More from 1954… Industry’s Pulse
Happy 60th, Control Engineering! Our magazine first published in September 1954. This monthly column in 2014 will resurrect some of our favorite material from the 1954 and 1955 issues. Technologies have progressed, but they continue to pave the way for today’s innovations. Here is a full-length article penned in 1954 about the complexity of control engineering and how associations are developing a common language for engineers in the field.
Pity the ambitious technician who wants to study up on control engineering. He borrows a couple of standard texts and wades in. Almost immediately he runs into a wall-a barrier of words. The engineers who have roused his interest in the subject and the authors of both texts are all speaking different languages. His enterprise squelched, the poor technician abandons his program of self-improvement. If his is a sensitive nature, he may flee to a job in a bakery, where flour is flour, dough is dough, and an oven is unambiguously an oven.
The sad fact is that the man who would keep up with control engineering today must be, to be a great extent, multilingual. The concept and practice of automatic control has many roots, which are only now merging into a main stem. Engineers who entered this field by way of the process industries tend to think and talk in terms of valves, nozzles, and other hardware. Those who made their approach through servomechanism theory modulate their speech with the dynamics of components and systems.
Several dialects and dozens of pet terms introduced by various experts further muddy the linguistic stream. So horrendous is the semantic confusion that a speaker at a recent meeting on automatic control complained afterward that he could hardly fathom the two papers preceding and following his own.
Fortunately, control engineering has its own lexicographers. With remarkable patience, these few men have been defining a language common to all approaches to their field. In the United States to date, the most comprehensive results have come from two groups: the Terminology Committee of the Instruments and Regulators Division from the American Society of Mechanical Engineers (ASME), and the Subcommittee on Terminology and Nomenclature of the Feedback Control Systems Committee from the American Institute of Electrical Engineers (AIEE).
The ASME has been laboring at the language problem for 11 years; the AIEE for five. Their latest proposals, released last June and April, respectively, are reassuringly similar.
First, the committees agree that the performance of all control systems can be discussed in terms of a simple and basic block diagram. Whether the system is a gun pointer or a petroleum fractionating tower, the same concepts apply.
The committees are likewise in full accord on the symbols they use to label parts of the block diagram. With a charitable attitude toward typist and printer, they have stuck to the English alphabet. The thetas, indicative of rotary motion, suit servomechanism thinking. But they don’t apply generally to all means of control. So, they had to go. Other taboo letters were "d", which might be confused with differential, and the operators "s" and "p."
Agreement on specific terms is less close. But for 15 basic words, most relating to the block diagram, the committees have essentially identical definitions. Each term applies to all the jobs that automatic controls can handle. "Error," for example, is a descriptive word in the discussion of servomechanism positioning. However, it is inappropriate to the control of fluid flow in a chemical plant. Here, both committees endorse "actuating signal" to label the force that directs a controller to take action.
A standard terminology is in sight. The American Standards Association (ASA) is now setting up a committee to write the dictionary of automatic control. The committee will draw representatives from some 30 or 40 technical societies, government bureaus, and industry groups. With each member organization having, in effect, one vote, progress may be slow. But the very breadth of the consensus should produce a readily accepted standard.
The men who have been wrestling with the terminology problem for years cautiously avoid predicting when the ASA committee will finish its task. It may well be 10 years before every term and symbol is settled upon. Even if standardization takes somewhat longer, control engineers will have a decided edge over mathematicians, who pride themselves on logical and unambiguous thinking. Almost three centuries ago, Sir Isaac Newton and Baron Gottfried Wilhelm von Leibniz independently developed differential calculus. Each had his own symbol for the derivative of a function. Did their followers standardize? Indeed not. With high disdain for the universality of their language, they created a whole family of symbols, all meaning one and the same thing.
Our policy: Much as they would like to, the editors of Control Engineering will not attempt to specify the terminology that will be used in this magazine. For the time being, Control Engineering will follow ASME and AIEE proposed standards wherever they agree. And when the new ASA committee promulgates its standard, this magazine will adopt it as the universal language of automatic control.
– 2014 Edits by Chris Vavra, content specialist, CFE Media, firstname.lastname@example.org