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An important issue in the operational control of an automated job shop is the prevention and resolution of shop deadlocks. In this paper, we discuss the problems and solutions of deadlocks in manufacturing systems with automated guided vehicle systems, describe a banker's algorithm for the control of material flow in job shops, and present the results of simulation experiments to compare the performance of several deadlock handling methods.

This paper introduces the segmented bidirectional single-loop (SBSL) flow topology for carrier-based material handling systems. This configuration is based on a single-loop flow-path structure that is divided into non-overlapping segments, each containing a single carrier operating in a bidirectional mode. The design procedure comprises a 0 - 1 mixed-integer formulation to determine the single-loop including the pickup and delivery station location. The second stage is a segmentation procedure to determine the non-overlapping segments in the loop. Finally the performance of the SBSL is evaluated by means of simulation., 1. Introduction Material handling continues to play a critical role in the operation of manufacturing systems. Although not a value-adding step in manufacturing, an efficient delivery system of materials on [...]

This research investigates the importance of the within-building constraints on the solution speed of the machine layout problem. The machine layout problem, or the more general facility layout problem, has been well studied. Often, practical constraints such as within-building constraints are ignored when the modeller is not space-restricted. This research develops an ‘implied’ within-building constraint for the single-row machine layout model. The incorporation of such constraints may assist layout planners in obtaining higher quality (or known-quality) solutions within shorter planning periods. The impact of the constraint is assessed in several ways. First, the constraint is evaluated on several problems arising from the literature using the time to solution and objective function value as metrics using mixed-integer linear and nonlinear formulations. In addition, statistical assessments are made using the time to solution and objective function value metrics. [ABSTRACT FROM PUBLISHER]

This research studies the facility layout problem from the perspective of geometric structures. It reports that a regular hexagonal floor plan has shorter expected travel distance using rectilinear and Euclidean distance compared to popular floor plans having equal area in practice, including rectangular, square, and square-diamond. For this analysis, both probability and simulation models were developed. Based on this result, this paper proposes two layout applications using the regular hexagonal floor plan and its compatible material flow patterns. The analyses show that the newly proposed layout applications perform better than conventional layout alternatives used for flexible manufacturing systems. [ABSTRACT FROM AUTHOR]

This research explores the double row layout problem (DRLP) that deals with how to place departments or machines on both sides of a central corridor. This type of layout problem is commonly observed in production and service facilities. Over the last 40 years, researchers have extensively studied a similar problem called the single row layout problem (SRLP) or one dimensional space allocation problem (ODSAP); as a result, several practical approaches are currently available for the problem. However, the DRLP has not received much attention in the literature although it often provides a better structure for layout designers. In this research, we first develop an MIP model for the DRLP that involves more variables and constraints than existing formulations of the SRLP. In turn, conditions yielding a good solution are analysed based on the proposed model. Five heuristic algorithms are developed to provide a reasonably good initial solution and corresponding upper bound of the DRLP. The performance of these heuristic algorithms, as well as MIP solutions by CPLEX 10.2, is compared in a series of experiments. [ABSTRACT FROM AUTHOR]

The design and justification of an integrated manufacturing system and all of the supporting sub-systems (e.g. material handling system) is a difficult task. One of the most difficult aspects in the design process is determining how and where to proceed. This paper proposes the use of a marginal, analysis-directed branch and bound approach as the basis for directing the design process so that a combined economic and performance justification path results. The background and rationale for a marginal analysis guided design approach is given and an example of a material handling system design is presented to illustrate the development of a design justification decision path. [ABSTRACT FROM AUTHOR]

Due to increases in versatility and the complexity of demands in modern manufacturing systems a growing need has evolved to simplify the control of these systems while maintaining a high degree of efficiency and flexibility in operation. The segmented flow approach (SFT) suggested in this paper is a possible solution to these needs. This structure simplifies the control task by reducing the need for dispatching and by eliminating the need for routeing material handling devices and scheduling traffic at intersections. Each task involves only one material handling device and one possible route. This structure maintains a high degree of efficiency by operating material handling devices in a bidirectional mode and eliminates congestion and blocking by operating them on mutually exclusive tracks. This paper introduces a design procedure for an SFT implemented system using a minimum cost objective, and compares the throughput and time in system performance of this system to a conventional system and a tandem type system by means of simulation. [ABSTRACT FROM AUTHOR]

Here introduced a framework for the evaluation of material flow system models diagnosis of model performance problems, selection of model improvement actions and the implementation of these actions. Many of the actions in this model evaluation and redesign process cannot be modelled through specific procedures. Whenever this is the case we encourage the involvement of the designer by providing decision support, e.g. in determining whether the model performance is actually met and in selecting model improvement actions. In situations in which design tasks can be automated, the framework allows the integration of design tools that can take over these tasks. We present strategies for addressing tasks within the evaluation and redesign process as well as their implementation. The concepts presented are implemented in a design workstation for material flow systems. [ABSTRACT FROM AUTHOR]

The design of material flow systems is a multifaceted problem. The designer is required to process large amounts of information and make complex decisions concerning the design objectives. A design framework for building material flow system models has been developed by the authors to take key steps towards the management of design complexity. This paper addresses the issue of selecting and sequencing software tools for building material flow system models within a design environment that contains a variable set of design tools. Strategies for performing these tasks as well as their implementation are discussed. [ABSTRACT FROM AUTHOR]

In this paper we propose a framework for the management of the complexity involved in building material flow system models. The object-orientated paradigm is applied as a tool to break down the material flow system model, as well as the design environment, into modules. The designer is provided with a generic material flow system model from which to start with the design process. The model is built, evaluated and improved using a collection of software applications that have been developed to address partial problems in the material flow system design process. The organization of design data and design tools into logical units clearly establishes precedence between software and data. This feature opens up possibilities for computer-assisted design tool sequencing. [ABSTRACT FROM AUTHOR]

Bidirectional AGV systems are intuitively more attractive than unidirectional systems in terms of efficiency because of shorter travel distances. An efficient algorithm for finding conflict-free shortest-time routes for automated guided vehicles moving in a bidirectional flow path network has been proposed in a previous paper. This paper is a sequel and describes a conservative myopic strategy to coordinate the movements of vehicles in a bidirectional AGV system. Simulation results are presented to compare the performances of unidirectional and bidirectional systems. [ABSTRACT FROM AUTHOR]

In this paper, we suggest a branch-and-bound procedure for designing flow paths of fixed-path material handling systems. The method may be applied to automated monorail systems (AMS), automated guided vehicle systems (AGVS), flexible conveyor systems and other fixed-path material handling systems. We formulate an economic model which considers the construction cost of each path segment as well as the travel cost. A procedure is developed to determine the configuration of flow path and the direction of each flow path segment. A tight lower bound for the optimal objective function and an efficient search strategy are suggested. Computational performance of this procedure is compared with a procedure previously developed by Kaspi and Tanchoco for the special case of AGV systems. [ABSTRACT FROM AUTHOR]

Guide path simplification can potentially reduce the complexity inherent in conventional, multi-loop automated guided vehicle systems (AGVs). A single-loop configuration is one alternative. A procedure for designing single-loop AGV systems, the OSL method was presented in a previous paper. In this paper, we suggest faster and more efficient methods for solving the two mathematical models in the OSL procedure. The first model called the valid single-loop problem (VSLP) is used to determine an initial single loop for the procedure. The method suggested is a heuristic procedure that starts from a loop around one of the departments and keeps adding departments to the loop until a valid single loop is constructed. The second model called the single-loop station location problem (SLSLP) is used to determine the location of the pick-up and delivery stations along a given loop. The method suggested converts the mixed integer formulation into a linear formulation. [ABSTRACT FROM AUTHOR]

The integrating nature of material handling systems renders their design and economic justification critical to the performance of a manufacturing system. This paper describes a framework for the concurrent design and economic justification of a material handling system (MHS). An approach to concurrent design and economic justification termed design justification is presented, followed by a discussion of the nature of the MHS selection and specification problems. The design justification framework utilizes a modified branch and bound concept which is guided by a marginal-analysis-based modification strategy. The prototype implementation of the design procedure involves automatic generation of discrete optimization, capacity, queueing network and simulation models. Illustrative examples are given of the design logic and information used within the framework. The application of the design justification framework enables system designers to develop material handling systems that are justifiable from both a performance and economic perspective. [ABSTRACT FROM AUTHOR]

With the increasing trend in the use of automated guided vehicles systems (AGVS) in manufacturing, the need for design tools becomes greater. The problem is that optimized static design models do not ensure expected performance due to the difficulty in capturing the dynamic operational characteristics of the vehicle system. This study shows that by using the single-loop guide path configuration some of the dynamic features of the system, like the impact the empty vehicle flow has on the system's performance, is reduced. Thus, a more reliable prediction of system performance is achieved. [ABSTRACT FROM AUTHOR]

One of the important issues in the design of an automated guided vehicles system (AGVS) is the determination of the number of vehicles needed to operate the system in an efficient and economical way. In this paper a multi-criteria optimization model is developed using two goals, cost and throughput performance. By using a trade-off ratio between the goals the number of AGVs needed in the systems is determined. Use of management decision tables to enhance the solution procedure is introduced. [ABSTRACT FROM AUTHOR]

This study deals with the Automated Guided Vehicle System guide path design problem. We suggest a single closed loop guide path layout configuration as an alternative to conventional but more complex guide path designs. The benefits of using a simple guide path versus more complicated guide paths are discussed. A procedure for designing an optimal single loop guide path for a given facility layout is presented. Finally, the single loop's throughput performance is tested and compared to that of a more complex guide path. [ABSTRACT FROM AUTHOR]

This paper presents an efficient algorithm for finding conflict-free shortest-time routes for automated guided vehicles moving in a bidirectional flow path network. The proposed algorithm is based on Dijkstra's shortest-path method. It maintains, for each node, a list of time windows reserved by scheduled vehicles and a list of free time windows available for vehicles to be scheduled We introduce the concept of time window graph in which the node set represents the free time windows and the arc set represents the reachability between the free time windows. Then the algorithm routes the vehicles through the free time windows of the time window graph instead Cf the physical nodes of the flow path network. It requires o(v4n2) computations in the worst case. where v is the number of vehicles and ii is the number of nudes. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the Intersection Graph Method for solving the AGV Flow Path Optimization Model developed by Kaspi and Tanchoco (1990). A branch-and-bound procedure is described wherein only a reduced subset of all nodes in the flow path network is considered. Only intersection nodes are used to obtain optimal solutions. Two examples are given to illustrate the proposed method. [ABSTRACT FROM AUTHOR]

In today's globally competitive world it is essential to design products with maximized functionality and minimized costs. An environment that facilitates the interactions between design and justification would enhance such a decision process. A conceptual framework for such a concurrent design and justification system is presented in this paper. A prototype implementation was developed to explore the usefulness of the design justification concept. Actual data from the design of an electromagnetic/radio frequency shield, a component in electrical metering equipment, was used. In this implementation the design justification environment allowed the decision maker to see the potential economic implications of different design alternatives. It also enabled the decision maker to take advantage of their present knowledge and combine it with that of the environment to better analyse the design of the shield throughout the entire product development period. [ABSTRACT FROM AUTHOR]

This paper presents a vehicle system simulator, AGVSim2, to be used in the evaluation of control strategies of real-time free-ranging vehicle supervisory controllers. The C-based discrete-event simulator is designed to be flexible so that many system configurations can be modelled. Also, the simulator allows for complex free-ranging vehicle manoeuvres, bidirectional flow, multiple vehicle types, and multiple loads on a vehicle. Instead of modelling the vehicle controller logic, the simulator is linked directly to the vehicle supervisory controller software. The simulator reports a variety of performance statistics and a trace of the system activities so that the performance of the supervisory controller can be evaluated. To improve the evaluation procedure, the simulator is also designed to be linked to an animation module that graphically displays the vehicle movements. [ABSTRACT FROM AUTHOR]

This paper describes the development of an intelligent controller for a fleet of free-ranging automated guided vehicles. The vehicle controller will operate in real-time. Once a transportation request is received, the location where the demand is generated and the nature of the demand is sent to the vehicle controller. Based on this information and the current status of the system, the vehicle controller will perform dispatching, routing, and scheduling tasks for the free-ranging vehicles. For the selected vehicle, the vehicle controller finds a route and then it will schedule the vehicle along that route in a non-conflicting manner. The vehicle controller is capable of detecting and preventing collisions before they occur. Once a collision is detected, the vehicle controller will explore different solutions to prevent the collision. The alternative which will result in the least delay time is the solution which will be selected by the vehicle controller. The inputs to the system are the layout topology, the number of vehicles in the system, and the vehicles' characteristics. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of loading pallets with multiple size boxes. It focuses on the physical aspects of using a robot to load multiple size boxes on pallets. The paper presents an algorithm that determines individual box placement on a multiple layer pallet, assuming that multiple box sizes is a limitation. This study was done using an algorithm and a robot sequence program. The program was run on an IBM RS-1 robot. The problems associated with robotic implementation are discussed in detail. [ABSTRACT FROM AUTHOR]

Discusses the potentials for bi-directional guide-path for automated guided vehicle based systems (AGVS). Applications of AGVS in manufacturing shop environments; Comparison between uni-directional and bi-directional flows.

Provides a two rectilinear single-spine and double-spine layout configuration for overhead track design. Difference between single-spine and double-spine; Comparison on spine layout result and Minimum Rectilinear Steiner Tree and Shortest Rectilinear Flow Network layouts; Improvement on flow distances by using Euclidean track design.

Discrete transform theory has previously been shown to offer many operational advantages in the computation of the present worths of discrete cash-flow patterns. This paper extends its application to equipment replacement models. Terborgh's classical model is used as the basis. An after-tax analysis using the latest depreciation schedule based on the Economic Recovery Tax Act of 1982 is incorporated in the analysis. Included is an example on determining the optimal replacement life cycle. [ABSTRACT FROM AUTHOR]