Abstract
This paper gives standards for the presentation of frequency-response data. The standards are recommended by the ASME-IRD Dynamic Systems Committee to facilitate the exchange of information directly and through the medium of publications. The Committee recommends that magnitude curves be plotted on logarithmic co-ordinates, and phase on the linear scale versus frequency on the log scale. Further recommendations involve transfer functions, measurements, nonlinearity, ambient effects, and other factors. The paper was written with the technician in mind, as well as the automatic control engineer and scientist. For this reason the reader with little or no mathematical background is carried as far as possible into the theory of the frequency-response field. Basic design criteria, in common use, as well as others, are given, and it is shown that control design, in so far as dynamic performance is concerned, can be reduced, at least in rough analyses, to simple properties of curves that may be either theoretically or experimentally obtained. From the slope of one such curve the designer can often say whether or not a controller will be stable when placed on the system to be controlled. It is hoped that this paper will enable as many readers as possible to start on the scientific design of controls, and where they do so to use the standards here recommended. It is not implied that the reading of this paper is a substitute for a knowledge of some of the vast body of mathematics on which it is based. One objective of the paper is to give management, at least technical management, some insight into how automatic controls can be designed scientifically. The paper concludes with a discussion of the role the frequency-response approach plays among the design techniques available to the worker in the automatic control field.
