ex8_2b.m

离散控制系统设计的MATLAB 代码

%%%%%%%%%%%%%%%%% Example 8.2(b) %%%%%%%%%%%%%%%%
%   Discrete-Time Control Problems using        %
%       MATLAB and the Control System Toolbox   %
%   by J.H. Chow, D.K. Frederick, & N.W. Chbat  %
%         Brooks/Cole Publishing Company        %
%                September 2002                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ----  Root-locus plot for PI control  ----
%
clear
disp('Example 8.2(b)')

Ts = 0.1;			                % sampling period
Gp_s = tf(4,conv([2 1],[0.5 1]));   % continuous process
H_s = tf(1,[0.05 1]);		        % continuous sensor
Gp_z = c2d(Gp_s,Ts,'zoh');	        % discrete plant (no sensor)
HGp_z = c2d(H_s*Gp_s,Ts,'zoh');     % discrete plant + sensor

KI = 0.5
KP = 1;		                        % fix KP at unity for root-locus plot
Gc  = KP*tf([1+KI*Ts  -1],[1 -1],Ts);     % PI control law
Gol = HGp_z*Gc;

%---- first, show large area ------
figure, ucircle, hold on
rlocus(Gol)
zgrid(0.8,[]),hold off
axis([-8 2 -5 5])
title('Example 8.2(b) - Large-area Root locus for PI control')
disp('******>'), pause

%---- then show smaller area ------
figure, ucircle, hold on
rlocus(Gol)
zgrid(0.8,[]), hold off
axis([-1.5 1.5 -1.5 1.5])
title('Example 8.2(b) - Root Locus for PI control with KP varying, KI fixed')
text('Units','norm','Pos',[0.1,0.1],'Str',['KI = ',num2str(KI)])

disp('******>'), pause

%---- then show smaller area for use with rlocfind cmd ------
figure, ucircle, hold on           % add unit circle plot
rlocus(Gol), hold off
axis([0.6 1.2 -0.1 0.55])          % adjust region plotted
title('Example 8.2(b) - Root Locus for PI control with KP varying, KI fixed')
text('Units','norm','Pos',[0.1,0.1],'Str',['KI = ',num2str(KI)])

disp('select point for marginal stablity')
[kk,pCL] = rlocfind(Gol)           % calibrate locus with gains
[mag_pCL,theta_pCL] = xy2p(pCL);
[kk,pCL] = rlocfind(Gol)
[mag_pCL,theta_pCL] = xy2p(pCL);
[kk,pCL] = rlocfind(Gol)
[mag_pCL,theta_pCL] = xy2p(pCL);
[kk,pCL] = rlocfind(Gol)
[mag_pCL,theta_pCL] = xy2p(pCL);
[kk,pCL] = rlocfind(Gol)
[mag_pCL,theta_pCL] = xy2p(pCL);
[kk,pCL] = rlocfind(Gol)
[mag_pCL,theta_pCL] = xy2p(pCL);
disp('Click on root locus curve to find gain, pole, ')
disp('damping ratio, overshoot, and frequency.')
%%%%%%%%%%