Pulsed Analog Computer for Simulation of Aircraft

This article describes the logical design of a pulsed analog-digital computer which could be used to solve the system of nonlinear differential equations normally encountered in the simulation of aircraft. The design calls for a magnetic drum to perform the functions of storing the program and the aerodynamic data required in the computation. Time-shared analog computing elements encompassing the normal arithmetic operations of addition, subtraction, multiplication and division are used. They are connected to a common bus through gating circuits. In addition, electronic integrators (one for each integration required) and analog-storage elements are provided. Utilizing these elements sequentially, it is possible to complete a computation cycle in each revolution of the drum. Function generation is accomplished in this computer by means of specialized circuitry which determines the position of the four surrounding break points of a given value of a function of two or more variables. The discrete values of the function at the break points are selected from digital drum storage for an interpolation procedure. A type of "floating point" system is included to scale automatically all voltages to fall within optimum levels for the operating elements. The computer appears to offer the advantages of flexibility, compactness, ease of programming, and economy commensurate with the limited accuracies required in flight-training simulation.