What does the notation LOO indicate in Cartesian coordinate body-and-arm assembly?

• A. Three rotational joints in a plane
• B. A single sliding joint with a rotational capability
• C. A combination of one translational and two rotational joints
• D. Three sliding joints, two of which are orthogonal, known as a rectilinear robot or x-y-z robot

Answer: (D)

LOO means the joints are linear (sliding) actuators arranged so their motion directions are orthogonal. In a Cartesian coordinate body-and-arm, that gives three translational joints along X, Y, and Z, allowing movement in three perpendicular directions without rotation. All joints are sliding, and their axes are at right angles to each other, which is characteristic of a rectilinear or x-y-z robot. That’s why three sliding joints with two (actually all) orthogonal directions best matches LOO. The other descriptions involve rotational joints or mixed joint types, which do not fit this notation.