Digitalization of continuous control systems

Abstract

ACM. He is the recipient of a Northrop Scholarship, a Telemeter Magnetics Fellowship, and a faculty citation from UCLA. FOREWORD This tutorial paper, through a series of examples, covers the elements of continuous and sampled-data control systems including time and frequency analysis, z-and modified z-transforms, and the simulation of a hybrid control system (i.e., a system consisting of both analog and digital equipment) on a hybrid computer. The example considered in the second half of this paper consists of a continuous control system of known characteristics. An &dquo;equivalent&dquo; digitalized feedback network is then designed, and the results of simulating this new system are presented.Hence, the characteristics of both systems can be easily compared. Such topics as computation delay, extrapolation, quantization error, hold devices, and sampling rate are discussed. Work related to the example given in this paper has continued into the area of adaptive systems and variable sampling rate, both areas of which are important when using a time-sharing digital computer in which the amount of computation time is to be minimal. ABSTRACT This paper deals with the development of methods for analysis, and derivation of computer programs, for digitalizing continuous control systems. More specifically, given a continuous control system, we wish to determine an "equivalent" computer program to take the place of some analog shaping network in the system. An equivalent program is one for which the response of the digital system approximates the response of the continuous system in the time domain. Time and frequency comparisons between the responses of continuous and digitalized systems to step inputs are given. Equivalent computer programs for various standard shaping networks are derived.Revised programs are determined, where use is made of prediction and extrapolation techniques to compensate for digital computation delay time.Finally, the feedback network in a missile control system containing an unstable aerodynamic airframe is digitalized, and the simulated system is run on an analog-digital hybrid computer system. Results are given, indicating system performance as a function of sampling rate, computation delay, and system gains.