Actuators: Their Types and Functions

An actuator is a machine component responsible for moving and controlling a mechanism or system by opening a valve or carrying out a similar function. In essence, an actuator is a ‘mover.’ To function, an actuator requires a control signal and a source of energy. The control signal can be electric voltage or current, pneumatic or hydraulic fluid pressure, or even human power, and is relatively low energy. An actuator's energy sources can be electric current, hydraulic pressure, or pneumatic pressure. Upon reception of a control signal, the actuator responds by converting this energy into mechanical motion.

Actuators are used in control systems to perform operations or tasks. The control system can be simple (a fixed mechanical or electronic system), software-based (such as a printer driver or robot control system), a human, or any other input. There are many different types of actuators used in a broad range of applications. The most common types of actuators are hydraulic, pneumatic, electrical, mechanical, thermal/magnetic, and soft. This blog will explain their unique characteristics and provide examples of each type.

The first type of actuator, hydraulic actuators, are used to convert mechanical motion into linear, rotary, or oscillatory motion. Actuators of this type consist of a cylinder or fluid motor that utilizes hydraulic power to provide mechanical operation. Because liquids are especially difficult to compress, hydraulic actors are capable of considerable force. However, the limited acceleration of actuators restrict their usage. A common example of a hydraulic actuator is in a vehicle’s hydraulic brake system. Hydraulic actuators are designed with a hollow cylindrical tube that allows a piston to easily slide within it. When pressure is applied to one side of the piston, it is known as single acting. In this case, the piston moves in just one direction and a spring is used for the return stroke. However, pressure can be applied to both sides, and this is known as double acting. In this case, pressure variance between the two sides is what causes the piston to move on either side.

The function of a pneumatic actuator is to convert energy formed by a vacuum or high-pressure compressed air into linear or rotary motion. Simply put, pneumatic actuators convert pressure into force. This type of actuator offers many advantages over others. For one, pneumatic energy responds quickly to start and stop signals. Pneumatic actuators are also able to produce large forces even from relatively minute changes in pressure. A drawback of these actuators is that they require a power source to be stored in reserve for their operation. Two examples of pneumatic actuators are rack and pinion actuators, which are used for controls in valves and pipe, and pneumatic brakes found in vehicles, which are very responsive to small pressure changes applied by the driver.

The third type of actuator, an electrical actuator, is powered by a motor that converts electrical energy into mechanical torque. These actuators are commonly used to actuate equipment like solenoid valves that control water flow in pipes in response to electrical signals. The main advantages of electrical actuators are that they are a cheap, clean, and fast-working option. Another example of the use of electrical actuators is in solenoid-based electric bell ringing mechanisms. Because electrical actuators do not use oil, they are both the most widely-available and cost-efficient type of actuator.

Within electrical actuators, there are two subtypes: electromechanical and electrohydraulic. An electromechanical actuator works by converting the rotational force of an electric rotary motor into a linear motion to create a desired linear movement. The advantages of these actuators are their high level of accuracy and their long life cycles, though their drawbacks include limited speed and their size & weight. In electrohydraulic actuators, the electric motor remains the prime mover and creates torque to operate a hydraulic accumulator. This accumulator is then used to transmit an actuation force similar to the way that diesel engines and hydraulics are typically used in heavy equipment.

Mechanical actuators are a type of actuator that convert rotary motion into linear motion. They consist of gears, pulleys, rails, chains, and similar devices for their operation. Common examples of mechanical actuators can be found in rack and pinion mechanisms and crank shafts. Yet another type of actuator, thermal/magnetic actuators, are operated by the application of thermal or magnetic energy. These actuators utilize shape memory materials such as shape memory alloys and offer the advantages of being compact, lightweight, economic, and providing high power density.

The final type of actuator, soft actuators, are polymer based and designed to work in fragile & sensitive applications like fruit harvesting in agriculture or surgical operations in biomedicine. Examples of soft actuators include shape memory polymers and photo polymers. The function of shape memory polymers is similar to that of our muscles. It provides a response to many stimuli such as light, electricity, heat, magnetic fields, pH, moisture, and more. The advantages of these polymers are their low density, high strain recovery, bio-compatibility, and biodegradability. Photo polymers are also referred to as light activated polymers. They are a special type of shape memory polymer activated by stimulus from light.

While these are the most common types of actuators, other types include comb drives, electric motors, digital micromirror devices, electroactive polymer, piezoelectric actuators, screw jacks, and hydraulic cylinders. For actuators of all types and much more, look no further than Paragon Purchasing, a trusted supplier of parts for a wide range of industries. We are an online distributor of aircraft parts as well as parts pertaining to the aerospace, civil aviation, defense, electronics, and IT hardware markets. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-914-359-2001 or email us at sales@paragonpurchasing.com. Our dedicated account managers are standing by and will respond to your inquiries in 15 minutes or less.


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