In general, degrees of freedom (DOF) are the set of independent displacements that specify completely the displaced or deformed position of the body or system.
In robotics, degrees of freedom is often used to describe the number of directions that a robot can move a joint. A robot that has mechanisms to control all the six physical degrees of freedom is said to be holonomic. An object with fewer controllable degrees of freedom that the total degrees of freedom is said to be non-holonomic, and an object with more controllable degrees of freedom than total degrees of freedom is said to be redundant.
A manipulator consists of joints and links. Joints provide relative motion. Links are rigid members between joints. There are various joint types, linear and rotary. Each joint provide a “degree of freedom”. Most robots possess five or six degrees of freedom
A robot manipulator consists of two sections:
• Body and arm – for positioning of objects in the robot’s work volume
• Wrist assembly – for the orientation of objects
A robot architecture is the combination and disposition of the different kinds of joints that configure the robot kinematical chain.
There are five common body-and-arm configurations for industrial robots.
• Polar coordinate body-and-arm assembly
• Cylindrical body-and-arm assembly
• Cartesian coordinate body-and-arm assembly
• Jointed-arm body-and-arm assembly
• Selective Compliance Assembly Robot Arm (SCARA)
SCARAT stands for Compliance Assembly Robot Arm. SCARA Robot are similar to jointed-arm robot except that vertical axes are used for shoulder and elbow joints to be compliant in horizontal direction for vertical insertion tasks.