Constant-length joint connector with two spatially separated revolute axes
First Generation/Joints/Massless Connectors
This content is specific to Simscape™ Multibody™ First Generation software. First-generation features are slated to be deprecated and should be avoided.
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.
This joint becomes singular if the two revolute primitive axes align with the vector separating the primitives. The simulation stops with an error in this case.
Massless Connector Between Revolute and Revolute Joints
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 a default of 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) point.
You specify the joint primitive axes, if any, in the Joint dialog.
You cannot connect an Actuator or Sensor to a Massless Connector.
The distance separating the two ends of the connector is computed automatically from the Body CS origins to which the Joint is connected. This distance (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.
The dialog has two active areas, Connection parameters and Parameters.
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.
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 figure, Revolute-Revolute Base and Follower Body Connector Ports.
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 figure, Revolute-Revolute Base and Follower Body Connector Ports.
Revolute-Revolute 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 rotation axes of these DoFs that the Revolute-Revolute represents.
This column automatically displays the name of each primitive
joint contained in the Joint block. For Revolute-Revolute, there are
two revolute primitives, labeled
connecting to base and follower, respectively.
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
Enter here as a three-component vector the directional axis
about which these rotational DoFs can move. The default vectors are
0 1] and
[0 1 0]. The axes are directed
vectors whose overall signs matter.
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
The Advanced tab is optional. You use it to control the way Simscape Multibody 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 Massless Connectors.