![\"MultiBody.World\"](\"modelica://Modelica/Resources/Images/Mechanics/MultiBody/world.png\")
Replaceable function to define the gravity field. Default is function standardGravityAcceleration that provides some simple gravity fields (no gravity, constant parallel gravity field, point gravity field). By redeclaring this function, any type of gravity field can be defined, see example Examples.Elementary.UserDefinedGravityField.
")); /* The World object can only use the Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape model, but no other models in package Modelica.Mechanics.MultiBody.Visualizers, since the other models access data of the "outer Modelica.Mechanics.MultiBody.World world" object, i.e., there are mutually dependent classes. For this reason, the higher level visualization objects cannot be used. */ protected // Parameters to define axes parameter SI.Length headLength=min(axisLength, axisDiameter*Types.Defaults. FrameHeadLengthFraction); parameter SI.Length headWidth=axisDiameter*Types.Defaults. FrameHeadWidthFraction; parameter SI.Length lineLength=max(0, axisLength - headLength); parameter SI.Length lineWidth=axisDiameter; // Parameters to define axes labels parameter SI.Length scaledLabel=Modelica.Mechanics.MultiBody.Types.Defaults.FrameLabelHeightFraction* axisDiameter; parameter SI.Length labelStart=1.05*axisLength; // x-axis Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape x_arrowLine( shapeType="cylinder", length=lineLength, width=lineWidth, height=lineWidth, lengthDirection={1,0,0}, widthDirection={0,1,0}, color=axisColor_x, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape x_arrowHead( shapeType="cone", length=headLength, width=headWidth, height=headWidth, lengthDirection={1,0,0}, widthDirection={0,1,0}, color=axisColor_x, r={lineLength,0,0}, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Internal.Lines x_label( lines=scaledLabel*{[0, 0; 1, 1],[0, 1; 1, 0]}, diameter=axisDiameter, color=axisColor_x, r_lines={labelStart,0,0}, n_x={1,0,0}, n_y={0,1,0}, specularCoefficient=0) if enableAnimation and animateWorld and axisShowLabels; // y-axis Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape y_arrowLine( shapeType="cylinder", length=lineLength, width=lineWidth, height=lineWidth, lengthDirection={0,1,0}, widthDirection={1,0,0}, color=axisColor_y, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape y_arrowHead( shapeType="cone", length=headLength, width=headWidth, height=headWidth, lengthDirection={0,1,0}, widthDirection={1,0,0}, color=axisColor_y, r={0,lineLength,0}, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Internal.Lines y_label( lines=scaledLabel*{[0, 0; 1, 1.5],[0, 1.5; 0.5, 0.75]}, diameter=axisDiameter, color=axisColor_y, r_lines={0,labelStart,0}, n_x={0,1,0}, n_y={-1,0,0}, specularCoefficient=0) if enableAnimation and animateWorld and axisShowLabels; // z-axis Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape z_arrowLine( shapeType="cylinder", length=lineLength, width=lineWidth, height=lineWidth, lengthDirection={0,0,1}, widthDirection={0,1,0}, color=axisColor_z, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape z_arrowHead( shapeType="cone", length=headLength, width=headWidth, height=headWidth, lengthDirection={0,0,1}, widthDirection={0,1,0}, color=axisColor_z, r={0,0,lineLength}, specularCoefficient=0) if enableAnimation and animateWorld; Modelica.Mechanics.MultiBody.Visualizers.Internal.Lines z_label( lines=scaledLabel*{[0, 0; 1, 0],[0, 1; 1, 1],[0, 1; 1, 0]}, diameter=axisDiameter, color=axisColor_z, r_lines={0,0,labelStart}, n_x={0,0,1}, n_y={0,1,0}, specularCoefficient=0) if enableAnimation and animateWorld and axisShowLabels; // Uniform gravity visualization parameter SI.Length gravityHeadLength=min(gravityArrowLength, gravityArrowDiameter*Types.Defaults.ArrowHeadLengthFraction); parameter SI.Length gravityHeadWidth=gravityArrowDiameter*Types.Defaults.ArrowHeadWidthFraction; parameter SI.Length gravityLineLength=max(0, gravityArrowLength - gravityHeadLength); Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape gravityArrowLine( shapeType="cylinder", length=gravityLineLength, width=gravityArrowDiameter, height=gravityArrowDiameter, lengthDirection=n, widthDirection={0,1,0}, color=gravityArrowColor, r_shape=gravityArrowTail, specularCoefficient=0) if enableAnimation and animateGravity and gravityType == GravityTypes.UniformGravity; Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape gravityArrowHead( shapeType="cone", length=gravityHeadLength, width=gravityHeadWidth, height=gravityHeadWidth, lengthDirection=n, widthDirection={0,1,0}, color=gravityArrowColor, r_shape=gravityArrowTail + Modelica.Math.Vectors.normalize( n)*gravityLineLength, specularCoefficient=0) if enableAnimation and animateGravity and gravityType == GravityTypes.UniformGravity; // Point gravity visualization Modelica.Mechanics.MultiBody.Visualizers.Advanced.Shape gravitySphere( shapeType="sphere", r_shape={-gravitySphereDiameter/2,0,0}, lengthDirection={1,0,0}, length=gravitySphereDiameter, width=gravitySphereDiameter, height=gravitySphereDiameter, color=gravitySphereColor, specularCoefficient=0) if enableAnimation and animateGravity and gravityType == GravityTypes.PointGravity; /* function gravityAcceleration = gravityAccelerationTypes ( gravityType=gravityType, g=g*Modelica.Math.Vectors.normalize( n), mu=mu); */ // Ground plane visualization Modelica.Mechanics.MultiBody.Visualizers.Advanced.Surface surface( final multiColoredSurface=false, final wireframe=false, final color=groundColor, final specularCoefficient=0, final transparency=0, final R=Modelica.Mechanics.MultiBody.Frames.absoluteRotation( Modelica.Mechanics.MultiBody.Frames.from_nxy(n, groundAxis_u), Modelica.Mechanics.MultiBody.Frames.axesRotations({1,2,3}, {pi/2,pi/2,0}, {0,0,0})), final r_0=zeros(3), final nu=2, final nv=2, redeclare function surfaceCharacteristic = Modelica.Mechanics.MultiBody.Visualizers.Advanced.SurfaceCharacteristics.rectangle( lu=groundLength_u, lv=groundLength_v)) if enableAnimation and animateGround and gravityType == GravityTypes.UniformGravity; equation Connections.root(frame_b.R); assert(Modelica.Math.Vectors.length(n) > 1e-10, "Parameter n of World object is wrong (length(n) > 0 required)"); frame_b.r_0 = zeros(3); frame_b.R = Frames.nullRotation(); annotation ( defaultComponentName="world", defaultComponentPrefixes="inner", missingInnerMessage="No \"world\" component is defined. A default world component with the default gravity field will be used (g=9.81 in negative y-axis). If this is not desired, drag Modelica.Mechanics.MultiBody.World into the top level of your model.", Icon(coordinateSystem( preserveAspectRatio=true, extent={{-100,-100},{100,100}}), graphics={ Rectangle( extent={{-100,100},{100,-100}}, fillColor={255,255,255}, fillPattern=FillPattern.Solid), Line( points={{-100,-118},{-100,61}}, thickness=0.5), Polygon( points={{-100,100},{-120,60},{-80,60},{-100,100},{-100,100}}, fillPattern=FillPattern.Solid), Line( points={{-119,-100},{59,-100}}, thickness=0.5), Polygon( points={{99,-100},{59,-80},{59,-120},{99,-100}}, fillPattern=FillPattern.Solid), Text( extent={{-150,145},{150,105}}, textString="%name", textColor={0,0,255}), Text( extent={{95,-113},{144,-162}}, textString="%label1"), Text( extent={{-170,127},{-119,77}}, textString="%label2"), Line(points={{-56,78},{-56,-26}}, color={0,0,255}), Polygon( points={{-68,-26},{-56,-66},{-44,-26},{-68,-26}}, fillColor={0,0,255}, fillPattern=FillPattern.Solid, lineColor={0,0,255}), Line(points={{2,78},{2,-26}}, color={0,0,255}), Polygon( points={{-10,-26},{2,-66},{14,-26},{-10,-26}}, fillColor={0,0,255}, fillPattern=FillPattern.Solid, lineColor={0,0,255}), Line(points={{66,80},{66,-26}}, color={0,0,255}), Polygon( points={{54,-26},{66,-66},{78,-26},{54,-26}}, fillColor={0,0,255}, fillPattern=FillPattern.Solid, lineColor={0,0,255})}), Documentation(info="Model World represents a global coordinate system fixed in ground. This model serves several purposes:
Since the gravity field function is required from all bodies with mass and the default settings of animation properties are required from nearly every component, exactly one instance of model World needs to be present in every model on the top level. The basic declaration needs to be:
inner Modelica.Mechanics.MultiBody.World world
Note, it must be an inner declaration with instance name world in order that this world object can be accessed from all objects in the model. When dragging the \"World\" object from the package browser into the diagram layer, this declaration is automatically generated (this is defined via annotations in model World).
All vectors and tensors of a mechanical system are resolved in a frame that is local to the corresponding component. Usually, if all relative joint coordinates vanish, the local frames of all components are parallel to each other, as well as to the world frame (this holds as long as a Parts.FixedRotation, component is not used). In this \"reference configuration\" it is therefore alternatively possible to resolve all vectors in the world frame, since all frames are parallel to each other. This is often very convenient. In order to give some visual support in such a situation, in the icon of a World instance two axes of the world frame are shown and the labels of these axes can be set via parameters.
")); end World; annotation ( Documentation(info="Library MultiBody is a free Modelica package providing 3-dimensional mechanical components to model in a convenient way mechanical systems, such as robots, mechanisms, vehicles. Typical animations generated with this library are shown in the next figure:
![](\"modelica://Modelica/Resources/Images/Mechanics/MultiBody/MultiBody.png\")
For an introduction, have especially a look at:
Copyright © 1998-2025, Modelica Association and contributors
"), Icon(coordinateSystem(preserveAspectRatio=false, extent={{-100,-100}, {100,100}}), graphics={ Polygon( points={{-58,76},{6,76},{-26,50},{-58,76}}, lineColor={95,95,95}, fillColor={255,255,255}, fillPattern=FillPattern.Solid), Line( points={{-26,50},{28,-50}}), Ellipse( extent={{-4,-14},{60,-78}}, lineColor={135,135,135}, fillPattern=FillPattern.Sphere, fillColor={255,255,255})})); end MultiBody;