Bennett Stuart. A History of Control Engineering, 1930-1955

Peter Peregrinus Ltd, 1993. — 250 p.In 1930 the behaviour of the many devices and systems incorporating feedback loops was poorly understood: at the most fundamental level there was still confusion between positive and negative feedback. The crucial role of time delays-both time constants and transport lags -was not understood and engineers attempting to build control systems lacked both the theoretical and practical tools necessary to construct such systems. Engineers turned to feedback control only when they found themselves at an impasse. The lack of knowledge and understanding of the effect of feedback in systems resulted in reverse salients developing in many areas of engineering and, as a consequence of this, there was greater interest in the problems of control. Gradually, engineers began to realise that feedback control was not just a last resort solution, but an essential part of complex engineering systems. The changes taking place were described in an article published in 1930 in the newly published journal, Instruments: Great as has been the extension of temperature control in industry, it is in its infancy, and its adolescence waits upon the growth and manifestation of a greater interest on the part of precisely that group of industrial engineers who would reap its greatest benefits. Let us not forget that there is a limit, after all, to the mind-reading ability of the instrument maker and to the power of advertising and salesmanship. The further development of automatic control and of controllers, demands first, a greater temperature consciousness on the part of prospective users of temperature controllers in industry; second, the granting of a freer entree to instrument men by the former and, third, a more receptive attitude on the part of the equipment manufacturer. It is high time for builders and manufacturers of furnaces, kilns, melting pots and tanks, lehrs, ovens, boilers, kettles, stills, towers, vats and of all other diversified industrial equipment, to realise that some among them are holding up the procession. It is high time for all to follow the example of a few who make ‘controllability’ a part of design routine.