US Patent 10029369 Collaborative robot

A collaborative robot employs low ratio drives for three or more axes of movement, such as three primary axes. An arm assembly may be mounted to a support for movement along a vertical linear axis, and the arm assembly may include first and second arm links that are each rotatable about vertical axes, e.g., such that the arm links move in a horizontal plane. Low ratio drives may be used for movement along the vertical linear axis and the rotary axes for the first and second arm links. Feedforward and feedback control may be employed to control the movement of the arm assembly and arm links, and feedback torque components may be limited to 25% or less of the maximum drive torque.