Adams Basic Package > Adams View > Adams View > Dialog box - F1 help > A - D > Create/Modify Differential Equation

Create/Modify Differential Equation

Ribbon menu → Elements Tab → System Elements container → Differential Equation
or
(Classic) Build → System Elements → Differential Equation→ New/Modify
Creates or modifies a differential equation.
Learn about:
 
For the option:
Do the following:
Name
Enter the name of the differential equation.
Type
Select either Explicit or Implicit to indicate that the function expression or subroutine defines the explicit or implicit form of the equation.
Definition
Set to either:
■Run-time Expression to enter a function expression that Adams Solver evaluates during a Simulation. In the function expression, the system variable DIF(i) is the value of the dependent variable that the differential equation defines, and DIF1(j) is the first derivative of the dependent variable that the differential equation defines.
■User written subroutine to enter a subroutine that defines the equation.
y' =
■If you selected Run-time Expression, enter the function expression that defines the differential equation. Select the More button to display the Function Builder and build an expression. See the Adams View Function Builder online help.
■If you selected User written subroutine, enter constants to the User-written subroutine DIFSUB to define a variable. See the Adams Solver Subroutines online help.
Routine
Specify an alternative library and name for the user subroutine DIFSUB. Learn about ROUTINE Argument.
Initial Conditions
Specify:
■The initial value of the differential equation at the start of the simulation.
■Optionally, if you are defining an implicit equation, an approximate value of the initial time derivative of the differential equation at the start of the simulation. (You do not need to supply a second value when you enter a explicit equation because Adams Solver can compute the initial time derivative directly from the equation.)
Adams Solver might adjust the value of the time derivative when it performs an initial conditions simulation. Entering an initial value for the time derivative helps Adams Solver converge to a desired initial conditions solution.
Keep value constant during static analyses.
Select whether or not Adams Solver should hold constant the value of the differential equation during Static equilibrium and Quasi-static simulations. Learn about Controlling Equilibrium Values When Using System Elements.
Keep value constant during dynamic analyses.
Select whether or not Adams Solver should hold constant the value of the differential equation during dynamic simulation.