Couplers

A coupler entity defines an algebraic relationship between the degrees of freedom of two or three joints.

This constraint element may be used to model idealized spur gears, rack and pinion gears, and differentials as simple constraints that relate the displacements in a set of joints. Couplers can be used to specify relationships between translational, rotational, and cylindrical joints only.

For information on how to add or edit an entity like a coupler, see Entity Creation.

Couplers Properties

Descriptions of couplers properties in the Property Editor.

Table 1.
Property Name Description
General
Name Name of the entity
Variable Name The variable name, a unique identifier string of the entity
ID A unique identifying integer
Type Defines the number of joints to be constrained
Joint 1 First joint selection
Joint 1 Coupling Axis Defines the type of displacement to be controlled and is automatically specified. In the case of a cylindrical joint, you should manually select the type of displacement (translational or rotational).
Joint 2 Second joint selection
Joint 2 Coupling Axis Defines the type of displacement to be controlled and is automatically specified. In the case of a cylindrical joint, you should manually select the type of displacement (translational or rotational).
Joint 3 Third joint selection

This is only available when Type is 3.
Joint 3 Coupling Axis Defines the type of displacement to be controlled and is automatically specified. In the case of a cylindrical joint, you should manually select the type of displacement (translational or rotational). This is only available when Type is 3.
Use Virtual Virtual is an expert option that is very similar to a rigid joint, but with "soft constraint" behavior that is useful for avoiding redundant joints. Default uses the global setting from the Run Motion Analysis window.
Symmetry
  • To make the entity symmetric about the x-z plane, set Symmetry to LEFT or RIGHT. The side on the positive y-axis is considered the RIGHT side and will act as the leader if selected. The opposite side will follow.
  • To make the entity asymmetric, set Symmetry to NONE.
For more information, see Pairs and Symmetric Modeling in Inspire Motion.
Properties
Ratio Displacement ratio between first and second joint
Ratio 2 Displacement ratio between second and third joint

This is only available when Type is 3.
Signal
User-defined Use a subroutine to define the coupler.
  • For User expr, provide an expression with the USER solver function with parameters being passed to the user subroutine.
  • Turn on Use local file and function name to provide a local file for the subroutine. Otherwise, Inspire Motion will search for the subroutine within its search path.
    1. Specify a Local file where the subroutine code can be accessed by the solver. If this option is not specified, the application will search for a subroutine following its user subroutine loading rules.
      Note: The type of file to be specified will depend on the selected function type. For example, if DLL/SO is selected, you can specify a file with a .dll extension (for Windows) or an .so extension (for Linux).
    2. Select a Function type from the dropdown menu:
      • DLL/SO
      • Python
      • MatLab
      • Compose
    3. Specify the Function name in the subroutine that defines the entity, or accept the default name provided by the application.
Notes and Tags
Attachment Candidate Add an attachment candidate tag. See Attachments.