Spherical-Spherical

Constant-length joint connector with two spatially separated spherical pivot points

Library

Joints/Massless Connectors

Description

The Spherical-Spherical block represents a composite joint composed of two spherical joint primitives. The Body coordinate system (CSs) on either side of the Joint are connected to the spherical primitives. The primitives are separated spatially by a vector of constant length but variable direction connecting the two Body CS origins.

Massless Connector Between Spherical and Spherical Joints

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 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.

Assembly Restrictions on Massless Connectors

Both joint primitives are assembled but spatially separated. That is, the connected Body CS origins must not be spatially collocated points.

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.

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 rotation is the base or follower pivoting as shown by the motion figure in the Spherical block reference page.

Current base

When you connect the base (B) connector port on the Spherical-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, Spherical-Spherical Base and Follower Body Connector Ports.

Current follower

When you connect the follower (F) connector port on the Spherical-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, Spherical-Spherical Base and Follower Body Connector Ports.

Spherical-Spherical Base and Follower Body Connector Ports

Parameters

Switch between the Axes and Advanced tabs.

Axes Tab

The entries on the Axes tab are automatic. They specify the orientation of the spherical DoFs that the Spherical-Spherical represents.

Name

This column automatically displays the name of each primitive joint contained in the Joint block. For Spherical-Spherical, there are two spherical primitives, labeled S1 and S2, connecting to base and follower, respectively.

Primitive

This column automatically displays the type of each primitive joint contained in the Joint block. For Spherical-Spherical, there is only one primitive type, labeled Spherical.

Axis of Action [x y z]

These fields are not active.

Reference CS

These fields are not active.

 Restricted Parameters

Advanced Tab

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

Mark as the preferred cut joint

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 Also

Spherical

See Modeling Degrees of Freedom for more on representing DoFs with Massless Connectors.

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

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