The exhibition at the New York Hall of Science helped me to explore how machines and living things sense changes in their environment and how they adapt as a result. A wide range of mechanical and biological systems use the same essential method, called "feedback". At the museum I was able to pedal an airplane propeller, direct a chain on a spinning windmill and observe an old-fashion steam engine as I explored self-sensing machines and how they work.The organization for the automatic regulating of an electrical, mechanical, or biological system by sending part of its output as input is feedback. An example of feedback is a governor of an engine. If the speed of the engine exceeds a certain limit, the governor reduces the supply of fuel and hence the speed decreases. Electronic control systems employ feedback extensively. In voltage and current systems, part of the output is used as a control input, and this provides the system with self-regulation. An example would be if the output becomes too large, it acts through a feedback loop that causes it to reduce itself. Living organisms such as human beings possess feedback control systems that are of great complexity. For example, when your hand reaches for something, the information about its position is continuously fed back to the brain, by both the eyes and by nerves in the arm; the brain uses the information to lead the hand to the object. Another example of feedback that occurs in the human body is while your taking a shower. Before you get into the shower you feel the water to make sure that it is the right temperature. If it is not then you control the hot and cold water until your desired temperature is achieved. Such feedback can be called voluntary, since it is under conscious control. Automatic, involuntary feedback is also taking place as well, controlling processes such as respiration, circulation, digestion, and helping to maintain body temperature. There are many d...
