An actuator is an electromechanical device or a motor that controls movement in a robotic system by converting electrical energy into motion. The source of energy of the actuators can be compressed air, pressurized fluid or electric current. Actuators are operated based on the response to the signal from the control unit.
Principle of Operation
The three major types of actuators and the principles they are based on are as follows:
Hydraulic actuators – Hydraulic actuators follow Pascal’s law. The most common type of power source that drives the hydraulic system is a pump. The pump works by generating pressure waves which is continuously transmitted via the hydraulic fluid tubes, i.e., return and supply lines. The pressure waves eventually come in contact with a piston surface thereby exerting a force on the surface. This force enables the piston to move forward and backward causing a pressure difference between two sides of the piston.
Pneumatic actuators – Pneumatic actuators are operated by converting the effect of compressed air into linear or rotational motion. The expansion of compressed air filled in a cylinder to achieve atmospheric pressure level exerts a force on a piston to which the actuator is attached. Pneumatic actuators are often employed in applications that require a rapid and precise response.
Electric actuators – Electric actuators consist of a reversible synchronous motor that converts electrical energy into mechanical energy. The motor is connected to a gear train that reduces the speed of the motor thereby increasing the mechanical torque. These actuators have more than 90% efficiency and are the safest of all types.
Some of the typical applications of robotic actuators are listed below:
Pneumatic actuators are used in robotic systems such as legged robots and haptic devices which require high payload to weight ratio, small size, and lightweight characteristics.
Hydraulic actuators are widely employed in remotely operated vehicles for underwater applications and other heavy-duty industrial applications such as nuclear operations.
Electric actuators such as servo motors are used for controlling the position of robots while performing pick and place operations.
Sources and Further Reading