ep8_2.m

离散控制系统设计的MATLAB 代码

%%%%%%%%%%%% Exploratory problem 8.2 %%%%%%%%%%%%
%   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                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ---- PD controller design ----
%
clear
disp('Exploratory Problem 8.2')

Ts = 0.005;	             		    % sampling period
Gp_s = tf(1200,conv(conv([1 0],[1 10]),conv([1 30],[1 40])));
Gp_s = ss(Gp_s);                    % continuous process
H_s = tf(1,[0.02 1]);
G_s = [1; H_s]*Gp_s;                % form 1 input, 2 output system
G_z = c2d(G_s,Ts,'zoh');	        % discrete plant

dtime  = 0:Ts:1;
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: 35, 40, 45, 50, 55
    KP = 35+5*ii;
    %-- write Gc(z) as sum of 3 LTI objects in TF form --
    Gc = KP*(tf(1,1,Ts) ...			% porportional
	+ tf(KD*[1 -1],[Ts 0],Ts)); 	% derivative

    % reference input - CL transfer fcn
    Tref_z = feedback(G_z*Gc,1,1,2);
    y = step(Tref_z,dtime);         % CL response to step input
    ref = dcgain(Tref_z(1,1));
    y1 = y(:,1);
    [Mo,tpeak,trise,tsettle,ess] = kstats(dtime,y1,ref);
    ymax = y1(find(dtime == tpeak));
    yss = y1(length(dtime));
    results = [results; [KP KD trise tpeak tsettle  Mo]];
    Pgains = [Pgains KP];
    disp(['KP = ',num2str(KP)])
    plot(dtime,y1,symbols(ii))
    pause(1)

  end  % for ii..
  hold off                          % turn hold off after last plot
  xlabel('Time (s)')
  ylabel('Step Response')
  title(['EP8.2 - Step Responses for Different ',...
        'Values for KP, where and KD = ',num2str(KD)]) 
  grid on
  text('Units','norm','Pos',[0.2,0.10],'Str',['KD = ',num2str(KD)])

  legend('KP = 35','KP = 40','KP = 45','KP = 50','KP = 55')
 
  %----- print results table
  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 KP = 50 and KD = 0.1')
disp('Completed EP8.2')
%%%%%%%%%%