Battery Impedance Measurement Using Sum of Sinusoids Excitation
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Solution Overview
Problem
Existing electrochemical impedance measurement systems for batteries are time-consuming due to their serial nature, requiring multiple frequency measurements and averaging processes, which hinder real-time acquisition and diagnostics.
Innovation Solution
A parallel approach using a single time record with a Sum of Sinusoids (SOS) excitation signal allows for real-time battery impedance measurement by synchronizing and processing the response to obtain frequency components, minimizing errors through Compensated Synchronous Detection (CSD) or neural network enhancements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a serial approach with multiple frequency measurements and averaging processes is used, then measurement precision is improved, but productivity deteriorates due to time-consuming testing
Solution Approach 1:
The patent combines multiple frequency measurements into a single parallel measurement process. Instead of sequentially measuring impedance at different frequencies and averaging the results, the invention applies a multi-frequency excitation signal simultaneously and processes the combined response to extract impedance information at all frequencies in one measurement cycle, thereby maintaining precision while dramatically improving productivity
Solution Approach 2:
The patent employs periodic excitation signals at multiple frequencies simultaneously to elicit impedance responses. By using periodic signals with known frequency components and processing the steady-state response through spectral analysis, the system can accurately determine impedance at each frequency without requiring separate measurements, thus resolving the contradiction between measurement precision and testing speed
2Reliability
If multiple time records with averaging processes are used, then reliability is improved, but loss of time increases due to serial processing
Solution Approach 1:
The patent merges multiple frequency measurements into a single time record by applying a multi-frequency excitation signal. The system captures one comprehensive time record containing responses to all frequency components, then uses spectral analysis to extract reliable impedance data for each frequency simultaneously, eliminating the need for multiple sequential measurements and their associated time delays
Solution Approach 2:
The patent replaces the mechanical/sequential averaging process with a computational approach using Fast Fourier Transform (FFT) and spectral analysis. Instead of physically acquiring multiple time records and averaging them in sequence, the invention uses mathematical transformations to process a single time record and extract reliable impedance information, substituting computational power for time-consuming physical measurement cycles
3Productivity
If a parallel approach with a single time record is used, then productivity is improved, but measurement precision may deteriorate without proper error compensation
Solution Approach 1:
The patent implements a feedback mechanism where the measured response is processed through spectral analysis to extract impedance information, and this information is used to refine and compensate for measurement errors. The system continuously monitors and adjusts for distortions introduced by the measurement process itself, ensuring high precision even when using a single time record for parallel multi-frequency measurement
Solution Approach 2:
The patent changes the parameter of excitation signal structure by using a multi-frequency composite signal with specific frequency relationships. By carefully selecting frequency components and their amplitudes, and by applying appropriate windowing and spectral analysis parameters, the system optimizes the measurement process to maintain high precision while achieving real-time productivity through parallel measurement
Data Source
AI summary
Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. A time profile of this sampled signal has a duration that is a few periods of the lowest frequency. A voltage response of the battery, average deleted, is an impedance of the battery in a time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time profile by rectifying relative to sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.