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g)
h)
i)
j)
INTEROPLATE=ON in GSTIFF slightly slows down the simulation. The HHT
integrator in ADAMS/SolverC++ only marginally slows down when in
interpolate mode.
MAXIT is an attribute not recommended to change unless you have a very good
reason to do so. One thing that has been reported to be useful was to set
MAXIT=7, and PATTERN=F:F. By doing this, the Solver only re-evaluates the
integration Jacobian when the corrector fails to converge, which happens after 7
iterations in this case. This has resulted in fast simulations for models that are
close to linear, or which do not change much their configuration in time.
If you set PATTERN=T, then the jacobian is evaluated at each iteration (very
expensive!!!), but the rate of convergence is theoretically quadratic since the
resulting method is Newton-Raphson (see section 1.1). On the other hand, if
PATTERN=F:F, then the jacobian is only evaluated when the corrector fails to
converge. Note one important difference between the FORTRAN and C++
solvers. If PATTERN=F in the C++ solver, that means that the integrator is given
control how often to evaluate the Jacobian. Remember that doing it too often is in
general expensive; doing it too seldom might lead to convergence failure. The
C++ Solver tries to reach a compromise with an adaptive Jacobian pattern, and as
indicated this strategy kicks in by setting PATTERN=F. To conclude, in C++
Solver, you can obtain the FORTRAN PATTERN=F behavior by setting
PATTERN=F:F.
The attribute KMAX is not something that is usually modified. It has been
noticed that for models that have very high mechanical stiffness, such as models
with flexible bodies, setting KMAX=2 sometimes results in shorter simulation
times.
The CORRECTOR attribute might come handy for models where the corrector
has a hard time converging the Newton-Raphson process. By choosing the
MODIFIED corrector the integrator will accept more readily a system
configuration as being “converged”. This is useful for models with contacts and
discontinuities. Use this feature with care, since this approach can sometimes
lead to results that are different than the actual solution.
8.2. Settings in the EQUILIBRIUM Statement
Static analyses in ADAMS are mostly carried out using the STATIC rather than
the DYNAMIC approach, and the focus of the discussion below is reflecting this bias. It
should be pointed out that finding an equilibrium configuration is a challenging task,
particularly when the initial configuration of the system if far from the equilibrium
configuration. When the STATIC approach is used, the equilibrium configuration is
obtained as a solution of a non-linear system, and therefore if the initial guess is far from
the solution the Newton-Raphson algorithm diverges (see section 1.1)
As a general piece of advice, always consider turning on the debug information
during the static analysis (having DEBUG/EPRINT in your command file before the
static simulation turns on the debug information; you can turn it off with
DEBUG/NOEPRINT afterwards; see section 8.5.1 for more information on
DEBUG/EPRINT).
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