Prismatic Joint
Use the Prismatic Joint node for 2D and 3D components to create a joint between two components such that they are free to translate relative to each other along the joint axis.
The Constraints, Locking, Spring and Damper, Prescribed Motion, Applied Force and Moment, and Friction subnodes can be added to modify the properties of the joint.
Attachment Selection
Select a Source and a Destination attachment from the lists. You can select any Attachment, Rigid Domain, Spur Gear, Helical Gear, Bevel Gear, Worm Gear, Spur Rack, or Helical Rack that is defined for the model. In Source an additional option, Fixed, is also available. When Fixed is selected, the source side of the joint is fixed in space, and not connected to any modeled parts. If any Base Motion nodes are present in the model, these also appear in the list for the Source attachment. Selecting a base motion gives a behavior similar to using Fixed, with the exception that the base now can have a nonzero prescribed displacement, velocity, or acceleration.
In large models, the list of available attachments can become long. You can then create geometric filters to narrow down the search. When the Use selection filter check box is selected, two subnodes named Source Filter and Destination Filter are added to the joint node. In these subnodes you can make graphic selections of the objects whose attachments should be shown in the Source and a Destination lists.
Center of Joint
The center of joint is the point about which displacements and rotations of source and destination boundaries are interpreted. Select an option from the list — Centroid of source, Centroid of destination, Centroid of selected entities, or User defined.
For Centroid of source and Centroid of destination, the joint is located at the centroid of the selection giving the source or destination, respectively.
For Center of mass, the center of joint is taken as the center of mass of the gear.
For Centroid of selected entities select an Entity levelBoundary, Edge, or Point. The available choices depend on geometrical dimension. The center of joint is located at the centroid of the selected entities. As a special case, you can select a single point, and thus use that point as center of joint.
For User defined, enter the Global coordinates of center of rotation, Xc, in the table.
Select the Offset check box to add an optional offset vector to the definition of the center of rotation. Enter values for the offset vector Xoffset.
The center of rotation used is the sum of the vector obtained from any of the input methods and the offset vector.
Axis of Joint
The axis of joint is the axis along which the relative motion is allowed. Select an option from the list — Specify direction, Select a parallel edge, or From selected coordinate system.
For Specify direction enter a value or expression for e0. The default is (1, 0, 0). The direction is specified in the selected coordinate system.
For Select a parallel edge an edge can be selected on the Joint Axis subnode, which is added automatically. The vector from the first to the last end of the edge is used to define the joint axis. Any edge in the model can be used. Select the Reverse direction check box to reverse the direction of the joint axis.
For From selected coordinate system the joint axis is formed using the selected coordinate system. With Axis to use you select the axis (first, second, or third) that is parallel to the joint axis.
Joint Elasticity
Select an option from the list to determine whether the joint should be fully rigid or elastic — Rigid joint or Elastic joint. For Elastic joint, the properties of an elastic joint are given in the Joint Elasticity subnode, which is added automatically.
Joint Forces and Moments
Select an option from the list to use the method of computation for the forces and moments — Computed on destination, Computed on source, Do not compute, Computed using weak constraints, or Computed using penalty method. For Computed using penalty method, enter the Penalty factor pj. The default is (mbd.prj1.Eequ*(0.1*mbd.diag)). The exact naming of the variable depends on the tags of the nodes in the model tree.
Location in User Interface
Context Menus
Multibody Dynamics>Joints>Prismatic Joint
Ribbon
Physics tab with Multibody Dynamics selected:
Global>Joints>Prismatic Joint