Four Common Robot Configuration – Pedagogy Zone

Industrial robots are available in a wide variety of sizes, shapes and physical configurations. The vast majority of today’s commercially available robots possess one of four basic configurations:

1. Polar configuration
2. Cylindrical configuration
3. Cartesian coordinate configuration
4. Jointed-arm configuration

The four basic configurations are illustrated in the schematic diagrams of fig. The polar configuration is pictured in part (a) of fig. It uses a telescoping arm that can be raised or lowered about a horizontal pivot. The pivot is mounted on a rotating base.

These various joints provide the robot with the capability to move its arm within a spherical space, and hence the name “spherical coordinate” robot is sometimes applied to this type.

The cylindrical configuration as shown in fig (b), uses a vertical column and a slide that can be moved up or down along the column.

The robot arm is attached to the slide so that it can be moved radially with respect to the column. By rotating the column, the robot is capable of achieving a work space that approximates a cylinder.

The cartesian coordinate robot illustrated in fig (c), uses three perpendicular slides to construct the x,y, and z axes.

Other names are sometimes applied to this configuration, including xyz robot and rectilinear robot. By moving the three slides relative to one another, the robot is capable of operating within a rectangular work envelope.

The jointed-arm robot as shown in Fig (d) is made up of rotating joints. This robot configuration is also sometimes called anthropomorphic as its anatomy is similar to the human-arm.

There are relative advantages and disadvantages to the four basic robot anatomies simply because of their geometries. In terms of repeatability of motion (the capability to move to a taught point in space with minimum error), the box-frame cartesian robot probably possesses the advantage because of its inherently rigid structure. In terms of reach (the ability of the robot to extend its arm significantly beyond its base), the polar and jointed arm configurations have the advantage.

The lift capacity of the robot is important in many applications. The cylindrical configuration and the gantry  robot can be designed for high rigidity and loadcarrying capacity. For machine-loading applications, the ability of the robot to reach into a small opening without interference with the sides of the opening is important. The polar configuration and the cylindrical configuration possess a natural geometric advantage in terms of this capability.