Modern Control Engineering

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Section 5–5 / Transient-Response Analysis with MATLAB 187

MATLAB Program 5–2

% ***** In this program we plot step-response curves of a system

% having two inputs (u1 and u2) and two outputs (y1 and y2) *****

% ***** We shall first plot step-response curves when the input is

% u1. Then we shall plot step-response curves when the input is

% u2 *****

% Enter matrices A, B, C, and D

A = [-1 -1;6.5 0];

B = [1 1;1 0];

C = [1 0;0 1];

D = [0 0;0 0];

% ***** To plot step-response curves when the input is u1, enter

% the command 'step(A,B,C,D,1)' *****

step(A,B,C,D,1)

grid

title ('Step-Response Plots: Input = u1 (u2 = 0)')

text(3.4, -0.06,'Y1')

text(3.4, 1.4,'Y2')

% ***** Next, we shall plot step-response curves when the input

% is u2. Enter the command 'step(A,B,C,D,2)' *****

step(A,B,C,D,2)

grid

title ('Step-Response Plots: Input = u2 (u1 = 0)')

text(3,0.14,'Y1')

text(2.8,1.1,'Y2')

To plot two step-response curves for the input u 1 in one diagram and two step-response curves

for the input u 2 in another diagram, we may use the commands

step(A,B,C,D,1)

and

step(A,B,C,D,2)

respectively. MATLAB Program 5–2 is a program to plot two step-response curves for the

inputu 1 in one diagram and two step-response curves for the input u 2 in another diagram.

Figure 5–19 shows the two diagrams, each consisting of two step-response curves. (This

MATLAB program uses text commands. For such commands, refer to the paragraph following

this example.)