WOLFRAM SYSTEMMODELER

SphericalSpherical

Spherical - spherical joint aggregation (1 constraint, no potential states) with an optional point mass in the middle

Wolfram Language

In[1]:=
SystemModel["Modelica.Mechanics.MultiBody.Joints.SphericalSpherical"]
Out[1]:=

Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

Joint that has a spherical joint on each of its two ends. The rod connecting the two spherical joints is approximated by a point mass that is located in the middle of the rod. When the mass is set to zero (default), special code for a massless body is generated. In the following default animation figure, the two spherical joints are represented by two red spheres, the connecting rod by a grey cylinder and the point mass in the middle of the rod by a light blue sphere:

model Joints.SphericalSpherical

This joint introduces one constraint defining that the distance between the origin of frame_a and the origin of frame_b is constant (= rodLength). It is highly recommended to use this joint in loops whenever possible, because this enhances the efficiency considerably due to smaller systems of non-linear algebraic equations.

It is sometimes desirable to compute the rodLength of the connecting rod during initialization. For this, parameter computeLength has to be set to true and instead one other, easier to determine, position variable in the same loop needs to have a fixed attribute of true. For example, if a loop consists of one Revolute joint, one Prismatic joint and a SphericalSpherical joint, one may fix the start values of the revolute joint angle and of the relative distance of the prismatic joint in order to compute the rodLength of the rod.

It is not possible to connect other components, such as a body with mass properties or a special visual shape object to the rod connecting the two spherical joints. If this is needed, use instead joint Joints.UniversalSpherical that has this property.

Parameters (10)

animation

Value: true

Type: Boolean

Description: = true, if animation shall be enabled

showMass

Value: true

Type: Boolean

Description: = true, if mass shall be shown (provided animation = true and m > 0)

computeRodLength

Value: false

Type: Boolean

Description: = true, if rodLength shall be computed during initialization (see info)

rodLength

Value:

Type: Length (m)

Description: Distance between the origins of frame_a and frame_b (if computeRodLength=true, guess value)

m

Value: 0

Type: Mass (kg)

Description: Mass of rod (= point mass located in middle of rod)

sphereDiameter

Value: world.defaultJointLength

Type: Diameter (m)

Description: Diameter of spheres representing the spherical joints

rodDiameter

Value: sphereDiameter / Types.Defaults.JointRodDiameterFraction

Type: Diameter (m)

Description: Diameter of rod connecting the two spherical joint

massDiameter

Value: sphereDiameter

Type: Diameter (m)

Description: Diameter of sphere representing the mass point

kinematicConstraint

Value: true

Type: Boolean

Description: = false, if no constraint shall be defined, due to analytically solving a kinematic loop ("false" should not be used by user, but only by MultiBody.Joints.Assemblies joints)

checkTotalPower

Value: false

Type: Boolean

Description: = true, if total power flowing into this component shall be determined (must be zero)

Inputs (4)

sphereColor

Default Value: Modelica.Mechanics.MultiBody.Types.Defaults.JointColor

Type: Color

Description: Color of spheres representing the spherical joints

rodColor

Default Value: Modelica.Mechanics.MultiBody.Types.Defaults.RodColor

Type: Color

Description: Color of rod connecting the two spherical joints

massColor

Default Value: Modelica.Mechanics.MultiBody.Types.Defaults.BodyColor

Type: Color

Description: Color of sphere representing the mass point

specularCoefficient

Default Value: world.defaultSpecularCoefficient

Type: SpecularCoefficient

Description: Reflection of ambient light (= 0: light is completely absorbed)

Connectors (2)

frame_a

Type: Frame_a

Description: Coordinate system a fixed to the component with one cut-force and cut-torque

frame_b

Type: Frame_b

Description: Coordinate system b fixed to the component with one cut-force and cut-torque

Components (5)

world

Type: World

shape_rod

Type: Shape

shape_a

Type: Shape

shape_b

Type: Shape

shape_mass

Type: Shape

Used in Components (2)

JointSSR

Modelica.Mechanics.MultiBody.Joints.Assemblies

Spherical - spherical - revolute joint aggregation with mass (no constraints, no potential states)

JointSSP

Modelica.Mechanics.MultiBody.Joints.Assemblies

Spherical - spherical - prismatic joint aggregation with mass (no constraints, no potential states)