Fields

Use the Fields tool to create a compliant connection between two bodies where stiffness or damping in one direction can be a function of displacement in another direction

Create Fields

  1. From the Model Browser, select the system to which the field entity is to be added.
  2. Right-click on a system in the Model Browser and select Add > Force Entity > Field from the context menu.
    OR
    Right-click on a field folder in the Model Browser and select Add Field from the context menu.
    OR
    From the Model ribbon, click the arrow next to the Entities tool set name, then select Fields icon.
    The Add Field or FieldPair dialog is displayed.
  3. Specify a label for the field.
  4. Specify a variable name for the field.
    By default, variables names of entities in MotionView follow a certain convention. For example, all field entities have a variable name starting with “fld_”. This is the recommended convention to follow when building models in MotionView since it has many advantages in model editing and model manipulation.
  5. Select whether to create a single field or a field pair.
    A field entity, like most of the entities that are created in MotionView, can be a single entity or a pair entity. Pair entities help in creating models which have symmetric properties.
  6. Click OK to close the window or Apply to continue creating entities.
    Once a field entity has been added to the model, the panel for the field will automatically be displayed in the panel area.

Edit Fields

Define the Connectivity of Fields

The Connectivity tab allows you to define the bodies and orientation used by the compliant connection.

  1. If the Fields panel is not currently displayed, select the desired field by clicking on it in the Model Browser or in the modeling window.
    The Fields panel is automatically displayed.
  2. Click the Body 1 collector and select the first body to be used by the field from the modeling window, or double click the collector to open the Model Tree (from which the desired body can be selected).
    Note: If the selected field is a pair entity, first distinguish between the Left and Right tabs in the panel, and then edit the properties. When defining a pair field, use pair entities for Body, Origin, etc.
  3. Similarly, click Body 2 and select the desired body from the modeling window (or use the Model Tree).
  4. Click the Point collector (under Origin) and select a point from the modeling window, or double click the Point collector to open the Model Tree (from which the desired point can be selected).
  5. Use the orientation options to orient the coordinate system.
Tip: Click [DC] to view the direction cosines' matrix for a coordinate system.

Define the Stiffness of Fields

The Stiffness tab allows you to enter stiffness values into a 6x6 matrix. The stiffness values along the diagonal of the matrix represent stiffness in the direction of displacement, whereas the other values represent cross-coupling stiffness.

  1. Click the Stiffness tab.
  2. Enter values for stiffness in each of the 36 fields.
    The rows and columns from the top left are: X, Y, Z, Rx, Ry, Rz.
Tip:
  • Click to define an MDL expression for any one of the values.
  • If the field is a pair entity, click Symmetric stiffness to make the stiffness values symmetric. Once this option is activated, MotionView will ask you which side of the values of the pair entity (left or right) is to be used. Selecting any one side will make values of that side as “leader” and the values of the other side ("follower") will gray out and follow the values on the leader side.

Define the Damping of Fields

The Damping tab allows you to enter damping values into a 6x6 matrix. The damping values along the diagonal of the matrix represent stiffness in the direction of velocity, whereas the other values represent cross-coupling damping.

  1. Click the Damping tab.
  2. Select a damping option from the drop-down menu.
    If CRATIO is chosen, enter a value in the field and MotionView applies the given fraction to each of the 36 fields to obtain the 36 values for the damping matrix.
    If MATRIX is chosen, enter a damping value in each of the 36 fields.
    The rows and columns from the top left are: X, Y, Z, Rx, Ry, Rz.

Define the Preload and Freelength of Fields

The Preload/Freelength tab allows you to provide initial forces or free lengths along the six primary directions of the field connection.

  1. Click the Preload/Freelength tab.
  2. Enter values in the Preload fields.
    Fx, Fy, and Fz are the preload values in the translational direction while Tx, Ty, and Tz are the preload values in the rotational direction.
  3. Enter values in the Freelength fields.
    Lx, Ly, and Lz are the freelength values in the translational direction while Lrx, Lry, and Lrz are the freelength values in the rotational direction.

Use User-Defined Properties for a Field

If desired, define the field using the User-Defined tab, which will allow you to specify the properties of the field using user subroutines.

  1. From the Connectivity tab, click the User-defined properties check box.
    The Stiffness, Damping, and Preload/Freelength tabs are removed.
  2. Click the newly added User-Defined tab.
  3. Define the user subroutine.
    1. Provide an expression with the USER solver function with parameters being passed to the user subroutine.
    2. Alternatively, activate the Use local file and function name check box to specify a local file where the subroutine code can be accessed by the solver.
      If this option is not specified, MotionSolve will search for a subroutine following its user subroutine loading rules.
    3. Select a function type from the drop-down menu.
    4. Select the local file for the subroutine.
      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).
    5. Specify the function name in the subroutine that defines the entity, or accept the default name provided by MotionView.