SimMechanics    
Revolute-Revolute

Represent a composite joint composed of two revolute primitives spatially separated by a massless connector of constant length

Library

Joints/Massless Connectors

Description

The Revolute-Revolute block represents a composite joint composed of two revolute joint primitives. The Body coordinate systems (CSs) on either side of the Joint are each connected to a revolute primitive. The primitives are separated spatially by a vector of constant length but variable direction connecting the two Body CS origins. Both revolute primitives are assembled.

You specify the two revolute axes of these two joint primitives in the dialog box. The distance separation between the two axes is computed automatically from the Body CS origins to which the Joint is connected. This distance separation (the magnitude of the vector between the Body CS origins) remains fixed at its initial value during the simulation. This initial value must be nonzero.

You cannot connect a Massless Connector to an Actuator or a Sensor block.

You can connect any Joint block to two and only two Body blocks, and Joints have a default of two Connector Ports for connecting to base and follower Bodies.

A Joint block represents only the abstract relative motion of two bodies, not the bodies themselves. You must specify a reference CS to define the directions of the joint axes.

Massless Connector between Revolute and Revolute Joints

Dialog Box and Parameters

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

Connection Parameters

Current base
When you connect the base (B) Connector Port on the Revolute-Revolute block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Revolute-Revolute base and follower Body Connector Ports figure.
Current follower
When you connect the follower (F) Connector Port on the Revolute-Revolute block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Revolute-Revolute base and follower Body Connector Ports figure.

The base (B)-follower (F) Body sequence determines the sense of positive motion. Positive rotation is the base or follower rotating in the right-handed sense about its respective rotation axis.

Revolute-Revolute base and follower Body Connector Ports

Parameters

Toggle between the Axes and Advanced panels with the tabs.

The entries on the Axes pane are required. They specify the direction of the rotation axes of these DoFs that the Revolute-Revolute represents.

Name
This column automatically displays the name of each primitive joint contained in the Joint block. For Revolute-Revolute, there are two revolute primitives, labeled R1 and R2, connecting to base and follower, respectively.
Primitive
This column automatically displays the type of each primitive joint contained in the Joint block. For Revolute-Revolute, there is only one primitive type, labeled Revolute.
Axis of rotation [x y z]
Enter here as a three-component vector the directional axis about which these rotational DoFs can move. The default vectors are [0 0 1] and [0 1 0]. The axes are directed vectors whose overall signs matter.
Reference csys
Using the pull-down menu, choose the coordinate system (World, the base Body CS, or the follower Body CS) whose coordinate axes the vector axes of rotation are oriented with respect to. These CSs also determine the absolute meaning of torque and motion about the primitive axes. The defaults are WORLD.

The Advanced pane is optional. You use it to control the way SimMechanics interprets the topology of your schematic diagram.

Mark as the preferred cut joint
In a closed loop, one and only one joint is cut during the simulation. SimMechanics does the cutting internally and automatically.
If you want this particular joint to be weighted preferentially for cutting during the simulation, select the check box. The default is unselected.

See Also

Revolute

See Modeling Joints for more on representing DoFs with Massless Connectors.

See Checking Schematic Topology and How SimMechanics Works for more on closed loops and cutting.


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