Nonlinear compensation of an aircraft instrument servomechanism by analog simulation

Combination of certain analog computer techniques with the direct synthesis philosophy applied to a particularly appropriate servo configuration results in a method for direct specification of compensator design. The method centers about a calibration technique which is simple and easily applicable to nonlinear control systems of considerable generality. Mathematical representation of the physical system is maintained at the realistic level typical of analog simulation. A detailed description of the method is presented by means of its application to a practical example - nonlinear compensation of an instrument servomechanism. Equations governing the behavior of the unalterable components were written and substantiated experimentally. These equations uniquely determine the form of the ideal compensation for the designated system performance and system configuration. The actual unalterable elements are then employed as an analog simulator to "compute" the specified compensator characteristics. A compensator possessing these characteristic is assembled and over-all system performance obtained. An electronic analog computer is employed as a computer simulator for this work. The majority of servo compensators designed in the past has been of the Linear type. It is well known that this partiality is not due to superiority of the linear over the nonlinear kind but rather that linear designs have been much simpler to perform and nonlinear components hard to come by. The advent of analog computers, the extensive progress made in components development, plus the increasing need for "getting the most" out of available power transducers combine to encourage removal of the highly restrictive linearity condition. Nonlinear design techniques available to the engineer have frequently 0 suffered from mathematical complexity or computational drudgery on the one hand, or unrealistic simplification on the other. Recently, however, considerable progress has been made in the region between these extremes. This paper attempts to further such progress and its dissemination.