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Types Of Industrial Robots -Robot Classification

Robot Classification

Robots are being classified on the basis of their physical configuration and control systems adopted. These classifications are briefly described as follows :

1.Classification on the Basis of Physical Configurations

On the basis of physical configuration industrial robots are classified in four different types. They are :
(i) cartesian configuration,
(ii) cylindrical configuration,
(iii) polar configuration, and
(iv) jointed-arm configuration.

Cartesian Configuration
Robots having cartesian configurations consist of links connected by linear joints (L). As the configuration has three perpendicular slides, they are also called rectilinear robots. Robot having a similar configuration is known as Gantry Robots. Its structure resembles a gantry-type crane.

Cylindrical Configuration
In the cylindrical configuration, robots have one rotatory (R) joint at the base and linear (L) joints succeed to connect the links. The space in which this robot operates is cylindrical in shape, hence the name cylindrical configuration.

Polar Configuration
Polar robots have a work space of spherical shape. In general, the arm is linked to the base with a twisting (T) joint and rotatory (R) and or linear (L) joints. The designation of the arm for this arm can be TRL or TRR. Robots with the description of TRL are also called spherical robots. Those having the designation of TRR are called as articulated robots. It resembles a human arm in terms of configuration.

Jointed-Arm Configuration
The combination of cylindrical and articulated configurations is known as jointed-arm configuration. The arm of the robot is connected to the base with a twisting joint. Rotatory joints are used to connect the links in the arm. Generally, the rotation takes place in the vertical plane. Popular robot falling under this category is called SCARA (Selective Compliance Assembly Robot Arm). It is basically used for the assembly purpose.

2. Classification based on Control Systems

On the basis of the control systems adopted, robots are classified into the following categories :
(i) Point-to-point (PTP) control robot
(ii) Continuous-path (CP) control robot
(iii) Controlled-path robot

Point-to-Point (PTP) Control Robot
The PTP robot is capable of moving from one point to the other point. The locations are recorded in the control memory. The paths are not controlled by the path guide. Instead the desired path is traced by programming a series of points. Component insertion, spot welding, hole drilling, machine loading, unloading and crude assembly are some of the common applications of this type of robot.

Continuous-Path (CP) Control Point
The movement along the controlled path is performed by the CP robot. Along the controlled path, with CP control, the robot can stop any specified point. In the robot’s control memory, all the points must be stored explicitly. Straight-line motion is being carried out by these types of robots. Some continuous-path controlled robots also have the capability to follow a smooth curve path that has been defined by the programmer. Here, the programmer manually moves the robot arm through the desired path and the controller unit stores a large number of individual point locations along the path in memory.

Controlled-Path Robot
In controlled-path robots, the control equipment can develop paths of different geometry such as straight lines, circles, and interpolated curves with a high degree of accuracy. Good accuracy can be obtained at any point along the specified path. Only the start and finish points and the path definition function must be stored in the robot’s control memory. It is important to mention that all controlled-path robots have a servo capability to correct their path.