Linearizing a Simscape model with Model Linearizer

Dear community,

I´m trying to develop a model of a furuta pendulum with a DC motor in Simscape. Unfortunately I do struggle quite a lot with the Model Linearizer. As you can see from the screenshot, the tool creates five states of which the last one is completely unknown to me. When I click on it, the solver configurations block is highlighted, but I can´t figure out how it is related or how I can get rid of this state.

The aim is to implement a state feedback controller with the linearized model.

Does someone have an idea how to solve that problem?

The model is attached to this post if needed.

Answer 1

[Vasco Lenzi]

Hi Jooo

I am almost certain that state is the filter that you can check or uncheck in the solver configuration block when connecting 1D with 3D component. Unfortunately your attached model misses all the CAD files so it doesn't run or compile, so I cannot confirm it.

solver configuration block:

You had the right idea on how to setup the kinematic connection between Simscape 1D Motor and 3d Multibody joint, but there is a more refined variant of your method that may remove the need to filter between 1D and 3D. Look up this package on the file Exchange:

https://www.mathworks.com/matlabcentral/fileexchange/37636-simscape-multibody-multiphysics-library

There are really nice example and there is even a DC Motor model that you can apply to your rotational joint:

When you work on a project with multiple files such as with CAD files for Multibody, I recommend to setup and work within a Project. Projects allow you to relate all files with one another and export a working environment as a single Project Archive, that other user can easily open and work with.

Link: Projects Page

Hope this all helps, good luck!

Vasco

[Jooo]

Hey Vasco,

thanks a lot for your response, that was very helpful. This was indeed the problem and I managed to solve it!

And you´re right, I´ll try to put everything in a project next time.

Best regards!

Jooo

[Jooo]

Hi Vasco,

I actually noticed, that my problem hasn´t been gone completely. When I copy and paste the DC components from the example you mentioned, the model works. However, when I replace the DC components with the predefined DC Motor block from Simscape, I again run into the filter problem. I can´t figure out why this happens...

This time I put the model with all its components in a project file. (see my edited first post)

Do you have an idea why I still get this filteredOutput as state variable in the Model Linearizer?

[Vasco Lenzi]

Hi Jooo

The predefined, more complex DC motor block from Simscape Electrical can be configured for initial condition. This may clash with the kinematic loop established by the Angular Speed sources and therefore it needs a filter in between.

My suggestions is to use the simplified block from the Multiphysics library, because that works without adding filters (initial conditions are optionals) and you can create your state space control.

Once the control is created, if you prefer to use the more complex model, you can switch it back - the 1d/3d filtering shouldn't have an impact.

Hope this helps

Vasco