ep8_1.m

离散控制系统设计的MATLAB 代码

%%%%%%%%%%%% Exploratory problem 8.1 %%%%%%%%%%%%
%   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                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ---- PID controller design ----
%
clear
disp('Exploratory Problem 8.1')

Ts = 0.05;	             		    % sampling period
Gp_s = tf(500*[1 10],conv(conv([1 2],[1 5]),conv([1 6 25],[1 20])));
                                    % continuous process
G_z = c2d(Gp_s,Ts,'zoh');	        % discrete plant (no sensor)

dtime  = 0:Ts:4;
KI = 2.0;
symbols = ['o' '+' '*' 'd' 'v'];    % different plot symbols
for KD = 0.1:0.1:0.4,
  figure
  results = [];
  Pgains = [];
  hold on
  for ii = 1:5,		                % KP values are: 1.1, 1.2, 1.3, 1.4, 1.5
    KP = 1.1+0.1*ii;
    %-- 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 = feedback(G_z*Gc,1);
    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));
    results = [results; [KP KD trise tpeak tsettle  Mo]];
    Pgains = [Pgains KP];
    disp(['KP = ',num2str(KP)])
    plot(dtime,y,symbols(ii))
    pause(1)

  end  % for ii..
  hold off                          
  xlabel('Time (s)')
  ylabel('Step Response')
  title(['EP8.1 - Step Responses for Different ',...
        'Values for KP, where KI = ',num2str(KI),...
        ' and KD = ',num2str(KD)]) 
  grid on
  text('Units','norm','Pos',[0.2,0.15],'Str',['KI = ',num2str(KI)])
  text('Units','norm','Pos',[0.2,0.10],'Str',['KD = ',num2str(KD)])

  legend('KP = 1.1','KP = 1.2','KP = 1.3','KP = 1.4','KP = 1.5')
  
  %----- print results table
  disp(['KI = ',num2str(KI),' and KD = ',num2str(KD)]) 
  disp(' ')
  disp('      KP       KD     t_rise      t_peak      tsettle     M_o (pct)')
  disp('    ---------------------------------------------------------------')
  disp(results)
  disp('    ---------------------------------------------------------------')
  disp(' ')
end  % for KD..

disp('A good choice is KI = 2, KP = 1.4, and KD = 0.3')
disp('Completed EP8.1')
%%%%%%%%%%