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Prismatic - Represent prismatic joint with one translational degree of freedom

Library

Joints/Assembled Joints

Description

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)

Satisfying Joint Requirements

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.

Assembly Restrictions on Assembled Joints

This Joint block is assembled and places restrictions on the connected Body CSs.

If the Joint has no prismatic primitives, the origins of the connected Body CSs on either side of the Joint must be spatially collocated points, to within assembly tolerances.
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

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

Dialog Box and Parameters

The dialog has two active areas, Connection parameters and Parameters.

Connection Parameters

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.

Current base

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.

Current follower

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.

Number of sensor/actuator 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

Parameters

Switch between the Axes and Advanced tabs.

Axes Tab

The entries on the Axes tab are required. They specify the direction of the translational DoF that the Prismatic represents.

Name: 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.
Primitive: 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.
Axis of translation [x y z]: 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.
Reference CS: 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.