# How to connect a dc motor simulink model into a structure of simmechanics?

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Eleni.T on 30 Jun 2020
Commented: Vasco Lenzi on 19 Aug 2020
Hello! I have a simulink model of a solar tracker, and the output is the angular position of a dc motor which rotates a solar panel. I have a CAD model of a solar tracker and i want to import it to simechanics. Wha t i have to do is relate the motor angular position to the joint where the motor is? Also, in the transfer function of the motor, i inlcuded the inertia of the motor+tracker's structure, and in the torque term i used motor torque-load torque. Now that i am going to connect it to a simmechanic model, are the torque and inertia automatically computed so do i have to remove them from the simulink equation? Any help would be appreciated.
Thank you

Vasco Lenzi on 30 Jun 2020
Hi Eleni
what you are suggesting goes in the right direction. We do have a multibody example of solar panel tracking if you want some Multibody files to prototype:
We released a free blockset addon with example of blocks that connect 1D simulation with 3D simulation in Simscape:
For older release than 20a look at the link in the File Exchange entry:
There is even a DC motor with Multibody ports that you can apply to move a rotational joint:
After you have looked at the example I believe you are going to understand properly the connection of 1D with 3D. You need to create a kinematic relationship between the components, here the screenshot fro mone of the example:
Hope that helps
Vasco
Eleni.T on 11 Aug 2020
Thank you again so much! I am not sure what is an appropriate time constant. Is there a way to estimate it?
Vasco Lenzi on 19 Aug 2020
It depends on the dynamics of your system. I would take the response time of your motor and divide it by 10-100 at least depending on how accuate you want it.
So if your motor has a rising time of 100 ms, put 1 ms as a filtering time.

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