Analog Computers

English translation

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Analog Computer Dornier 720

This document is an English translation of the original German-language brochure “Analogrechner Dornier 720” published by Dornier Electronic (Dornier AG), Friedrichshafen.

Introduction

The DORNIER 720 is a fully transistorized precision analog computer with a computing voltage of 10 volts. It is designed in a modular architecture that allows it to be configured to meet widely varying requirements. Starting from an economical basic configuration with a maximum of 145 amplifiers, the DORNIER 720 can be populated such that 36 of these serve as electronically controlled integrators.

Fully equipped, the DORNIER 720 forms a highly capable hybrid analog computer suited to solving nearly all problems in science and technology involving analog computation. Its mature design concept permits simple coupling to a digital computer for the purpose of hybrid computation — a task for which the DORNIER 720 is particularly well suited, not least because of its electronic servo-potentiometers (setting time: 10 milliseconds).

A high degree of flexibility for users of multiple Dornier analog computers is achieved through the interchangeability of computing elements between the DORNIER 720 and the DORNIER 240. This allows an optimum configuration for each individual machine when operated as standalone units.

Display and Control Panel

The display and control panel in the middle section of the DORNIER 720 contains all elements required for machine operation and the servo-potentiometer coefficients.

At the top is a row of indicator lamps for the digital voltmeter (Anzeigevoltmeter) and the servo-potentiometer coefficients.

The four-digit address of a computing element is entered via the white keys at the lower portion of the panel, numbered 0 through 9 in sequence. For example, pressing keys 2, 3, V, 07 selects amplifier No. 7 in sector 2, and the output of that amplifier appears on the digital voltmeter. Address entry is signaled by the blinking of the address display. Selection of the computing element requires pressing a series of keys in order:

  • ERHÖHEN: Increments the address register by one.
  • AUTOM. ERHÖHEN: Automatically increments the address register by the set increment.
  • All valid addresses are accepted (e.g., for automatic sequential measurement of potentiometer settings).

The ten white keys serve for coefficient entry. After entering a potentiometer coefficient, pressing the POT SET key causes a digital command to be sent to the potentiometer. In AUTOM. SETZEN mode, the coefficient entry is performed automatically after key 4 is pressed. For servo-potentiometers there is a digital individually adjustable potentiometer with a setting time of 10 ms.

The DIGITALRECHNER key (Digital Computer) passes control to the connected digital computer. Operational control is then accomplished via the digital computer interface. The operating mode keys are: POT (set potentiometer), AB (initial condition), HT (halt), DR (continuous run), and RR (repeat calculation). These allow individual selection of the computer operating modes. The keys X10, X10, X100, X1000 allow selection of time scale factors by those ratios.

The Repetierstart in operating mode RR starts the computer cyclically from the standard minimum install time set at the potentiometers (values between 0 and approx. 78 Hz are pre-wired). An optional built-in digital clock drives the three operating modes AB, DR, and HT in sequence; the clock runs from 1 to 99 seconds.

Control in operating mode RR likewise starts cyclically by adding the auxiliary amplifier. The RAMP function in operating mode DR generates a slow ramp as a reference for the slowly increasing (zeroing) of reference variables. The STFSF function (statistical setting of function generators) serves as the reference for variable function generators. Pressing keys INT SP and INT SP x 1 mixes the variable auxiliary amplifier to the sum of all input voltages to the amplifiers. The sum gain is 1 or 0.1, respectively.

Logic Add-on

On request, the DORNIER 720 can be fitted with an extensive logic add-on whose full expansion is described further below. The logic add-on has its own operating mode control via the AB and ASYN keys. The ASYN key enables all 24 flip-flops to switch between synchronous (clocked) and asynchronous (unclocked) operation. With key AB, all flip-flops can be reset to a defined initial state. A further run-through then begins again. The general LÖSCH key clears all flip-flops and counters.

Each of the six indicator lamps is of the type employed as Drucktasten (push-buttons), and the state of the flip-flops is always reset and described in terms of their meaning. Above these keys, the counters can be pre-set.

The analog programming board makes six operating mode control lines available, and the digital signal lines HT and DR can be looped through for logic control. The logic add-on also provides a clock generator whose frequency is adjustable via the Rändel (thumb wheels) in the range of 1 to 99 per second. The clock generator can be set in 1 MHz steps to triple, decade-adjustable values. Each counter state is shown in the LED display.

The logic add-on offers a convenient digital clock generator at all computing signal outputs as well as separately available logic programming boards. The servo-potentiometers can be set to a special coefficient mode without forced initialization of current machine states.

Application Areas

Analog computers are used wherever differential equations must be solved. They enable, among other things, real-time simulation of dynamic systems, and reduce the time and cost of complex, expensive, or hazardous practical experiments.

Typical analog computer problems arise in the following areas:

  • Control engineering: Simulation of control systems, parameter studies, frequency response measurements
  • Aeronautics and astronautics: Simulation of aircraft and spacecraft flight dynamics
  • Medicine and biology: Simulation and investigation of biomedical processes
  • Automotive industry: Vibration problems, investigation of vehicle behavior
  • Nuclear engineering: Reactor simulations
  • Chemistry: Simulation of chemical reactions
  • Education: Demonstration of dynamic processes
  • Measurement technology: Filter design, adaptive systems

Use in Hybrid Computing Systems

The concept of the DORNIER 720 enables its use as the analog component of a hybrid computing system. The external inputs/outputs for computer control and monitoring of operational modes, etc., are pre-wired in the 720 base unit. The analog programming board includes a standard 78-position analog programming field and a 90-position logic programming field, as well as connections to and from the connected coupling network.

In particular, the rapid electronic servo-potentiometers and the fully electronic control of all main operating modes allow comfortable hybrid computation. The servo-potentiometers can be set to a special coefficient mode without forced initialization of current machine states, thereby eliminating automatic destruction of the current values of the individual variables.

Further details on hybrid computing with the DORNIER 720 can be found in the relevant specialized documentation.

Layout of the Programming Board

The programming board of the DORNIER 720 is divided into six identical sectors. The numbering of individual computing components (amplifiers, potentiometers, etc.) is repeated in each individual sector, so that specifying an element’s address also indicates the sector in which the element is located. For example, the specification 3/V07 refers to amplifier No. 7 in sector 3.

Each sector is subdivided into three modules, of which the two outer ones (Type I.005) are identical and the inner one (Type I.105) differs. These modules accommodate the computing elements (relays, Beschaltungswiderstände/termination resistors, etc.).

Each individual plug-in board position within a module is numbered from bottom (1) to top (8), so that the position can be determined from the sector, module, and card position.

The positions within a module carry the following components:

Module I.005:

  • Positions 1 and 2: Summing amplifier
  • Positions 3 and 4: Summing amplifier/integrator
  • Position 5: Comparator and switching network
  • Position 6: high-quality Multiplier 3.030
  • Positions 7 and 8: two Multipliers 3.040

Module I.105:

  • Positions 1 and 2: Summing amplifier
  • Positions 3 and 4: Summing amplifier/integrator for 2 integrators
  • Position 5: Comparator and switching network for 2 integrators
  • Position 6: 7-bit digital potentiometer
  • Position 7: fixed diode function generator
  • Position 8: fixed diode function generator

Additionally, each module’s plug-in board positions include connections for reference voltages, potentiometers, auxiliary multipliers, control inputs, function relays, and the connections for a function switch.

Further details can be found in the photograph on the adjoining page.

Programming Board — Annotated Example (Pages 10–11)

(The final pages show detailed color photographs of the programming board with annotations identifying key connections and component positions, including:)

  • Amplifier 2 as auxiliary amplifier for Mult. A
  • Inputs of Multiplier A
  • Amplifier 1 with limiter populated
  • Inverting output of Mult. A
  • AB-input of Integrator 3
  • Input FDFG
  • Amplifier 5 populated with FDFG
  • Output FDFG
  • Amplifier 7 with 10 kΩ feedback
  • Output auxiliary amplifier
  • Amplifier 11 as summing amplifier
  • Amplifier 11 with extended inputs
  • Outputs operating mode control
  • HT-inputs for Integrators 3 and 4
  • Comparator
  • Logic connection lines
  • Amplifier 8 as complementary integrator
  • Amplifier 3 and 4 as integrator populated
  • DR-inputs for Integrators 3 and 4
  • Amplifier 7 as auxiliary amplifier for 7-bit digital potentiometer
  • Amplifier 13 as integrator with time constant × 100
  • Variable diode function generator

(Page 11 shows the external connection lines of the programming board in a full-color layout, including REFERENCE, REF, AUTOM., GIG POT, KONDENSATOR, BEINIESART, and EXTERN. VERBINDUNGSLEITUNGEN (external connection lines) sections.)

Publisher Information

Dornier AG
Vertrieb Electronic
799 Friedrichshafen
Postfach 317
Tel. (07545) 811, App. 2678
Telex: 07-34372