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Manually fix bodies
Manually fix bodies
In order to build more complex models, I need to understand why a so simple project is failing because of equations>variables.
It's a simple free-falling object that is fixed in two different ways: the first using MultiBody "Fixed", the second one by manually fixing a frame, using the exact same equations.
The only difference is where the equations reside.
First script:
Code:
model freefalling
inner Modelica.Mechanics.MultiBody.World world(enableAnimation = false, n = {0, 0, -1});
Modelica.Mechanics.MultiBody.Parts.Body body1(m = 10, r_CM = {0, 0, 0}) ;
Modelica.Mechanics.MultiBody.Parts.Fixed fixed1;
equation
connect(fixed1.frame_b, body1.frame_a);
annotation(
uses(Modelica(version = "3.2.2")));
end freefalling;
The second
Code:
model freefalling2
inner Modelica.Mechanics.MultiBody.World world(enableAnimation = false, n = {0, 0, -1});
Modelica.Mechanics.MultiBody.Parts.Body body1;
Modelica.Mechanics.MultiBody.Interfaces.Frame_b frame_b;
equation
connect(frame_b, body1.frame_a);
Connections.root(frame_b.R);
frame_b.r_0 = zeros(3);
frame_b.R = Modelica.Mechanics.MultiBody.Frames.nullRotation();
annotation(
uses(Modelica(version = "3.2.2")));
end freefalling2;
In the second script I just replicated the same equations as script 1: however, at the end there are 6 more equations! Namely
Code:
frame_b.t[...] =0
frame_b.f[...] =0
that I didn't actually write and I don't know where they come from.
Why that happens? What am I doing wrong?
- DarioMangoni
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