Design Variables

The first step in the Optimization process is to identify the Design Variables (DVs) in your model.

MotionView allows the use of the following data-members of the entities listed below to be declared as DVs (in other words, made designable) for Optimization using MotionSolve:
Designable Entities Designable Data-Members
Points x, y, z

(Coordinates)
Bodies (Rigid Bodies and Point Masses) mass, Ixx, Iyy, Ixy, Ixz, Iyz

(Mass and Inertias)
SpringDampers k, kt, c, ct, f, t, len, ang

(Stiffness, Damping, Preload and Free Length)
Bushings kx, ky, kz, ktx, kty, ktz, cx, cy, cz, ctx, cty, ctz, fx, fy, fz, tx, ty, tz

(Stiffness, Damping, Preload)
Forces Fx, Fy, Fz, Tx, Ty, Tz, F, T

(Components)
Datasets** value

(Real)
Note: **Datasets that are used in other entities in this list are only designable.

MotionView supports expression-based, parametric definitions wherein new quantities can be defined using existing quantities, free parameters (to be defined later) and expressions. A dependent quantity (that is defined parametrically in terms of other quantities) cannot be defined as a DV. Only quantities that are “independent” can be selected as DVs.

For instance, you may choose to define the mass of a sphere as a function of two parameters – its radius (r) and its density (ρ). Once you choose to define the model in this way, you cannot select the mass or inertia of the sphere as a DV. This is because:
  • Sphere mass:
  • Sphere inertia:
If you select a dependent quantity as a DV, a message similar to the one shown below will be displayed, indicating the variables it is dependent on and the action will not be completed.
Figure 1.
The ‘Design Variables’ step in the wizard allows you to add DVs to an optimization study. You can select model entity data-members as DVs by stepping through the various tabs to make your selections. Each tab lists entities of a specific type that are available in the current model.
Figure 2.

Once DVs are added, you can modify or remove existing DVs at any time in the definition of the Optimization Study.