Robotic actuators – Hydraulic and Pneumatic

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


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.

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