Robotics

The humanlike movements that a robot makes as it works can be accomplished with a relatively small number of mechanical systems. One of those systems is known as the rectangular or Cartesian coordinate system. This system consists of a set of components that can move in any one of three directions, all at right angles to each other.

Think of a three-dimensional system in which an x-axis and a y-axis define a flat plane. Perpendicular to that plane is a third axis, the z-axis. A rule can be made to travel along the x-axis, along the y-axis, or along the z-axis. Overall, the ruler has the ability to move in three different directions, back and forth along the x- and y-axes and up and down along the z-axis. A system of this type is said to have three degrees of freedom because it has the ability to move in three distinct directions.

Another type of mechanical system is the cylindrical coordinate system. This system consists of a cylinder with a solid column through the middle of it. The cylinder can move up and down on the column (one degree of freedom), and an arm attached to the outside of the cylinder can rotate around the central column (a second degree of freedom). Finally, the arm can be constructed so that it will slide in and out of its housing attached to the cylinder (a third degree of freedom).

A third type of mechanical system is the spherical coordinate system. To understand this system, imagine a rectangular box-shaped component attached to a base. The box can rotate on its own axis (one degree of freedom) or tilt up or down on its axis (a second degree of freedom). An arm attached to the box may also be able to extend or retract, giving it a third degree of freedom.

Many robots have more than three degrees of freedom because they consist of two or more simple systems combined with each other. For example, a typical industrial robot might have one large arm constructed on a Cartesian coordinate system. At the end of the arm there might then be a wrist-type component with the same or a different mechanical system. Attached to the wrist might then be a hand with fingers, each with a mechanical system of its own. Combinations of mechanical systems like this one make it possible for an industrial robot to perform a variety of complex maneuvers not entirely different from those of a human arm, wrist, hand, and finger.