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Fix position prescribed friction #4256

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merged 3 commits into from
Jan 12, 2024
Merged

Fix position prescribed friction #4256

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519bf15
Revert "Merge pull request #4255 from modelica/revert-4129-fix-friction"
m-kormann Jan 12, 2024
97f0fdc
Enhance a_relfric for forward/backward sliding
tobolar Jan 12, 2024
008b61a
Merge pull request #1 from tobolar/issue4255_enhance_a_relfric
m-kormann Jan 12, 2024
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6 changes: 3 additions & 3 deletions Modelica/Mechanics/Rotational/Interfaces/PartialFriction.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -54,9 +54,9 @@ equation
mode) == Backward or startBackward);

a_relfric/unitAngularAcceleration = if locked then 0 else if free then sa
else if startForward then sa - tau0_max/unitTorque else if
startBackward then sa + tau0_max/unitTorque else if pre(mode) ==
Forward then sa - tau0_max/unitTorque else sa + tau0_max/unitTorque;
else if startForward then sa - tau0_max/unitTorque
else if startBackward then sa + tau0_max/unitTorque
else sa - sign(w_relfric)*tau0_max/unitTorque;

/* Friction torque "tau" has to be defined in a subclass. Example for possible
realization of a clutch utilizing interpolation by ExternalCombiTable1D see:
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8 changes: 4 additions & 4 deletions Modelica/Mechanics/Translational/Interfaces/PartialFriction.mo
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Expand Up @@ -51,10 +51,10 @@ equation
locked = not free and not (pre(mode) == Forward or startForward or pre(
mode) == Backward or startBackward);

a_relfric/unitAcceleration = if locked then 0 else if free then sa else
if startForward then sa - f0_max/unitForce else if startBackward then
sa + f0_max/unitForce else if pre(mode) == Forward then sa - f0_max/
unitForce else sa + f0_max/unitForce;
a_relfric/unitAcceleration = if locked then 0 else if free then sa
else if startForward then sa - f0_max/unitForce
else if startBackward then sa + f0_max/unitForce
else sa - sign(v_relfric)*f0_max/unitForce;

/* Friction force "f" has to be defined in a subclass. Example for possible
realization of a brake utilizing interpolation by ExternalCombiTable1D see:
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48 changes: 48 additions & 0 deletions ModelicaTest/Rotational.mo
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Expand Up @@ -1623,6 +1623,54 @@ they were not deleted yet.")}));
annotation (experiment(StopTime=1.1));
end TestFriction;

model TestFrictionPosition
extends Modelica.Icons.Example;

parameter Real fric=155.9218;
Modelica.Mechanics.Rotational.Sources.Position position(exact=true)
annotation (Placement(transformation(extent={{-10,30},{10,50}})));

Modelica.Blocks.Sources.Sine sine(
amplitude=0.1,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,30},{-50,50}})));

Modelica.Mechanics.Rotational.Components.BearingFriction bearingFriction(tau_pos=[0,5; 100,5],
peak=1.001)
annotation (Placement(transformation(extent={{46,30},{66,50}})));
Modelica.Mechanics.Rotational.Sources.Torque torque
annotation (Placement(transformation(extent={{-10,-50},{10,-30}})));
Modelica.Blocks.Sources.Sine sine1(
amplitude=25,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,-50},{-50,-30}})));
Modelica.Mechanics.Rotational.Components.BearingFriction bearingFriction1(tau_pos=[0,5; 100,5], peak=1.001)
annotation (Placement(transformation(extent={{46,-50},{66,-30}})));
Modelica.Mechanics.Rotational.Components.Inertia inertia(J=1, w(start=-2, fixed=true))
annotation (Placement(transformation(extent={{74,-50},{94,-30}})));
Modelica.Mechanics.Rotational.Sources.Position position1(exact=true)
annotation (Placement(transformation(extent={{-10,-10},{10,10}})));
Modelica.Blocks.Sources.Sine sine2(
amplitude=0.3,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,-10},{-50,10}})));
Modelica.Mechanics.Rotational.Components.BearingFriction bearingFriction2(tau_pos=[0,5; 100,5], peak=1.001)
annotation (Placement(transformation(extent={{46,-10},{66,10}})));
equation

connect(sine.y, position.phi_ref) annotation (Line(points={{-49,40},{-12,40}}, color={0,0,127}));
connect(position.flange, bearingFriction.flange_a) annotation (Line(points={{10,40},{48,40},{48,40},{46,40}}, color={0,0,0}));
connect(sine1.y, torque.tau) annotation (Line(points={{-49,-40},{-12,-40}}, color={0,0,127}));
connect(torque.flange, bearingFriction1.flange_a) annotation (Line(points={{10,-40},{46,-40}}, color={0,0,0}));
connect(bearingFriction1.flange_b, inertia.flange_a) annotation (Line(points={{66,-40},{74,-40}}, color={0,0,0}));
connect(sine2.y, position1.phi_ref) annotation (Line(points={{-49,0},{-12,0}}, color={0,0,127}));
connect(position1.flange, bearingFriction2.flange_a) annotation (Line(points={{10,0},{46,0}}, color={0,0,0}));
annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
end TestFrictionPosition;

model TestBraking
extends Modelica.Icons.Example;
Modelica.Mechanics.Rotational.Components.Inertia inertia1(
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70 changes: 70 additions & 0 deletions ModelicaTest/Translational.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -313,4 +313,74 @@ extends Modelica.Icons.ExamplesPackage;
annotation (
experiment(StopTime=2));
end Vehicles;

model TestFrictionPosition
extends Modelica.Icons.Example;

parameter Real fric=155.9218;
Modelica.Mechanics.Translational.Sources.Position position(exact=true)
annotation (Placement(transformation(extent={{-10,30},{10,50}})));

Modelica.Blocks.Sources.Sine sine(
amplitude=0.1,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,30},{-50,50}})));

Modelica.Mechanics.Translational.Components.SupportFriction supportFriction(f_pos=
Modelica.Mechanics.Translational.Examples.Utilities.GenerateStribeckFrictionTable(
1,
5,
10,
1,
12,
50), peak=1.001)
annotation (Placement(transformation(extent={{46,30},{66,50}})));
Modelica.Mechanics.Translational.Sources.Force force
annotation (Placement(transformation(extent={{-10,-50},{10,-30}})));
Modelica.Blocks.Sources.Sine sine1(
amplitude=25,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,-50},{-50,-30}})));
Modelica.Mechanics.Translational.Components.SupportFriction supportFriction1(f_pos=
Modelica.Mechanics.Translational.Examples.Utilities.GenerateStribeckFrictionTable(
1,
5,
10,
1,
12,
50), peak=1.001)
annotation (Placement(transformation(extent={{46,-50},{66,-30}})));
Modelica.Mechanics.Translational.Components.Mass mass(m=1, v(start=-2, fixed=true))
annotation (Placement(transformation(extent={{74,-50},{94,-30}})));
Modelica.Mechanics.Translational.Sources.Position position1(exact=true)
annotation (Placement(transformation(extent={{-10,-10},{10,10}})));
Modelica.Blocks.Sources.Sine sine2(
amplitude=0.3,
f=1,
phase=0.78539816339745,
offset=0.5) annotation (Placement(transformation(extent={{-70,-10},{-50,10}})));
Modelica.Mechanics.Translational.Components.SupportFriction supportFriction2(f_pos=
Modelica.Mechanics.Translational.Examples.Utilities.GenerateStribeckFrictionTable(
1,
5,
10,
1,
12,
50), peak=1.001)
annotation (Placement(transformation(extent={{46,-10},{66,10}})));
equation
connect(sine.y, position.s_ref) annotation (Line(points={{-49,40},{-12,40}},
color={0,0,127}));

connect(position.flange, supportFriction.flange_a) annotation (Line(points={{10,40},{46,40}},
color={0,127,0}));
connect(force.flange, supportFriction1.flange_a) annotation (Line(points={{10,-40},{46,-40}}, color={0,127,0}));
connect(supportFriction1.flange_b, mass.flange_a) annotation (Line(points={{66,-40},{74,-40}}, color={0,127,0}));
connect(sine1.y, force.f) annotation (Line(points={{-49,-40},{-12,-40}}, color={0,0,127}));
connect(sine2.y, position1.s_ref) annotation (Line(points={{-49,0},{-12,0}}, color={0,0,127}));
connect(position1.flange, supportFriction2.flange_a) annotation (Line(points={{10,0},{46,0}}, color={0,127,0}));
annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
end TestFrictionPosition;
end Translational;