Primitive joint with one translational degree of freedom
The Prismatic block represents a single translational degrees of freedom (DoF) along a specified axis between two bodies. A prismatic joint is one of SimMechanics™ primitive joints, along with revolute and spherical.
Prismatic Motion of Follower (blue) Relative to Base (red)
A Joint block represents the relative degrees of freedom between two bodies, not the bodies themselves.
You must connect any Joint block to two and only two Body blocks, the base and the follower. All Joints have two connector ports for these connections, defining the direction of joint motion (base to follower). You connect each side of the Joint block to these Body blocks at a Body coordinate system (CS) port.
You specify the joint primitive axes, if any, in the Joint dialog.
This Joint block is assembled and places restrictions on the connected Body CSs.
If the Joint has one or more prismatic primitives, the origins of the connected Body CSs must lie in the span of the prismatic axes:
|Number of Prismatic Primitives||Span of Primitive Axes|
|One||Along the primitive axis|
|Two||In the plane of the primitive axes|
|Three||Anywhere in three-dimensional space|
The base (B)-follower (F) Body sequence determines the sense of positive motion. Positive translation is the follower moving in the direction of the translation axis.
When you connect the base (B) connector port on the Prismatic block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following figure, Prismatic Base and Follower Body Connector Ports.
When you connect the follower (F) connector port on the Prismatic block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following figure, Prismatic Base and Follower Body Connector Ports.
Using this spinner menu, you can set the number of extra connector ports needed for connecting Joint Actuator and Joint Sensor blocks to this Joint. The default is 0.
The motion of a Prismatic is specified in linear units.
Prismatic Base and Follower Body Connector Ports
Switch between the Axes and Advanced tabs.
The entries on the Axes tab are required. They specify the direction of the translational DoF that the Prismatic represents.
This column automatically displays the name of each primitive joint contained in the Joint block. For Prismatic, there is only one primitive joint, a prismatic, labeled P1.
This column automatically displays the type of each primitive joint contained in the Joint block. For Prismatic, there is only one primitive type, labeled Prismatic.
Enter here as a three-component vector the directional axis along which this translational DoF can move. The default vector is [0 0 1]. The axis is a directed vector whose overall sign matters.
Using the pull-down menu, choose the coordinate system (World, the base Body CS, or the follower Body CS) whose coordinate axes the vector axis of translation is oriented with respect to. This CS also determines the absolute meaning of force and motion along the joint axis. The default is World.
The Advanced tab is optional. You use it to control the way SimMechanics simulation interprets the topology of your schematic diagram.
In a closed loop, the simulation internally and automatically cuts one and only one joint.
If you want this particular joint to be weighted preferentially for cutting during the simulation, select the check box. The default is not selected.
See Modeling Degrees of Freedom for more on representing DoFs with Joints.