| SimMechanics™ | |
Represent composite joint composed of revolute and spherical primitives spatially separated by massless connector of constant length
Joints/Massless Connectors
The Revolute-Spherical block represents a composite joint composed of a revolute and a spherical joint primitive. The base Body coordinate system (CS) on one side of the Joint is connected to the revolute primitive, and the follower Body CS is connected to the spherical primitive. The primitives are separated spatially by a vector of constant length but variable direction connecting the two Body CS origins. Both primitives are assembled.
Warning This joint becomes singular if the revolute primitive axis aligns with the vector separating the primitives. The simulation stops with an error in this case. |
You specify the revolute axis of the revolute joint primitives in the dialog. 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 an Actuator or Sensor to a Massless Connector.
You must 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 direction of the joint axis.
Massless Connector Between Revolute and Spherical Joints
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 rotating in the right-handed sense about its rotation axis or the follower pivoting as shown for the Spherical Joint.
When you connect the base (B) connector port on the Revolute-Spherical 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-Spherical Base and Follower Body Connector Ports.
When you connect the follower (F) connector port on the Revolute-Spherical 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-Spherical Base and Follower Body Connector Ports.
Revolute-Spherical Base and Follower Body Connector Ports
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 axis of one of the DoFs that Revolute-Spherical represents.
This column automatically displays the name of each primitive joint contained in the Joint block. For Revolute-Spherical, there are one revolute and one spherical primitive, labeled R1 and S, connecting to base and follower, respectively.
This column automatically displays the type of each primitive joint contained in the Joint block. For Revolute-Spherical, there are two primitive types, labeled Revolute and Spherical.
Enter here as a three-component vector the directional axis about which the rotational DoF can move. The default vector is [0 0 1]. The axis is a directed vector whose overall sign matters.
This field is not active for the Spherical primitive.
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 rotation is oriented with respect to. This CS also determines the absolute meaning of torque and motion about the primitive axis. The default is World.
This field is not active for the Spherical primitive.
The Advanced pane 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 Massless Connectors.
See Verifying Machine Topology and How SimMechanics™ Software Works for more on closed loops and cutting.
| Revolute-Rotational Interface | RotationMatrix2VR | |
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