Learn more about SimMechanics Link

Supported Autodesk Inventor Constraints and Their Corresponding Joints

On this page…
Degrees of Freedom and Constraints Supported Autodesk Inventor Constraint Entities Supported Autodesk Inventor Constraint–Constraint Entity Combinations Supported SimMechanics Joints Limitations

Degrees of Freedom and Constraints

In Autodesk Inventor, an unconstrained part has six degrees of freedom (DoFs). You reduce these DoFs by inserting constraints between bodies.

A SimMechanics body has no DoFs until you connect joints to it. Each joint is a combination of these joint primitives.

Primitive	Abbreviation	Motion Type	Number of DoFs
Prismatic	P	Translational	1
Revolute	R	Rotational	1
Spherical	S	Rotational	3
Weld	W	None	0

CAD translation maps the Inventor constraints between parts to SimMechanics joint primitives between bodies. In general, the mapping of constraints to joints is not one-to-one. When you generate a SimMechanics model from a CAD assembly, the primitives are combined into the appropriate Joints.

Back to Top

Supported Autodesk Inventor Constraint Entities

The SimMechanics Link utility conditionally supports the following Inventor constraint entities, depending on what constraints they are combined with.

Entity	Description
Circle/Arc	Circular edge/arc sketch segment*
Ellipse/Arc	Elliptical edge/arc sketch segment*
Cone	Conical face
Cylinder	Cylindrical face
Line	Linear edge/sketch segment/reference axis
Plane	Reference plane or planar face
Point	Vertex/sketch point/reference point

* A complete circle or ellipse is a special case of a circular or elliptical arc.

Back to Top

Supported Autodesk Inventor Constraint–Constraint Entity Combinations

The SimMechanics Link utility conditionally supports the following Inventor constraint–constraint entity combinations. The combinations are grouped by constraint according to the structure:

Constraint Entity1 — Constraint — Constraint Entity2

Note   A combination listed here might be supported, depending on the overall geometry of the assembly. A combination not listed here is not supported. If the SimMechanics Link exporter cannot translate a constraint–constraint entity combination into a supported SimMechanics joint with DoFs, it converts the combination into a weld (W) primitive.

Coincident Constraint

The paired entities indicated with a plus (+) sign are supported when linked with a Coincident constraint.

Constraint Entity2	Point	Line	Plane	Cylinder	Cone	Circle/Arc
Constraint Entity1
Point	+
Line		+	+
Plane		+	+			+
Cylinder				+	+	+
Cone				+	+	+
Circle/Arc			+	+	+	+

Concentric Constraint

The paired entities indicated with a plus sign (+) are supported when linked with a Concentric constraint.

Constraint Entity2	Point	Line	Plane	Cylinder	Cone	Circle/Arc
Constraint Entity1
Point
Line					+	+
Plane
Cylinder				+	+	+
Cone		+		+	+	+
Circle/Arc		+		+	+	+

Distance Constraint

These entity pairs are supported when linked with a Distance constraint:

• Point — Point

• Plane — Plane

• Line — Plane or Plane — Line

• Plane — Point or Point — Plane

Angle Constraint

These entity pairs are supported when linked with an Angle constraint:

• Line — Line

• Plane — Plane

Back to Top

Supported SimMechanics Joints

The SimMechanics Link utility supports the following SimMechanics primitives and primitive combinations.

Primitive Combination	Description
P	Prismatic
PP	Planar: P and P are perpendicular
PPP	Custom
PPPR	Custom
S	Spherical
R-S	Revolute-spherical massless connector
R	Revolute
PR	Cylindrical: P and R are parallel
PPR	In-plane: R is perpendicular to PP
PPPS	Six-DoF
R-R	Revolute-revolute massless connector
S-S	Spherical-spherical massless connector
W	Weld: Rigid with no DoFs

Tips for Specific Constraints

• You form a spherical primitive with a Point-Point Coincident constraint.

• You form a spherical-spherical massless connector joint with a Point-Point Distance constraint.

Back to Top

Limitations

Default Weld Joint Primitive in Case of Constraint Translation Failure

The weld (W) is the default target primitive if the exporter is unable to convert a constraint–constraint entity combination into a moving joint.

Restriction on Point-Point Distance Constraint and Spherical-Spherical Massless Connector

For the exporter to translate a Point-Point Distance constraint successfully into a spherical-spherical massless connector joint, this constraint must be the only one between the two parts so constrained.

Back to Top

Linking and Unlinking Autodesk Inventor

Configuring SimMechanics Link Settings in Autodesk Inventor

© 1984-2009- The MathWorks, Inc.    -   Site Help   -   Patents   -   Trademarks   -   Privacy Policy   -   Preventing Piracy   -   RSS