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 a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), or a human or other agent.
An actuator is a device responsible to control the starting and stopping mechanisms or system. It takes hydraulic fluid, electric current or some other source of power and converts the energy to facilitate the motion. There are four types of actuators: Hydraulic, Pneumatic, Electric and Mechanical.
Hydraulic actuators are a cylinder or fluid motor that use hydraulic power to facilitate mechanical operation. The mechanical motion gives an output in terms of linear, rotary or oscillatory motion. Since liquid cannot be compressed, they take longer to gain speed and power while requiring more time to slow back down. Pneumatic actuators, on the other hand, convert energy formed by compressed air at high pressure into ether linear or rotary motion. Pneumatic energy is more desirable for main engine controls because it can quickly respond in starting and stopping as the power source does not need to be stored in reserve for operation. Another type of actuators is Electric. Electric actuators are devices powered by motor that converts electrical energy to mechanical torque. The electrical energy is used to actuate equipment that requires multi-turn valves like gate or globe valves. It is considered as one of the cleanest and readily available forms of actuator as it does not involve oil. Mechanical actuators happen when a rotary motion is converted into linear motion to execute a movement. It involves gears, rails, pulley, chain and other devices to operate. Knowing the aforementioned information is essential so the correct type of actuator can be selected.
Examples and applications
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. 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. Conversion between circular and linear motion 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 virtual instrumentation, actuators and sensors are the hardware complements of virtual instruments.
Performance metrics for actuators include speed, acceleration, and force (alternatively, angular speed, angular acceleration, and torque), as well as energy efficiency and considerations such as mass, volume, operating conditions, and durability, among others.
- Robot actuators
- Robotic hand end effector
- Nanotube nanomotor
- Linear actuator
- Hard disk drive actuator
- Sclater, N., Mechanisms and Mechanical Devices Sourcebook, 4th Edition (2007), 25, McGraw-Hill