Study of a rail-bound parallel robot concept with curvilinear closed-path tracks*

:Parallel robots are widely used within production facilities, especially for high speed tasks. To further increase speed when manipulating single objects in product streams, either faster robots or multiple robots working simultaneously have to be used. In this work, we present a multi-robot approach which consists of parallel robots that can travel independently along a linear, curvilinear open or closed-path track. Thus, the robots can perform manipulation tasks on moving objects, e.g. products being transported on a conveyor, over relatively long traveling distances. The presented approach is based on the commercially available Extended Transport System (XTS). The XTS allows high speed positioning of passive movers along a track, which consists of straight or curved linear motor modules. We propose a robot structure driven by four movers, able to travel along the tracks of two parallel XTS devices. Multiple robots can be used on the same pair of tracks and controlled independently, saving costs as the robots' structure includes no active elements. We propose both a three degrees of freedom (DOF) and a four DOF variant of the robot and discuss the problem of traversing curvilinear tracks. The kinematics of the redundant three DOF variant is then analyzed for the case of linear tracks: we present explicit solutions of the inverse and direct kinematic problem, determine workspace and singularities, and evaluate the robot's performance. Finally, we present a prototype based on a simple joint space control scheme to show the feasibility of our approach.