Under Control


Data collection has to be the most boring subject ever. How do I psyche myself up to talk about data collection? Bland city! Or so I thought. But as I started to write, I began to see that maybe the subject had some merit after all. Lets give it a shot.

The main theme of this issue is "Data Collection," the real technology problem today is implementing and maintaining complex systems. Sensing technology is adequate for today's computer and control systems, but changes are coming.

This magazine is Manufacturing Systems , not Manufacturing Components. We need to look at data collection as the sensory segment of a large, complex enterprise system, a piece in the overall system. The data collection segment of any system has no intellectual function. It exists to supply an image of the world state for the integrated enterprise.

Sensors transform the raw data into a form compatible with the processing expectations of the computing units. Sensor technologies such as bar codes convert labels into digital information. Using the location of the sensors, digital processors can infer the state of the system.

Often overlooked is the LAN used to send the sensed and converted information to the central or distributed computers. This is similar to the retina and optic nerve-system of the eye. Raw data (photons) changes into a form suitable for brain processing. The retina also compresses the image for transmission over the optic nerve.

These views allow us to predict future trends. Let's take a stab at a few:

We will be using bandwidths of 100 megabits (FDDI-the Fiber Distributed Data Interface standard) in the future to match the near-term computer power.

Generic primitive transforms on the data will make standards of sensing applicable to the industry.

Transformation of data will not be to identify "package number" or "temperature - F" but will match LAN requirements.

Linearization, identification and other application specific sensing will give way to transmission of raw information as described by C. Shannon in his 1948 paper on information theory.

When the volume of the data is high, cost is one of the major issues. Jim Pinto of Action Instruments suggests that the Echelon network and his ASIC (Application Specific Integrated Circuit) working together will improve the price / performance of analog sensing by a factor of ten.

Spread spectrum radio, powerline transmission, fiber optics and copper will soon play a strong role .

Sensors themselves will be more reliable and faster than today's offering. Most of the PLC vendors use the T1 rates (1.544 Mb) to collect data. This rate is at least one order of magnitude too slow.

As next-generation controls enter the market, next-generation sensors will have to be ready. The next-generation controller (NGC) effort of the Air Force under the direction of Martin Marietta, will demand new standards of performance. Independent Canadian, German and Japanese advanced controller efforts may eclipse the US effort. Data collection technology will keep pace with these fast moving events.

Standardization, high-speed generic sensing, and ability to send large masses of data to demanding computers must be the offering of the modern vendor of sensors and sensing systems.

Recently, I was at the supercollider site in Texas. This site requires more than 50 miles of control. The 250,000 points of control require fast conversion and transmission to the processing and control computers. By comparison, a single department in discrete manufacturing may now have 3000 points of control, mostly binary. Newer process ideas and implementations will require 10,000 points of analog for the same area. Enterprise requirements of high-speed conversion and transmission of more than 100,000 points will be common in the next decade.

Data collection is not the issue, but matching the sensing to the needs of the application is. Success is awareness of the world around us, and data collection is a part of it.

As appeared in Manufacturing Systems Magazine February 1992 Page 56

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