Rotary actuator

A rotary actuator is an actuator that basically delivers circular or rotary motion or torque in response of received control signal. They are used in a wide range of industrial applications where rotary positioning is needed. Such actuators can be either manual operated or powered by some energy source such as compressed air, fluid pressure, electrically powered. Mostly electrical motors are used for rotary actuator operation. Here rotary motion produced by an actuator may be either continuous rotation of electric motor or movement to a fixed angular position as for servomotors and stepper motors. Besides that, linear motion from cylinder piston can also be used to generate rotary motion using some geared mechanism. Maximum rotation angle delivered by it can be up to 45°, 90°, 135°, 180°, 225°, 270°, 315°, or 360°. Such actuators can be classified as mentioned below-

  • Manually operated rotary actuator
  • Pneumatic rotary actuator
  • Hydraulic rotary actuator
  • Electric motor actuator
  • Stepper Motor actuator
  • Servo motor Actuator
  • Torque motor

Different rotary actuator’s configurations are mentioned below-

Rotary Actuator

Pneumatic rotary actuator-

When pneumatic actuators deliver rotary motion in response of controlled air pressure applied to it, it is referred as pneumatic rotary actuator. Normally such actuator can turn to 90 degrees (quarter turn) during full scale movement. They are used to operate ball valves, butterfly valves. A diagram for pneumatic actuated ball valve & butterfly valve is shown below-

Pneumatic rotary actuator

Some examples of such pneumatic actuators are as mentioned below-

  • Diaphragm actuator
  • Rack and pinion actuator
  • Scotch yoke actuator
  • Vane actuator

Hydraulic rotary actuator-

When hydraulic actuators deliver rotary motion in response of controlled oil pressure applied to it, it is referred as hydraulic rotary actuator. Such actuator uses a pressurized, non-compressible fluid (oil) to rotate mechanical components. They offer faster response and are more powerful than pneumatic actuators because the high pressure used in hydraulic systems produce greater torque.  The key Performance specifications for these actuators include operating pressure range, maximum torque, load capacity, stroke size, operating temperature, and rotation angle. They are used for high torque, heavy-duty motion applications. They are coupled directly to a rotating load and provide good control for acceleration, operating speed, deceleration, smooth reversals, and positioning. They are used in a variety of marine, mining, military, construction, and recycling applications. A diagram for such hydraulic  actuator is shown below-

hydraulic rotary actuator

Electric rotary actuator-

When electric actuators provide circular or rotary motion in response of controlled signal applied to it, it is referred as electric rotary actuator. Normally electric motors drive components rotationally via electromagnetic power and speed, transmission line can be controlled with use of gear mechanism. Such actuators typically provide control and indexing capabilities to allow multiple position stops along strokes. The rotational element for rotary electric actuators can be either a circular shaft or a table. Performance parameters for electric actuator includes supply voltage, repeatability, maximum torque, load capacity, linear stroke, operating temperature, and rotation angle etc. Typically, rotation angle of such electric actuators can be maximum rotation angle of 45°, 90°, 135°, 180°, 225°, 270°, 315°, or 360°. There are so many applications of these actuators. Some of them are- for semiconductor manufacturing operations, for laboratory or medical use, in the electric power industry, high-power switching gears, and packaging applications, in the automotive industry etc. A diagram for such electric actuator is shown below-

Electric rotary actuator

Actuator motor-

Linear and rotary both electric actuators use various types of motor for their operation. Actuator motor varies in terms of motor specification such as supply voltage, power, efficiency, travel continuous or discrete type, etc.  Various types of linear actuator motor are DC Motor Types, DC brush motors, Brushless DC motor (BLDC), AC Motor Types, AC servomotors, AC stepper motors etc.

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