Actuator

An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which an agent acts upon an environment. The agent can be either an artificial intelligence agent or any other autonomous being (human, other animal, etc).

Examples and applications

Some examples of actuators of these various agents include:

Human - Arms, hands, fingers, legs

Part picking robot - Grasping mechanism, moving parts. Examples include solenoids and voice coil actuators.

Mail transfer agent - Update software

In engineering, actuators are a subdivision of transducers. They are devices which transform an input signal (mainly an electrical signal) into motion. Electrical motors, pneumatic actuators, hydraulic pistons, relays, comb drives, piezoelectric actuators, thermal bimorphs, Digital Micromirror Devices and electroactive polymers are some examples of such actuators. Motors are mostly used when circular motions are needed, but can also be used for linear applications by transforming circular to linear motion with a bolt and screw transducer. On the other hand, some actuators are intrinsically linear, such as piezoelectric actuators. In virtual instrumentation actuators and sensors are the hardware complements of virtual instruments. Computer programs of virtual instruments use motion into linear motion, or vice versa. Conversion is commonly made via a few simple types of mechanism including:

• Screw: Screw jack, ball screw and roller screw actuators all operate on the principle of the simple machine known as the screw. By rotating the actuator's nut, the screw shaft moves in a line. By moving the screw shaft, the nut rotates.

• Wheel and axle: Hoist, winch, rack and pinion, chain drive, belt drive, rigid chain and rigid belt actuators operate on the principle of the wheel and axle. By rotating a wheel/axle (e.g. drum, gear, pulley or shaft) a linear member (e.g. cable, rack, chain or belt) moves. By moving the linear member, the wheel/axle rotates.

• In engineering, actuators are frequently used as mechanisms to introduce motion, or to clamp an object so as to prevent motion. In electronic engineering, actuators are a subdivision of transducers. They are devices which transform an input signal (mainly an electrical signal) into motion. Specific examples include: electrical motors, pneumatic actuators, hydraulic actuators, linear actuators, comb drive, piezoelectric actuators and amplified piezoelectric actuators, thermal bimorphs, micromirror devices and electroactive polymers.
• Motors are mostly used when circular motions are needed, but can also be used for linear applications by transforming circular to linear motion with a bolt and screw transducer. On the other hand, some actuators are intrinsically linear, such as piezoelectric actuators.
• "Force fighting" can occur when two or more actuators provide conflicting inputs to the mechanism.
• It is used in output port of PLC for controlling the other mechanism or system

Thermodynamic efficiency

The efficiency of an actuator is a standard tool used to calculate or estimate the usefulness of any actuating mechanism. It is a dimensionless quantity which is lower than 1 expressing the energy conversion factor. For better explanation see Thermodynamic efficiency. Most of the wasted energy (due to friction, magnetic losses, eddy currents etc.) is thermally dissipated.

$\varepsilon = \frac{\text{useful work}}{\text{spent energy}}=\frac{\text{output energy}}{\text{input energy}}$

See also

• Robot actuators
• Robotic hand end effector
• Microactuator
• Nanotube nanomotor

External links

• Automotive Actuators
• Blog about Actuators