Robots have
mechanisms consisting of rigid links connected together by
joints with either linear (prismatic
P) or rotary (revolute
R) motion, or combinations of the two. Active prismatic
P and active revolute
R joints are driven by motors under programmable control to manipulate objects to perform complex automated tasks. The linear motion of active prismatic
P joints may be driven by rotary motors through gears or pulleys. Cartesian coordinate robots are controlled by mutually
perpendicular active prismatic
P joints that are aligned with the
X, Y, Z axes of a
Cartesian coordinate system. Although not strictly 'robots', other types of
manipulators, such as computer
numerically controlled (CNC) machines,
3D printers or
pen plotters, also have the same mechanical arrangement of mutually perpendicular active prismatic
P joints.
Joint topology A single chain of links and joints connects a moving object to a base of
serial manipulators. Multiple chains (limbs) connect the moving object to the base of
parallel manipulators. Most Cartesian coordinate robots are fully serial or a combination of serial and parallel connected linkages. However, there are some Cartesian coordinate robots that are
fully parallel-connected.
Degrees of freedom Since they are driven by linear active prismatic
P joints, Cartesian coordinate robots typically manipulate objects with only linear translation
T degrees of freedom. However, some Cartesian coordinate robots also have
rotational R degrees of freedom.
Construction Each axis of a Cartesian coordinate robot typically is a
linear stage consisting of a linear
actuator geometrically parallel with
linear bearings. The linear actuator is typically between two linear bearings spaced apart from each other to support
moment loads. Two perpendicular linear stages stacked on top of each other form a
XY table. Examples of XY tables include the XY axes of
milling machines or precision positioning stages. At least one of the linear stages of
cantilevered Cartesian coordinate robots is supported at only one end. Cantilevered construction provides accessibility to parts for pick-and-place applications such as
laboratory automation for example. Cartesian coordinate robots with the horizontal member supported at both ends are sometimes called gantry robots; mechanically, they resemble
gantry cranes, although the latter are not generally robots. Gantry robots are often quite large and may support heavy loads. ==Applications==