Question: Can a control system include a human operator as a component?

Chapter(s)	Introduction
Author(s)	Steve Waydo
Date	2004/09/28

Absolutely! Any time the output of one system influences a second, which in turn influences the first, we have a feedback system. If the purpose of the second system and the feedback connection is to alter the dynamics of the first, we have a control system. If one of the systems is a human operator, we have a "human-in-the-loop" system. A very early example of this is the Wright Flyer, described in the reading. The aircraft itself was unstable, and the pilot was a critical component of stabilizing the system and making controlled flight possible. The difficulty of analyzing human-in-the-loop system lies in modeling the behavior of the operator, which in general is much more complex (and non-smooth) than an engineered system. This is a very active area of current research.