fit

Class: tireModel

Optimize model parameter values to achieve model best fit to the input data

Since R2023b

Syntax

[fitObj,diffTable,errorStat,optimOutput,H]=fit(obj,data,fitType)

[fitObj,diffTable,errorStat,optimOutput,H]=fit(obj,data,fitType,Name=Value)

Description

This method requires Extended Tire Features for Vehicle Dynamics Blockset and Optimization Toolbox™.

[fitObj,diffTable,errorStat,optimOutput,H]=fit(obj,data,fitType) fits a tire model specified by obj with the data specified by data using the model fit type specified by fitType.

[fitObj,diffTable,errorStat,optimOutput,H]=fit(obj,data,fitType,Name=Value) fits a tire model with additional options specified by one or more Name=Value arguments.

Input Arguments

obj — Tire model to fit

tireModel object

Tire model to fit, specified as a tireModel object.

data — Tire data

array of tireData objects

Tire data, specified as an array of tireData objects.

fitType — Fit type

"Fx Pure" | "Fy Pure" | "Fx Combined" | "Fy Combined" | "Mz Pure" | "Mz Combined" | "Mx" | "My"

Fit type, specified as one of these values:

• "Fx Pure"

• "Fy Pure"

• "Fx Combined"

• "Fy Combined"

• "Mz Pure"

• "Mz Combined"

• "Mx"

• "My"

The order in which parameters are fit is important. If you fit a set of parameters that have a dependency to another parameter set, do not refit the upstream parameter set without refitting the parameter set with the dependency. Refer to the table for dependencies between parameters.

Fit type	Response Fitted	Dependency	Data Expected
Fx Pure	Longitudinal Force	None	Longitudinal slip sweep at zero degrees slip angle
Fy Pure	Lateral Force	None	Slip angle sweep at free rolling
Fx Combined	Combined Longitudinal Force	Fx Pure Fy Pure	Longitudinal slip sweep at non zero degrees slip angle
Fy Combined	Combined Lateral Force	Fx Pure Fy Pure	Longitudinal slip sweep at non zero degrees slip angle
Mz Pure	Aligning Torque	Fy Pure	Slip angle sweep at free rolling
Mz Combined	Combined Aligning Torque	Fx Combined Fy Combined Mz Pure	Longitudinal slip sweep at non zero degrees slip angle
Mx	Overturning Moment	All applicable Fy fits	Slip angle sweep at free rolling
My	Rolling Resistance	All applicable Fx fits	Longitudinal slip

Data Types: string

Name-Value Arguments

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: fit(tm, lateral_data, "Fy Pure", solver=fminunc, PlotFit=true)

Parameters — Model parameters to optimize

string vector

Model parameters to optimize, specified as a string vector.

Note

By default, if the Parameters argument is not specified, the parameters to optimize are determined by the input tire model and fit type.

Data Types: string

FixedParameters — Fixed parameters

string vector

Fixed parameters, specified as a string vector.

Note

By default, if the FixedParameters argument is not specified, the parameters to fix are determined by the input tire model and fit type.

Data Types: string

LowerBounds — Lower bounds of parameter optimization limit

column vector

Lower bounds of the parameter optimization limit, specified as a column vector.

Note

The vector length must equal the length of the parameter set being fitted.

Data Types: double

UpperBounds — Upper bounds of parameter optimization limit

column vector

Upper bounds of the parameter optimization limit, specified as a column vector.

Note

The vector length must equal the length of the parameter set being fitted.

Data Types: double

Weight — Weighting scheme

1-D cell array

Weighting scheme, specified as a 1-D cell array.

Note

The 1-D cell array length must be the same length as the tire data input array. Each cell of the array must be a numeric vector that is the same length as the corresponding tireData object. Elements must be nonnegative.

Data Types: cell

Solver — Solver

"fmincon" (default) | "fminunc" | "fsolve" | "lsqnonlin"

Solver, specified as one of these values:

• "fmincon"

• "fminunc"

• "fsolve"

• "lsqnonlin"

Example: Solver="fsolve"

Data Types: string

optimoptions — Optimization options

output of optimoptions

Optimization options, specified as the output of optimoptions. Use this table to find the link to the options table for each solver.

Solver	Link to Options Table
fmincon	options (Optimization Toolbox)
fminunc	options (Optimization Toolbox)
fsolve	options (Optimization Toolbox)
lsqnonlin	options (Optimization Toolbox)

PlotFit — Option to plot model fit

false (default) | true

Option to plot model fit, specified as false or true.

Example: PlotFit=true

Data Types: logical

Output Arguments

fitObj — Fitted model

tireModel object

Fitted model, returned as a tireModel object.

Note

Only parameters specified in the Parameters argument or parameters selected by default have revised values.

diffTable — Table of revised parameters

table object

Table of revised parameters, returned as a table object, with a row for each value changed.

errorStat — Error statistics of model fit

structure

Error statistics of the model fit, returned as a structure. The structure contains the error algorithm, the initial error before the fit, and the final error after the fit.

optimOutput — Information about optimization process

structure

Information about the optimization process, returned as a structure. The returned structure fields depend on the selected solver. This table provides links to the fields returned for each solver.

Solver	Link to Structure Fields
fmincon	output (Optimization Toolbox)
fminunc	output (Optimization Toolbox)
fsolve	output (Optimization Toolbox)
lsqnonlin	output (Optimization Toolbox)

H — Handle to axes

object handle

Handle to axes, returned as an object handle.

Version History

Introduced in R2023b