Defining Non-linear Properties Using Curves

An interpolation method and an independent variable are required to define a Fx, Fy, Fz curve. The interpolation method determines how the solver computes y values on the curve between data points. There are three interpolation methods:
  • Cubic
  • AKIMA
  • Linear

The CUBIC and AKIMA interpolators are spline functions that are evaluated internally by the solver. The LINEAR interpolator is implemented using a series of IF statements.

The independent variable of the curve is specified after an interpolation method is selected. For example, for a non-linear spring, the independent variable of the curve is typically the deflection of the spring. The independent variable in a non-linear property varies during the solution and is usually written in the form of an expression. Expressions allow you to use any formula to define the independent variable. MotionView provides an appropriate default expression for the independent variable for most springs, bushings, and forces.

Define a Non-linear Property Using a Curve

  1. If the Forces panel is not currently displayed, select the desired force by clicking on it in the Project Browser or in the modeling window.
    The Forces panel is automatically displayed.
  2. Select Curve from the Property drop-down menu.
    The Value text box becomes a collector.
  3. Double click the curve collector to display the entity selector for curves.
  4. Select a curve.
  5. Select an interpolation method.
  6. Specify the independent variable of the curve.