Improved Decentral Task Allocation for Autonomous Guided Vehicle Systems based on Karis Pro

In this paper, we extended an existing decentralised method for allocating tasks to AGVs, by additionally considering vehicles which already are assigned to a task. This was achieved by also taking into account the opportunity costs arising from a vehicle passing a current task to another vehicle and subsequently accepting a new task. This loosened restriction is enabling the vehicle fleet for a higher flexibility, which can be used for improving the efficiency of the overall system. By means of simulation, our findings confirm the notion that our extended method - namely Karis Pro+ - leads to lower traffic density and higher flexibility, both of which are important KPI for large-scale transport vehicle systems.In this paper, we extended an existing decentralised method for allocating tasks to AGVs, by additionally considering vehicles which already are assigned to a task. This was achieved by also taking into account the opportunity costs arising from a vehicle passing a current task to another vehicle and subsequently accepting a new task. This loosened restriction is enabling the vehicle fleet for a higher flexibility, which can be used for improving the efficiency of the overall system. By means of simulation, our findings confirm the notion that our extended method - namely Karis Pro+ - leads to lower traffic density and higher flexibility, both of which are important KPI for large-scale transport vehicle systems

Enterprise Boundaries and Employee Representation: Deutsche Telekom and NTT Compared

This paper investigates how employee representation affects, and is affected by, the way corporations structure themselves. In the analytical framework employed in the paper, the structure of the corporation and national labour institutions constitute key constraints on the goals of unions and management, but their strategic choices and interactions also alter and transform those structures. This perspective attempts to reconcile classical approaches to strategy (e.g. by Chandler) with institutional or systemic accounts (e.g. by Hall and Soskice) by examining industrial relations as structured interaction. The interaction between corporate strategy and labour strategy, for instance, may give rise to an outcome other than what is predicted on the basis of existing national institutional arrangements. Our approach is therefore a less deterministic version of institutionalism, allowing scope for strategy that is rooted in the contested nature of institutional and organisational boundaries. Empirical analysis of the telecommunications sector - Deutche Telekom in Germany and NTT in Japan -- reveals that such structured interaction has led to markedly different outcomes, despite a broadly similar corporate strategy of diversification. In particular, we find that a relatively centralised managerial structure within the DT Group is matched with a decentralised works council structure and a declining presence of the unions (Verdi and IG Metall) at the DT companies, leading to a great diversity of human resource systems within the corporate group. By contrast, in Japan, despite a relatively weak position of the holding company in the NTT Group, the presence of a highly centralised NTT Union resulted in the application of a uniform human resource system for the whole corporate group.

Decentralised vs partially centralised self-organisation model for mobile robots in large structure assembly

Currently, manufacturing companies are heavily investing into the automation of manufacturing processes. The push to improve productivity and efficiency is increasing the demand for more flexible and adaptable solutions than the currently common dedicated automation systems. In this paper, the planning problem for mobile robots in large structure assembly was addressed. Despite near-optimal results, the previously developed hybrid agent behaviour model was found to lack responsiveness and scalability. For that reason, an alternative, fully decentralised agent behaviour model was developed and compared to the hybrid one. Through simulated experiments, it was found that the decentralised agent behaviour model achieved much higher responsiveness; however, it required additional spare capacity to compensate for its decision-making imperfections

Self-organisation of mobile robots in large structure assembly using multi-agent systems

Competition between manufacturers in large structure assembly (LSA) is driven by the need to improve the adaptability and versatility of their manufacturing systems. The lack of these qualities in the currently used systems is caused by the dedicated nature of their fixtures and jigs. This has led to their underutilisation and costly changeover procedures. In addition to that, modern automation systems tend to be dedicated to very specific tasks. This means that such systems are highly specialised and can reach obsolescence once there is a substantial change in production requirements. In this doctoral thesis, a dynamic system consisting of mobile robots is proposed to overcome those limitations. As a first knowledge contribution in this doctoral thesis, it is investigated under which conditions using mobile robots instead of the traditional, fixed automation systems in LSA can be advantageous. In this context, dynamic systems are expected to be more versatile and adaptive than fixed systems. Unlike traditional, dedicated automation systems, they are not constrained to gantry rails or fixed to the floor. This results in an expanded working envelope and consequently the ability to reach more workstations. Furthermore, if a product is large enough, the manufacturer can choose how many mobile robots to deploy around it. Accordingly, it was shown that the ability to balance work rates on products and consequently meet their due times is improved. For the second knowledge contribution, two fundamentally different decision-making models for controlling mobile agents in the complex scheduling problem are investigated. This is done to investigate ways of taking full advantage from the potential benefits of applying mobile robots. It is found that existing models from related academic literature are not suited for the given problem. Therefore, two new models had to be proposed for this purpose. It was plausible to use an agent-based approach for self-organisation. This is because similarly to agents, mobile robots can perform independently of one-another; and have limited perception and communication abilities. Finally, through a comparison study, scenarios are identified where either model is better to use. In agreement with much of the established literature in the field, the models are shown to exhibit the common advantages and disadvantages of their respective architecture types. Considering that the enabling technologies are nearing sufficient maturity for deploying mobile robots in LSA, it is concluded that this approach can have several advantages. Firstly, the granularity and freedom of movement enables much more control over product completion times. Secondly, the increased working envelope enables higher utilisation of manufacturing resources. In the context of LSA, this is a considerable challenge because products take a very long time to get loaded and unloaded from workstations. However, if the product flow is steady, there are rare disruptions and rare production changes, fixed automation systems have an advantage due to requiring much less time (if any) for moving and localising. Therefore, mobile systems become more preferred to fixed systems in environments where there is an increasing frequency of disruptions and changes in production requirements. The validation of agent-based self-organisation models for mobile robots in LSA confirms the expectations based on existing literature. Also, it reveals that with relatively low amounts of spare capacity (5%) in the manufacturing systems, there is little need for sophisticated models. The value of optimised models becomes apparent when spare capacity approaches 0% (or even negative values) and there is less room for inefficiencies in scheduling

Knowledge and agent-based system for decentralised scheduling in manufacturing

The aim of the research paper is to develop algorithms for manufacturers’ agents that would allow them to sequence their own operation plans and to develop a multi-agent infrastructure to allow operation pair agents to cooperatively adjust the timing of manufacturing operations. The scheduling problem consisted of jobs with fixed process plans and of manufacturers collectively offering the necessary operations for the jobs. Manufacturer agents sequenced and pair agents timed each operation as and when required. Timing an operation triggered a cascade of conflicts along the job process plan that other pair agents would pick up on and would take action accordingly. The conventional approach performs conflict resolution in series and manufacturer agents as well as pair agents wait until they are allowed to sequence and time the next operation. The limiting assumption behind that approach was systematically removed, and the proposed approach allowed manufacturers to perform operation scheduling in parallel, cutting down tenfold on the computation time. The multi-agent infrastructure consists of the Protégé knowledge base, the Pellet semantic reasoner and the Workflows and Agent Development Environment (WADE). The case studies used were the MT6, MT10 and LA19 job shop scheduling problems; and an industrial use case was provided to give context to the manufacturing environment investigated. Although there were benefits from the decentralised manufacturing system, we noted an optimality loss of 34% on the makespans. However, for scalability, our approach showed good promise

Metaphor-based negotiation and its application in AGV movement planning

The theme of this thesis is "metaphor-based negotiation". By metaphor-based negotiation I mean a category of approaches for problem-solving in Distributed Artificial Intelligence (DAI) that mimic some aspects of human negotiation behaviour. The research in this dissertation is divided into two closely related parts. Cooperative interaction among agents in a multiagent system (MAS) is discussed in general, and the discussion leads to a formal definition of metaphor-based negotiation. Then, as a specific application, a "spring-based" computational model for metaphor-based negotiation is developed as an approach to solving movement planning, specifically the AGV scheduling problem (AGVSP) — determing the timings of AGVs' activities, of automated guided vehicles (AGVs) in a factory.By formally addressing the multi-agent cooperative interaction problem and assuming that agents in a MAS are rational, benevolent and fully informed, an initial strategy set of cooperative interaction can be reduced to a strategy set by eliminating strategies that are irrational in a group sense. However, it is proved in this dissertation that, in the remaining strategy set, no unique strategy can be found that is acceptable to all agents according their individual preferences. More specifically, in this smaller strategy set, if one agent moves from one strategy to another in an attempt to better its individual goal achievement, then there is at least one agent whose goal achievement will be negatively affected by such a move. So, the cooperative interaction problem can only be partially solved if no further knowledge is given to those agents. The idea of a common sense principle is introduced in this dissertation to overcome the deficiencies of the assumptions of rationality, benevolence and full-informedness.In reality, the assumption of full-informedness of agents may not be practical. Communication is needed for agents to (1) exchange their local problem solving information, and (2) exchange proposals for global problem solving, when their views are in conflict. Based on the discussion of cooperative interaction, a formal definition of metaphorbased negotiation is proposed to formally indicate what is a proposal and what is the condition for accepting a proposal from another agent. In this definition, the common sense principle is one of the most important features, not found in definitions of negotiation available so far in the literature, which guides agents to find an agreement when negotiation is running into difficulties.The AGVSP involves timing activities for each AGV in a AGV-based factory. The AGVSP is naturally distributed: the whole problem can be easily divided into several subproblems each of which involves timing of activities of one AGV. Therefore, it is intuitively straightforward for us to seek DAI approaches to solving the AGVSP. In spired by Kwa's Iterative Negotiation Model [Kwa 88b] [Kwa 88a] for the AGVSP, we developed a spring-based (metaphor-based) negotiation model for the AGVSP to overcome some vital problems in Kwa's model. The idea of the spring-based negotiation model is described below:The AGVSP can be regarded as a Distributed Constraint Satisfaction Problem (DCSP) and solved in a MAS. Each agent in the MAS is designed to solve a subproblem — a local scheduling problem which is a small Constraint Satisfaction Problem (CSP). Conflicts exist when intra-agent constraints or inter-agent constraints are violated. These constraints can be classified into hard constraints— those that can not be relaxed at the agent level unless the system designer permits (e.g., by providing an arbitrator), and soft constraints — those that can be relaxed at the agent level when necessary. When agents are in conflict, i.e, when some inter-agent constraints are violated (or say, when one agent's timings of its activities overlap those of some other agents), these agents involved will resolve the conflicts through a (metaphor-based) negotiation procedure in which conflicts will be gradually resolved by each agent's relaxation of its intra-agent constraints, i.e, by yielding some amount of its initially allocated resources to other agents or by shifting its initially allocated resources. The negotiation can be viewed as a process of exchanging proposals (of cooperative strategies) between conflicting agents, where a cooperative strategy is a possible resolution to a conflict according to the viewpoint of the proposing agent. However, since agents are designed to be rational, each agent that is involved in the conflicts will try hard to relax its intra-agent constraints as little as possible. Further, it is reasonably acceptable that the more an intra-agent constraint has been relaxed the less the respective agent is willing to relax it further. This feature can be modeled by a spring — the more it has been compressed the harder it is to compress it further. Based on this inspiration, a spring-based computational model of metaphor-based negotiation is proposed: each agent's local schedule is represented by a local spring network in which each spring element represents a soft intra-agent constraint. Relaxation of an intra-agent constraint is likened to a spring being compressed by external forces from other agents. As a consequence, the compressed spring will also show a reacting force upon those compressing agents. An agreement will be reached when those forces and reacting forces are balanced. This is the common sense principle in the spring-based negotiation. The model solves some key issues, e.g., how to select negotiation techniques and skills during the process of negotiation, that have not been solved by Kwa's iterative negotiation model. Some experimental evidence of the value of this model is presented

Agent-based distributed manufacturing scheduling: an ontological approach

The purpose of this paper is the need for self-sequencing operation plans in autonomous agents. These allow resolution of combinatorial optimisation of a global schedule, which consists of the fixed process plan jobs and which requires operations offered by manufacturers. The proposed agent-based approach was adapted from the bio-inspired metaheuristic- particle swarm optimisation (PSO), where agents move towards the schedule with the best global makespan. The research has achieved a novel ontology-based optimisation algorithm to allow agents to schedule operations whilst cutting down on the duration of the computational analysis, as well as improving the performance extensibility amongst others. The novelty of the research is evidenced in the development of a synchronised data sharing system allowing better decision-making resources with intrinsic manufacturing intelligence. The multi-agent platform is built upon the Java Agent Development Environment (JADE) framework. The operation research case studies were used as benchmarks for the evaluation of the proposed model. The presented approach not only showed a practical use case of a decentralised manufacturing system, but also demonstrated near optimal makespans compared to the operational research benchmarks

Case Studies of Automation in Services. A workplace analysis of logistics, cleaning and health sectors in Italy

A full understanding of the technological complexity underlying robotics and automation is still lacking, most of all when focusing on the impacts on work in services. By means of a qualitative analysis relying on the administration of more than 50 interviews to HR managers, IT technicians, workers and trade union delegates, this work provides evidence on the main changes occurring at shopfloor level in selected Italian companies having adopted technological artefacts potentially affecting labour tasks by automating processes. The analysis of interviews complemented with visits to the companies and desk research on business documents highlights that so far labour displacement due to the adoption of automation technologies is not yet in place, while tasks and organizational reconfiguration appear more widespread. Major heterogeneity applies across plants due to the final product/service produced, the techno-organizational capabilities of the firm and the type of strategic orientation versus technological adoption. These elements also affect drivers and barriers to technological adoption. Overall, the analysis confirms the complexity in automating presumably low-valueadded phases: human labour remains crucial in conducting activities that require flexibility, adaptability and reconfiguration of physical tasks. Further, human agency and worker representation, in particular the role of trade unions, are almost disregarded and not considered by the firms when deciding to introduce a new technology

Case studies of automation in services

A full understanding of the technological complexity underlying robotics and automation is still lacking, most of all when focusing on the impacts on work in services. By means of a qualitative analysis based on over 50 interviews to HR managers, IT technicians, workers and trade union delegates, this work provides evidence on the main changes occurring at shopfloor level in selected Italian companies having adopted technological artefacts potentially affecting labour tasks by automating processes. The analysis of interviews complemented with visits to the companies and desk research on business documents highlights that so far labour displacement due to the adoption of automation technologies is not yet in place, while tasks and organizational reconfiguration appear more widespread. Major heterogeneity applies across plants due to the final product/service produced, the techno-organizational capabilities of the firm and the type of strategic orientation versus technological adoption. These elements also affect drivers and barriers to technological adoption. Overall, the analysis confirms the complexity in automating presumably low-value-added phases: human labour remains crucial in conducting activities that require flexibility, adaptability and reconfiguration of physical tasks. Further, human agency and worker representation, in particular the role of trade unions, are almost disregarded and not considered by the firms when deciding to introduce a new technology