George Michalos

Digital manufacturing: History, perspectives, and outlook

Abstract Digital manufacturing has been considered, over the last decade, as a highly promising set of technologies for reducing product development times and cost as well as for addressing the need for customization, increased product quality, and faster response to the market. This paper describes the evolution of information technology systems in manufacturing, outlining their characteristics and the challenges to be addressed in the future. Together with the digital manufacturing and factory concepts, the technologies considered in this paper include computer-aided design, engineering, process planning and manufacturing, product data and life-cycle management, simulation and virtual reality, automation, process control, shopfloor scheduling, decision support, decision making, manufacturing resource planning, enterprise resource planning, logistics, supply chain management, and e-commerce systems. These technologies are discussed in the context of the digital factory and manufacturing concepts.

An intelligent search algorithm-based method to derive assembly line design alternatives

In this work, a method of deriving assembly line design alternatives and evaluating them against multiple user-defined criteria has been presented. The design problem has been formulated in a way that it can be transformed from a decision-making problem into a search problem. A systematic way of generating the solution space of the search problem, based on the real-life design project requirements, has been described in detail. An intelligent search algorithm that uses the three control factors to guide the search was introduced and applied to efficiently derive high-quality line designs. Investment cost, availability, equipment reutilisation, annual production volume and flexibility metrics have been used for evaluating the alternative designs. The method was implemented in a software tool, which can automatically generate discrete event simulation models for the calculation of several performance metrics. The results of the application, in an automotive case, indicate that the tool is appropriate for supporting decision making during the stage of rough planning, although several functionalities can be used during more advanced stages such as the detailed planning concept.

Industrial applications with cooperating robots for the flexible assembly

This article discusses the key features of cooperating robotic cells in the automotive assembly, highlighting the key elements in the engineers’ decision-making process, while designing and implementing an assembly line for the Body In White. The main issues, affecting the performance of cooperating robotic cells, are discussed with the aid of a case study, where two different scenarios are compared. The first scenario uses a conventional fixture-based configuration of a robotic cell for performing a welding operation, while the second features the use of cooperating robots. The cases are compared with the aid of a simulation platform, and future potential developments are also discussed.

Virtual Commissioning of an Assembly Cell with Cooperating Robots

The Virtual CommissioningVCtechnology is the latest trend in automotive assembly which, among other benefits, promises a more efficient handling of the complexity in assembly systems, a great reduction in the systems ramp-up time, and a resulting shortening of the products time to market. This paper presents the application of VC techniques to the case of an industrial robotic cell, involving cooperating robots. The complete workflow of the virtual validation of the cell is presented, and the implementation requirements are discussed. Based on the findings, the outlook and challenges for the wide-range adoption of VC technologies in large-scale assembly systems are provided.

An agent-based methodology for manufacturing decision making: a textile case study

Decentralised decision making and real-time response to the unforeseen changes, often taking place in both the manufacturing and market environments, are two important factors that affect the flexibility, required for a production chain to follow demand. This article describes an agent-based methodology, for addressing both real-time and decentralised manufacturing decision-making challenges. At the manufacturing levels of production and processes, the agents employ a mechanism to generate local alternatives as well as a message exchange procedure to build decision trees, which are traversed and evaluated via user-defined objective functions. The generic structure used in the approach allows in a wide range the application of production system configurations. The real-time information, required for monitoring the system status and for generating valid alternatives, is obtained through integration with the existing information systems. An application to the textile industry is presented and discussed.

The new assembly system paradigm

The aim of this paper is to describe an assembly line paradigm that exploits the latest trends in handling and assembly technologies. Mobile robotic units, flexible and exchangeable end effectors, equipped with automated integration capabilities are used to achieve a highly reconfigurable and autonomous line as opposed to the existing fixed assembly lines, which are difficult to be reconfigured. In a study for the automotive assembly case, the benefits of the new paradigm over the traditional assembly schemes are quantified with the help of different simulated operational conditions.

On a human–robot workplace design and task allocation system

This paper proposes a method for human–robot (HR) task planning, considering at the same time, the design of the workplace. A model for the representation of humans and robots as a team of active resources is proposed, while equipment such as working tables and fixtures are considered passive resources. The HR workload is structured in a three-level model. A multi-criteria decision-making framework is used for the formulation of alternative layouts and task allocations. Both analytical models and simulation are used for the estimation of the criteria values, allowing for the evaluation of the different alternatives. A software prototype has been implemented and tested in white goods and in automotive industry cases, demonstrating that the tool can identify good quality solutions in a short time frame.

Wireless information system for rotating operators in human-based assembly lines

This article suggests an information system for the support of human operators in an assembly line. The information system utilises mobile devices and a pushlet-based infrastructure for automatically providing the mobile line operators with information in real time. The Radio Frequency Identification technology is used for tracking the location of a vehicle, its parts and the operator on the assembly line. An intelligent decision-making algorithm is paired with this information along with a communication infrastructure for enabling a dynamic job rotation during assembly. The system enables the reduction of errors in multivariant assembly lines, the reduction of time for information retrieval and the efficient allocation of assembly tasks to operators. The system has been implemented in a truck assembly line.

Scheduling of smart intra – factory material supply operations using mobile robots

This paper presents the design and prototype implementation of a service-based control system responsible for the material supply operations planning and coordination in assembly lines. The material supply processes are carried out by autonomous mobile units that are responsible for the transportation of the consumables from the warehouse to the production stations. The plan generation based on time and inventory level driven criteria is automatically carried out by a web-based software that can also distribute the derived plan to the autonomous mobile units. The proposed system was implemented on a case inspired by an actual production line from the automotive assembly sector. Discrete event simulation has been employed for the investigated production system, to derive the specifications for the mobile units (e.g. number of boxes that can carry simultaneously) that may serve the system efficiently. The results indicate that the proposed architecture integrated with the discussed mobile assistant units may provide high quality solutions with respect to the end user criteria.