Actuators

An actuator converts a control signal into motion or force — spinning a shaft, opening a valve, pushing a load. The three families are electric, pneumatic, and hydraulic, each with distinct strengths.

Overview

• Electric — precise, clean, easy to control.
• Pneumatic — fast, simple, inherently overload-safe.
• Hydraulic — enormous force in a small package.

Electric

• AC induction — workhorse for pumps, fans, conveyors.
• AC servo (PMSM) — high dynamic response, closed-loop.
• BLDC — small, efficient, integrated drive electronics.
• Stepper — open-loop indexing; no feedback needed for many tasks.
• DC brushed — simple, low cost, brush wear.
• Linear motor — direct linear force, no transmission backlash.
• Solenoid / voice coil — short-stroke, fast switching.

Pneumatic

• Cylinders — single- vs double-acting, rodless, rotary.
• Air motors / vane motors.
• Grippers — parallel, angular, vacuum.
• Typical supply 6–8 bar (90–116 psi).
• Speed control via flow regulators on the exhaust port (meter-out).

Hydraulic

• Cylinders — tie-rod, welded; bore 1.5–24+ inches.
• Hydraulic motors — gear, vane, piston; up to thousands of Nm.
• System pressures typically 1,500–5,000 psi (mobile up to 6,000+).
• Force F = P × A; piston-side vs rod-side area differ.

Selection & Sizing

• Define load — force, torque, inertia, friction, duty cycle.
• Define motion profile — stroke, speed, acceleration, dwell.
• Apply service factor (typ. 1.25–2.0).
• Check thermal duty (RMS torque, ED%).
• Verify environment — IP rating, temperature, EX, washdown.

Control & Feedback

• VFD for AC induction; servo drive (e.g. Kinetix, Sinamics, Beckhoff, Yaskawa, Mitsubishi) for servo.
• Encoders / resolvers / Hall sensors for position.
• Current sense for torque control.
• PID loops for position, velocity, torque (cascaded).
• Safety functions — STO, SS1, SLS per IEC 61800-5-2.