How to insert a spring with preload between a file solid and a brick solid in Simscape/Simulink

Hello, I'm new to Simscape so I don't know how to use it well. My problem should be quite simple to solve, but I still don't know how.

I have a system formed by a brick solid (a support) and suspended in the air, a rod is attached to this support through a spring and damper in parallel. This spring has a preload and I want to know the free motion of the rod under gravity (as well as the force due to preload and damping).

My problem is: I know the natural length of the spring, the stiffness and the deformation that cause the preload, and I know the damping. I have tried using the block "Spring and Damper Force", but I have two problems: 1) the direction of the natural length is opposite to that I want (is upwards and instead I would like it downwards). 2) I don't know how to set the initial deformation of the spring because there is no option for this.

Does anyone know how to solve these issues or if there is a better way to model the spring and damper between the two solids?

Thanks

Answer 1

[Anurag Ojha]

Hi Raffaele,

I understand that you have queries with setting the initial deformation of the spring and the difference in direction of the natural length of the spring.

To access spring double click on the Simulink model and search for “Translational Spring block” and select “Translational Spring block” from the drop-down menu. Once you have the block in your model double click on it and you would see this dialog box

Now, to set initial deformation of the spring.

1. In the block dialog box, expand the Initial Targets section
2. Select the check box next to the Deformation variable. Keep its Priority High.
3. Change the Value to whatever you want to set.

For your query related to the difference in expectation of direction of the natural length of the spring, kindly provide more information to better understand the context of the issue

To know more about how to model the spring and damper between the two solids, kindly refer to the following MATLAB Documentation link:

Mass-Spring-Damper in Simulink and Simscape

To explore more you can follow these links:

Initialize Variables for a Mass-Spring-Damper System

Double Mass-Spring-Damper in Simulink and Simscape

Hope it helps!!

[Raffaele]

Hi Anurag

First, thank you for the answer. I have tried using translation spring block in parallel to a translational damper block to model my system, but then I don't know how to link these locks to the brick solid from the Simscape Multibody library. This is why I tried using the "Spring and Damper Force" block with the problems explained in the first question.