I don' know why simulink parameter estimation failed. Please help me

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인규
인규 2024-11-11，2:45
评论： Yifeng Tang 2024-11-21，14:37
I want to know battery’s internal parameter (internal resistance, diffusion reisister, tau) when i modelling a battery to ECM using a simscape battey.
For parameter estimation, I use hppc profile for input
i make a new experience in parameter estimation app and choose parameter i want to know. Then Run estimating
Simulated Output cannot follow the experienced output.. Cost is also too high.
For Result parameter is not converged..
what’s wrong.. is it important parameter’s initial value, min, max?
Is Input signal too complicated to estimate parameters?
Please give me some tips. Expert of simulink members..
[Below, Text in report translated in English ]
' Optimization started on 2024-Nov-11, 10:50:02.
Estimation converged on 2024-Nov-11, 11:24:53.
One error occurred in the solver during estimation. For more details on the error, check 'EvalErrors_2' in the results workspace.
'ingyu' has been updated with the estimated parameter values.
The estimated parameter values are recorded in 'EstimatedParams'.
The estimated experiment values are recorded in 'Exp'.
Solver output for estimation:
A local minimum may exist.
lsqnonlin stopped because the final change in the sum of squares relative to the initial value was smaller than the function tolerance.
<Details of the stopping criterion>
Optimization stopped because the relative change in the sum of squares (r) was smaller than options.FunctionTolerance = 1.000000e-03.'
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인규
인규 2024-11-11，4:15
.
EvalErrors_2 is same as EvalErrors.
when i used fast reload option, Error occured.
not using fast option error didn't occured and parameter estimation was completed. But it was not correct.
Walter Roberson
Walter Roberson 2024-11-11，17:59
Sorry, I am unable to change how Simulink FastRestart works so that it will permit changing those parameters. You could file an enhancement request to permit parameters to be changed for FastRestart.

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回答（1 个）

Yifeng Tang
Yifeng Tang 2024-11-20，14:25
Looks like the error message is trying to tell you that the Parameter Estimater cannot change the parameters it tries to estimate. This is because the "compile-time" parameters in Simscape (to be explained later) can't be modified from simulation to simulation when the Fast Restart is turned on. The solution is simple:
(1) NOT recommended: turn off fast restart. This will allow the parameters to be modified, but also add compile time to the start of each simulation.
(2) Do this instead: for the parameters you try to estimate, at every place it's used, make them "run-time". This way, Simscape will keep a placeholder for them and allow the values to be modified from run to run in Fast Restart mode.
See these two documentation pages for more details:
https://www.mathworks.com/help/simscape/run-time-parameters.html?s_tid=CRUX_lftnav
https://www.mathworks.com/help/simscape/ug/specify-and-change-a-run-time-configurable-parameter.html
The 2nd page talks about runing run-time parameters with fast restart. It's a common practice when doing parameter estimation.
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인규
인규 2024-11-21，6:13
Yifeng Tang , Thank you for your kind response.
As you suggested, setting the parameters at runtime resolved the errors. However, I still have a few issues. The main reason I wanted to use the fast restart option was to speed up the simulation.
Currently, I am using the Parameter Estimator to estimate the internal parameters of a battery, but the time domain of the input current profile obtained from the experiment is a bit long. The simulation time seems to be around 300,000.
Is there any way to further reduce the time required when using the Parameter Estimator for estimation?
I thought using the fast restart option would significantly reduce the simulation time for parameter estimation, but it didn’t. Could you let me know if there’s any other way?
Yifeng Tang
Yifeng Tang 2024-11-21，14:37
It would indeed be nicer if the simulation runs fast during a parameter estimation exercise because the model has to run many times. Fast Restart feature only reduces the "compile" time but has no impact on the simulation time.
There can be a LOT of reasons that may affect your simulation speed. I can't give more specific help without seeing the actual model. Is that something you can share?

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