| This work presents the collaborative robot or “cobot”, a novel approach to providing a high-performance intelligent assist device, which can enhance ergonomics, productivity, and safety. Cobots are a class of hybrid human-controlled/computer-controlled robotic devices, thus falling in the area known as haptic display.; Cobots implement software-defined virtual guiding surfaces, as well as in some cases providing amplification of human power (“power assist”). To do these cobots, make use of steerable nonholonomic joints to produce the guiding surfaces that aid the operator. This unique steering system, in place of powerful actuators, results in guiding surfaces that are smooth, frictionless, and intrinsically stable making cobots particularly appropriate for safety-critical tasks.; This thesis focuses on prototype development, cobot architecture, and cobot control. Prototypes include the unicycle cobot, the simplest cobot, which employs one servo-steered wheel to guide and direct motions imparted by the operator. A second, three-wheeled cobot, “Scooter”, requires a set of kinematic transformations relating configuration space to joint space. These transformations play a role in cobot control like that of the jacobian in robot control.; Two fundamental control modes of cobots, “virtual caster ” and “virtual wall”, are presented. Virtual caster control aims to perceptually eliminate the wheels and make the cobot behave like a point mass in space. Virtual wall control aims to create the perception of a hard, smooth surface that the cobot can move along but not penetrate. Since cobot wheels do exhibit sideslip, however, we develop a feedback controller to compensate for errors.; Pleasing results are given by the cobots. Virtual walls implemented by cobots are hard, smooth, and realistic. Virtual caster mode is smooth and easy to maneuver. To change directions, the operator need apply only small forces. These benefits stem from the fact that cobots redirect motion by steering, and therefore conserve kinetic energy.; Early industrial applications of cobots in automobile final assembly plants are underway, and two cobots presently in industrial environments are described. The preliminary results are promising. The “cobot door unloader” is reported to cut cycle time by half, improve ergonomics, and improve process quality. |
