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Nonlinear Control Sy.. - Free

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248 CHAPTER 9. DISSIPATIVITY<br />

d<br />

G<br />

u I I y<br />

C<br />

Figure 9.4: Standard setup.<br />

To fix ideas and see that this standard setup includes the more "classical " feedback<br />

configuration, consider the following example:<br />

Example 9.2 Consider the feedback system shown in Figure 9.5.<br />

Suppose that our interest is to design a controller C to reduce the effect of the exogenous<br />

disturbance d over the signals Y2 and e2 (representing the input and output of the<br />

plant). This problem can indeed be studied using the standard setup of Figure 9.4. To see<br />

this, we must identify the inputs and outputs in the generalized plant G. In our case, the<br />

several variables in the standard setup of Figure 9.4 correspond to the following variables<br />

in Figure 9.5:<br />

y = el (the controller input)<br />

u = yl (the controller output)<br />

d: disturbance (same signal in both Figure 9.5 and the generalized setup of Figure<br />

9.4).<br />

Z= L<br />

e2 J, i.e., z is a vector whose components are input and output of the plant.<br />

Y2<br />

z

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