www.gusucode.com > robust 案例源码程序 matlab代码 > robust/DiskGainAndPhaseMarginsExample.m
%% Disk Gain and Phase Margins % %% % When you call |dmplot| without an argument, the % resulting plot and text shows a comparison of a disk margin analysis with the % classical notations of gain and phase margins. The Nyquist plot is % of the loop transfer function L(s): %% % % $$L(s) = \frac{{\frac{s}{{30}} + 1}}{{(s + 1)({s^2} + 1.6s + 16)}}.$$ % dmplot %% % The _x_-axis corresponds to the gain variation in dB and the _y_-axis % corresponds to the allowable phase variation in degrees. For a disk gain % margin corresponding to 3 dB (1.414), the closed-loop system is stable % for all phase and gain variations inside the blue ellipse. For example, % the closed-loop system can simultaneously tolerate +/– 2 dB gain % variation and +/– 14 deg phase variations. To see the allowable % variations for a given disk gain margin, use the given value as an input % to |dmplot|. figure % new figure window dmplot(1.414)