David Sinriech

OSL—optimal single-loop guide paths for AGVS

SUMMARY 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 loops throughput performance is tested and compared to that of a more complex guide path.

Solution methods for the mathematical models of single-loop AGV systems

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.

Intersection graph method for AGV flow path design

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.

An economic model for determining AGV fleet size

SUMMARY 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

An introduction to the segmented flow approach for discrete material flow systems

Due to increases in versatility and the complexity of demands in modern manufacturing systems a growing need has evolved t0 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 ty...

Network design models for discrete material flow systems: A literature review

The effectiveness of a material handling system depends on several factors, among them a well-thought-out flow-path design. The flow path has a significant effect on the travel time, the operating expenses, and the installation costs of the system. Moreover, the flow-path configuration has a significant impact on the complexity of the systems control software. The literature review presented in this paper describes several approaches to the design of material flow networks, including conventional type systems and more recent developments like the single-hoop, tandem configuration, SBSL, and SFT.

Impact of empty vehicle flow on performance of single-loop AGV systems

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 systems performance, is reduced. Thus, a more reliable prediction of system performance is achieved

Landmark configuration for absolute positioning of autonomous vehicles

Landmark navigation is a common positioning method of material handling vehicles operating in industrial environments. The position is calculated based on relative measurements to landmarks, the locations of which are known in advance. This paper presents a nonlinear optimization model used to determine the position of the minimum number of beacons required by a shop floor to guarantee accurate and reliable performance of AGVs. This position is based on guidelines developed by a previous error analysis study. The model is later converted to a binary linear programming model which is used as a lower bound to a heuristic solution procedure. Finally, two examples are used to illustrate the procedure.

The segmented bidirectional single-loop topology for material flow systems

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.

Sequencing, Scheduling and Tooling Single-Stage Multifunctional Machines in a Small Batch Environment

Single-Stage multifunctional Machining Systems (SSMSs) are an important integral part of automated, flexible manufacturing systems. However, the SSMS frequently becomes the bottleneck of the entire manufacturing system by virtue of protracted internal set-up requirements. A key aspect of achieving full SSMS utilization is the ability to reduce as much as possible these demands at the expense of increasing external set-up. As of today, fixturing devices have not received much attention in the modeling literature. Nevertheless, fixturing devices are in some cases a limited resource which, may affect the shop scheduling decisions and the shop performance and as such can not be omitted. This study presents a {0–1} programming model which takes the fixturing devices limitation in to consideration when determining the weekly sequence of jobs to be produced. The model tries to minimize the nonproductive machine time. Based on this model, a heuristic procedure is developed and tested using data of four production weeks obtained from a hi-tech company that produces medical imaging systems.