of the traction battery may be estimated. To ensure accurate estimation results, certain persistent excitation criteria may be met. These conditions may not always be met, in which case active excitation of the traction battery power demand may be initiated. The invocation of active battery excitation may be based on a variability of estimates of a battery parameter and an age of a most recent estimate of the battery parameter. As the variability of the parameter estimates increases, the time between active battery excitation requests may decrease.