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Four Types of Actuators

6/28/2013 8:11:21 AM | by Anonymous


An actuator is a kind of motor that controls or moves mechanisms or systems. It takes hydraulic fluid, electric current or other sources of power and converts the energy to facilitate the motion. Actuators are extremely useful devices and have a diverse range of uses in fields such as engineering, electronic engineering and can be found in many kinds of machinery such as printers, cars or disk drives. Most actuators produce either linear (straight line), rotary (circular) or oscillatory motion.

Actuators allow more load, force, control, ruggedness, speed and duty cycle to be supported. Speed is vital especially in the case of motion control equipment. The process of converting sources of power into energy has been a great innovation to machinery. The efficiency brought about by actuators make them a cost effective alternative to human operation.

There are four main types of actuators: Hydraulic, Pneumatic, Electric and Mechanical.

Hydraulic actuators consist of a cylinder or fluid motor that utilizes hydraulic power to facilitate mechanical process. The mechanical motion gives an output in terms of linear, rotary or oscillatory motion. Since liquids are nearly incompressible, they take longer to gain speed and power and also slow back down, but they can exert great force. The hydraulic actuator also allows for very precise control of the movement produced. In linear hydraulic actuators, a typical set-up is made up of a hollow cylinder that contains a liquid, usually oil, and a piston that is inserted in it. When pressure is applied onto the piston, objects can be moved by the force produced. Hydraulic actuators can be operated manually, such as a hydraulic car jack, or they can be operated through a hydraulic pump, which can be seen in construction equipment such as cranes or excavators.

Pneumatic actuators work on the same concept as hydraulic actuators except compressed gas is used instead of liquid. Energy, in the form of compressed gas, is converted into linear or rotary motion, depending on the type of actuator. Pneumatic energy is more desirable for main engine controls because it can quickly respond in starting and stopping as the power source does not need to be stored in reserve for operation. Also, pneumatic actuators are preferred in places where cleanliness is important, since the fluid in hydraulic actuators might leak and contaminate the surroundings. However, pneumatic actuators are still likely to leak, making them less efficient compared to mechanical actuators. Another downside is that they take up a lot of space, create a lot of noise and are difficult to transport once installed in a place.

Another type of actuators is electric actuators. Electric actuators are devices powered by motors that convert electrical energy to mechanical torque. The electrical energy is used to create motion in equipment that require multi-turn valves like gate or globe valves. Since no oil is involved, electrical actuators are considered to be one of the cleanest and readily available forms of actuators. Electric actuators are typically installed in engines, where they open and close different valves. There are many designs of electric actuators and this depends on their function in the engine that they are installed in.

Mechanical actuators function through converting rotary motion to linear motion.when a rotary motion. Devices such as gears, rails, pulley, chain and others are used to help convert the motion. Some of the simple mechanisms used to convert motion are screws, where the rotation of the actuator's nut causes the screw shaft to move in a straight line, the wheel and axle, where the rotating motion of a wheel causes a belt or something similar to move in a linear motion.

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