www.gusucode.com > robust 案例源码程序 matlab代码 > robust/ComputeGapAndNugapMetricsForStableAndUnstablePlantModelsExample.m
%% Compute gap and nugap Metrics for Stable and Unstable Plant Models %% % Create two plant models. One plant is unstable, first-order, with % transfer function 1/( _s_ -0.001). The other plant is stable and first-order % with transfer function 1/( _s_ +0.001). % Copyright 2015 The MathWorks, Inc. p1 = tf(1,[1 -0.001]); p2 = tf(1,[1 0.001]); %% % Despite the fact that one plant is unstable and the other is stable, % these plants are close in the |gap| and |nugap| metrics. [g,ng] = gapmetric(p1,p2) %% % Intuitively, % this result is obvious, because, for instance, the feedback controller |K = 1| % stabilizes both plants and renders the closed-loop systems nearly % identical. K = 1; H1 = loopsens(p1,K); H2 = loopsens(p2,K); subplot(2,2,1); bode(H1.Si,'-',H2.Si,'--'); subplot(2,2,2); bode(H1.Ti,'-',H2.Ti,'--'); subplot(2,2,3); bode(H1.PSi,'-',H2.PSi,'--'); subplot(2,2,4); bode(H1.CSo,'-',H2.CSo,'--'); %% % Next, consider two stable plant models that differ by a first-order % system. One plant is the transfer function 50/( _s_ +50) and the other plant % is the transfer function 50/( _s_ +50) * 8/( _s_ +8). p3 = tf([50],[1 50]); p4 = tf([8],[1 8])*p3; %% % Although the two systems have similar high-frequency dynamics and the % same unity gain at low frequency, the plants are modestly far apart in % the |gap| and |nugap| metrics. [g,ng] = gapmetric(p3,p4) %%