A Cartesian coordinate robot (also called linear robot) is an

industrial robot An industrial robot is a robot system used for manufacturing. Industrial robots are automated, programmable and capable of movement on three or more axes. Typical applications of robots include welding, painting, assembly, disassembly, pick a ...

whose three principal axes of control are linear (i.e. they move in a straight line rather than rotate) and are at

right angle In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the ad ...

s to each other. The three sliding joints correspond to moving the wrist up-down, in-out, back-forth. Among other advantages, this mechanical arrangement simplifies the

robot control Robotic control is the system that contributes to the movement of robots. This involves the mechanical aspects and programmable systems that makes it possible to control robots. Robotics could be controlled in various ways, which includes using ma ...

arm solution In the engineering field of robotics, an arm solution is a set of calculations that allow the real-time computation of the control commands needed to place the end of a robotic arm at a desired position and orientation in space. A typical indust ...

. It has high reliability and precision when operating in three-dimensional space. As a robot coordinate system, it is also effective for horizontal travel and for stacking bins.

Configurations

Robot A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be c ...

s have mechanisms consisting of rigid links connected together by

joints A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

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 In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It can ...

active prismatic ''P'' joints that are aligned with the ''X, Y, Z'' axes of a

Cartesian coordinate system A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured in t ...

. Although not strictly ‘robots’, other types of manipulators, such as computer numerically controlled (CNC) machines,

3D printers 3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer co ...

pen plotters A pen is a common writing instrument that applies ink to a surface, usually paper, for writing or drawing. Early pens such as reed pens, quill pens, dip pens and ruling pens held a small amount of ink on a nib or in a small void or cavity whic ...

, 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 manipulator Serial manipulators are the most common industrial robots and they are designed as a series of links connected by motor-actuated joints that extend from a base to an end-effector. Often they have an anthropomorphic arm structure described as havin ...

s. Multiple chains (limbs) connect the moving object to the base of

parallel manipulator A parallel manipulator is a mechanical system that uses several computer-controlled serial chains to support a single platform, or end-effector. Perhaps, the best known parallel manipulator is formed from six linear actuators that support a mova ...

s. 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 A linear stage or translation stage is a component of a precise motion system used to restrict an object to a single axis of motion. The term linear slide is often used interchangeably with "linear stage", though technically "linear slide" refe ...

consisting of a linear

actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...

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 an XY table. Examples of XY tables include the XY axes of

milling machines Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done by varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of d ...

or precision positioning stages. At least one of the linear stages of

cantilever A cantilever is a rigid structural element that extends horizontally and is supported at only one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a canti ...

ed Cartesian coordinate robots is supported at only one end. Cantilevered construction provides accessibility to parts for pick-and-place applications such as

laboratory automation Laboratory automation is a multi-disciplinary strategy to research, develop, optimize and capitalize on technologies in the laboratory that enable new and improved processes. Laboratory automation professionals are academic, commercial and gover ...

for example. Cartesian coordinate robots with the horizontal member supported at both ends are sometimes called gantry robots; mechanically, they resemble

gantry crane A gantry crane is a crane built atop a gantry, which is a structure used to straddle an object or workspace. They can range from enormous "full" gantry cranes, capable of lifting some of the heaviest loads in the world, to small shop cranes, us ...

s, although the latter are not generally robots. Gantry robots are often quite large and may support heavy loads.

Applications

Popular applications for Cartesian coordinate robots are computer numerical control machine (

CNC machine Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a ...

) and

3D printing 3D printing or additive manufacturing is the Manufacturing, construction of a three-dimensional object from a computer-aided design, CAD model or a digital 3D modeling, 3D model. It can be done in a variety of processes in which material is ...

. The simplest application is used in milling machines and

plotter A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like vinyl or leather. In the latter case, they are sometimes known as a cutting pl ...

s where a tool such as a router or pen translates across an ''X-Y'' plane and is raised and lowered onto a surface to create a precise design. Pick and place machines are another application for Cartesian coordinate robots. For example, overhead gantry Cartesian robots ar
applied
for continuous parts loading and unloading on

CNC Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a p ...

lathes production lines, performing 3-axis ''(X, Y, Z)'' pick and place operations of heavy loads with high speed performance and high positioning accuracy. In general, overhead gantry Cartesian robots are suitable for many

automation Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...

systems.

References