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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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Input<br />

instances<br />

Learning<br />

parameters<br />

Neural Net<br />

Learning Rule<br />

GA<br />

Fig. 15.11: Adaptation of the learning rule by using GA.<br />

GA can also be used for the adaptation of the control laws in self-tuning<br />

adaptive control systems. For instance, consider a self-tuning P-I-D controller.<br />

Here, the control law can be expressed as<br />

u(t) = KP e(t) + KI ∫ e(t) dt + KD (de/dt )<br />

where e (t) denotes the error (desired output ⎯ computed output), u (t) the<br />

control signal <strong>and</strong> KP, KI <strong>and</strong> KD are the proportional, integral <strong>and</strong> derivative<br />

co-efficients. The optimization of KP, KI <strong>and</strong> KD is required to satisfy some<br />

criteria, like minimization of the integral square error:<br />

ISE = ∫ e 2 (t) dt.<br />

-<br />

Output instances<br />

Error vector<br />

GA here may be employed to emulate various control laws by r<strong>and</strong>omly<br />

selecting different vectors [ K p KI K D ] T . In other words these vectors<br />

represent the population. The ISE, here, has been used as the fitness<br />

-<br />

+<br />

+<br />

d1<br />

d2<br />

d3

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