WOLFRAM SYSTEMMODELER

SphericalSpherical

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

Wolfram Language

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Click for copyable input
SystemModel["Modelica.Mechanics.MultiBody.Joints.SphericalSpherical"]
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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.

Connectors (2)

frame_a

Type: Frame_a

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

frame_b

Type: Frame_b

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

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)

Components (5)

world

Type: World

Description:

shape_rod

Type: Shape

Description:

shape_a

Type: Shape

Description:

shape_b

Type: Shape

Description:

shape_mass

Type: Shape

Description:

Used in Components (2)

JointSSR

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

JointSSP

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