The actuators are used in the robots for providing the power to the robot joints. It can be powered by anyone of the following sources:

• Hydraulic – pressurized fluid
• Pneumatic – compressed air
• Electric – electricity

Hydraulic and Pneumatic actuators:

Both hydraulic and pneumatic actuators use moving fluids for powering a device. Here, the fluid represents pressurized oil for hydraulic and compressed air for pneumatic actuators.

When these actuators are compared with each other, two things can be observed such as:

• Both actuators are similar in terms of their operational functions.
• These actuators differ only in their capability to pressure the fluid.

The hydraulic actuator is capable of providing the pressure at 1000 – 3000 lb/in², while the pneumatic actuator can only deliver around 100 lb/in².

Let us consider a cylinder, which is one of the simplest devices for powering the fluids. In this device, a moving piston is available for actuating the linear joint.

This type of device is known as single – ended cylinder, because it has only one end in which the piston rod comes out. There are also some types of cylinders like:

• Rodless cylinder
• Double – ended cylinder

A set of relationships describe the particular interest of the actuators:

• The actuator velocity relating to the input power.
• The actuator force relating to the input power.

These relationships for a cylinder-type actuator can be given by:

V (t) = f (t) / A

F (t) = P (t) A

Here,

P (t) represents the fluid pressure.

V (t) represents the piston velocity.

F (t) represents the force.

A represents the piston area.

f (t) represents the flow rate of the fluid.

The relations illustrated to select a suitable robot can be according to the requirements of a robot that is necessary for carrying a load at a specified speed.