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Analog Computers Solve Complex Problems
November 1951 Radio & Television News Article

November 1951 Radio & TV News
November 1951 Radio & Television News Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

Charles Babbage's 19th century Difference Engine might be considered the beginning of complex mechanical calculators' use in science and engineering. It really was not all that long ago. Massive single-purpose analog computers were designed and constructed in the middle of the last century for calculating, among other things, projectile trajectories, multi-body orbits, electrical circuit functions, nuclear detonations, calculation of mathematical function tables, and navigation. Eventually electrical computers joined the arsenal of tools available to significantly reduce the amount of time required to carry out complex calculations requiring multiple iterations using a range of input variables. Programmable vacuum tube and then transistorized digital computers expanded the range of applications, but recall that even by the early 1960s, during the early manned space flight projects, human "calculators" were employed by NASA, corporations, and universities to turn out reams of pages of numerical calculations. As is often pointed out, your cellphone has vastly more computational power than the best computers of the Apollo era.

Analog Computers Solve Complex Problems

Analog Computers Solve Complex Problems, November 1951 Radio & Television News - RF CafeBy Louis L. Grandi and Don Lebell

University of California, Dept. of Eng., Los Angeles

The University of California has within the last few years added four new analog computers to its facilities. It is the first time in West Coast history that such an elaborate array of equipment has been made available to students, staff members, and industry.

The complex-looking piece of equipment pictured on this month's cover is one of the four analog computers operated by the Engineering Department of the University of California on its Los Angeles campus.

Although such equipment is in operation at other locations throughout the country, this installation is the first on the West Coast. This means that not only can students receive thorough practical training on this increasingly-important equipment, but manufacturers in the West Coast area have such facilities immediately available for the most expeditious handling of their research problems.

The analog facilities include a thermal analyzer, a mechanical differential analyzer, an electrical differential analyzer, and a network analyzer. These four units comprise a formidable battery of research weapons in widely diversified fields of endeavor.

Presenting a problem to network analyzer equipment - RF Cafe

Presenting a problem to network analyzer equipment.

View of University of California differential analyzer - RF Cafe

View of University of California differential analyzer.

Electronic analog simulating equipment - RF Cafe

Electronic analog simulating equipment. This is part of the one-hundred amplifier installation and demonstrates the solution of a simple beam problem. Equipment was built at University.

Output table of differential analyzer - RF Cafe

Output table of differential analyzer. "Solutions" appear on graph paper in the form of curves.

Wheel disc integrator of the mechanical differential analyzer - RF Cafe

Wheel disc integrator of the mechanical differential analyzer. A polarized light beam transmits integrator wheel motion directly to the torque amplifier unit.

Measuring the output data obtained from the mechanical differential analyzer - RF Cafe

Measuring the output data obtained from the mechanical differential analyzer.

In over-simplified terms, an analog computer is nothing more nor less than a piece of equipment which can be manipulated in such a way that it duplicates mathematically the physical problems under study.

Differential Analyzers

The University has two types of differential analyzers - mechanical and electrical. Basically, both differential analyzers are the same - the function of each varying only slightly to handle the different requirements.

The electrical differential analyzer is interconnected in accordance with a carefully prepared schematic diagram. The resulting system thus becomes a physical counterpart of the mathematical equations being analyzed. Where it is desired to set up a physical reproduction of an electrical circuit for analysis and study, voltages are used to represent the terms of the original equation. By varying the voltages, the mathematical functions of addition, multiplication, integration, and differentiation may be performed in the circuit. In addition, the analyzer can be used to generate particular functions within the machine. Components are available in the equipment to supply special "engineering functions." Output information is obtained from the screen of an oscilloscope.

This particular unit has been used in primary research on transformer equivalent circuits, to obtain data on relay servomechanisms, and to determine structural characteristics of critically loaded beams.

In general, the electrical differential analyzer can handle mathematical problems involving simultaneous, nonlinear differential equations with variable coefficients. In the realm of physical sciences, the analyzer will handle systems containing nonlinear, lumped parameters.

The mechanical counterpart of the electrical differential analyzer solves problems involving physical properties reduced to mathematical equations. This is accomplished by interconnecting the basic units (integrators, adders, multipliers, etc.) in accordance with the equations being studied. Unlike the electrical differential analyzer, the circuit variables are mechanical, thus the actual variables correspond to the angular displacement of the shafts in the machine.

The equipment features a flexible system whereby the units that perform the basic operations of addition, subtraction, multiplication, division, and integration can be interconnected to meet the particular requirements of the problem being studied. Functions that cannot be expressed as simple mathematical functions can be handled directly in graphical form by means of special input tables. This feature permits the solution of problems which contain functions capable of being expressed graphically.

Problems involving the flight and stability of aircraft, airfoil de-icing, landing gear design, missile trajectory, missile stability design, and stresses in aerodynamically loaded wings in aeronautics and the field of aerodynamics can be handled by this unit. In the electrical and electronics fields, this equipment can be used in research problems arising in the design of pulse transformers, in electron accelerator studies, in engineering magnetic amplifiers, and in determining electron trajectories. The fields of oceanography, meteorology, servomechanisms. geophysics, and fluid flow can all be served by presenting the basic problems to this analyzer.

Network Analyzer

 - RF Cafe

Working a problem on network analyzer.

The University's a.c. network analyzer differs from the differential analyzers in that it is best suited to the solution of problems by means of physical duplication of the problems rather than by breaking down the problem into a mathematical formula and then feeding the problem to the machine.

This unit consists of banks of resistance, inductance, and capacitance elements which can be varied individually to simulate the circuit conditions of the network under analysis. In addition to these components, the analyzer contains a number of generators, a switchboard-type interconnecting system (patch panel), and all of the meters and testing devices necessary to record the circuit's performance.

For example, in operation a large power system can be duplicated in a limited space by replacing the various elements of the power system with equivalent electrical circuits. It can also be used to solve problems where the equivalent circuits consist of multiple networks of lumped R, L, and C circuit elements.

The network analyzer has proven to be of particular value in handling such problems as load division, short circuit, and stability in electrical power systems and in providing the analogs of heat transfer, mechanical vibrations, and in intake and exhaust gas systems.

Thermal Analyzer

The thermal analyzer was designed and completely constructed by the University's Department of Engineering. It is used primarily for the solution of heat conduction problems. Like the network analyzer, it is particularly valuable in cases where the particular problem can be duplicated physically.

The unit consists of sections of resistance-capacitance elements of different values which can be connected into the networks and to various types of voltage and current generators. These generators are used to simulate the heat sources and impose the boundary conditions of the problem.

Each section of these RC elements contains two independently variable resistors which are used when two-dimensional heat flow problems are under consideration. The desired solutions appear in the form of oscilloscope traces or as meter readings.

This analyzer has been used to handle such diversified problems as aircraft icing, temperature distribution in gun barrels, forest fire control research, foundry studies, and various phases or melting and freezing processing.

Today the University of California has the research tools required by industry, pure science, and in basic research and foremost among these tools are the analog computers which can be used in man's quest for knowledge.  

 

 

Posted September 15, 2020

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