Motions

Use the Motions tool to create motions and to edit the initial conditions, displacements, velocities, and acceleration of joints.

Create Motions Using the Motion Tool

The following are the standard initial steps to create any type of motion.
  1. From the Model Browser, select the system to which the motion entity is to be added.
  2. From the Model ribbon, click the Motions icon to invoke the Motions create/edit context.
    A Motions guide bar appears.
    Tip: A new motion can be created from the Model Browser by right-clicking on the Model label (or any system/analysis of your choice) and selecting Add > Constraint Entity > Motion or by right-clicking Motions and selecting Add Motion.
  3. Optional: Select the Create Pair check box below the guide bar to create a pair entity.
    A motion entity, like most of the entities that are created in MotionView, can be a single entity or a pair entity. Pair entities help to create models that are symmetric about the Z-X plane of the model. Their properties can also be symmetric about the Z-X plane (in other words, the Y property is mirrored). Asymmetry or symmetry of the motions can be decided or specified when editing the created motion.
  4. Select whether the motion will be applied to joints or markers.
    • On Joint
    • Using Markers
    If On Joint is chosen:
    1. Select a joint reference.
      • Select a joint in the modeling window.

        OR

      • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
    If Using Markers is chosen:
    1. Select the first marker reference (Marker 1).
      • Select a marker in the modeling window.

        OR

      • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
    2. Select the second marker reference (Marker 2).
      • Select a marker in the modeling window.

        OR

      • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
  5. Optional: Click to reset the entity selections and select new entities.
  6. Once the reference selections are made, create the marker using one of the following methods:
    • Click on the guide bar to create and orient the entity.
    • Click the button that appears at the mouse location in the modeling window.
    • Click to create the entity and exit the guide bar selections for this motion.
    Once the motion has been added to the model, the corresponding motion will automatically be displayed in the browser area.
    Note: By default, variables names of entities in MotionView follow a certain convention. For example, all motion entities have a variable name starting with 'mot_'. This is the recommended convention to follow when building models in since it has many advantages in model editing and model manipulation.

Edit Motions

A motion can be a displacement, velocity, or acceleration and can be applied to some joint types or between markers. Motion properties can be edited using the Entity Editor and are listed below.

Note: If the selected motion is a pair entity, first distinguish between the Left and Right side in the Entity Editor, and then edit the properties. When defining a pair motion, use pair entities for Joint, Marker, and so on.
Tip: Use the Symmetry option to adjust the symmetry of motion’s properties. Leading-Left indicates symmetry with the left side being the leader and Leading-Right indicates symmetry with right side being the leader. The other side ("follower") will gray out and follow the values on the leader side. Asymmetric indicates the properties as non-symmetric and both sides properties are editable.

Motion Properties

Property Description
General
Label Descriptive label for the entity.
Varname Variable name of the entity.
ID Integer identifier.
Active Active state of the entity. True or False. Entity is deactivated if False.
Use virtual Represent the motion as a virtual constraint.
Define Motion Select the method for defining motion.
On Joint Define the motion on a joint.
Joint Select a Revolute, Translation or a Cylindrical joint on which motion has to be applied.
Joint Type Indicates the type of joint that is selected.
Motion Type Applicable for Cylindrical joint. Select the type of motion – Translational or Rotational.
Using Markers Define the motion using markers. The markers should belong to two different bodies.
Marker 1 Select the 1st marker on which motion is applied.
Marker 2 Select the 2nd Marker. The motion is applied on the 1st marker with reference to this marker.
Direction Select the direction along which the motion is applied. The choices offer applying motion either along translation or rotation direction of Marker 2.
Property Select the kinematic method for applying Motion. Displacement, Velocity or Acceleration.
Properties
Type Select the type of input for Motion.
Linear Indicates a constant value of motion.
Value A real value (or a reference data member of type real value).
Curve Indicates motion input using a curve.
Curve Select a 2D cartesian or parametric curve.
Interpolation Interpolation scheme to be used for the curve – AKIMA, CUBIC, LINEAR or QUINTIC.
Independent variable Solver expression to consider as the independent variable for the curve.
Spline3D Indicates motion input using a 3D spline.
Spline3D (value) Select a Spline3D entity.
Interpolation Interpolation scheme to be used for the curve – AKIMA, CUBIC, LINEAR or QUINTIC.
Independent variable X Solver expression to consider as the first independent variable (X) for the Spline3D.
Independent variable Z Solver expression to consider as the second independent variable (Z) for the Spline3D.
Expression Indicates motion input using a solver expression.
Expression Solver expression that describes the motion.
User defined This is an alternate to the Type choices. Motion can be defined using a user subroutine.
User expr
Use local file and function name Optional. Provide a local file and function for the sub-routine.
Local file Select a file for the subroutine based on Function type.
Function type Select the type of file. DLL, Python, MATLAB or Compose.
Function name Name of the function within the subroutine file that needs to be called.
Note: If local file and filename is not used, the solver may use the subroutine based on its default search criteria. Refer the solver reference guide to learn more.
Initial Conditions
Displacement initial condition Applicable for Property as Velocity or Acceleration and type is not User-defined. Enter a value for the initial position of the motion.
Velocity initial condition Applicable for Property as Velocity or Acceleration and type is not User-defined. Enter a value for the initial velocity of the motion.
Note & Tags
Note Optional descriptive note.
Attachment Candidates Add tags for the entity to use as possible attachments to Systems/Assemblies/Analyses.