There are several commands that con modify the normal mode
vector space. In addition to the obvious ones such as READ NORMal-modes
and DIAGonalize, there is also an EDIT command which can be used to
modify the normal mode data structure. The EDIT DELETE command will
delete specified modes from the date structure. The EDIT ORTHogonalize
command is used to orthogonalize and optionally normalize a particular
subset of normal modes. Additional modes can be added three at a time
with the EDIT INCLude TRANslation and EDIT INCLude ROTAtion commands.
These commands will add on the translation and rotation eigenvectors
respectively. This option is important when individual Coreolis
coupling terms are needed. Single additional modes may be added with
the EDIT INCLude COMP or the EDIT INCLude FORCe or the EDIT INCLude USER
commands. For the COMP option, the difference between the comparison
and main coordinate sets will be appended, for the FORCe option, the
current values in the force arrays (from the last energy evaluation)
will be appended. There is also the ability to specify a user vector.
this is done by the inclusion of the subroutine
USERNM in your
and using the
USERLINK facility, see CONGEN Modifications. For all of the EDIT INCLude options,
the defaults are to mass weight, normalize, and orthogonalize to the
rest of the vector space. To skip any of these steps, the NOMA, NONO, and
NOOR keywords must be specified.
There are two commands which are used to obtain information about particular normal modes without modifications. These are the PRINT NORMal-modes and PROJect subcommands. The PROJect command will project one of; FORCe (the current force), COMParison (the difference between the main coordinates and the comparison set), and USER (a user supplied mode or coordinate displacement). The information displayed is:
MODE integer - mode number FREQUENCY - frequency of this mode NORMAL DOTPR - actual dotproduct of normalized vectors PROJECTION - ratio of guess vector projection to step length APPROX DEL E - estimate of energy increase along this mode TYPE - type of step (FACT, RMS, KCAL, TEMP) STEP - step length for this step type
The NOMAss and NONOrm keywords may be used to prevent mass weighting or normalization of modes.
The comparison coordinates can be modified with the FILL COMP command. This command will copy the main coordinate set to the comparison set, and then step along the specified mode by the specified magnitude. When the append (APPE keyword) is used, the main coordinates are not first copied. The FILL NORM command will fill the normal mode coordinate displacement arrays with the specified vector. Again, the append option will prevent the zeroing of these arrays before stepping along the mode. Several other commands use and modify the normal coordinate displacement vectors, so the FILL NORM command should be executed just before exiting to CONGEN with the END command.