This article assesses the benefits of implementing a dual-arm robot in a flow shop manufacturing cell. Such a robot has the ability to tend (unload or load) to two adjacent machines simultaneously. This significantly changes the analysis required to find sequences of robot actions that maximize a cell's throughput. For cells processing identical parts, optimal sequences are identified for two- and three-machine cells and also structural results are derived for cells with an arbitrary number of machines. Cells processing different part-types are fully analyzed for the case of two-machine cells. For each case the productivity of single-arm and dual-arm robotic cells is compared.

A robotic cell - manufacturing system widely used in industry - contains two or more robot-served machines, repetitively producing a number of part types. In this paper, we consider scheduling of operations in a bufferless dual-gripper robotic cell processing multiple part types. The processing constraints specify the cell to be a flowshop. The objective is to determine the robot move sequence and the sequence in which parts are to be processed so as to maximize the long-run average throughput rate for repetitive production of parts. We provide a framework to study the problem, and address the issues of problem complexity and solvability. Focusing on a particular class of robot move sequences, we identify all potentially optimal robot move sequences for the part-sequencing problem in a two-machine dual-gripper robot cell. In the case when the gripper switching time is sufficiently small, we specify the best robot move sequence in the class. We prove the problem of finding an optimal part sequence to be strongly NP-hard, even when the robot move sequence is specified. We provide a heuristic approach to solve the general two-machine problem and evaluate its performance on the set of randomly generated problem instances. We perform computations to estimate the productivity gain of using a dual-gripper robot in place of a single-gripper robot. Finally, we extend our results for the two-machine cell to solve an m-machine problem.

A great deal of work has been done to analyze the problem of robot move sequencing and part scheduling in robotic flowshop cells. We examine the recent developments in this literature. A robotic flowshop cell consists of a number of processing stages served by one or more robots. Each stage has one or more machines that perform that 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.

This book focuses on the design of Robotic Flexible Assembly Cell (RFAC) with multi-robots. Its main contribution consists of a new effective strategy for scheduling RFAC in a multi-product assembly environment, in which dynamic status and multi-objective optimization problems occur. The developed strategy, which is based on a combination of advanced solution approaches such as simulation, fuzzy logic, system modeling and the Taguchi optimization method, fills an important knowledge gap in the current literature and paves the way for future research towards the goal of employing flexible assembly systems as effectively as possible despite the complexity of their scheduling.

Industrieroboter gehoren heute zum Alltag. In den letzten zehn Jahren verlagerte sich der Schwerpunkt der Neuentwicklungen weg von den Robotern selbst, hin zu alternativen Formen der kunstlichen Intelligenz, mit denen die Gerate ausgestattet werden. Dem Rechnung tragend, beschaftigt sich die zweite Auflage dieses Handbuchs vor allem mit Anwendungen und Strategien zur Problemlosung in der Industrie. Angesprochen werden Themen wie Graphiksimulatoren, objektorientierte Software, Kommunikationssysteme und Mikro- und Nanoroboter. (04/99)