Rotary actuators and servos turn an electrical command into a precise angular movement. On drones they move ailerons, elevators, rudders and flaps, steer nose wheels, adjust propeller pitch and tilt rotors or wings. On eVTOL aircraft, larger rotary actuators drive tilt mechanisms and flight controls as part of fly-by-wire systems.
Types
Servos: compact units with motor, gear train, position sensor and electronics in one housing. Industrial UAV servos use metal gears, brushless motors and sealed housings.
Rotary electromechanical actuators: larger units with gearboxes or harmonic drives for high torque, often with redundant motors and electronics.
Direct-drive rotary actuators: torque motors without gearing, for precise, backlash-free motion.
Key specifications
Torque (continuous and stall) and speed.
Angular range and resolution / accuracy.
Backlash and stiffness, important for flutter prevention on control surfaces.
Interface: PWM, CAN, RS-485, with position, current and temperature feedback.
Redundancy: dual motors or channels for critical functions.
Environmental qualification: temperature, humidity, sealing, vibration and EMC.
Mass and power.
Choosing
Hinge moments set the torque; flutter and control performance set the stiffness and backlash limits. Professional servos with telemetry let the autopilot detect a failing actuator before it causes a loss of control.
What is the difference between a servo and a rotary actuator?
A servo is a compact, integrated actuator, typically for small and medium aircraft. "Rotary actuator" usually refers to larger, higher-torque units for bigger aircraft, though the terms overlap.
Why does backlash matter in control surface servos?
Free play lets the surface move without command, which degrades control and can contribute to flutter, a dangerous aeroelastic vibration.
Should UAV servos use CAN instead of PWM?
CAN servos report position, current and temperature to the autopilot and resist noise better, which helps detect faults. PWM is simpler and still common on smaller aircraft.
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FeaturedRotary actuators
FeaturedRotary actuators
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FeaturedRotary actuators
FeaturedRotary actuators
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FeaturedRotary actuators
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FeaturedRotary actuators
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