Real-Time Analog-Digital Computation

The relative advantages of analog and digital techniques in simulating complex, nonlinear systems in real-time are discussed. A hybrid configuration is suggested consisting of a basic digital computer and peripheral, high-speed analog elements used on a time-shared basis under the control of the digital program. Programs for function generation and for the solution of the aircraft roll equation are presented to illustrate the operation of the hybrid computer and the significant increase in the effective computing speed of the digital computer that results from the incorporation of peripheral analog elements. Further gains can be made by tailoring the order code and logic of the digital computer to the specific problem class of interest. The hypothesis is presented that a hybrid computer is technically feasible today that would be competitive with analog techniques on the basis of both cost and the ability to simulate natural aircraft frequencies in real-time. Moreover, such a computer would offer substantial advantages with respect to accuracy, dynamic range, flexibility, size, power consumption, and reliability.