Mechanism Design and Mechanism Dynamics > Mechanism Design > Creating Mechanism Models > Modeling Entities > Servo Motors > User Defined Expression Definition > About the Constants Dialog Box
About the Constants Dialog Box
Access this dialog box from the Expression Definition dialog box, or when creating a user-defined measure in the Measure Definition dialog box. Use this dialog box to select the constants in the table or add parameters to your expressions:
Click to add a predefined parameter as a constant. The Select Parameter dialog box opens listing acceptable parameters in a read-only table. When you select a parameter, the parameter name and its current value appear in the list. Keep the following in mind when using parameters:
The parameter type must be an integer or a real number.
The parameter name must contain only alphanumeric characters, underscores (_), or colons (:). These can be in any language, including Asian-language characters.
The parameter name must not include spaces.
The parameter name cannot be any of the reserved words e, pi, or t.
You can add parameters from any level-top-level assembly, sub-assembly, or component.
The value of the constant is the value of the parameter at the beginning of the analysis. The value does not change during the analysis.
If you change a parameter value after including it in the user-defined function, the value in the profile of your force motor, servo motor, or force/torque, or in your user-defined measure expression is updated.
If you include a parameter in a user-defined expression, and then delete it, the measure, servo motor, force motor, or force/torque based on that expression becomes incomplete.
For more information on creating parameters, search for parameters in the Help Center.
Click to remove a selected constant or parameter that you previously added as a constant from the table.
After you close the Constants dialog box, the parameter name appears as part of your expression definition on the Expression Definition or Measure Definition dialog box.