ex8_3b2.m

离散控制系统设计的MATLAB 代码

%%%%%%%%%%%%%%%% Example 8.3(b2) %%%%%%%%%%%%%%%%
%   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                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ----  Proportional-Integral-Derivative Control  ----
%
clear
disp('Example 8.3(b2)')

Ts = 0.1;			                % sampling period
dtime  = 0:Ts:2;

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 = 0.50; 	
KD = 0.45;
KP = 1.95;

%-- write Gc(z) as sum of 3 LTI objects in TF form --
Gc = KP*(tf(1,1,Ts) ...				% porportional
	+ tf([KI*Ts  0],[1 -1],Ts) ...	% integral
	+ tf(KD*[1 -1],[Ts 0],Ts)); 	% derivative

%------- reference input - CL transfer fcn
Tref_z = Gp_z*Gc/(1+HGp_z*Gc);
Tref_z = minreal(Tref_z);           % remove pole-zero cancellations
y = step(Tref_z,dtime);             % CL response to step input
ref = dcgain(Tref_z);
[Mo,tpeak,trise,tsettle,ess] = kstats(dtime,y,ref);
ymax = y(find(dtime == tpeak));
yss = y(length(dtime));

figure
plot(dtime,y,'o'); grid
xlabel('Time (s)')
ylabel('Step Response')
title(['Example 8.3(b2) - Step Response for KP = ',num2str(KP),...
	'; KI = ',num2str(KI),'; KD = ',num2str(KD)]) 
%%%%%%%%%%