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Hurricane Katrina forced my friend Steve O’Keefe to evacuate New Orleans, but thanks to local blogs he has been able to keep up with what’s happening in New Orleans right down to the neighborhood level. He also made his own urgent calls here on how to help those left behind. In both cases, we see individuals using blogs to create ad hoc communication channels that provide vital information and perhaps help save lives.

This is an example of how Blogs and other Internet technologies, such as websites and email, are facilitating the growth and speed of networked social feedback loops. Such feedback loops are not new, but their numbers and power have been multiplied and amplified by the Internet and other electronic media.

To appreciate the power of feedback loops, it’s useful to look at its application to feeding technology. Accurate feeder control depends on the microprocessor and its ability to process timely data from a feedback loop on what’s happening as the feeder discharges.

A Brief Explanation of Feeders and Feedback Loops
You can think of feeders as automation’s alternative to a scoop or shovel. A feeder delivers bulk material (usually dry, though liquids are also fed) into a process. It’s a feeder, not a scoop, that puts the two scoops of raisons into your breakfast cereal.

Volumetric feeders are the simplest type of industrial feeder. As the name implies, they measure material by volume. Most use a screw or auger to deliver the material into the process. An open loop control on a volumetric feeder provides no feedback as to how the feeder is performing. You're feeding blind and have no way of knowing (short of watching it) whether the feeder is running at all. A closed loop control tells us only whether the feeder motor is running at the speed we expected. It does not tell us if material is actually being delivered into the process, nor does it tell if the amount of material delivered is exactly what we wanted.

Gravimetric feeders, such as loss in weight or weigh belt feeders, tell us how much material was actually delivered by weight. Since weight is a more accurate measure than volume, the feedback information is more reliable than what can be expected from a volumetric feeder. Since the weight feedback is fast, as well as accurate, it is also possible for the controller to adjust the feed rate on the fly to makeup for variations in bulk density. This ability to monitor and adjust continuously is essential to producing many modern materials, ranging from high-tech plastics to life-saving pharmaceuticals.

Social Feedback Loops
Consider now, the feedback loops found in the business, economic and political arenas--the social feedback that keeps an organization or a society on track. In business, price and profits are the main signals that keep companies in business. In economics, we’ve seen that--despite its apparent chaos--a free market works better in the long run than a command economy because the market has more information and more accurate feedback mechanisms. In government--for all its apparent inefficiency and noise--democracy governs best because it is structured to seek and respond to the flow of information from a diverse public.

Feedback Is Important to Industry and Society
In industry, we see that feedback keeps a process on track so it achieves its targeted outcome. For those tasked with designing industrial control technology, the microprocessor was a liberating force that allowed a precision in machine and process control that simply wasn't possible with mechanical controls.

Today, it's remarkable to see how closely computer-aided human interactions have begun to parallel earlier developments in computer-aided machine interactions. That is, the networked computer has greatly expanded and enhanced the ability and ease with which we can give, receive and process feedback of a social nature. One of the more promising aspects of the blog is its power as a feedback loop.

Don Dunnington

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