www.gusucode.com > control 案例程序 matlab源码代码 > control/RecommendedModelTypeForBuildingBlockDiagramsExample.m
%% Recommended Model Type for Building Block Diagrams % This example shows how choice of model type can affect numerical accuracy % when interconnecting models. % % You can represent block diagram components with any model type. However, % certain connection operations yield better numerical accuracy for models % in |ss| form. % % For example, interconnect two models in series using different model % types to see how different representations introduce numerical % inaccuracies. %% % Load the models |Pd| and |Cd|. These models are ninth-order and % second-order discrete-time transfer functions, respectively. % Copyright 2015 The MathWorks, Inc. load numdemo Pd Cd %% % Compute the open-loop transfer function |L = Pd*Cd| using the |tf|, % |zpk|, |ss|, and |frd| representations. Ltf = Pd*Cd; Lzp = zpk(Pd)*Cd; Lss = ss(Pd)*Cd; w = logspace(-1,3,100); Lfrd = frd(Pd,w)*Cd; %% % Plot the magnitude of the frequency response to compare the four % representations. bodemag(Ltf,Lzp,Lss,Lfrd) legend('tf','zpk','ss','frd') %% % The |tf| representation has lost low-frequency dynamics that other % representations preserve.