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An electromechanical actuator is a device that converts electricity to mechanical force in such a way as to perform some type of work, most often physically moving some object or device. They can have a very wide range of shapes, sizes, and designs, but all work on the same basic principle of converting electricity to motive force. The motive force generated can be used to move large doors, to operate switches for sorting conveyor systems, or to move powered valves. In some cases, an electromechanical actuator can be designed to hold an object or to prevent a particular type of motion.
Every device that directly converts electricity to some type of motion is an electromechanical actuator. The number of devices covered by this term is extremely large. Several main types cover a very large percentage of these devices, however, and they are classified in two ways, by the type of mechanism that converts the electricity to motion and by the direction of motion achieved.
One of the most common devices of this type is the linear actuator. A linear actuator moves in a straight line. A linear electromechanical actuator is used to move objects like louvers on windows, sliding doors, the position of a tool or other machine, or to move flight control surfaces on aircraft. These are just a few examples and many more are common in all phases of industry and every day life. A rotary actuator moves something with a spinning or rotary motion, such as a rotating fan.
Linear actuators can convert electricity to motion in one of two main ways, through an electric motor and through piezoelectricity. Electric motors use an electric current to create a magnetic field, which results in the rotary motion of a spindle or wheel. For linear actuators, this rotary motion is converted to linear motion through the use of gears or a type of assembly called a bolt and screw transducer. This consists of essentially two cylinders with matched helical grooves that lie parallel to and in contact with each other. One is turned by the electric motor, and as it spins, it spins the other cylinder, moving it in a linear fashion.
Piezoelectric actuators use a phenomenon called piezoelectricity, in which certain materials generate a weak electric charge when subjected to physical pressure. The forces and charges generated are often very small, and these types of actuators are also small. They are used in applications where great precision is desired.