EE341: MATLAB M-FILE DEMONSTRATING MOTOR FREQUENCY RESPONSE.

% Filename:  example9.m
%
% Description: This m-file plots the spectra (frequency response)
%              of a DC Motor.

clear;				       % clear matlab memory

KT = 4.07;			       % motor torque constant
L = 0.00156;                           % motor inductance
J = 2*pi*1000*0.00059/60;              % motor rotor inertia (converted to
                                       % units of oz.in.sec/krpm)
R = 1.89;                              % motor resistance
B = 6.68;                              % motor friction
Kb = 3.01;                             % motor back emf constant

num = [KT];			       % numerator of motor TF
den = [L*J R*J+B*L B*R+KT*Kb];	       % denominator of motor TF

printsys(num,den,'s');		       % display H(s)

w = -2000:1:2000;		       % frequency range
H = polyval(num,j*w)./polyval(den,j*w);% FT of h(t), H(w)

figure(1); clf; 		       % open and clear figure 1
subplot(2,1,1);			       % plot magnitude of H(w)
plot(w,abs(H)); grid;
xlabel('\omega (rad/sec)');
ylabel('|H(\omega)|');
title('Magnitude of H(\omega)');

subplot(2,1,2);			       % plot phase of H(w)
plot(w,angle(H)*180/pi); grid;
xlabel('\omega (rad/sec)');
ylabel('\angle(H(\omega)) (deg)');
title('Phase of H(\omega)');

figure(2); clf;		               % open and clear figure 2
subplot(2,1,1);			       % plot poles & zeros of H(w)
pzmap(num,den);	
title('Pole-Zero Diagram');

t = 0:0.00005:0.03;		       % plot response to Va=15u(t)
y = step(num*12,den,t);
subplot(2,1,2);
plot(t,y); grid;
xlabel('time (sec)');
ylabel('Motor Speed (krpm)');
title('Motor Step Response for v_a=12u(t)');

num/den = 
 
                    4.07
   -------------------------------------
   9.6384e-005 s^2 + 0.12719 s + 24.8759