Cleveland State University

Department of Electrical and Computer Engineering

EEC 510

Linear Systems

function Ex04

% function Ex04.

% Simulate a series RLC circuit.

% The output is the voltage across the capacitor.

% Set the R, L, and C values.

R = 1;

L = 10e-3;

C = 200E-4;

% Set the system matrices.

% xdot = Ax + Bu, y = Cx + Du.

A = [0 1/C; -1/L -R/L];

B = [0; 1/L];

C = [1 0];

D = [0];

% Create a Matlab state-space model.

sys = ss(A, B, C, D);

% Close all figures.

close 'all';

% Compute and plot the step response.

figure;

[y, t] = step(sys);

plot(t, y);

title('Step Response');

% Compute and plot the impulse response.

figure;

[y, t] = impulse(sys);

plot(t, y);

title('Impulse Response');

% Compute and plot the zero-state response to a sinusoidal input.

figure;

dt = 0.002;

tf = 4;

t = 0 : dt : tf;

u = sin(t);

[ysine, t] = lsim(sys, u, t);

plot(t, ysine);

title('Sine Response');

% Compute and plot the zero-input response.

figure;

x0 = [1; 1];

[yinitial, t] = initial(sys, x0, t);

plot(t, yinitial);

title('Initial Condition Response');

% Manually compute the total response, taking into account

% both initial conditions and external input.

% Note that if dt is too large this simulation will not work.

x = x0;

u = sin(0);

yarray = [C * x + D * u];

for t = dt : dt : tf

xdot = A * x + B * u;

x = x + xdot * dt;

y = C * x + D * u;

yarray = [yarray y];

u = sin(t);

end

% Compare the total response obtained manually with the total

% response obtained by superimposing the zero-state and the

% zero-input responses.

figure;

t = 0 : dt : tf;

plot(t, ysine+yinitial, '-', t, yarray, '--');

title('Total Response');

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Department of Electrical and Computer Engineering

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Last Revised: March 13, 2001