Total Degrees of Freedom
|
Rotation Axis
|
Translation Axis
|
Connection Type
|
Constraints associated with specific DOF
|
---|---|---|---|---|
0
|
0
|
0
|
Weld—Glues two rigid bodies together.
|
|
0
|
0
|
0
|
Rigid—Glues two parts together while changing the underlying rigid body definition. Parts constrained by a rigid connection constitute a single rigid body.
|
|
1
|
0
|
1
|
Slider—Translates along an axis.
|
Plane-plane coincident
|
1
|
1
|
0
|
Pin—Rotates about an axis.
|
|
2
|
2
|
0
|
General
|
Point-point align if the point is on an edge.
Edge on plane.
|
2
|
1
|
1
|
Cylinder—Translates along and rotates about a specific axis.
|
Point on line
Plane-plane orient
|
2
|
0
|
2
|
General
|
Edge on plane provided the plane is neither perpendicular nor parallel to the edge
Plane-plane orient
|
3
|
3
|
0
|
Ball—Rotates in any direction.
|
Point-point align
|
3
|
2
|
1
|
General
|
Edge on plane
Point on line (line and edge must align)
|
3
|
1
|
2
|
Planar—Rigid bodies connected by a planar constraint move in a plane with respect to each other. Rotation is about an axis perpendicular to the plane.
|
Plane-plane coincident/parallel
|
3
|
0
|
3
|
General
|
Plane-plane orient
Plane-plane orient (not parallel to the first set of planes)
|
4
|
3
|
1
|
Bearing—Combines a ball connection and a slider connection.
|
Point on edge
|
4
|
2
|
2
|
General
|
Edge on plane
|
4
|
1
|
3
|
General
|
Plane-plane orient
|
4
|
3
|
1
|
Slot
|
Point on a non-straight trajectory
|
3
|
3
|
0
|
Gimbal—Aligns the centers of two CSYS (see below).
|
Point to point
|
5
|
3
|
2
|
General (see below).
|
Point on plane
|
6
|
3
|
3
|
6DOF—Rotates and translates in any direction (see below).
|
|
In addition to the connection set constraints, you must consider the constraints imposed by the servo motors you apply to your model. Servo motors are enforced displacements, velocities, and accelerations that remove degrees of freedom.
Be careful to apply only as many predefined constraint sets as you need to restrict the mechanism's movement. If you overconstrain the mechanism, you will have redundancies, which can give inaccurate reaction results in dynamic analyses.
For more detailed information on component placement and constraint sets, search the Assembly area of the Help Center.
|