Solver Settings - IC (Initial Conditions)
Settings → Solver → IC (Initial Conditions)
Sets error tolerances and other parameters for an
Initial conditions simulation. By default, the integrators ABAM, WSTIFF, and HASTIFF reconcile integrator results to be consistent with constraints; GSTIFF does not, unless you set
Interpolate to Yes in
Solver Settings - Dynamics.
The initial conditions simulation ensures that the system satisfies all constraints within the system. If necessary, Adams Solver moves parts until both parts of each joint are in contact. The simulation involves three separate phases:
■First, Adams Solver makes the displacements between all parts and joints in the system physically consistent. This requires the use of Newton-Raphson iteration to solve a set of nonlinear algebraic equations. (To learn more about Newton-Raphson solutions, see the
DEBUG statement in the
Adams Solver online help.)
■Once the displacements are consistent, Adams Solver makes the velocities physically consistent. Because this requires solving a set of linear equations, iteration is not necessary.
■Finally, Adams Solver calculates consistent accelerations and forces. This solution also requires solving a set of nonlinear equations using Newton-Raphson iteration.
When reconciling, the integrator uses the initial conditions solution process at each
Output step to ensure that velocities, accelerations, and forces are consistent with the system constraints. If you set
Interpolate to Yes, the integrator also uses the initial conditions solution at each output step to ensure displacements are consistent with the constraints. The IC parameters control those solutions as well as the initial conditions solution.
Because the initial conditions simulation relies on an iterative procedure, it is possible for it to fail if model inconsistencies are initially too large. If this ever occurs, you should review your model for errors in part and constraint inconsistencies. When using the Stabilized Index 2 (SI2) and Stabilized Index 1 (SI1) integrators, it is also important to ensure that initial velocities do not introduce discontinuities at time equal to zero. The initial conditions settings can be used to adjust the convergence criteria as appropriate for problematic modeling scenarios. See
Equation Formulation Comparison for more information.
To set the Jacobian matrix for initial condition simulations, see
Solver Settings - Pattern for Jacobian.
For the option: | Do the following: |
|---|
Category | Set to IC (Initial Conditions). |
Error | Specify the maximum displacement error Adams Solver is to allow for the assembly process. The default is 1.0E-10 and the range is Error > 0. |
Tlimit | Specify the maximum translational increment Adams Solver is to allow while testing trial solutions during a solution step. The default is 1.0E10 (no limit) and the range is Tlimit > 0. |
Alimit | Specify the maximum angular increment Adams Solver is to allow while testing trial solutions for a set of consistent initial conditions that satisfy all system constraints. The default units for Alimit are radians. To specify Alimit in degrees, add a D after the value. The default is 30D and the range is Alimit > 0. |
More | Click to set more advanced options. |
Maxit | Specify the maximum number of iterations Adams Solver is to allow for finding displacements during initial conditions, or when reconciling displacement output. The default is 25 and the range is Maxit > 0. |
Amaxit | Specify the maximum number of iterations Adams Solver is to allow for finding accelerations during an initial conditions solution or for reconciling acceleration output. The default is 25 and the range is Amaxit > 0. |
Aerror | Specify the maximum acceleration error Adams Solver is to allow during an initial conditions solution or for reconciling acceleration output. The default is 1.0E-4 and the range is Aerror > 0. |