Since constraint entities add or remove Degree of Freedom for Bodies from a model, they prohibit or prescribe motion. They may be used for ideal representation of a connection such as the hinge or to restrict a relative movement between two bodies. Motion supports various constraint types and they can be classified as follows.
Idealized Joints
These constraints represent an ideal connection between two bodies such as by bolting, gluing, or using a hinge. Each participating body must have a physical counterpart.
Figure 5.1: List of idealized joints
| Type | Description |
| Revolute Joint | Use to allow one rotational DOF of a body relative to the counterpart, in a particular direction. |
| Translational Joint | Use to allow one translational DOF of a body relative to the counterpart, in a particular direction. |
| Fixed Joint | Use not to allow any DOF of a body relative to the counterpart. |
| Ball Joint | Use to allow three rotational DOFs of a body relative to the counterpart. |
| Cylindrical Joint | Use to allow one translational and one rotational DOF of a body relative to the counterpart, in a particular direction. |
| Plane Joint | Use to allow two translational DOFs and one rotational DOF of a body relative to the counterpart, in a particular direction. |
| Distance Joint | Use to allow two translational DOFs and three rotational DOFs of a body relative to the counterpart. |
| Universal Joint | Use to allow two rotational DOFs of a body relative to the counterpart, in particular directions. |
| Screw Joint | Use to allow one translational and one rotational DOF of a body relative to the counterpart, in a particular direction. In this special case, the translational and rotational DOFs are coupled to each other. |
| Constant Velocity Joint | Use to allow two rotational DOFs of a body relative to the counterpart, in particular directions. In this special case, the two rotational motions are coupled, having the same angular velocities. |
Primitive Joints
These constraints place a restriction on relative motion such as the restriction that the orientation of one body must always be same as that of another body. The combination of some primitive joints may realize ideal joints.
Figure 5.2: List of primitive joints
| Type | Description |
| Orientation Primitive | Use to restrict three rotational DOFs of a body relative to another body. |
| Parallel Primitive | Use to restrict two rotational DOFs of a body relative to another body in particular directions. |
| Inline Primitive | Use to restrict two translational DOFs of a body relative to another body in particular directions. |
| Inplane Primitive | Use to restrict one translational DOF of a body relative to another body in particular directions. |
| Perpendicular Primitive | Use to restrict one rotational DOF of a body relative to another body. |
Coupler
These constraints restrict the relative motion between joints.
Figure 5.3: List of couplers
| Type | Description |
| Coupler | Use to set relative motion between revolute, translational or cylindrical joints. |
| Gear | Use to set relative motion between two revolute joints. |
| Rack and Pinion | Use to set relative motion between one revolute joint and one translational joint |
| Cable | Use to set relative motion between two translational joints. |
Constraint Contact
These constraints restrict the relative motion between a point and a curve.
Single Body Constraint
These constraints have no reaction body.
Figure 5.5: List of single body constraint
| Type | Description |
| Boundary Condition | Use to restrict the nodal positions in a Nodeset. This entity is only available for a Nodal FE Body. |