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Since our interest is frequently in the dynamic behavior of physical systems, the
mathematical equations are usually differential equations having time as the in-
dependent variable.
In order to solve such equations, the standard components of
the computer must perform the following operations: inversion, algebraic summation,
integration with respect to time, multiplication and division, and function generation.
The sequence of steps for constructing a dynamic model on an analog computer requires
first a mathematical description of the physical system, usually in equation form.
From this description the operator derives the information necessary to set up a
computer program for interconnecting the computing components and determines the
required initial conditions and forcing functions.
The computing components are
interconnected with wires called patch cords.
The input and output terminations of
the computing components are brought out to a patch bay which is usually fitted with
a removable Pre-Patch Panel so that patching may be accomplished away from the com-
puter.
The problem is placed on the computer by inserting the patch panel and ad-
justing the problem parameters to the value of the first case to be investigated.
Selected voltages are applied to various components in the form of inputs or initial
conditions.
These voltages
are derived from a precise reference voltage.
Once the computing elements have been patched, adjusted, and energized, the computer
is switched into the operate mode.
The.voltages on the computer change with time in
accordance with the equations that govern the physical system variables.
The be-
havior of the computer model is viewed through an output device such as an X-Y plotter,
oscilloscope, strip-chart recorder, or digital voltmeter.
This TR-20 Reference Handbook has been prepared to serve as a working guide to the
analog programmer or computer operator.
The information contained presupposes a
knowledge of the analog computer, its basic principles of operation, and programming
procedures.
(Instructional information in these areas can be obtained from "Basics of
Analog Computer Programming"
by the
EAr
Education and Training Group.)
Reaaers
interestea in more detailed circuit information are referred to the TR-20 Maintenance
·Manual.
2
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