Sequencing and Scheduling in Robotics Cells:  Recent Developments

Abstract:  A great deal of work has been done to analyze the problem of robot move sequencing and part scheduling in robotic cell flowshops.  We examine the recent developments in this literature.  A robotic cell flowshop consists of a number of processing stages served by one or more robots. Each stage has one or more machines that perform the stage's processing.  Types of robotic cells are differentiated from one another by certain characteristics, including robot type, robot travel-time, number of robots, types of parts processed, and use of parallel machines within stages.  We focus on cyclic production of parts.  A cycle is specified by a repeatable sequence of robot moves designed to transfer a set of parts between the machines for their processing.

We start by providing a classification scheme for robotic cell scheduling problems that is based on three characteristics:  machine environment, processing restrictions, and objective function, and discuss the influence of these characteristics on the methods of analysis employed.  In addition to reporting recent results on classical robotic cell scheduling problems, we include results on robotic cells with advanced features such as dual gripper robots, parallel machines and multiple robots.  Next, we examine implementation issues that have been addressed in the practice-oriented literature and detail the optimal policies to use under various combinations of conditions.  We conclude by describing some important open problems in the field.