actuator

An actuator is a component of a machine that converts one form of energy into mechanical motion. It is used to create linear or rotary motion, providing displacement, velocity, or torque as required by a system. Actuators differ from motors in that they typically receive a control signal and produce motion as output, rather than simply providing continuous torque.

There are several common actuator types. Electrical actuators include electric motors (DC, servo, and stepper) that provide rotary motion and can be paired with gears for linear actuation, as well as solenoids that generate linear force. Fluid power actuators use compressed fluid to create motion: hydraulic cylinders produce large forces with slow, smooth movement, while pneumatic cylinders are lighter and faster but offer lower force. Thermal actuators rely on thermal expansion or phase-change materials; piezoelectric and electrostrictive actuators use electric fields to induce small, precise displacements. Magnetic and electrostatic actuators use magnetic or electric field effects for motion and control.

Control of actuators can be open-loop or closed-loop. Feedback devices such as encoders, potentiometers, or limit switches enable precise positioning, speed control, and torque regulation. Actuators are chosen for factors such as force or torque, speed, travel, stiffness, energy efficiency, size, cost, and environmental tolerance.

Common applications include robotics, manufacturing automation, aerospace, automotive systems, and consumer devices. Understanding the requirements of force, distance, speed, and precision is essential to selecting an actuator suitable for a given function.