An actuator is a component of a machine that is responsible for moving or controlling a mechanism or system, by converting energy into motion. It is the mechanism by which a control system acts upon an environment. It can be a simple system, such as fixed or electronic, or software-based, such as robot control.
Motion is usually created by air, electricity or liquid. The types of motion created by actuators are linear, rotary or oscillatory.
The most common types of actuator are as follows:
Pneumatic actuators convert energy formed by a vacuum or compressed air at high pressure into either linear or rotary motion. The advantage of this type of actuator is that has a quick response time as the power source doesn’t need to be stored in reserve. Large forces can be produced from relatively small pressure changes.
Hydraulic actuators consist of a cylinder or fluid motor that uses hydraulic power to drive mechanical operation. The motion output can be linear, rotary or oscillatory. The cylinder consists of a hollow tube along which a piston can slide. Despite having limited acceleration, a hydraulic actuator can exert considerable force as liquids are virtually impossible to compress.
Hydraulic actuators can be either single acting – when fluid pressure is applied to one side of the piston only – or double acting – where pressure is applied on both sides.
An electric actuator is powered by electrical energy converted by a motor. Electrical energy is used to actuate equipment such as multi-turn valves. Its advantage is that it is one of the cleanest forms of actuator as no oil is required.
 Thermal or magnetic
These actuators tend to be compact, lightweight and with high power density. They are actuated by applying thermal or magnetic energy.
A mechanical actuator functions by converting rotary motion into linear motion to execute movement. It involves gears, rails, pulleys, chains and other devices to operate. An example is a rack and pinion mechanism.
 Related articles on Designing Buildings Wiki
Featured articles and news
Graphene has many potential applications, but when will it start being used in civil engineering?
Increasing productivity – now more than ever as we lead up to Brexit – should be the sector’s number one priority in 2018.
Carillion's collapse causes Construction Leadership Council to delay the construction sector deal report.
Urban Heritage, Development and Sustainability: international frameworks, national and local guidance.
What will the General Data Protection Regulations (GDPR) mean for you when they come into force in May?
Business Secretary chairs a new taskforce to monitor and advise on mitigating the impacts of Carillion’s liquidation.
Sir John Armitt is appointed the new chair of the National Infrastructure Commission.
High quality and high density homes - is it what we need or is it storing up trouble?
Government announces its intention to strengthen planning rules to protect music venues and neighbours.
National Audit Office reports that there is little evidence that PFI offers better value than other forms of contracting.
What is liquidation and how does it apply to contractors in the construction industry?
Scrutiny is placed on Carillion's controversial 2013 decision to extend subcontractor payment terms to 120 days.