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modelica / ModelicaStandardLibrary

Free (standard conforming) library to model mechanical (1D/3D), electrical (analog, digital, machines), magnetic, thermal, fluid, control systems and hierarchical state machines. Also numerical functions and functions for strings, files and streams are included.
https://doc.modelica.org
BSD 3-Clause "New" or "Revised" License
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Proposal - Add new VariableTranslation component to MSL #4138

Closed BasilioPV closed 1 year ago

BasilioPV commented 1 year ago

I have created a simple Variable Translation component based on a translation with a vector[3] real input.

image

This component is very useful to place forces over a body that their application point changes over time. The 3D animation was disabled.

If this has interest to add to MSL, please indicate on the issue how can I help on this. Oterwise close the issue. Thanks!

Source code:

model VariableTranslation "Derivative work of Translation component of MSL"
  import Modelica.Mechanics.MultiBody.Types;
  import Modelica.SIunits.Conversions.to_unit1;
  Modelica.Mechanics.MultiBody.Interfaces.Frame_a frame_a "Coordinate system fixed to the component with one cut-force and cut-torque" annotation(
    Placement(transformation(extent = {{-116, -16}, {-84, 16}})));
  Modelica.Mechanics.MultiBody.Interfaces.Frame_b frame_b "Coordinate system fixed to the component with one cut-force and cut-torque" annotation(
    Placement(transformation(extent = {{84, -16}, {116, 16}})));
  Modelica.Blocks.Interfaces.RealInput r_vect[3] annotation(
    Placement(visible = true, transformation(origin = {-4, -106}, extent = {{-20, -20}, {20, 20}}, rotation = 90), iconTransformation(origin = {-2, -100}, extent = {{-20, -20}, {20, 20}}, rotation = 90)));
protected
  outer Modelica.Mechanics.MultiBody.World world;
equation
  Connections.branch(frame_a.R, frame_b.R);
  assert(cardinality(frame_a) > 0 or cardinality(frame_b) > 0, "Neither connector frame_a nor frame_b of FixedTranslation object is connected");
  frame_b.r_0 = frame_a.r_0 + Modelica.Mechanics.MultiBody.Frames.resolve1(frame_a.R, r_vect);
  frame_b.R = frame_a.R;
// Force and torque balance
  zeros(3) = frame_a.f + frame_b.f;
  zeros(3) = frame_a.t + frame_b.t + cross(r_vect, frame_b.f);
  annotation(
    Icon(coordinateSystem(preserveAspectRatio = true, extent = {{-100, -100}, {100, 100}}), graphics = {Text(textColor = {0, 0, 255}, extent = {{-150, 85}, {150, 45}}, textString = "%name"), Text(extent = {{150, -50}, {-150, -20}}, textString = "r=%r_vect"), Text(textColor = {128, 128, 128}, extent = {{-89, 38}, {-53, 13}}, textString = "a"), Text(textColor = {128, 128, 128}, extent = {{57, 39}, {93, 14}}, textString = "b"), Line(origin = {-10, 0}, points = {{10, 20}, {-10, -20}}), Line(origin = {10, 0}, points = {{10, 20}, {-10, -20}}), Polygon(origin = {-54, 0}, fillPattern = FillPattern.Solid, points = {{-46, 4}, {46, 4}, {42, -4}, {-46, -4}, {-46, 4}}), Polygon(origin = {54, 0}, rotation = 180, fillPattern = FillPattern.Solid, points = {{-46, 4}, {46, 4}, {42, -4}, {-46, -4}, {-46, 4}})}),
    Diagram(coordinateSystem(preserveAspectRatio = true, extent = {{-100, -100}, {100, 100}}), graphics = {Rectangle(fillPattern = FillPattern.Solid, extent = {{-100, 5}, {100, -5}}), Line(points = {{-95, 20}, {-58, 20}}, color = {128, 128, 128}, arrow = {Arrow.None, Arrow.Filled}), Line(points = {{-94, 18}, {-94, 50}}, color = {128, 128, 128}, arrow = {Arrow.None, Arrow.Filled}), Text(textColor = {128, 128, 128}, extent = {{-72, 35}, {-58, 24}}, textString = "x"), Text(textColor = {128, 128, 128}, extent = {{-113, 57}, {-98, 45}}, textString = "y"), Line(points = {{-100, -4}, {-100, -69}}, color = {128, 128, 128}), Line(points = {{-100, -63}, {90, -63}}, color = {128, 128, 128}), Text(textColor = {128, 128, 128}, extent = {{-22, -39}, {16, -63}}, textString = "input r"), Polygon(fillPattern = FillPattern.Solid, points = {{88, -59}, {88, -68}, {100, -63}, {88, -59}}), Line(points = {{100, -3}, {100, -68}}, color = {128, 128, 128}), Line(points = {{69, 20}, {106, 20}}, color = {128, 128, 128}, arrow = {Arrow.None, Arrow.Filled}), Line(points = {{70, 18}, {70, 50}}, color = {128, 128, 128}, arrow = {Arrow.None, Arrow.Filled}), Text(textColor = {128, 128, 128}, extent = {{92, 35}, {106, 24}}, textString = "x"), Text(textColor = {128, 128, 128}, extent = {{51, 57}, {66, 45}}, textString = "y")}),
    Documentation(info = "<html><head></head><body><p>This component is a modification of \"fixedTranslation\" of Modelica.Mechanics.Multibody to enable a real time bar changing. 3D visualization was disabled.</p><pre style=\"font-size: 12px;\"><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><u>Copyright:</u></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><br></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><span style=\"font-family: 'Times New Roman'; orphans: 2; widows: 2;\">Original Work:&nbsp;</span></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><span style=\"font-family: 'Times New Roman'; orphans: 2; widows: 2;\">Copyright&nbsp;</span><span style=\"font-family: -webkit-standard;\">©</span><span style=\"font-family: 'Times New Roman'; orphans: 2; widows: 2;\">&nbsp;2021-2022 Modelica Association</span></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><span style=\"font-family: 'Times New Roman'; orphans: 2; widows: 2;\"><br></span></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><span style=\"font-family: 'Times New Roman'; orphans: 2; widows: 2;\">Derivative Work:&nbsp;</span></div><div style=\"font-family: 'MS Shell Dlg 2'; white-space: normal;\"><p style=\"font-size: 10pt; font-family: Arial, sans-serif;\"><b style=\"font-size: 10pt;\">ShipSIM package</b></p><p style=\"font-size: 10pt; font-family: Arial, sans-serif;\"><em style=\"font-size: 10pt;\">(for license see ShipSIM.UsersGuide.License)</em></p></div></pre>
</body></html>", revisions = "<html><head></head><body><span style=\"font-family: 'MS Shell Dlg 2'; font-size: 12px;\">Rev. 0.0: (01/03/2021): Initial release</span></body></html>"));
end VariableTranslation;
tobolar commented 1 year ago

Even if helpful in some models, IMO we shall not implement this. The reason especially is that this in principle changes a particular variable from being a parameter (parameter SI.Position r[3]) to being an input (RealInput r_vect[3]). Doing so, we should also accordingly change e.g. r and rotation parameters in Mechanics.MultiBody.Parts.FixedRotation or Mechanics.MultiBody.Parts.Fixed. And so on in further models for (arbitrary) parameters.

So the rationale behind this change (incl. all known overhead) is not clearly declared and I don't believe we will be able to do so.

HansOlsson commented 1 year ago

As far as I understand it can also be modeled with 3 translation position components (with exact=true) connected to 3 prismatic joints (I believe I have seen that used somewhere). I don't know whether that is an argument for adding it - or for not adding it.

BTW: The world and import Modelica.SIunits.Conversions.to_unit1; should just be removed as not needed.

BasilioPV commented 1 year ago

@HansOlsson You are right, this can be modelled using other MSL components. Mi intention is to crerate a shortcut for use this funcionality. Thanks for point on the not needed lines!