A review of recent theoretical development in scheduling dual-gripper robotic cells

A robotic cell is a set of machines or processing centres served by a robot or a set of robots. Robotic cells can be classified by certain physical and operating characteristics such as robot type (single- or dual-gripper), robot travel-time (constant, additive or Euclidean) and types of parts processed (no-wait, interval processing time or free-pickup). Robotic cells are used in automated manufacturing systems where jobs or parts are produced in a typical flow shop type environment. A significant research effort has been directed towards analysing the problem of robot move sequencing in robotic cells served by single- or dual-gripper robot. In this review paper, we examine the recent theoretical developments on the analysis of throughput optimisation in robotic cells served by a dual-gripper robot. We focus on the problem of scheduling operations in dual-gripper robotic cells that produce identical parts. The objective is to find a cyclic sequence of robot moves that minimises the long-run average time to produce a part or, equivalently, maximises the throughput. The goals of this review paper are to: (i) provide a discussion of existing structural analysis, algorithmic and complexity results for robotic cells under conditions that are common in practice and (ii) present a set of open problems and future research directions. In addition to reporting recent results for dual-gripper robotic cell scheduling problems, we provide insight into a class of cyclic sequences that are not considered in practice but can improve throughput.