executive_control set equilibrium_parameters
Controls the error tolerance and other parameters for execution of static equilibrium and quasi-static equilibrium analyses.
You would set these parameters only when you are requesting a static equilibrium or a quasi- static equilibrium analysis and you want to change one or more of the tolerances and other parameters from the default values.
Format:
executive_control set equilibrium_parameters | |
model_name = | an existing model |
dynamic = | yes/no |
alimit = | real |
error = | real |
imbalance = | real |
maxit = | integer |
pattern_for_jacobian = | string |
stability = | real |
tlimit = | real |
global_damping = | real |
settling_time = | real |
acceleration_error = | real |
kinetic_energy_error = | real |
static_method = | original/advanced/aggressive/all |
atol = | real |
rtol = | real |
maxitl = | integer |
etamax = | real |
eta = | real |
Example:
executive_control set equilibrium_parameters & | |
model_name = | .model_1 & |
dynamic = | no & |
static_method = | all & |
atol = | 1.0e-005 & |
rtol = | 1.0e-007 & |
maxitl = | 30 & |
etamax = | 0.8 & |
eta = | 1.0e-003 |
Description:
Parameter | Value Type | Description |
|---|---|---|
model_name | An existing model | Specify an existing model. |
dynamic | yes/no | Specifies if dynamic simulation needs to be performed or not to find the static equilibrium. |
alimit | real | Specifies the maximum angular increment allowed per iteration. |
error | real | Specifies the relative correction convergence threshold. |
imbalance | real | Specifies the equation imbalance convergence threshold. |
maxit | integer | Specifies the maximum number of iterations allowed for finding static equilibrium. |
pattern_for_jacobian | string | Specifies the pattern for evaluating Jacobian matrix. |
stability | real | Specifies the fraction of mass and damping matrices to be added to stiffness matrix to stabilize the iteration process. |
tlimit | real | Specifies the maximum translational increment allowed per iteration during static simulations. |
global_damping | real | Specifies the coefficient for global damping applied to all bodies during static simulations performed using dynamic analyses. |
settling_time | real | Specifies the maximum time allowed to reach equilibrium during static simulations performed using dynamic analyses. |
acceleration_error | real | Specifies the maximum acceleration error allowed during static simulations performed using dynamic analyses. |
kinetic_energy_error | real | Specifies the maximum kinetic energy error allowed in static simulations performed using dynamic analyses. |
static_method | original/advanced/aggressive/all | Specifies the type of static method to be selected to perform static equilibrium analyses. |
atol | real | Specifies the absolute tolerance value. |
rtol | real | Specifies the relative tolerance value. |
maxitl | integer | Specifies the maximum number of allowed inner non-linear iterations. |
etamax | real | Specifies the maximum error tolerance for residual in the inner iteration. |
eta | real | Specifies the inner iteration error control parameter. |
Extended Definition:
1. You use model_name parameter to identify the existing model to be affected with this command. You may identify a model by typing its name or by picking it from the screen. If the model is not visible on the screen, you must type the name. You may also find it convenient to type the name even if the model is displayed. You must separate multiple model names by commas. If the model is visible in one of your views, you may identify it by picking on any of the graphics associated with it.
2. The default for alimit parameter is 100 and the range is alimit > 0. You should specify the value in current modeling units (degrees by default).
3. The iterative process carried out during the equilibrium analysis can not converge prior to all relevant relative corrections being smaller than the value specified by error parameter. The default for this parameter is 1.0E-04 and the range is error > 0.
4. The iterative process carried out during the equilibrium analysis can not converge prior to each equation imbalance being smaller than the value specified by imbalance parameter. The default for this parameter is 1.0E-04 and the range is imbalance > 0.
5. The default for maxit parameter is 25 and the range is maxit > 0.
6. Often the stiffness matrix is singular for a system because the system is neutrally stable (for example, the system moves in certain directions without affecting the potential energy). Adding a fraction of the mass and damping matrices to the stiffness matrix removes this singularity and makes it possible to solve for equilibrium positions. The value of parameter stability does not affect the accuracy of the solution, but it does affect the rate of convergence of the iteration process. The default is 1.0E-05 and the range is 
.
. 7. The default for tlimit parameter is 20 and the range is tlimit > 0.
8. The default for global_damping parameter is 0 and the range is 
.
. 9. The default for settling_time is 100 and the range is > 0.
10. The default for acceleration_error is 1.0e-2 and the range is > 0.
11. The default for kinetic_energy_error is 1.0e-2 and the range is > 0.
12. The static_method parameter chooses the method to perform static equilibrium analysis as follows:
■ORIGINAL, for running only the ORIGINAL Solver
■ADVANCED, runs, in order, the following methods until one shows progress:
ORIGINAL
ORIGINAL+Krylov
ORIGINAL+UMF
Newton+Krylov
Tensor-Krylov block-3
Tensor-Krylov block-2+
■AGGRESSIVE, runs, in order, the following methods until one shows progress:
ORIGINAL
ORIGINAL+Krylov
ORIGINAL+UMF
Newton+Krylov
Tensor-Krylov block-3
Tensor-Krylov block-2+
Broyden-Armijo
Trust-Region
■ALL, runs, in order, all the available methods, until one shows progress:
ORIGINAL
ORIGINAL+Krylov
ORIGINAL+UMF
Newton+Krylov
Tensor-Krylov block-3
Tensor-Krylov block-2+
Broyden-Armijo
Trust-Region
Hooke-Jeeves
Default: ORIGINAL
13. The default for atol is 1.0e-6 and the range is 
.
. 14. The default for rtol is 0.0 and the range is 
.
. 15. For all solvers, except ORIGINAL and ORIGINAL+Krylov, the tolerance is defined as : TOL=ATOL+||xIC||*RTOL.
For ORIGINAL and ORIGINAL+Krylov solvers the tolerance is equal to error.
16. ORIGINAL, ORIGINAL+Krylov and ORIGINAL+UMF solver methods ignore maxitl parameter. For Hooke-Jeeves method, allowed budget of function evaluations is set to maxitl*N, where N is the size of the problem (number of unknowns).
17. The default for maxitl is 40 and the range is 
.
. 18. The parameter etamax specifies the maximum threshold for the error tolerance of the linear Krylov solver (for Newton+Krylov and Tensor-Krylov methods) that solves the linear systems required by Krylov algorithm. Maximum error tolerance for residual in inner iteration. The inner iteration terminates when the relative linear residual is smaller than eta*| F(x_c) |. eta is determined by the modified Eisenstat-Walker formula if etamax > 0. If etamax < 0, then eta = |etamax| for the entire iteration.
19. The default for etamax is 0.9 and the range is 
.
. 20. The parameter eta specifies the initial residual tolerance for the linear Krylov Solver for Tensor_Krylov method. The Tensor-Krylov eta parameter is maintained adaptively by the Krylov algorithm but eta is the indicated starting value, while etamax is the maximum threshold for eta. The default for eta is 1.0e-4 and the range is 
.
. 21. The parameter eta specifies the dimensionless radius of the trust-region for Trust-region method. The smaller the value, the more the refinement of Trust-region solution (hence more work). The range is 
.
.