www.gusucode.com > robust 案例源码程序 matlab代码 > robust/GridOpenLoopAndClosedLoopResponsesOfUncertainSystemExample.m

    %% Grid Open-Loop and Closed-Loop Responses of Uncertain System
%%   
% Create two uncertain real parameters |gamma| and |tau|.
% The nominal value of |gamma| is 4 and its range is
% 3 to 5. The nominal value of |tau| is 0.5 and its
% value can vary by +/- 30 percent.

% Copyright 2015 The MathWorks, Inc.

gamma = ureal('gamma',4); 
tau = ureal('tau',.5,'Percentage',30); 
%% 
% These uncertain parameters are used to construct an uncertain transfer function |p|.
% An integral controller, |c|, is synthesized for the
% plant |p| based on the nominal values of |gamma| and |tau|.
% The uncertain closed-loop system |clp| is formed.
p = tf(gamma,[tau 1]); 
KI = 1/(2*tau.Nominal*gamma.Nominal); 
c = tf(KI,[1 0]); 
clp = feedback(p*c,1); 
%%
% The figure below shows the open-loop unit step response (top plot) and
% closed-loop response (bottom plot) for a grid of 20 values of
% |gamma| and |tau|.
subplot(2,1,1); step(gridureal(p,20),6) 
title('Open-loop plant step responses') 
subplot(2,1,2); step(gridureal(clp,20),6)
%%
% The plot illustrates the low-frequency closed-loop insensitivity
% achieved by the PI control system.