Cobot control

Abstract

Cobots are a class of mechanically passive robotic devices, intended for direct physical collaboration with a human operator. The operator supplies all motive power while the cobot enforces software-defined guiding surfaces, or constraints. Cobots are intrinsically passive, safe devices. This is because, rather than employ powered actuators to produce constraint forces, cobots use "steerable" nonholonomic joints. Constraint forces are mechanical in origin, yet software defined. The simplest possible cobot is a unicycle which is steered by a servo system acting under computer control, but which is moved by a human operator. The unicycle cobot requires essentially no consideration of kinematics. Two fundamental control modes of the unicycle cobot, "virtual caster" and "constraint tracking", are reviewed. More complicated cobots, such as the three-wheeled "Scooter", require a set of kinematic tranformations relating configuration space to joint space. These transformations play a role in cobot control like that of the Jacobian in robot control.