Cobots: robots for collaboration with human operators

A 'cobot' is a robotic device which manipulates objects in collaboration with a human operator. A cobot provides assistance to the human operator by setting up virtual surfaces which can be used to constrain and guide motion. While conventional servo-actuated haptic displays may be used in this way also, an important distinction is that, while haptic displays are active devices which can supply energy to the human operator, cobots are intrinsically passive. This is because cobots do not use servos to implement constraint, but instead employ 'steerable' nonholonomic joints. As a consequence of their passivity, cobots are potentially well-suited to safety-critical tasks (e.g. surgery) or those which involve large interaction forces (e.g. automobile assembly). This paper focuses on the simplest possible cobot, which has only a single joint (a steerable wheel). Two control modes of this 'unicycle cobot', termed 'virtual caster' and 'virtual wall' control, are developed in detail. Experimental results are also presented.