Simulation in Automated Guided Vehicle System Design

The intense global competition that manufacturing companies face today results in an increase of product variety and shorter product life cycles. One response to this threat is agile manufacturing concepts. This requires materials handling systems that are agile and capable of reconfiguration. As competition in the world marketplace becomes increasingly customer-driven, manufacturing environments must be highly reconfigurable and responsive to accommodate product and process changes, with rigid, static automation systems giving way to more flexible types. Automated Guided Vehicle Systems (AGVS) have such capabilities and AGV functionality has been developed to improve flexibility and diminish the traditional disadvantages of AGV-systems. The AGV-system design is however a multi-faceted problem with a large number of design factors of which many are correlating and interdependent. Available methods and techniques exhibit problems in supporting the whole design process. A research review of the work reported on AGVS development in combination with simulation revealed that of 39 papers only four were industrially related. Most work was on the conceptual design phase, but little has been reported on the detailed simulation of AGVS. Semi-autonomous vehicles (SA V) are an innovative concept to overcome the problems of inflexible -systems and to improve materials handling functionality. The SA V concept introduces a higher degree of autonomy in industrial AGV -systems with the man-in-the-Ioop. The introduction of autonomy in industrial applications is approached by explicitly controlling the level of autonomy at different occasions. The SA V s are easy to program and easily reconfigurable regarding navigation systems and material handling equipment. Novel approaches to materials handling like the SA V -concept place new requirements on the AGVS development and the use of simulation as a part of the process. Traditional AGV -system simulation approaches do not fully meet these requirements and the improved functionality of AGVs is not used to its full power. There is a considerflble potential in shortening the AGV -system design-cycle, and thus the manufacturing system design-cycle, and still achieve more accurate solutions well suited for MRS tasks. Recent developments in simulation tools for manufacturing have improved production engineering development and the tools are being adopted more widely in industry. For the development of AGV -systems this has not fully been exploited. Previous research has focused on the conceptual part of the design process and many simulation approaches to AGV -system design lack in validity. In this thesis a methodology is proposed for the structured development of AGV -systems using simulation. Elements of this methodology address the development of novel functionality. The objective of the first research case of this research study was to identify factors for industrial AGV -system simulation. The second research case focuses on simulation in the design of Semi-autonomous vehicles, and the third case evaluates a simulation based design framework. This research study has advanced development by offering a framework for developing testing and evaluating AGV -systems, based on concurrent development using a virtual environment. The ability to exploit unique or novel features of AGVs based on a virtual environment improves the potential of AGV-systems considerably.University of Skovde. European Commission for funding the INCO/COPERNICUS Projec

PERFORMANCE IMPACT OF DISPATCHING AND ROUTING IN AN AUTOMATED GUIDED VEHICLE SYSTEM

Dispatching and routing are fundamental operational decisions in automated material-handling systems. Numerous studies have been conducted on these two operational decisions, with more focus being recently made on intelligent routing decisions. However, comparative studies between the effects of dispatching and routing methods have not been reported so far. In this study, we have investigated three dispatching and three routing algorithms and measured their impacts using a simulation model for an automated guided vehicle (AGV) system designed for a real-world production line, in which a grid-type material flow layout is used, and the AGVs need to stop before changing their direction of movement. Two routing algorithms are developed in this study. Simulation experiments revealed that both dispatching and routing algorithms affect the performance of the AGV system, although dispatching methods showed a more significant impact. Good dispatching and routing algorithms are mandatory to improve the overall performance of AGV systems

Design and operational control of an AGV system

In this paper we first deal with the design and operational control of Automated Guided Vehicle (AGV) systems, starting from the literature on these topics. Three main issues emerge: track layout, the number of AGVs required and operational transportation control. An hierarchical queueing network approach to determine the number of AGVs is decribed. Also basic concepts are presented for the transportation control of both a job-shop and a flow-shop. Next we report on the results of a case study, in which track layout and transportation control are the main issues. Finally we suggest some topics for further research

Cyber physical systems in mechatronic research centre

K

Intelligent Simulation Modeling of a Flexible Manufacturing System with Automated Guided Vehicles

Although simulation is a very flexible and cost effective problem solving technique, it has been traditionally limited to building models which are merely descriptive of the system under study. Relatively new approaches combine improvement heuristics and artificial intelligence with simulation to provide prescriptive power in simulation modeling. This study demonstrates the synergy obtained by bringing together the "learning automata theory" and simulation analysis. Intelligent objects are embedded in the simulation model of a Flexible Manufacturing System (FMS), in which Automated Guided Vehicles (AGVs) serve as the material handling system between four unique workcenters. The objective of the study is to find satisfactory AGV routing patterns along available paths to minimize the mean time spent by different kinds of parts in the system. System parameters such as different part routing and processing time requirements, arrivals distribution, number of palettes, available paths between workcenters, number and speed of AGVs can be defined by the user. The network of learning automata acts as the decision maker driving the simulation, and the FMS model acts as the training environment for the automata network; providing realistic, yet cost-effective and risk-free feedback. Object oriented design and implementation of the simulation model with a process oriented world view, graphical animation and visually interactive simulation (using GUI objects such as windows, menus, dialog boxes; mouse sensitive dynamic automaton trace charts and dynamic graphical statistical monitoring) are other issues dealt with in the study

Simulation of a Production Line with Automated Guided Vehicle: A Case Study

Currently, companies have increasingly needed to improve and develop their processes to flexible the production in order to reduce waiting times and increase productivity through smaller time intervals. To achieve these objectives, efficient and automated transport and handling material systems are required. Therefore, the AGV systems (Automated Guided Vehicle) are often used to optimize the flow of materials within the production systems. In this paper, the author evaluates the usage of an AGV system in an industrial environment and analyzes the advantages, disadvantages of the project. Furthermore, the author uses the systems simulation software Promodel® 7.0 to develop a model, based on data collected from real production system, in order to analyze and optimize the use of AGVs. Throughout this paper, problems are identified as well as solution adopted by the author and the results obtained from the simulations

Evaluating the performance of an AGV fleet in an FMS under minimizing part movement and balancing workload rules

The performance of an FMS with respect to AGV utilization is assessed using a simulation model. AGV fleets of different sizes are evaluated. Under OOM, an assignment rule designed to decrease time in system by minimizing part movements among machine tools, AGV utilization is lower than under WINO, an assignment rule that seeks to balance machine workload. For a given AGV fleet, machine utilization imbalance is more levelled under WINO than OOM, however comparing across the three AGV fleets, the maximum machine imbalance is smoother under OOM than under WINO. AGV utilization consistently decreases as the number of AGVs increases from eight to nine and then to 10. The system performance is adversely affected not only by too many AGVs but also by surplus spots in both inbound and outbound queues placed in front of the machine tools

Synthesis about a collaborative project on “Technology Assessment of Autonomous Systems”

The project started in 2009 with the support of DAAD in Germany and CRUP in Portugal under the “Collaborative German-Portuguese University Actions” programme. One central goal is the further development of a theory of technology assessment applied to robotics and autonomous systems in general that reflects in its methodology the changing conditions of knowledge production in modern societies and the emergence of new robotic technologies and of associated disruptive changes. Relevant topics here are handling broadened future horizons and new clusters of science and technology (medicine, engineering, interfaces, industrial automation, micro-devices, security and safety), as well as new governance structures in policy decision making concerning research and development (R&D).Robotic systems, Autonomous systems, Technology assessment, Germany, Portugal

Optical tomography: Image improvement using mixed projection of parallel and fan beam modes

Mixed parallel and fan beam projection is a technique used to increase the quality images. This research focuses on enhancing the image quality in optical tomography. Image quality can be defined by measuring the Peak Signal to Noise Ratio (PSNR) and Normalized Mean Square Error (NMSE) parameters. The findings of this research prove that by combining parallel and fan beam projection, the image quality can be increased by more than 10%in terms of its PSNR value and more than 100% in terms of its NMSE value compared to a single parallel beam

Technical Needs Assessment of North Dakota Manufacturers

The problem of this study was to identify, document, and prioritize technical assistance needs of North Dakota manufacturers. The primary objective was to determine the technical assistance needs of North Dakota manufacturers as they relate to: a) education; b) consulting; c) research and development. A secondary objective was to prioritize the ten most pertinent technical areas of need as determined by the North Dakota manufacturers. This study used a descriptive survey research method. The researcher devised a survey instrument and was validated by a panel of experts. The instrument included fifty-three technical areas, most of which are emerging technologies. The questionnaire asked the manufacturers to assess their degree of technical need as it related to education, consulting and research and development. The questionnaire was sent to six hundred seventy North Dakota manufacturers. The study was divided into six sections: (a) devise a survey questionnaire, (b) perform a pilot study, (c) identify the population, (d) collect the data, (e) organize the data, and (f) statistical analysis of the data. Central tendency, standard deviation, rank order, and correlation were the four statistical tests used for analyzing the data The following conclusions were made after the completion of the study: 1) The type of technical assistance most evident was for education. 2) The top ten technical areas correlate closely with technical concepts that are on the cutting edge of technology 3) North Dakota manufacturers are interested in acquiring the information needed to make an informative decision on whether or not to implement these pertinent technologies The following recommendations are offered for further study: 1 . A follow-up study be performed in three years to determine if the technical assistance needs of North Dakota manufacturers have changed. 2. Set-up a program that would allow the manufacturers and the higher education community to accumulate and disseminate information pertinent to their wants and needs. 3. A study that encompasses more of the business and administrative end of manufacturing. 4. Design a study that would continue to acquire information for a manufacturers\u27 database for North Dakota. 5. Conduct a feasibility study to determine the need for a manufacturing extension service in North Dakot