Engineering Connections and Degrees of Freedom

The table below summarizes the predefined engineering connections, their associated number of degrees of freedom (DOF), whether they can include controlled constraints, and which types of controlled constraints can be used as commands in the mechanism.

See Also
About Engineering Connections
Engineering Connections Joint type Translation DOF Rotation DOF Can be controlled? Command Types
Cylindrical Lower pair 1 1 YES Length, Angle, or both
Planar Lower pair 2 1 NO N/A
Prismatic Lower pair 1 0 YES Length
Revolute Lower pair 0 1 YES Angle*
Rigid Lower pair 0 0 NO N/A
Screw Lower pair 1 1 YES Length, Angle, or both
Spherical Lower pair 0 3 NO N/A
Cable Higher pair 1 0 YES Length
Gear Higher pair 0 1 YES Angle
Point Curve Higher pair 1 3 YES** Length
Point Surface Higher pair 2 3 NO N/A
Rack Higher pair 1 1 YES Length or Angle
Roll Curve Higher pair 1 1 YES Length
Slide Curve Higher pair 2 1 YES Length
Universal connection Compound 0 2 NO N/A
Fix Constraint between instances and axis-systems 0 0 NO N/A
User Defined N/A Depends on the combination of constraints Depends on the combination of constraints NO N/A

* To control the rotation direction of a revolute joint driven by a motor in a mechanism, replace the angle by a hinge. A hinge allows you to specify the desired rotation axis by selecting it directly on the element.

To do so, open the Engineering Connection Definition dialog box, right-click the revolute angle and transform it into a hinge. For more information, see Creating Engineering Connections for Mechanisms.

**Point curve connections must be created using either a controlled curvilinear distance constraint or a coincidence constraint (for an engineering connection that cannot be controlled by commands). Point curves engineering connections using driving curvilinear distance constraints or measured curvilinear distance constraints cannot be simulated.