Modal analysis

Linearization of the model around the equilibrium configuration.
Computation of the system eigenmodes.
For more information, see Robotran theoritical framework.

Code sample

For running the modal analysis, insert the following code in your main script and adapt it to your need :

%% 7. Modal analysis [mbs_exe_equil ==> mbs_exe_modal]
%--------------------------------------------------------------------------
MBS_user.process = 'equil';                                                 % Premilinary equilibrium 
 
opt.equil = {'solvemethod','fsolvepk',...
    'relax',1.0,'equitol',1e-7,'itermax',30,'verbose','yes'};
% other options : 'smooth', 'xeqchoice', 'visualize', 'clearmbsglobal'      % Help about options on www.robotran.be
%                 'senstol', 'static'
 
[mbs_equil,mbs_data] = mbs_exe_equil(mbs_data,opt.equil);                   % Equilibrium process
%
 
MBS_user.process = 'modal';                                                 % Modal analysis
 
opt.modal = {'time',0.0,'mode_ampl',0.2...
    'save2file','yes','renamefile','no','verbose','yes'};
% other options : 'lintol', 'relincr', 'absincr', 'clearmbsglobal'          % Help about options on www.robotran.be
%                 'senstol', 'equitol', 'OptionDjief'
 
[mbs_modal,mbs_data] = mbs_exe_modal(mbs_data,opt.modal);                   % Modal analysis process
 

Use

The modal analysis is performed by the function mbs_exe_modal().

The user specifies the desired options of the modal analysis in MBS_modal_opt structure. The results are provided in the MBS_modal structure.

The function calls successively :

See diagram below for more details :

modal analysis function diagram