Package Modelica.​Mechanics.​MultiBody.​Joints.​Constraints
Components that define joints by constraints

Information

This package contains constraint components, that is, idealized, massless elements that constrain the motion between frames by means of kinematic constraints. The constraint elements are especially aimed to be used for multibody models which contain kinematic loops. Usually, kinematic loops are automatically handled. However, the performance might be improved by either solving certain kinds of loops analytically with the help of the components of subpackage Assemblies, or by providing numerically better loop constraint formulations with the help of the components of this subpackage.

Extends from Modelica.​Icons.​Package (Icon for standard packages).

Package Contents

NameDescription
PrismaticPrismatic cut-joint and translational directions may be constrained or released
RevoluteRevolute cut-joint and translational directions may be constrained or released
SphericalSpherical cut joint and translational directions may be constrained or released
UniversalUniversal cut-joint and translational directions may be constrained or released

Model Modelica.​Mechanics.​MultiBody.​Joints.​Constraints.​Prismatic
Prismatic cut-joint and translational directions may be constrained or released

Information

This model does not use explicit variables e.g. state variables in order to describe the relative motion of frame_b with respect to frame_a, but defines kinematic constraints between the frame_a and frame_b. The forces and torques at both frames are then evaluated in such a way that the constraints are satisfied. Sometimes this type of formulation is also called an implicit joint in literature.

As a consequence of the formulation the relative kinematics between frame_a and frame_b cannot be initialized.

In particular in complex multibody systems with closed loops this may help to simplify the system of non-linear equations. Please compare the translation log using the classical joint formulation and the alternative formulation used here in order to check whether this fact applies to the particular system under consideration.

In systems without closed loops the use of this implicit joint does not make sense or may even be disadvantageous.

See the subpackage Examples.Constraints for testing the joint.

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

Parameters

TypeNameDefaultDescription
Booleanx_lockedtrue= true: constraint force in x-direction, resolved in frame_a
Booleany_lockedtrue= true: constraint force in y-direction, resolved in frame_a
Booleanz_lockedtrue= true: constraint force in z-direction, resolved in frame_a
Booleananimationtrue= true, if animation shall be enabled (show sphere)
DistancesphereDiameter0.333333333333333 * world.defaultJointLengthDiameter of sphere representing the spherical joint

Connectors

TypeNameDescription
Frame_aframe_aCoordinate system a fixed to the component with one cut-force and cut-torque
Frame_bframe_bCoordinate system b fixed to the component with one cut-force and cut-torque

Model Modelica.​Mechanics.​MultiBody.​Joints.​Constraints.​Revolute
Revolute cut-joint and translational directions may be constrained or released

Information

This model does not use explicit variables e.g. state variables in order to describe the relative motion of frame_b with respect to frame_a, but defines kinematic constraints between the frame_a and frame_b. The forces and torques at both frames are then evaluated in such a way that the constraints are satisfied. Sometimes this type of formulation is also called an implicit joint in literature.

As a consequence of the formulation the relative kinematics between frame_a and frame_b cannot be initialized.

In particular in complex multibody systems with closed loops this may help to simplify the system of non-linear equations. Please compare the translation log using the classical joint formulation and the alternative formulation used here in order to check whether this fact applies to the particular system under consideration.

In systems without closed loops the use of this implicit joint does not make sense or may even be disadvantageous.

See the subpackage Examples.Constraints for testing the joint.

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

Parameters

TypeNameDefaultDescription
Booleanx_lockedtrue= true: constraint force in x-direction, resolved in frame_a
Booleany_lockedtrue= true: constraint force in y-direction, resolved in frame_a
Booleanz_lockedtrue= true: constraint force in z-direction, resolved in frame_a
Booleananimationtrue= true, if animation shall be enabled (show sphere)
Axisn[3]{0, 1, 0}Axis of rotation resolved in frame_a (= same as in frame_b)
DistancesphereDiameter0.333333333333333 * world.defaultJointLengthDiameter of sphere representing the spherical joint

Connectors

TypeNameDescription
Frame_aframe_aCoordinate system a fixed to the component with one cut-force and cut-torque
Frame_bframe_bCoordinate system b fixed to the component with one cut-force and cut-torque

Model Modelica.​Mechanics.​MultiBody.​Joints.​Constraints.​Spherical
Spherical cut joint and translational directions may be constrained or released

Information

This model does not use explicit variables e.g. state variables in order to describe the relative motion of frame_b with to respect to frame_a, but defines kinematic constraints between the frame_a and frame_b. The forces and torques at both frames are then evaluated in such a way that the constraints are satisfied. Sometimes this type of formulation is also called an implicit joint in literature.

As a consequence of the formulation the relative kinematics between frame_a and frame_b cannot be initialized.

In particular in complex multibody systems with closed loops this may help to simplify the system of non-linear equations. Please compare the translation log using the classical joint formulation and the alternative formulation used here in order to check whether this fact applies to the particular system under consideration.

In systems without closed loops the use of this implicit joint does not make sense or may even be disadvantageous.

See the subpackage Examples.Constraints for testing the joint.

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

Parameters

TypeNameDefaultDescription
Booleanx_lockedtrue= true: constraint force in x-direction, resolved in frame_a
Booleany_lockedtrue= true: constraint force in y-direction, resolved in frame_a
Booleanz_lockedtrue= true: constraint force in z-direction, resolved in frame_a
Booleananimationtrue= true, if animation shall be enabled (show sphere)
DistancesphereDiameter0.333333333333333 * world.defaultJointLengthDiameter of sphere representing the spherical joint

Connectors

TypeNameDescription
Frame_aframe_aCoordinate system a fixed to the component with one cut-force and cut-torque
Frame_bframe_bCoordinate system b fixed to the component with one cut-force and cut-torque

Model Modelica.​Mechanics.​MultiBody.​Joints.​Constraints.​Universal
Universal cut-joint and translational directions may be constrained or released

Information

This model does not use explicit variables e.g. state variables in order to describe the relative motion of frame_b with respect to frame_a, but defines kinematic constraints between the frame_a and frame_b. The forces and torques at both frames are then evaluated in such a way that the constraints are satisfied. Sometimes this type of formulation is also called an implicit joint in literature.

As a consequence of the formulation the relative kinematics between frame_a and frame_b cannot be initialized.

In particular in complex multibody systems with closed loops this may help to simplify the system of non-linear equations. Please compare the translation log using the classical joint formulation and the alternative formulation used here in order to check whether this fact applies to the particular system under consideration.

In systems without closed loops the use of this implicit joint does not make sense or may even be disadvantageous.

See the subpackage Examples.Constraints for testing the joint.

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

Parameters

TypeNameDefaultDescription
Axisn_a[3]{1, 0, 0}Axis of revolute joint 1 resolved in frame_a
Axisn_b[3]{0, 1, 0}Axis of revolute joint 2 resolved in frame_b
Booleanx_lockedtrue= true: constraint force in x-direction, resolved in frame_a
Booleany_lockedtrue= true: constraint force in y-direction, resolved in frame_a
Booleanz_lockedtrue= true: constraint force in z-direction, resolved in frame_a
Booleananimationtrue= true, if animation shall be enabled (show sphere)
DistancesphereDiameter0.333333333333333 * world.defaultJointLengthDiameter of sphere representing the spherical joint

Connectors

TypeNameDescription
Frame_aframe_aCoordinate system a fixed to the component with one cut-force and cut-torque
Frame_bframe_bCoordinate system b fixed to the component with one cut-force and cut-torque

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