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.
By Frank J. Bartos, PE September 19, 2014

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.

(See also, previous page.)

40 to 50 years ago: Rotary servoactuator, adjustable SCR drives, computer-controlled positioning…

Choppers Compensate AC Servos

E.R. Schlesinger, Perkin-Elmer Corp., Sept. 1964 CE, Vol.11, No.9 (pp. 113-114)

Lag and lead compensating networks for ac servos can get quite complex, especially if the system carrier frequency cannot be tightly controlled. Here is a circuit that uses an electromechanical chopper to permit RC compensating networks nearly as simple as those used in dc servos.

Figure 5: Rotary servo actuator, Oct. 1964. Courtesy: Control Engineering archiveRotary servoactuator positions final elements

New Product Developments, Oct. 1964 CE, Vol.11, No.10 (p. 134)

Comprised of power supply, motor, gearing, transistorized amplifier, and feedback element, Servoactuator Model CSI-133—for one- or two-speed synchro dc or ac command signals—is one of a series of systems that provides torques of 100 oz-in. to 750 oz-in. [0.71-5.3 N-m] and output speeds of 30 deg per second or higher. Overall system accuracy is 0.2 percent. Operating temperature is -55 deg C to +100 deg C, power required is 115 vac, 400 cps or 60 cps, and output shaft dia is 0.25 in. [6.35 mm]. [See Figure 5.]

Control Technology Co., Inc. Long Island City, N.Y.

Figure 6: SCR drive, Nov. 1964. Courtesy: Control Engineering archiveAdjustable SCR drives

New Product Developments, Nov. 1964 CE, Vol.11, No.11 (p. 126)

Available in a range of 1/8 hp through 1 hp [0.09-.75 kW], these SCR drives consist of a controller for stepless control of motor speed, operator’s pushbutton station, and dc motor. A closed-loop feedback circuit is said to maintain an essentially constant motor speed despite varying motor loads. Standard features include a 20-to-1 speed range (100-to-1 for light intermittent duty), speed regulation of ±3 percent or less, time limit acceleration for cushioned starts, a run-jog selector switch, uni-junction firing circuit, and protection against short circuits, motor overloads, and transients. [See Figure 6.]

Cutler-Hammer Inc., Milwaukee, Wis.

Figure 7: Logic stepper motor, Dec. 1964. Courtesy: Control Engineering archiveLogic stepper motor

New Product Developments, Dec. 1964 CE, Vol.11, No.12 (p. 111)

Only 1.378 in. in diam [and] 0.858 in. long [35 x 21.8 mm], logic stepper motor K82201 operates when pulses are applied in logical sequence to its windings. Step rate is 0 to 360 steps per second, and maximum stepping torque 0.486 oz-in. [3.43 x 10-3 N-m]. The K82201 is rated for continuous duty, is bidirectional, and can be used as a synchronous motor. [See Figure 7.]

A. W. Haydon Co., Waterbury, Conn.

Figure 8: Solid-state DC drive, Jan. 1965. Courtesy: Control Engineering archiveDC drive

New Product Developments, Jan. 1965 CE, Vol.12, No.1 (p. 150)

Newest addition to the company’s line of solid state dc drives is the Statohm 250 HP. Said to be 96 percent efficient and have low maintenance requirements, it features controlled acceleration, adjustable IR compensation for 2 percent regulation over the speed range—speed regulation to ±0.1 percent is possible, protection against under- and over-voltage, positive disconnect dc contactor, and automatic phase-rotation interlock with lamp display. [See Figure 8.]

Electric Regulator Corp., Norwalk, Conn.

Eddy-current drive

New Product Developments, Feb. 1965 CE, Vol.12, No.2 (p. 108)

High-output torques and low-output inertia for dynamic response are features of eddy-current variable speed drives designated Electro-Drive servos. Standard NEMA D-flange ac motors from ¾ to 30 hp [0.56-22 kW] provide the constant input speed. Externally accessible magnetic pickups supply feedback to solid state SCR servocontrols. Regulation is to ±1 percent of full speed to a low of 50 rpm, with loads ranging from 25 to 100 percent of capacity; and logarithmic acceleration, adjustable from 2 to 15 sec, is a standard.

The WER Industrial Corp., Buffalo, N.Y.

Figure 9: Servo amp, Feb. 1972. Courtesy: Control Engineering archiveServoamp for fast position control

New Product Developments, Feb. 1972 CE, Vol.19, No.2 (p. 37)

Model A5261 servoamplifier features fast response with high torque. A low-inertia motor driven by the A5261 can reach 1,000 rpm in less than 1 millisec, and a low-speed 40-frame motor can develop 350 oz-in. [2.47 N-m] of continuous torque. The amplifier is rated at 4.5 amps continuous into a short circuit. It is complete with power supply for 115/220 volts, 50/60 cps, with three adjustable-gain signal inputs, balance and current-limit adjustments, and provision for system compensation. Priced under $350. [See Figure 9.]

Westamp Inc., Santa Monica, Calif.

Computer Controlled Positioning System is Accurate to 1 in 50,000

New Product Developments, March 1972 CE, Vol.19, No.3 (p. 71)

System 1100 is a digitally programmed position control system designed for industrial applications. It is accurate to better than 1 part in 50,000, with positioning speeds up to 1,000 rpm. The system uses absolute type (not pulse counting) position transducers, which provide immunity to stray pulses and loss of the zero reference position. Interface electronics can be adapted to any digital computer output or other digital command generator. The self-contained slew control system permits only the end points to be commanded, thus saving considerable computer software and time. In continuous path applications, the step size can be changed automatically by the computer to provide an optimum speed consistent with desired smoothness and overall accuracy. The complete system is a closed-loop position servo with rate feedback for stabilizing and slewing control. The actuator consists of a direct-drive torque motor, tachometer, and position feedback transducer, all contained in a single assembly.

Control Systems Research, Pittsburgh

Solid-State DC Motor Drives

May 1972 CE, Vol.19, No.5 (pp. 54-61)

[Comment: This major CE article sums up the large presence of dc drive technology at that point in time. Six full-page tables detailed specifications and features of 78 dc drive products available from 46 manufacturers.]

Figure 10: 98% efficient ac drive, Dec. 1972. Courtesy: Control Engineering archiveAdjustable frequency motor control system is 98% efficient

New Product Developments, Dec. 1972 CE, Vol.19, No.12 (p. 57)

An expanded line of adjustable frequency motor controls and systems has been announced for handling ac motors from ¾ to 150 hp. The controls incorporate current limit acceleration with overload capabilities of 225 percent. Speed ranges up to 40:1 are available as well as NEMA 1 construction and a totally enclosed, nonventilated NEMA 12 construction. With an efficiency of 98%, these adjustable frequency motor controls can be adapted to run standard ac motors, either individually or in a group operating as a system. [See Figure 10.]

Ramsey Controls Inc., Mahwah, N.J.

Figure 11: High power thyristor, May 1973. Courtesy: Control Engineering archiveHigh power thyristors

New Product Developments, May 1973 CE, Vol.20, No.5 (p. 78)

Type T920 is a 50.8 mm thyristor that offers built-in amplification of the gate trigger current. The T920 also offers an rms current rating 1.57 kA, a high surge current rating of 16 kA, a dv/dt rating of 200 V/µsec, and a 3 kV forward voltage rating. The T920 comes in a "Pow-R-Disc" package—a flat design with single- or double-sided cooling. The units are priced from $92 to $400 per 100 pieces. [See Figure 11.]

Westinghouse Electric Corp.’s Semiconductor Div., Youngwood, Pa.

Figure 12: Miniature dc servo motor, Nov. 1973. Courtesy: Control Engineering archiveDC servomotor

New Product Developments, Nov. 1973 CE, Vol.20, No.11 (p. 90)

The Model 28TL is a miniature dc servomotor with a continuous rated torque output of 2 oz-in. Pulse torques in excess of 6 oz-in. may be used on a 25% duty cycle. Windings are available for 6, 12, 18, and 24 V, and the unit is designed for power dissipation of up to 6 W. Options include coupled low-ripple dc tach-generator. Price is below $13.50 in OEM quantities of 1,000 or more. [See Figure 12.]

Portescap U.S., New York.

Next page: Learn more about motor developments from 1974 to 1984.

(See also, previous pages.)

30 to 40 years ago: Regeneration with adjustments, microstepping, integrated feedback…

Figure 13: DC regen drive, Aug. 1974. Courtesy: Control Engineering archiveRegenerative drive

New Product Developments, Aug. 1974 CE, Vol.21, No.8 (pp. 78-79)

The PRD-2 is a regenerative drive system featuring independent adjustment of both speed and torque. The system includes a controller and a dc motor. Motor specs are shunt wound or permanent magnet, 1,450 or 2,000 rpm, 1/6 to 2/3 hp (115 V ac) or 2/3 to 1¼ hp (230 V ac). The unit offers ±20:1 constant torque speed range with matched motor, and a regulation of ±1 percent of base speed for 100% load change in either direction. [See Figure 13.]

Polyspede Electronics Corp., Dallas.

[Comment: This is an example of an early dc regenerative drive product.]

Techniques for Microstepping Control of Step Motors

Albert C. Leenhouts, The Superior Electric Co., March 1979 CE, Vol.26, No.3 (pp. 58-59)

It is often desirable to drive step motors at step increments that are substantially smaller than the natural full-steps produced by conventional drives. Thus, there are drives known as ministeppers and microsteppers. A great deal of work was done on microstepping in the early 1960s, but low-cost complex integrated circuits and good power switching devices have only recently made microstepping a practical option. Stepping resolutions can be improved ten times and more, and multiple resolutions can be realized from a single motor.

[Comment: Substantially higher stepping resolutions were made possible by later designs. Around 1985, some stepper drives were reportedly capable of 25,000 to 50,000 steps/revolution. However, practical questions arise with microstepping at higher motor speeds, as circuit design becomes more complex and high switching rates are imposed on the power supply. Accurate feedback also becomes necessary to hold the resolution, which goes against the basic aim of open-loop control for stepper systems.]

Figure 14: PWM servo controller, March 1982. Courtesy: Control Engineering archiveTwo-in-one PWM servo controller

Control Products Preview, March 1982 CE, Vol.29, No.3 (p. 89)

The Model 6020HRJ PWM servo controller can have its output doubled by selecting four field-selectable jumpers. This alteration converts the 6020 into a manufacturer’s [OEM] model 8030J…to minimize the necessary inventory.

The preamplifier has three adjustable scale factors for the inverting input, a non-inverting input, balance adjustment, and a gain adjustment for lead-lag compensation. The lead-lag network and the three inverting input resistors are mounted on stand-offs for easy compensation changes. The PWM power state has constant, high-frequency switching for wide bandwidth operation and a negligible power factor. Circuitry, with LED indication and amplifier shutdown, protects against shorts, under voltage, over voltage, and low-level supply.

Peak output current ratings are (6020 then 8030): ±24 A or ±33 A with maximum pulse output current (2 sec) rated at ±20 A or ±30 A. Maximum continuous current is specified at ±10 A or ±15 A. [See Figure 14.] Aerotech Inc. Pittsburgh, Pa. ctl1409f3 – Online 3, Mar 82

Separate Controller Aids Tailoring of Motor Drives to Position Control Applications

E.J. Kompass, Control Engineering, Aug. 1983 CE, Vol.30, No.8 (pp. 72-73)

Electric motor drives for position control have traditionally included feedback controller circuitry together with the power amplifiers in a total drive package. A new direction in the marketing of servo position controllers is emerging in which a microprocessor-based feedback controller unit is supplied as a separate package that can be used with drive power amplifiers of many types and sizes. A first description is presented of a new digital controller of this kind designed to be especially friendly in end-user application—from Gould Motion Control Div.

Next page: Learn more about motor developments that happened from 1984 to 1994.

(See also, previous pages.)

20 to 30 years ago: Induction motor as servo, software adaptations, miniaturization…

Programmable Position Control Uses Standard Induction Motor as Servo

Thomas J. Keehbauch, Allen-Bradley Co., Drives Div., Jan. 1984 CE, Vol.31, No.1 (pp. 108-110)

Here’s a first description of a new ac servo drive that produces full torque from standstill to full-rated speed using a standard squirrel-cage induction motor as a high-performance servo. The secret involves rotor position sensing, a microprocessor-based field-vector generator, and high-voltage transistor servo power amplifiers. Features include direct serial interface to programmable controller I/O bus, built-in diagnostics, and an easy-to-use programming system.

Servo Design Today: Software-Driven Adaptations in the Feedback Loop

S.J. Bailey, Control Engineering, Feb. 1984 CE, Vol.31, No.2 (pp. 67-72)

Dynamically varied digital feedback compensation based on "If . . . then . . ." software rules can dramatically improve servo performance in today’s newest designs. Thus, gains or rate-stabilizing tuning constant can be adjusted to take account of actuator power limitations, for example. Any measurable parameter that can impair performance can be operated on in a feedback sub-loop to nullify or moderate its effects. One result is that complex frequency-domain modeling for stability might recede in urgency, as design attention is paid to primary servo objectives of positioning speed and accuracy.

New Motor Drives Can Be Tailored to Loads

S.J. Bailey, Control Engineering, Aug. 1984 CE, Vol.31, No. 8 (pp. 84-88)

Tailoring a motor drive to specific on-line tasks is made easier by the new microprocessor-based drive controllers. Software designed to match specific dynamic loadings can be developed by the supplier and loaded into read-only memory before shipment to the user. Such motor drives fit neatly into cells of flexible manufacturing because they can be updated to match changing requirements.

Figure 15: Miniature PWM amplifier, April 1991. Courtesy: Control Engineering archiveIt’s Not All Quiet on the Electric Servos Front

F.J. Bartos, Control Engineering, April 1991 CE, Vol.38, No.4 (pp. 60-63)

Miniaturization of servo amplifiers was well underway at this point, as illustrated by Galil Motion Control’s SBA Series designed for brushless servo motors of up to 2 kW power. The PWM amplifier measured 5.1 x 3 x 1.2 in (130 x 76 x 30.5 mm). [See Figure 15.]

[Comment: Today, 4- and 8-axis motion controllers from Galil come in packages not much bigger; however, they also house servo drives containing 4 and 8 comparable amplifiers, respectively, in the same unit (see the comparison in online extension 2, Ref. 2).]

DC Drives Still Have Miles to Go Before They Sleep

F.J. Bartos, Control Engineering, Aug. 1991 CE, Vol.38, No.8 (pp. 48-50)

Amidst competition, dc variable speed drives retain favor due to technological reasons and user familiarity.

[Comment: As mentioned in the main September 2014 article, the predicted early demise of dc drives was premature. They’re available from numerous manufacturers.]

Figure 16: Miniature PWM drive, Dec 1991. Courtesy: Control Engineering archiveNew AC Drives Combine Miniaturization Many Functions

F.J. Bartos, Control Engineering, Dec. 1991 CE, Vol.38, No.16 (pp. 69-70)

[This article included another glimpse of miniaturization in the form of variable-speed drives (VSDs). Smallest model in the Z024 Series drives from the Industrial Automation Div., of Mitsubishi Electronics America Inc.—rated for 1/8-¼ hp (0.09-0.19 kW)—could fit into the pocket of a technician’s coveralls. Yet, the drive came with noteworthy features, including a 16-bit microprocessor as its brain. See Figure 16.]

Figure 17: 600 hp brushless dc motor, Dec 1992. Courtesy: Control Engineering archiveBrushless DC motor line extended to 600 hp

New in Control, Dec. 1992 CE, Vol.39, No.14 (p. 79)

Said to be the largest of its kind, a line of ferrite permanent magnet brushless dc motors up to 600 hp [450 kW] output is available. Base speed of the 500AT is 300 to 1,750 rpm; it comes in air- and liquid-cooled versions and has about a 25 in. [635 mm] OD. Brushless dc controllers for these motors use PWM transistors able to handle currents of 1,000 A.

Powertec, Rock Hill, S.C. [See Figure 17.]

[Comment: The above company is now called Powertec Industrial Motors Inc. and currently makes brushless PM motors (and drives) up to 400 hp. A brief history of Powertec is available.]

Next page: Learn more about motor developments that happened from 1994 to recently. (See also, related articles).

(See also, previous pages.)

10 to 20 years ago: Digital servo systems, integrated motor-drives, intelligent motion…

Figure 18: DC drives, 1994 vs. 1954. Courtesy: Control Engineering archiveDC Drives Stay in Demand

F.J. Bartos, Control Engineering, Oct. 1994 CE, Vol.41, No.12 (pp. 61-64)

User loyalty and influx of new developments are keeping the mature technology of dc variable speed drives viable.

[Comment: Besides attesting to the staying power of dc drives overall, this article included an historic image that contrasted a new dc drive of the time from Reliance Electric Co. with one from 40 years earlier (see photo). The "new" drive was FlexPak 3000 digital drive with the latest in displays, setup, and controls, while the old drive represented technology from 1954—the inaugural year of Control Engineering magazine. Diagnostics available in the old drive "was a vacuum tube whose glow pattern gave indication of certain drive conditions." See Figure 18.]

Multiple Control Schemes Advance Motion Control

Carrol A. Wonthrop Jr., George Ellis, Kollmorgen Motion Technologies Group and Dr. Ilan Cohen, Servotronix Control Technologies Ltd., Oct. 1996 CE, Vol.43, No.10 (pp. 65-68,74)

Digital servo systems offer the most sophisticated motion control available today. Here is a look at some of the algorithms behind that performance.

[Comment: Newer motion controllers accommodate multiple control methods. Algorithms discussed go beyond proportional-integral-derivative (PID) control and include pseudo-derivative feedback—a special case of PID—pole placement, and advanced pole placement, which are higher order methods. Advantages and disadvantages of each are discussed.]

Figure 19: Load-to-motor inertia response, Sept. 1997. Courtesy: Control Engineering archiveElectric Servos Do More with Less

F.J. Bartos, Control Engineering, Sept. 1997 CE, Vol.44, No.12 (pp. 102-113)

Close matching of load-to-motor inertia offers the best dynamic performance from a servo drive. But it’s not always possible or practical to do so. Here are some ways to live with higher inertia ratios. Substantial tabular listings of servo controls and software products available at the time are included—along with ratings and features. [See Figure 19.]

Figure 20: Step motor and control combo from 1989. Courtesy: Control Engineering archiveIntegrated Motor-Drives Seek Wider Market, User Acceptance 

Dec. 2000 CE article (pp. 102-113)

Much fanfare marked the marriage of ac induction motors and variable-speed drives when integration of the two technologies became commercially practical in the mid-1990s.

[Comment: Servo (and step) motors with integrated drive packages also emerged quickly. This technology sector—so-called integrated motor-drives (IMDs)—was discussed in the main article and in online extension 1 (Ref. 1). The Dec 2000 article included a section on prior IMD developments that offers some historical interest.]

Who was first with IMD technology?

Ingenious designers integrated motors and electronic controls into a single unit in their development labs long before the 1990s. Concept models and prototypes were likewise demonstrated previously. Other topologies, such as stepper motor or servo motor-based systems, even reached limited production.

[Comment: Step motors were early candidates for drive integration because of smaller physical size of the drives. One of the earliest examples of such a product was Intellimotor, dubbed an "electronic position control system." Intellimotor consisted of a 2-phase step motor, intelligent controller, and power supply. It was introduced in 1989 by the former U.S. company Intellico Inc. (See photo.) Bodine Electric Co. acquired Intellico in 1991. Apparently, a new version of this product is available today from Bimba Manufacturing Co., trademarked as IntelliMotor. See Figure 20.]

Figure 21: Induction motor and VSD combo from 1993. Courtesy: Control Engineering archiveGrundfos of Denmark combined an induction motor and an inverter drive as early as 1991 to power its extensive line of pumps. Others launched specialty products, as well.

However, the German company Franz Morat KG was probably the first to produce an induction motor and variable-speed drive combination for industrial use in 1993. Its Fumo product line, rated 0.65-3 kW for 230/460 V input, was quite sophisticated and ahead of its time (see photo). Fumo incorporated a parallel processor device (transputer), several communication options, and its VSD had positioning capability using a built-in encoder option. [See Figure 21.]

Electric Servos Go for Ease of Use, Integrate with the Whole Plant 

June 2002 CE article (pp. 22-26)

Part of the article emphasizes the key role of high-resolution feedback for accurate servo motion control.

Bosch Rexroth noted that its feedback approach combines optical and electronic methods, where sine/cosine-type intermediate signals are electronically enhanced. By further resolving each sine wave signal into a large number of increments, digital feedback with over 4 million (or 2 x10+22) increments/revolution can be obtained.

The explanation went on to caution it doesn’t imply ability to position to one part in four million.

"However, it provides the resolution level needed to develop high-quality velocity feedback for the dynamic loops of motion systems. High resolution also limits effects of electronic noise."

Also illustrating the importance of accurate feedback, Industrial Indexing Systems (Victor, N.Y.) added a resolver card option on its Emerald EMC-2000 multi-axis motion controllers. Master Follower Resolver PMC card supplies absolute position information with 12-, 14-, or 16-bit resolution selectable via the application program.

Intelligent Motion Unites Diverse Worlds 

Dec. 2004 CE article (pp. 26-32)

Intelligence means different things to different people. Intelligent motion control generally has incorporated motion and machine logic, plus power switching, in the same control package. Lately, other functions such as predictive maintenance, machine safety, and advanced communications are increasingly part of the mix of "intelligent motion" architectures.

From the near term: Reducing EMI, interior permanent magnet motors, microchips help…

Silence of the Drives 

Figure 22: Effect of filtering conducted EMI, June 2008. Courtesy: Control Engineering archiveJune 2008 CE article (pp. 56-60) 

They’re great for saving energy and optimizing automation systems, but adjustable-speed drives (ASDs) inherently produce high-frequency electrical noise. Fast switching transistors producing large voltage changes in the drive’s power section are the prime source of electrical noise, also known as electromagnetic interference (EMI).

Electromagnetic compatibility (EMC) is an overall approach that addresses EMI mitigation and immunity for electrical/electronic equipment. Various recommendations and solutions are discussed. [See Figure 22.]

IPM motors for highest energy efficiency 

Oct. 2008 CE, Advancing Technology (pp. 22,24)

[Comment: As discussed in the main article and in online extension 1 (Ref. 1), interior permanent magnet (IPM) motor design buries flux-producing magnets within the rotor structure; thus it differs from conventional PM motor design that simply mounts magnets on the rotor surface.]

A different ac motor design with salient-pole, IPM rotor offers measurably higher energy efficiency and other benefits. IPM rotors have been used for some time in servo motors for CNC, machine tool, and other high-performance incremental motion systems. New for IPM rotors is their use in general-purpose motors for wider industrial and OEM applications.

Microchips doing more for motor, motion control 

Aug. 2010 CE, Advancing Technology (p. 23)

Sensorless vector control, power factor control, and higher temperature operation are among recent silicon developments.

– Compiled and edited by Frank J. Bartos, PE, a Control Engineering contributing content specialist; reach him at

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