Actuators

An actuator is a device that converts energy into mechanical motion or force. Actuators are core components of automated systems, providing linear or rotary movement, torque, and pressure. They are distinguished from sensors, which measure physical quantities, and from transducers that convert one form of energy to another. Actuators can be powered by electricity, hydraulics, pneumatics, thermal energy, or magnetic fields, and are used in a wide range of applications from simple valves to complex robotics.

Electrical actuators include electric motors (DC, AC, servo, and stepper) and solenoids. They offer relatively precise speed and position control, easy integration with electronics, and good efficiency. Control methods range from open-loop to closed-loop with feedback sensors such as encoders or linear potentiometers. Rotary motors generate torque, while linear actuators provide motion along a straight line.

Hydraulic actuators use incompressible fluid under high pressure to produce substantial force, typically in linear motion. They offer high power density and strong lifting capability but require pumps, reservoirs, and valves, and may leak. Pneumatic actuators use compressed air, are lighter and faster for short-stroke motion but deliver lower force and exhibit greater compressibility, complicating precise positioning. Both are common in industrial automation and mobile machinery.

Other actuation technologies include piezoelectric actuators, which exploit electric polarization to produce small, precise displacements at high frequency; shape memory alloys that change shape with temperature; and electroactive polymers. Thermal actuators rely on expansion with heat, often used for switching.

Selection depends on required stroke, force, speed, precision, environment, power availability, and control integration. Actuators enable automation, positioning, and responsive control across robotics, manufacturing, aerospace, automotive, and consumer devices.