fitECM

Perform impedance parameter estimation for battery ECM from time-based HPPC data

Since R2025a

Syntax

batteryECM = fitECM(pulseData)

batteryECM = fitECM(pulseData,Name=Value)

Description

The fitECM function performs impedance parameter estimation for a battery equivalent circuit model (ECM) from time-based hybrid pulse power characterization (HPPC) data. These parameters are then stored inside an ECM object that you can use to parameterize a Battery Equivalent Circuit block.

You can view a table with a summary of the parameter values by accessing the ParameterSummary property of the ECM object.

You can obtain the pulse power data at different battery operating conditions, such as different states of charge, temperature, load currents, and current directionality. You can specify the HPPC input as a matrix, table, or timetable containing information for a single constant current pulse, HPPCTest object, or HPPCTestSuite object.

To specify the ECM topology used to fit the data, set the ECM name-value argument. You can specify the desired fitting algorithm by defining the FittingMethod name-value argument.

This figure shows the typical workflow to estimate the parameters of an equivalent circuit model from HPPC test data:

batteryECM = fitECM(pulseData) performs impedance parameter estimation for an ECM object with default properties from the HPPC data, pulseData. The function returns an ECM object with the estimated parameters.

batteryECM = fitECM(pulseData,Name=Value) performs impedance parameter estimation from the HPPC data, pulseData, and specifies additional options using name-value arguments. The function returns an ECM object with the estimated parameters.

Input Arguments

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`pulseData` — Time-based HPPC data
matrix | table | timetable | `HPPCTest` object | `HPPCTestSuite` object

Time-based HPPC data used to perform impedance parameter estimation, specified as a matrix, table, timetable, HPPCTest object, or HPPCTestSuite object.

Name-Value Arguments

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Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: batteryECM = fitECM(myData,SegmentToFit="Relaxation")

`ECM` — Equivalent circuit model used to fit HPPC data
`ECM` object (default)

Equivalent circuit model used to fit the HPPC data, specified as an ECM object.

`SegmentToFit` — Segment of pulse to fit
`"Load"` (default) | `"LoadAndRelaxation"` | `"Relaxation"`

Segment or section of the pulse to fit, specified as "Load", "LoadAndRelaxation", or "Relaxation".

Data Types: char | string

`RelaxationSegmentFitTime` — Time duration of relaxation to add to fit
`10` (default) | positive scalar

Time duration of the relaxation to add to the fit, specified as a positive scalar.

Data Types: double

`ThresholdForR0` — Time frame at which to calculate instantaneous resistance
`0.1` (default) | positive scalar

Time frame, in seconds, at which to calculate the instantaneous resistance R0, specified as a positive scalar. This threshold serves as the definition for the value of R0.

Data Types: double

`FittingMethod` — Fitting method used to find ECM parameters that best fit time-based impedance data
`"fminsearch"` (default) | `"tfest"` | `"curvefit"` | `"mbc"`

Optimization or fitting method used to find the parameters of the ECM that best fit the time-based impedance data, specified as "fminsearch", "tfest", "curvefit", or "mbc".

The "tfest" option requires a license for the System Identification Toolbox™.

The "curvefit" option requires a license for the Curve Fitting Toolbox™.

The "mbc" option requires a license for the Model-Based Calibration Toolbox™.

Data Types: char | string

`CurrentSignConvention` — Sign convention of input current during discharge
`"negativeDischarge"` (default) | `"positiveDischarge"`

Sign convention of the input current during a discharge, specified as "negativeDischarge" or "positiveDischarge".

Data Types: char | string

`CurrentOnTreshold` — Threshold current that indicates whether charge or discharge is occurring
`0` (default) | nonnegative scalar

Threshold current value, in amperes, that indicates whether a charge or discharge is occurring, specified as a scalar.

Data Types: double

`InitialParameterEstimate` — Initial parameter values of ECM used in first iteration of fitting method
`[0.0250 0.0250 10 0.0125 100]` (default) | vector of nonnegative elements

Initial parameter values of the ECM used in the first iteration of the fitting method, specified as a vector of nonnegative elements.

Data Types: double

`LowerParametersBounds` — Lower parameter bounds of equivalent circuit parameters in fitting method
`[0 0 0 0 0]` (default) | vector of nonnegative elements

Lower parameter bounds of the equivalent circuit parameters used in the fitting method, specified as a vector of nonnegative elements.

Data Types: double

`UpperParameterBounds` — Upper parameter bounds of equivalent circuit parameters in fitting method
`[250 250 100000 125 1000000]` (default) | vector of nonnegative elements

Upper parameter bounds of the equivalent circuit parameters used in the fitting method, specified as a vector of nonnegative elements.

Data Types: double

`Options` — Fitting options
`"optimset"` (default) | `"fitoptions"` | `"idoptions.tfest"`

Fitting options for the method you specify in the FittingMethod name-value argument, specified as "fitoptions", ""idoptions.tfest", or "optimset".