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(control systems)
The electric, hydraulic, or other type of motor that serves as the final control element in a servomechanism; it receives power from the amplifier element and drives the load with a linear or rotary motion. Also known as servo.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a servomechanism that reproduces certain mechanical displacements of a controlled object by means of an actuating electric motor.

A servomotor includes a reference device, a measuring transducer, a comparator, an amplifier, and an actuating electric motor. The reference device produces the initial signal, which usually varies according to some arbitrary relationship. The measuring transducer continuously measures the actual value of the quantity being reproduced at the controlled object; this quantity is compared with the reference value by the comparator. The measuring transducer and the comparator are usually combined in a single unit that produces a deviation signal proportional to the difference between the reference value and the actual value of the quantity being reproduced. The deviation signal, in the form of a voltage or a current, then passes to the amplifier input and on to the actuating motor. The actuating motor moves the controlled object in such a way that the deviation signal is reduced. In the absence of a deviation signal, the rotor of the electric motor is at rest.

Servomotors provide continuous or discrete control. Continuous control affords an uninterrupted regulation of the voltage, or power, of the actuating motor as a function of the deviation signal. In the simplest case, this relationship is linear. Servomotors designed for discrete control are subdivided into relay and pulse drives. In relay drives, contactless relays serve as an amplifier. At a certain value of the deviation signal, the relays connect the actuating motor at the full power rating. In pulse drives, the actuating motor is connected to the circuit periodically at specified equal time intervals by pulses of the control current. The amplitude, duration, or frequency of these pulses are a function of the deviation signal.

In most servomotors the reference quantity is the rotation angle of the input shaft, and the controlled quantity is the rotation angle of the output shaft to which the controlled object is linked. In such systems the most widely used types of measuring transducers are potentiometers and alternating-current induction machines of the selsyn or rotary-transformer type. Servomotors are used in various control, data transmission, and telemetry systems.


Elektroprivodsistem upravleniia letatel’nykh apparatov. Moscow, 1973.

Osnovy avtomatizirovannogo elektroprivoda. Moscow, 1974.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A type of motor that receives a signal because of the action of the control system, which causes a mechanical movement of the primary controls. A servomotor can move the controls in either direction.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
The acceleration amplitude of the slider decreased during the starting period of the punching press, as shown in Figure 9, because large current was generated by the servomotor to produce large torque to overcome the resistance that acted on the crankshaft-connecting rod mechanism at the starting moment (i.e., at a time of 0 s), while the suddenly imposed large torque resulted in vibration in the punching press (where the acceleration amplitude of the slider was about 15 m/[s.sup.2]).
servomotor transfer function given by the relation (6) may be expressed under the following form:
Among the new all-electric Sumitomo machines is the SE-DU Direct-Drive series (20 to 198 tons), which features four direct-drive Sumitomo AC servomotors with full closed-loop control and digital sensors.
While the servo amplifier and servomotor are the core of the motion control system, the required movement originates with the controller.
Based on the first draft, results gained from performed experiments and the different servomotor integration decisions the design of the gearbox has been developed in a dynamic process until the final layout was decided.
Maxon Precision Motors RE 025 servomotors were selected for torque and responsiveness, and the encoders were chosen for their precision.
* All compact (CT) and high-dynamic (HD) servomotors in the 1FK7 family.
In the "initialization" step the robot will be in balanced condition and in this step the servomotors are made to return to home position.
Each hydraulic cylinder is directly connected with a hydraulic pump driven by a servomotor. The PPRM's bending force is proportional with the torque of the servomotor, which can be controlled for specific applications.
The drive provides users with a cost-effective means of increasing the speed and smoothness of existing automation through the application of advanced digital control technology, without having to replace the servomotor. It is also likely to prove popular with OEMs and machine builders designing servo-based systems for use in challenging environments, since resolvers are generally considered more mechanically and electrically robust than encoders, especially at elevated temperatures.
The new model incorporates a new high-speed pulse technology, which is based on a faster head action and servomotor control.
* Induction or synchronous servomotor designs for mating the right motor to the size requirements and dynamic response needs.