Motion

Analysis > Magnetic Transient Loads > Motion

Introduction

The Motion allows you to define the motion of some bodies and eventually Non-Meshed Coils of the solution.

Note: In Transient magnetic 3D, it allows to make the bodies and eventually Non-Meshed Coils moving with respects to the time or the position interval and step defined in the solution.

Dialog Box

Imposed position Imposed speed Coupled load
Note: The dialog boxes are similar for the Translation and Rotation Motion types.
  • Select bodies which are moving. At least, one body must be selected.
  • Select non-meshed coils which are moving (optional).
    Note: If the solution does not contain any Non-Meshed Coil, this input is not shown in the Motion dialog box.

  • Motion Type: Two choices are proposed:

    • Translation

      Translation direction has to be chosen through Define/Modify Direction button:



    • Rotation

      Rotation axis has to be chosen through Define/Modify Axis button:

  • Air type:

    Two choices are proposed, available for both Translation and Rotation:

    • Immersion in the air

      This air type is chosen when the moving bodies are immersed into a large air volume.

      The following example illustrates it:



      It is mostly used for translating motion.

    • Sliding airgap

      This air type is chosen when the moving bodies are sliding with respect to the fixed part. The sliding surface is located inside the airgap and separates the airgap into two bodies: moving airgap and fixed airgap.

      The following example illustrates it:



      Sliding airgap is mostly used for rotating motion, especially for motors.

  • Kinematic type:
    • Imposed position: The position of the selected bodies and non-meshed coils is imposed during the simulation with Position value. The Initial speed value is also entered.
    • Imposed speed: The speed of the selected bodies and non-meshed coils is imposed during the simulation with Speed value. The Initial position value is also entered.
    • Coupled load: The solving is done with the magneto-mechanical coupling. The inputs are the Initial position and the Initial speed.
  • Define Mechanical Characteristics:

    This button is available for the 3 kinematic types: Imposed position, Imposed speed, and Coupled load.

    The button opens another dialog box to define

    • the Internal and External load types
      • for the Translation motion type, there are 3 internal/external load types:
        • Mass and Resistive Force i.e. define the

          - Mass

          - Resistive force

        • Mass, Friction and Spring i.e. define the

          - Mass

          - Friction: Constant friction coeff, Viscous friction coeff, Friction coeff (speed^2)

          - Spring (optional): Spring constant, Initial stretching/compression

        • None
          Note: None is available only for Imposed position or Imposed speed kinematic type.
      • for the Rotation motion type, there are 3 internal/external load types:
        • Inertia and Resistive Torque i.e. define the

          - Moment of inertia

          - Resistive torque

        • Inertia, Friction and Spring i.e. define the

          - Moment of inertia

          - Friction: Constant friction coeff, Viscous friction coeff, Friction coeff (speed^2)

          - Spring (optional): Spring constant, Initial stretching/compression

        • None
          Note: None is available only for Imposed position or Imposed speed kinematic type.
    • the Mechanical stops

      The mechanical stops allow to block the minimal and/or the maximal position with the selected value.

      Optionally define the Minimal stop and the Maximal stop.
      Note: The Mechanical stops are available only for Imposed speed or Coupled load kinematic type.
      Imposed position Imposed speed Coupled load
      Translation type motion
      Rotation type motion

Motion parameters for solving

The solving parameters are defined in the solution dialog box.

It is possible to pilot either Time or Angular position or Linear position. Please refer to Magnetic Transient solution for more information on the solution dialog box.

Some control parameters are not compatible with some Motion types. Here is the table summing up the possible associations:
Table 1. Motion type compatibility with respects to the solution control parameter
Control Parameter / Motion type Translation Rotation
Time All types All types
Angular Position Not compatible Imposed Speed
Linear Position Imposed Speed Not compatible

The compatibility is checked: Error messages are displayed if an incompatible configuration has been selected.

Steps : Example of Translation Motion on a linear actuator

In this section, we will show the steps for translation case on an example of linear actuator:

  1. Click on the Motion button in analysis ribbon:

    → A default direction of the translation with an arrow on Z is visible at Motion box opening. This will be changed in following steps.



  2. Select bodies which are moving. In this case, the body highlighted in red in the upper image.

    → The selected bodies are highlighted, and the corresponding field in the dialog box is filled with selected bodies names.

  3. Select non-meshed coils: In this case, the existing non-meshed coil is not moving so it is not selected
  4. Select Motion type as Translation
  5. Open Define/Modify Direction. Select Y axis and OK.

    → The preview of the translation direction is correctly updated.

  6. Check that Air type is set to Immersion in the air (default choice for Translation).
  7. Define the Kinematic type for example as Coupled load (magneto-mechanical coupling).
  8. Open Define Mechanical Characteristics. Define Internal load type as Mass, Friction and Spring. And enter the Mass as 0.25Kg.
  9. Click on Ok.

    → The Motion is created and appears in the Model Browser of Solution tab in the node Loads and Constraints

  10. The solving must be piloted. This has to be done in the Solution box, before or after the Motion creation. In the case it is done after the Motion creation:

    1. Double click on the Solution in the Solution Browser to edit the solution and open the dialog box:

      → The following dialog box is opened:

    2. In this case, as we defined the Motion as Coupled load, the Control parameter is necessarily Time.
    3. The Final time and Time increment are entered with the values shown in the previous image
    4. Click on OK

      → The project is ready to be solved.

Advices

Here are some advices on the Motion:
  • In the use case of Immersion in the air air type (mostly for Translation use case), it is advised to reduce as much as possible the surrounding air body size. In fact, as this body is remeshed in Flux at each moving step, reducing its size will reduce memory storage requirements and solving time.
  • In the use case of Sliding airgap air type (mostly for Rotation use case), it is important that the areas of face to face surface elements be approximately the same for any rotating angle. This is illustrated in the figures below.
    Recommended meshing
    Non-recommended meshing (inhomogeneous density of nodes along the two circumferences)

Limitations

Here are some limitations on the Motion:
  • In this version: Only one motion entity can be created in a solution.
  • In this version: In the use case of Immersion in the air air type (mostly for Translation use case), the contact between the fixed device bodies (except surrounding air body) and moving bodies is forbidden. In consequence, user must choose carefully the motion parameters values in the solution box to keep a gap between the moving bodies and the fixed bodies for all solving steps.