An Actuator is a mechanical or electromechanical device that controls movement or positioning. Actuators are components within a machine that carry out the moving and controlling of a mechanism or system, such as the opening or closing of a valve. Because of this, actuators are sometimes called movers. To operate, actuators need a control signal and source of energy. Following receival of a control signal, the actuator uses energy from the source to foster mechanical motion. Actuators have many uses and therefore come in many types. In this blog, we will look at the most common types of actuators.
Mechanical actuators create movement by converting one type of motion, such as rotary, into another type, such as linear. An example of this is a rack and pinion or a chain block hoisting weight where the mechanical motion of the chain is used to lift a load. The function of mechanical actuators is dependent on the combinations of their structural components, such as gears and rails or pulleys and chains. The primary advantages of mechanical actuators are their high reliability, simplicity of utilization, easier maintenance, and precise positioning.
Hydraulic actuators feature a cylinder or fluid motor that uses hydraulic power to generate mechanical motion, which then turns into linear, rotary, or oscillatory motion. As liquids are nearly impossible to compress, hydraulic actuators are capable of exerting large forces. As the fluid enters the lower chamber of the actuator’s hydraulic cylinder, the pressure inside increases, exerting a force on the bottom of the piston and inside the cylinder. The pressure causes the sliding piston to move in the opposite direction of the force, moving the piston upward and opening the valve. The disadvantages of hydraulic actuators are the need for many parts and the possibility of fluid leakage.
Pneumatic actuators convert the energy from compressed air into mechanical motion. Pressurised gas or compressed air enters a chamber, causing pressure to build. Once the pressure suprasses the required pressure level compared to the outside atmospheric pressure, the piston or gear begins to move kinetically and create a straight or circular mechanical motion. Pneumatic actuators are typically less expensive and more powerful than other actuators while having the added advantage of being able to quickly start or stop without a reserve power source needed for operation. Examples of pneumatic actuators include pneumatic cylinders, air cylinders, and air actuators.
Electromechanical actuators are mechanical actuators with an electric motor in place of the control knob or handle. The rotary motion of the motor leads to linear displacement. Most electromechanical actuators are driven by the inclined plane concept; the lead screw’s threads serve as a ramp, converting the small rotational force by magnifying it across a long distance, therefore allowing a large load to be moved over a small distance. Although many different designs of electromechanical actuators exist, most have the lead screw and nut incorporated into the motion. The biggest advantages of these actuators are their greater accuracy when compared to pneumatic actuators, their longer life cycle, and low maintenance. Adversely, their main disadvantage is that they do not offer high speeds.
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