WorldWorld coordinate system + gravity field + default animation definition 
This information is part of the Modelica Standard Library maintained by the Modelica Association.
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.
enableAnimation 
Value: true Type: Boolean Description: = true, if animation of all components is enabled 

animateWorld 
Value: true Type: Boolean Description: = true, if world coordinate system shall be visualized 
animateGravity 
Value: true Type: Boolean Description: = true, if gravity field shall be visualized (acceleration vector or field center) 
animateGround 
Value: false Type: Boolean Description: = true, if ground plane shall be visualized 
label1 
Value: "x" Type: AxisLabel Description: Label of horizontal axis in icon 
label2 
Value: "y" Type: AxisLabel Description: Label of vertical axis in icon 
gravityType 
Value: GravityTypes.UniformGravity Type: GravityTypes Description: Type of gravity field 
g 
Value: Modelica.Constants.g_n Type: Acceleration (m/s²) Description: Constant gravity acceleration 
n 
Value: {0, 1, 0} Type: Axis Description: Direction of gravity resolved in world frame (gravity = g*n/length(n)) 
mue 
Value: 3.986004418e14 Type: Real (m³/s²) Description: Gravity field constant (default = field constant of earth) 
driveTrainMechanics3D 
Value: true Type: Boolean Description: = true, if 3dim. mechanical effects of Parts.Mounting1D/Rotor1D/BevelGear1D shall be taken into account 
axisLength 
Value: nominalLength / 2 Type: Distance (m) Description: Length of world axes arrows 
axisDiameter 
Value: axisLength / defaultFrameDiameterFraction Type: Distance (m) Description: Diameter of world axes arrows 
axisShowLabels 
Value: true Type: Boolean Description: = true, if labels shall be shown 
gravityArrowTail 
Value: {0, 0, 0} Type: Position[3] (m) Description: Position vector from origin of world frame to arrow tail, resolved in world frame 
gravityArrowLength 
Value: axisLength / 2 Type: Length (m) Description: Length of gravity arrow 
gravityArrowDiameter 
Value: gravityArrowLength / defaultWidthFraction Type: Diameter (m) Description: Diameter of gravity arrow 
gravitySphereDiameter 
Value: 12742000 Type: Diameter (m) Description: Diameter of sphere representing gravity center (default = mean diameter of earth) 
groundAxis_u 
Value: if abs(n[1]) >= 0.99 then {0, 1, 0} else {1, 0, 0} Type: Axis Description: Vector along 1st axis (called u) of ground plane, resolved in world frame (should be perpendicular to gravity direction) 
groundLength_u 
Value: 2 Type: Length (m) Description: Length of ground plane along groundAxis_u 
nominalLength 
Value: 1 Type: Length (m) Description: "Nominal" length of multibody system 
defaultAxisLength 
Value: nominalLength / 5 Type: Length (m) Description: Default for length of a frame axis (but not world frame) 
defaultJointLength 
Value: nominalLength / 10 Type: Length (m) Description: Default for the fixed length of a shape representing a joint 
defaultJointWidth 
Value: nominalLength / 20 Type: Length (m) Description: Default for the fixed width of a shape representing a joint 
defaultForceLength 
Value: nominalLength / 10 Type: Length (m) Description: Default for the fixed length of a shape representing a force (e.g., damper) 
defaultForceWidth 
Value: nominalLength / 20 Type: Length (m) Description: Default for the fixed width of a shape representing a force (e.g., spring, bushing) 
defaultBodyDiameter 
Value: nominalLength / 9 Type: Length (m) Description: Default for diameter of sphere representing the center of mass of a body 
defaultWidthFraction 
Value: 20 Type: Real Description: Default for shape width as a fraction of shape length (e.g., for Parts.FixedTranslation) 
defaultArrowDiameter 
Value: nominalLength / 40 Type: Length (m) Description: Default for arrow diameter (e.g., of forces, torques, sensors) 
defaultFrameDiameterFraction 
Value: 40 Type: Real Description: Default for arrow diameter of a coordinate system as a fraction of axis length 
defaultSpecularCoefficient 
Value: 0.7 Type: Real Description: Default reflection of ambient light (= 0: light is completely absorbed) 
defaultN_to_m 
Value: 1000 Type: Real (N/m) Description: Default scaling of force arrows (length = force/defaultN_to_m) 
defaultNm_to_m 
Value: 1000 Type: Real (N·m/m) Description: Default scaling of torque arrows (length = torque/defaultNm_to_m) 
axisColor_x 
Default Value: Modelica.Mechanics.MultiBody.Types.Defaults.FrameColor Type: Color Description: Color of xarrow 

axisColor_y 
Default Value: axisColor_x Type: Color 
axisColor_z 
Default Value: axisColor_x Type: Color Description: Color of zarrow 
gravityArrowColor 
Default Value: {0, 230, 0} Type: Color Description: Color of gravity arrow 
gravitySphereColor 
Default Value: {0, 230, 0} Type: Color Description: Color of gravity sphere 
groundColor 
Default Value: {200, 200, 200} Type: Color Description: Color of ground plane 
frame_b 
Type: Frame_b Description: Coordinate system fixed in the origin of the world frame 

x_arrowLine 
Type: Shape 


x_arrowHead 
Type: Shape 

x_label 
Type: Lines 

y_arrowLine 
Type: Shape 

y_arrowHead 
Type: Shape 

y_label 
Type: Lines 

z_arrowLine 
Type: Shape 

z_arrowHead 
Type: Shape 

z_label 
Type: Lines 

gravityArrowLine 
Type: Shape 

gravityArrowHead 
Type: Shape 

gravitySphere 
Type: Shape 

vis 
Type: Shape 
Modelica.Mechanics.MultiBody.Examples.Elementary Simple double pendulum with two revolute joints and two bodies 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate how to initialize a double pendulum so that its tip starts at a predefined position 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate usage of ForceAndTorque element 

Modelica.Mechanics.MultiBody.Examples.Elementary Free flying body attached by two springs to environment 

Modelica.Mechanics.MultiBody.Examples.Elementary Determine spring constant such that system is in steady state at given position 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate line force with two point masses using a JointUPS and alternatively a LineForceWithTwoMasses component 

Modelica.Mechanics.MultiBody.Examples.Elementary Simple pendulum with one revolute joint and one body 

Modelica.Mechanics.MultiBody.Examples.Elementary Simple spring/damper/mass system 

Modelica.Mechanics.MultiBody.Examples.Elementary Two point masses in a point gravity field 

Modelica.Mechanics.MultiBody.Examples.Elementary Two point masses in a point gravity field (rotation of bodies is neglected) 

Modelica.Mechanics.MultiBody.Examples.Elementary Rigidly connected point masses in a point gravity field 

Modelica.Mechanics.MultiBody.Examples.Elementary Simple spring/damper/mass system 

Modelica.Mechanics.MultiBody.Examples.Elementary Mass attached with a spring to the world frame 

Modelica.Mechanics.MultiBody.Examples.Elementary Point mass hanging on a spring 

Modelica.Mechanics.MultiBody.Examples.Elementary 3dim. springs in series and parallel connection 

Modelica.Mechanics.MultiBody.Examples.Elementary Single wheel rolling on ground starting from an initial speed 

Modelica.Mechanics.MultiBody.Examples.Elementary Rolling wheel set that is driven by torques driving the wheels 

Modelica.Mechanics.MultiBody.Examples.Elementary Rolling wheel set that is pulled by a force 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate the modeling of heat losses 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate the modeling of a userdefined gravity field 

Modelica.Mechanics.MultiBody.Examples.Elementary Demonstrate the visualization of a sine surface, as well as a torus and a wheel constructed from a surface 

Modelica.Mechanics.MultiBody.Examples.Loops Model of one cylinder engine 

Modelica.Mechanics.MultiBody.Examples.Loops V6 engine with 6 cylinders, 6 planar loops and 1 degreeoffreedom 

Modelica.Mechanics.MultiBody.Examples.Loops V6 engine with 6 cylinders, 6 planar loops, 1 degreeoffreedom and analytic handling of kinematic loops 

Modelica.Mechanics.MultiBody.Examples.Loops One kinematic loop with four bars (with only revolute joints; 5 nonlinear equations) 

Modelica.Mechanics.MultiBody.Examples.Loops One kinematic loop with four bars (with UniversalSpherical joint; 1 nonlinear equation) 

Modelica.Mechanics.MultiBody.Examples.Loops One kinematic loop with four bars (with JointSSP joint; analytic solution of nonlinear algebraic loop) 

Modelica.Mechanics.MultiBody.Examples.Loops Planar four bars mechanism with one kinematic loop (with RevolutePlanarLoopConstraint joint) 

Modelica.Mechanics.MultiBody.Examples.Loops Mechanism with three planar kinematic loops and one degreeoffreedom with analytic loop handling (with JointRRR joints) 

Modelica.Mechanics.MultiBody.Examples.Rotational3DEffects Demonstrates that a cylindrical body can be replaced by Rotor1D model 

Modelica.Mechanics.MultiBody.Examples.Rotational3DEffects Demonstrates usage of models Rotor1D and Mounting1D 

Modelica.Mechanics.MultiBody.Examples.Rotational3DEffects Demonstrates usage of model Rotor1D mounted on a moving body 

Modelica.Mechanics.MultiBody.Examples.Rotational3DEffects Demonstrate usage of GearConstraint model 

Modelica.Mechanics.MultiBody.Examples.Rotational3DEffects Demonstrates the usage of a BevelGear1D model and how to calculate the power of such an element 

Modelica.Mechanics.MultiBody.Examples.Constraints Body attached by one spring and two prismatic joints or constrained to environment 

Modelica.Mechanics.MultiBody.Examples.Constraints Body attached by one spring and revolute joint or constrained to environment 

Modelica.Mechanics.MultiBody.Examples.Constraints Body attached by one spring and spherical joint or constrained to environment 

Modelica.Mechanics.MultiBody.Examples.Constraints Body attached by one spring and universal joint or constrained to environment 
Modelica.Mechanics.MultiBody.Examples.Loops.Utilities Model of one cylinder engine with gas force 

Modelica.Mechanics.MultiBody.Examples.Systems.RobotR3.Components Model of the mechanical part of the r3 robot (without animation) 

Modelica.Mechanics.MultiBody.Interfaces Base model for components providing two frame connectors + outer world + assert to guarantee that the component is connected 

Modelica.Mechanics.MultiBody.Interfaces Base model for components providing two frame connectors + outer world + assert to guarantee that the component is connected (default icon size is factor 2 larger as usual) 

Modelica.Mechanics.MultiBody.Interfaces Base model for components providing one frame_a connector + outer world + assert to guarantee that the component is connected 

Modelica.Mechanics.MultiBody.Interfaces Base model for components providing one frame_b connector + outer world + assert to guarantee that the component is connected 

Modelica.Mechanics.MultiBody.Interfaces Base model for elementary joints (has two frames + outer world + assert to guarantee that the joint is connected) 

Modelica.Mechanics.MultiBody.Interfaces Base model to measure an absolute frame variable 

Modelica.Mechanics.MultiBody.Interfaces Base model to measure a relative variable between two frames 

Modelica.Mechanics.MultiBody.Interfaces Base model for visualizers (has a frame_a on the left side + outer world + assert to guarantee that the component is connected) 

Modelica.Mechanics.MultiBody.Joints Revolute joint (1 rotational degreeoffreedom, 2 potential states, optional axis flange) 

Modelica.Mechanics.MultiBody.Joints Revolute joint that is described by 2 positional constraints for usage in a planar loop (the ambiguous cutforce perpendicular to the loop and the ambiguous cuttorques are set arbitrarily to zero) 

Modelica.Mechanics.MultiBody.Parts Frame fixed in the world frame at a given position 

Modelica.Mechanics.MultiBody.Parts Fixed translation of frame_b with respect to frame_a 

Modelica.Mechanics.MultiBody.Parts Fixed translation followed by a fixed rotation of frame_b with respect to frame_a 

Modelica.Mechanics.MultiBody.Parts Rigid body with mass, inertia tensor and one frame connector (12 potential states) 

Modelica.Mechanics.MultiBody.Parts Rigid body with mass, inertia tensor, different shapes for animation, and two frame connectors (12 potential states) 

Modelica.Mechanics.MultiBody.Parts Rigid body with box shape. Mass and animation properties are computed from box data and density (12 potential states) 

Modelica.Mechanics.MultiBody.Parts Rigid body with cylinder shape. Mass and animation properties are computed from cylinder data and density (12 potential states) 

Modelica.Mechanics.MultiBody.Parts Rigid body where body rotation and inertia tensor is neglected (6 potential states) 

Modelica.Mechanics.MultiBody.Parts Propagate 1dim. support torque to 3dim. system (provided world.driveTrainMechanics3D=true) 

Modelica.Mechanics.MultiBody.Parts 1D inertia attachable on 3dim. bodies (3D dynamic effects are taken into account if world.driveTrainMechanics3D=true) 

Modelica.Mechanics.MultiBody.Parts.Rotor1D 1D inertia attachable on 3dim. bodies (3D dynamic effects are taken into account) 

Modelica.Mechanics.MultiBody.Parts 1D gearbox with arbitrary shaft directions and 3dim. bearing frame (3D dynamic effects are taken into account provided world.driveTrainMechanics3D=true) 

Modelica.Mechanics.MultiBody.Sensors Measure absolute kinematic quantities of frame connector 

Modelica.Mechanics.MultiBody.Sensors Measure relative kinematic quantities between two frame connectors 

Modelica.Mechanics.MultiBody.Sensors.Internal Base class to measure cut force and/or torque between two frames, defined by components 

Modelica.Mechanics.MultiBody.Sensors.Internal Base class to measure cut force and/or torque between two frames, defined by equations (frame_resolve must be connected exactly once) 

Modelica.Mechanics.MultiBody.Visualizers Visualizing an elementary shape with dynamically varying shape attributes (has two frame connectors) 

Modelica.Mechanics.MultiBody.Visualizers.Advanced Visualizing an arrow with variable size; all data have to be set as modifiers (see info layer) 

Modelica.Mechanics.MultiBody.Visualizers.Advanced Visualizing a double arrow with variable size; all data have to be set as modifiers (see info layer) 