Digitalization of continuous control systems

Abstract

This paper deals with the development of methods for analysis, and derivation of computer programs, for digitalizing continuous control systems. More spe cifically, 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 do main. 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 com pensate 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.