SimMechanics™

Spherical

Represent assembled spherical joint with three rotational degrees of freedom

Library

Joints

Description

The Spherical block represents three rotational degrees of freedom (DoFs) at a single pivot point, a "ball-in-socket" joint. Two rotational DoFs specify a directional axis, and a third rotational DoF specifies rotation about that directional axis. The sense of each rotational DoF is defined by the right-hand rule, and the three rotations together form a right-handed system. A spherical joint is one of the SimMechanics™ primitive joints, along with prismatic and revolute.

The Spherical block is assembled: you must connect each side of the Joint block to a Body block at a Body coordinate system (CS) point, and the origins of these Body CSs must be spatially collocated points, within assembly tolerances.

You cannot connect an Actuator to a Spherical. Unlike the Gimbal block, the Spherical block cannot become singular.

You can connect all Joint blocks to two and only two Body blocks, and Joints have a default of two connector ports for connecting to base and follower Bodies.

Any Joint block represents only the abstract relative motion of two bodies, not the bodies themselves.

Spherical Motion of Follower (blue) Relative to Base (red)

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 follower rotating in the right-hand sense as shown in the figure above.

Current base

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

Current follower

When you connect the follower (F) connector port on the 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 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 Sensor blocks to this Joint. The default is 0. A Spherical cannot be connected to a Joint Actuator.

The motion of a Spherical is three DoFs specified in quaternion form.

Spherical Base and Follower Body Connector Ports

Parameters

Toggle between the Axes and Advanced panels with the tabs.

The entries on the Axes pane are automatic. They specify the orientation of the spherical DoF that the Spherical represents.

Name: This column automatically displays the name of each primitive joint contained in the Joint block. For Spherical, there is only one primitive joint, a spherical, labeled S.
Primitive: This column automatically displays the type of each primitive joint contained in the Joint block. For Spherical, there is only one primitive type, labeled Spherical.
Reference orientation [x y z]: This field is not active.
Reference CS: This field is not active.

The Advanced pane 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.