A robot, also called a droid, is a machine, especially one programmable by a computer and capable of carrying out a complex series of actions automatically.
The structure of a robot is usually mostly mechanical and is called a kinematic chain. It is functionally similar to the skeleton of human body. The chain is formed of manipulators (its hands and legs), endeffectors (it's palms and fingers), locomotion devices or motors (its muscles), controllers (its brain) and sensors (its sense organs)
Just like the human arm, the robot consists of what is called a manipulator having several joints and links. Most robots arms are replaceable effectors, each allowing them to perform some small range of tasks. Some have a fixed manipulator which cannot be replaced, while a few have one very general purpose manipulator.
The base of the manipulator is fixed to base support and at its other free end, the Endeffector is attached. The Endeffector is expected to perform tasks normally performed by the palm and finger arrangements of the human arm.
3. The Locomotion Device:
In the case of Human Beings the power for the movement of the arm, the palm and fingers is provided by muscles. For the robot the power for the movement (locomotion) is provided by the motors. The motors used for providing locomotion in robots are of three types depending on the source of energy: Electric, Hydraulic or Pneumatic.
4. The Controller:
The digital computer (both the hardware and the software) acts as a controller to the robot. The controller functions in a manner analogous to the human brain. With the help of this controller, the robot is able to carry out the assigned tasks. The controller directs and controls the movement of the Manipulator and the Endeffector. In other words, the controller controls the robot.
5. The Sensors:
Without the data supplied by the sense organs, the brain would be incapable of intelligence. In other words the controller (the computer) of the robot cannot do any meaningful task, if the robot is not with a component analogous to the sense organs of the human body. Thus, the fifth and the most important component of the robot is the set of sensors. Sensors are nothing but measuring instruments which measures quantities such as position, velocity, force, torque, proximity, temperature, etc.