As shown in the figure below, properties such as Name, Formula, Equation Type, Symmetric and so on can be defined in the Differential Equation sub-entity window. General Sub-Entity Properties such as name, enable, and symmetric have been introduced in Figure 8.18: General properties of sub-entity pages and toolbar and the special properties are defined as shown in First Order Differential Equation Properties.
Note: A Second Order Differential Equation can not use a Function Expression or User Subroutine that refers to a marker created by Marker on Node.
If such Function or User Subroutine is used in a Second Order Differential Equation, solving is not processed and the following message is displayed:
"The marker on node is not allowed in variable equation and 1st & 2nd order differential equation."
In this case, fix a rigid body (small mass) on the node and create a marker on the rigid body. Then, refer to it as argument of the Function or User Subroutine to avoid the issue.
