Motion control from the archives

This motion control product and technology roundup looks at motor, motion, and drives developments from 60 years ago through 2008, with more than 20 historical images. Original wording of excerpts from the pages of Control Engineering has been kept where possible to portray the flavor of the times. See added remarks; add your comments.


Providing a retrospective into the world of motion control technology, on the occasion of Control Engineering's 60th anniversary, magazine archives deliver an amazing glimpse of what was available since 1954. Various motor and motion control developments were covered in the main article "Electronic motion control, then and now," appearing in Control Engineering's 60th anniversary issue, September 2014. This motion control product and technology roundup online looks at motor, motion, and drives developments from 60 years ago through 2008 in this online extension (3 of 4) of the main article.

"Content for engineers" was a guideline for Control Engineering magazine long before that phrase became part of the name for its present company, CFE Media. (CFE stands for Content for Engineers.) Original wording of excerpts below from the pages of CE has been kept where possible to portray the flavor of the times. Company names and locations are as they were then. Some editorial remarks provide context and commentary as indicated in square brackets. (Add your comments at the feedback area at the bottom of the page.) Online links supplant standard reference information for items after 1997.

50 to 60 years ago: Magnetic amplifiers, silicon rectifiers, turnoff SCRs...

Figure 1: Magnetic servo amplifier, Dec. 1954. Courtesy: Control Engineering archiveBasic Facts about Magnetic Amplifiers

Harold A. Goldsmith, Herbert Herz, Barney J. O'Neill, Magnetic Amplifiers Inc., Dec. 1954 Control Engineering, Vol.1, No.4 (pp. 40-47).

Magnetic amplifiers are among the most useful tools of modern control technology. They use the magnetic effects of small inputs to modulate large amounts of power. This article describes the performance of several good amplifier circuits, including two for specific servo applications. [Basic data for one of the applications, a medium-power positioning servo system, included]: Magnetic amplifier has 650 W output power, measures 10-3/8 x 20¼ x 8¾ in. [264 x 514 x 222 mm] and weighs 90 lb [41 kg]. Motor is a low-inertia, 2-phase induction servo motor that delivers 200 W to the load shaft.

Figure 1 shows a commercial version of a hermetically sealed push-pull magnetic servo amplifier.

Figure 2: High-power silicon, vintage 1955. Courtesy: Control Engineering archiveHigh-power silicon rectifiers are very efficient

New products, Sept. 1955 CE, Vol.2, No.10 (p. 191)

Newly available silicon rectifiers cover the voltage range from 10 amp at 50 v peak inverse voltage to 5 amp at 200 piv. They are rated to deliver continuous full power at 125 deg C. Silicon's high forward conductance and low leakage current give extremely high efficiency. In common applications, efficiencies range from 90 to 99 percent. Silicon exhibits no aging effects. The units are hermetically sealed and designed for conduction cooling. [See Figure 2; mouse over image to see caption.]

Transitron Electronic Corp., Melrose, Mass.

Figure 3: “Miniature” positional servo, Oct. 1955. Courtesy: Control Engineering archiveVolts converted to position through positional servo

New products, Oct. 1955 CE, Vol.2, No.11 (p. 104)

[The] mechanism is essentially a miniature positional servo. It converts an input voltage into a shaft position through the use of a servo motor and follow-up potentiometer. Internally the Datran Model C104 consists of a two-stage voltage amplifier, a magnetic power amplifier, a two-phase servo motor, a gear train, and follow-up pot. High accuracies despite normal line voltage variations are obtained through the use of the same power source for the input transducer and the servo. [See Figure 3.]

Datran Engineering Corp., Manhattan Beach, Calif.

Figure 4: Power transistor, March 1956. Courtesy: Control Engineering archiveTransistor dissipates 3.5 watts at 100 deg C

New products, March 1956 CE, Vol.3, No.3 (p. 126)

Said to be ideally suited for servo amplifiers, Type 970 silicon power transistor dissipates 8.75 watts at 25 deg C and 3.5 watts at 100 deg C. Power gain is 18 db at 25 watt output, class B operation.

Texas Instruments, Inc., Dallas, Tex. [See Figure 4.]

Consider Using Hybrid Amplifiers

George A. Attura, Industrial Control Co., May 1956 CE, Vol.3, No.5 (pp. 77-82)

A new technique is being used in automatic control—the hybrid amplifier. It's based partly on elements and components just recently developed and partly on older amplification methods involving the vacuum-tube amplifier with its associated components. [Comment: These amplifiers were intended for controlling 2-phase servo, PM dc servo, and torque motor types.]

Hybrids are formed by combining three signal amplifiers:

Vacuum tubes—Most widespread use, highly developed circuitry, appreciable dissipation per stage, reliability acceptable only with premium tubes and derated circuits, high stage gain.

Transistors—Recent development, manufacturing techniques not fully stabilized, circuitry under intense development, good reliability with best transistors available, low dissipation, moderate stage gain.

Magnetic amplifiers—High-speed circuits, core materials, and components well developed, good reliability possible, stage dissipation high in many circuit configurations, low stage gain.

[Comment: Magnetic amplifiers were high-tech items during the 1950s and 60s.]

GE, Westinghouse unveil turnoff SCRs

What's New, March 1963 CE, Vol.10, No.3 (p. 25).

New silicon controlled rectifiers can be turned off in dc circuits by drawing small reverse current from the gate for a few microseconds. Available now for 2 amps.

SCR Bang-Bang Control for Two-Phase Servomotors

D.J. Maxwell, Aeronca Mfg. Corp., June 1963 CE, Vol.10, No.6 (pp. 93-94)

Time-optimal (bang-bang) servomechanisms require the motor control circuits to apply full power forward, then full power reverse, with all power removed just as the motor stops. Relays have effected this type of motor control. Here's how to control a two-phase servomotor with silicon controlled rectifiers.

Next page: Learn more about motor developments that happened from 1964 to 1974.

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