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view m-toolbox/classes/@ssm/doBode.m @ 49:0bcdf74587d1 database-connection-manager
Cleanup
author | Daniele Nicolodi <nicolodi@science.unitn.it> |
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date | Wed, 07 Dec 2011 17:24:36 +0100 |
parents | f0afece42f48 |
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% DOBODE makes a bode computation from the given inputs to outputs. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % DESCRIPTION: makes a bode computation from all the inputs to all outputs. % % CALL: varargout = doBode(a, b, c, d, w, Ts) % % INPUTS: % 'sys' - ssm object % 'inputnames, statenames, outputnames' - 3 cellstr % % OUTPUTS: % % 'as' - array of output TFs containing the requested responses. % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% function varargout = doBode(a, b, c, d, w, Ts) f = w/(2*pi); %% dealing with timestep if(Ts ~= 0) % Compute discrete freq: f_disc = f*Ts; % Compute z = e^jw (with w discrete) z = exp(1i*2*pi*f_disc); end %% getting matrices properly ordered %% stop warnings s = warning; warning('off','MATLAB:nearlySingularMatrix'); % turn all warnings off %% looping over SISO systems Ni = size(b,2); No = size(c,1); G = zeros(No,Ni,length(f)); G2 = zeros(No,Ni,length(f)); %% compute responses % To conserve accuracy, the system is transformed to Hessenberg form [1] % Laub, A.J., "Efficient Multivariable Frequency Response Computations", % IEEE Transactions on Automatic Control, AC-26 (1981), pp. 407-408 % This transformation leads to a faster resolution and at the % same time to a more accurate and precise answer of C*(jw - A)^-1 *B + D reduce_a = a; reduce_c = c; %% loop on inputs if (Ts == 0) for ii=1:Ni reduce_b = b(:,ii); reduce_d = d(:,ii); [num,den] = ss2tf(reduce_a,reduce_b,reduce_c,reduce_d); denr = polyval(den, 2*pi*1i*f); for jj = 1:No numr = polyval(num(jj,:), 2*pi*1i*f); G(jj,ii,:) = numr./denr; end end else [T,H]=hess(reduce_a); % Step 1: P = reduce_c*T; reduce_b = b(:,1:Ni); reduce_d = d(1:No,1:Ni); Q = T'*reduce_b; I = eye(size(reduce_a)); %% time discrete for ff = 1:length(f) G(1:No,1:Ni,ff) = (P/(z(ff)*I - H))*(Q) + reduce_d; end end %% execute warnings [msg, msgid] = lastwarn; if(strcmp(msgid,'MATLAB:nearlySingularMatrix') == 1) %warning('This frequency response may be unaccurate because the system matrix is close to singular or badly scaled.') %#ok<WNTAG> end warning(s) % restore the warning state %% output varargout = {G}; end