Supporting adaptiveness of cyber-physical processes through action-based formalisms

Cyber Physical Processes (CPPs) refer to a new generation of business processes enacted in many application environments (e.g., emergency management, smart manufacturing, etc.), in which the presence of Internet-of-Things devices and embedded ICT systems (e.g., smartphones, sensors, actuators) strongly influences the coordination of the real-world entities (e.g., humans, robots, etc.) inhabitating such environments. A Process Management System (PMS) employed for executing CPPs is required to automatically adapt its running processes to anomalous situations and exogenous events by minimising any human intervention. In this paper, we tackle this issue by introducing an approach and an adaptive Cognitive PMS, called SmartPM, which combines process execution monitoring, unanticipated exception detection and automated resolution strategies leveraging on three well-established action-based formalisms developed for reasoning about actions in Artificial Intelligence (AI), including the situation calculus, IndiGolog and automated planning. Interestingly, the use of SmartPM does not require any expertise of the internal working of the AI tools involved in the system

A survey on performance analysis of warehouse carousel systems

This paper gives an overview of recent research on the performance evaluation and design of carousel systems. We discuss picking strategies for problems involving one carousel, consider the throughput of the system for problems involving two carousels, give an overview of related problems in this area, and present an extensive literature review. Emphasis has been given on future research directions in this area

A Roadmap towards an Automated Warehouse Digital Twin: current implementations and future developments

Automation and digitization increase the effectiveness and efficiency of logistics processes. In warehousing, Automated Storage and Retrieval Systems (AS/RS) are largely adopted due to their considerable advantages over traditional warehousing, namely high space utilization, shorter cycle times and improved inventory control. To further enhance such advantages, warehouse operations can be digitized via a Digital Twin (DT) which retrieves data from the real-world industrial process, mimics its behaviour and feeds specific inputs back to the real-world process, after elaboration from a simulation-based digital model. This work presents a DT proposal for a real-world AS/RS system, highlighting its current implementations together with its future developments

Issues in modelling and identification of Discrete Event Systems

2011 - 2012Discrete Event System (DES) are systems whose behavior is governed by discrete events occurring asynchronously over time and solely responsible for generating state transitions. DESs are particularly used in the field of the manufactured systems, handling systems and transportation systems: even if such system are being studying for long time, because of their complexity, they still present many issues that attract research interest. In particular this dissertation focuses about handling system modeling and DES identification. Obtaining a good model of a system (both time-driven and event-driven) allows to more easily execute operations as performance analysis, control, monitoring of system evolution. However, in some cases modeling of a system is not simple because of several complications due to the behavior of the system or of the context it belongs to. As example, sometimes, especially in the context of material handling and transportation, systems present both an event-driven and a time-driven behavior. In all that cases a very high accuracy is not requested it is usual neglect the latter and “looking” at the system as a DES (as example modeling a handling system it is possible to be interested in knowing if a vehicle is or not in a zone of the path while it is not important to know its exactly position). When the time-driven behavior plays a fundamental role in the obtaining the overall system performance, such dynamics cannot be neglected and they have to be explicitly modeled. This is the case, as example, of the automated warehouse systems, where the handling subsystem, as will be shown in the rest of this dissertation, presents time-driven dynamics that greatly influence the warehouse’s performance. Consequently a new way to model the system behavior has to be used. However, there are situation in which the difficult issue is not choosing the right formalism to model the system but it is the modeling itself. This is typical in many practical contexts, where it can occur that one has to work with unknown ready-made systems and no documentation about their behavior is available, or the model of a very complex system is needed. In these and other cases modeling becomes hard and another way to obtain the model of the system is needed: automated identification can be the solution. In the modeling environment, contribution of this thesis consists in presenting a new methodology to obtain a model oriented to the control and performance analysis of complex material handling systems that is highly modular, compact and made of parameterized modules. First a discrete event model is presented and then a new formalism that merges the concepts of Hybrid Petri Nets and Colored Petri Nets is introduced: the Colored Modified Hybrid Petri Nets (CMHPNs). Hence a new CMHPN model is proposed: it allows to model both the event nature and the continuous nature of the system. As more, to allow the monitoring of system evolutions, a freeware simulation tool for the CMHPNs is presented. Finally it is shown how the CMHPN model can be used to execute analysis and performance evaluation. Liveness analysis is performed by means of a hybrid automaton obtained from the net model. A deadlock prevention policy is synthesized working on an aggregated model. To prove the effectiveness of this new formalism an existing large automated warehouse system is presented as case study: its CMHPNs model is used to simulate the system behavior and to analyze the warehouse’s performance. In the identification environments, the guidelines of a new “active” approach to identify the model of a preexisting system is described. The proposed preliminary algorithm identifies a free labeled PN model on the basis of the observed output sequences and of the modifiable input consisting of the enabled controllable transitions set. The main idea is to use the knowledge of the set of enabled controllable transitions together with additional information on the conflicting transitions to accelerate the net identification with respect to the passive identification approaches. In particular, the system assumes that the maximum time that must elapse from the enabling of a transition until it fires is known and that it is possible to detect if the system is entered in a cyclic behavior. Using this additional information, it is possible to determine set of constraints to represent sequences that are not accepted by the system. Such constraints can be used to improve the net identification. [edited by author]XI n.s

Toward an Engineering Discipline of Warehouse Design

Warehouses today are complex dynamic engineered systems, incorporating automation, mechanization, equipment, fixtures, computers, networks, products and people, and they can support the flow of tens or hundreds of thousands of different items to enable fulfilling thousands or tens of thousands of orders daily. In that sense, they represent a design challenge that is not terribly different from the design of other complex dynamic engineered systems, such as a modern passenger airplane, an automobile, or a unique building. What is different is that the design of these other complex dynamic engineered systems typically follows some engineering design discipline. Here, we argue for the development of a corresponding engineering discipline of warehouse design

Collaborative information systems and business process design using simulation

The Information Systems (IS) community promotes the idea that IS analyst should have a clear understanding of the way the organization operates before attempting to propose an IS solution. It is argued that to take a complete advantage of the underlying Information Technology (IT), organizations should first identify any process flaw and then propose a suitable IT solution. Similarly, many process design approaches claim that Business Process (BP) design should be done considering the advantages provided and the limitations imposed by the underlying (IT). Despite this fact research in these domains provides little indication of which mechanisms or tools can help BP and IS analyst to understand the complex relationships amongst these two areas. This paper describes the insights gained during a UK funded research project, namely ASSESS-IT, that aimed to depict the dynamic relationships between IT and BP using simulation. One of the major limitations of the ASSESS-IT project is that it looked at relationship between BP and IT as a three layered structure, namely BP, IS and Computer Networks (CN), and did not explore in detail the relationships between BP and IS alone. This paper uses the outcomes derived from this project and suggests that, is some cases, the relationship between BP and IT could be analyzed by looking at the relationship between BP and IS alone. It then proposes an alternative simulation framework, namely BPISS, that provides the guideline to develop simulation models that portray BP and IS behavior performance measurements, offering in this way an alternative mechanism that can help BP and IS analyst to understand in more detail the dynamic interactions between BP and IS domains

Planning and managing the cost of compromise for AV retention and access

Long-term retention and access to audiovisual (AV) assets as part of a preservation strategy inevitably involve some form of compromise in order to achieve acceptable levels of cost, throughput, quality, and many other parameters. Examples include quality control and throughput in media transfer chains; data safety and accessibility in digital storage systems; and service levels for ingest and access for archive functions delivered as services. We present new software tools and frameworks developed in the PrestoPRIME project that allow these compromises to be quantitatively assessed, planned, and managed for file-based AV assets. Our focus is how to give an archive an assurance that when they design and operate a preservation strategy as a set of services, it will function as expected and will cope with the inevitable and often unpredictable variations that happen in operation. This includes being able to do cost projections, sensitivity analysis, simulation of “disaster scenarios,” and to govern preservation services using service-level agreements and policies