1,720,972 research outputs found
On the Impact of Transport Times in Flexible Job Shop Scheduling Problems
No full textManufacturing systems require a careful scheduling of the resource usage to maximize the production efficiency. In a completely automated environment, the transport system should be orchestrated to work smoothly with the other resources. While the impact of job characteristics, such as fixed or variable processing times of the tasks composing the jobs, or task dependencies, has been extensively studied, the role of the transport system has received less attention.In this paper we consider a conveyor belt as a mean of transportation among a set of production machines. In this scenario, there is no input or output buffer at the machines, and the transport times depend on the availability of the machines. We propose a heuristic based on randomization, called SCHED-T, which is able to find a near optimal joint schedule for job processing and transfer in few seconds. We test our solution on known benchmarks, along with real-world instances, showing that our scheduler is able to predict accurately the overall processing time of a production line
Integrating Smart Contracts in Manufacturing for Automated Assessment of Production Quality
No full textProducts and materials traceability is essential in modern manufacturing, where the production must meet certain standards that range from Quality Control (QC) to the quality of the used materials. In this environment, blockchain applications allow certifying data provenience and subsequent modification, offering trust and security along the entire supply chain. Nonetheless, the design and the development of such applications are usually performed manually and, thus, subject to errors.In this paper, we propose a methodology allowing to automatically generate smart contracts starting from a SysML model. This approach allows easing the integration of blockchain applications in a production system: by abstracting the implementations with models, it is possible to generate smart contracts for different blockchains, connecting to multiple production environments.We applied the proposed methodology on a real manufacturing system, assessing the quality of a case-study production
A Contract-based Methodology for Production Lines Validation
No full textThe approach we present in this paper exploits assume-guarantee reasoning through contracts to model a production line, and to generate its virtual prototype for efficient and correct plant simulation. Contracts are used to model the different parts composing the line; the modeling is guided by a well-known taxonomy associating industrial machines to manufacturing processes and their elementary actions, each represented by a contract. The composition of contracts representing the actions of a machine specifies each possible manufacturing process implemented by the machine. Then, automatic synthesis from contracts is used to generate an executable model of the machines composing the plant. The generated models are finally integrated into a state-of-the-practice industrial plant simulation software to validate the execution of the production line.The entire methodology is presented by showing its step-by-step application to a concrete scenario
RRPDG: A Graph Model to Enable AI-Based Production Reconfiguration and Optimization
Full text linkThis article introduces the regionalized resource process dependence graphs (RRPDGs): a manufacturing processes representation inspired by the regionalized value state dependence graphs traditionally used in software compilers. An RRPDG is an ordered sequence of nodes, each characterized by stereotyped input and output parameters, encapsulating a transformation of the process state (e.g., a manufacturing operation). RRPDG allow defining complex transformations by composing a set of nodes (i.e., regions), hiding the internal details. Then, RRPDGs are used to automatically reasoning over dynamic reconfiguration and process optimization: an instance of the A-star search algorithm is used to search for possible transformations while pursuing an optimization function. The rules defined in this article over RRPDG models enforce the transformations' correctness. We use RRPDGs to model a real production system while the transformation rules are applied to optimize the system's processes. The proposed representation reduced the search complexity in each experiment, allowing to reach an optimal solution also in the case for which classical approaches were unable to complete before reaching the timeout. In all the experiments, the cost of the solution produced by using the regionalized representation is minor than the the solution produced by using the classical representation
Compositional Design of Multi-Robot Systems Control Software on ROS
No full textThis paper presents a methodology that relies on Assume-Guarantee Contracts to decompose the problem of synthesizing control software for a multi-robot system. Initially, each contract describes either a component (e.g., a robot) or an aspect of the system. Then, the design problem is decomposed into different synthesis and verification sub-problems, allowing to tackle the complexity involved in the design process. The design problem is then recomposed by exploiting the rigorousness provided by contracts. This allows us to achieve system-level simulation capable to be used for validating the entire design. Once validated, the software synthesized during the process can be integrated into Robot Operating System (ROS) nodes and executed using state-of-the-practice packages and tools for modern robotic systems.We apply the methodology to generate a control strategy for an autonomous goods transportation system. Our results show a massive reduction of the time required to obtain automatically the control software implementing a multi-robot mission
Work-in-Progress: Introducing Assume-Guarantee Contracts for Verifying Robotic Applications
No full textThis paper summarizes the first steps toward an automatic framework, relying on Assume-Guarantee Contracts, for the verification of robotics applications. Classic HW and SW design and verification techniques are inadequate for robots due to the involved complexity. In this paper we advocate that contract-based methodologies allow safe problem decomposition easing system-level validation
A Software Architecture to Control Service-Oriented Manufacturing Systems
Full text linkThis paper presents a software architecture extending the classical automation pyramid to control and reconfigure flexible, service-oriented manufacturing systems. At the Planning level, the architecture requires a Manufacturing Execution System (MES) consistent with the International Society of Automation (ISA) standard. Then, the Supervisory level is automated by introducing a novel component, called Automation Manager. The new component interacts upward with the MES, and downward with a set of servers providing access to the manufacturing machines. The communication with machines relies on the OPC Unified Architecture (OPC UA) standard protocol, which allows exposing production tasks as “services”. The proposed software architecture has been prototyped to control a real production line, originally controlled by a commercial MES, unable to fully exploit the flexibility provided by the case study manufacturing system. Meanwhile, the proposed architecture is fully exploiting the production line's flexibility
Languages and Formalisms to Enable EDA Techniques in the Context of Industry 4.0
No full textThis paper analyzes a set of languages and standard used when designing industrial plants. It focuses on AutomationML and B2MML to specify respectively the architecture and the intended production of the system being designed. It also relies on the DIN 8580 standard to describe the actions performed by each machine composing the production line.Then, it outlines a methodology starting by mapping the information expressed by the analyzed languages and standards into the Assume-Guarantee Contracts formalism. It exploits contract-based design concepts to tackle the increase automation of the industrial plant design process and to enable the generation of digital twins. The approach is outlined by showing its applicability to a concrete manufacturing scenario
Dynamic Job and Conveyor-Based Transport Joint Scheduling in Flexible Manufacturing Systems
No full textEfficiently managing resource utilization is critical in manufacturing systems to optimize production efficiency, especially in dynamic environments where jobs continually enter the system and machine breakdowns are potential occurrences. In fully automated environments, co-ordinating the transport system with other resources is paramount for smooth operations. Despite extensive research exploring the impact of job characteristics, such as fixed or variable task-processing times and job arrival rates, the role of the transport system has been relatively underexplored. This paper specifically addresses the utilization of a conveyor belt as the primary mode of transportation among a set of production machines. In this configuration, no input or output buffers exist at the machines, and the transport times are contingent on machine availability. In order to tackle this challenge, we introduce a randomized heuristic approach designed to swiftly identify a near-optimal joint schedule for job processing and transfer. Our solution has undergone testing on both state-of-the-art benchmarks and real-world instances, showcasing its ability to accurately predict the overall processing time of a production line. With respect to our previous work, we specifically consider the case of the arrival of a dynamic job, which requires a different design approach since there is a need to keep track of partially processed jobs, jobs that are waiting, and newly arrived jobs. We adopt a total rescheduling strategy and, in order to show its performance, we consider a clairvoyant scheduling approach, in which job arrivals are known in advance. We show that the total rescheduling strategy yields a scheduling solution that is close to optimal
A Hierarchical Modeling Approach to Improve Scheduling of Manufacturing Processes
Full text linkTimely response to sudden production events and requirements shifts is a key feature of Industry 4.0. It requires techniques to manipulate and optimize the production processes, and components providing an high degree of reconfigurability. To acknowledge to such demands, this paper presents a multi-level and hierarchical approach to manufacturing processes modeling. Models are structured to represent the production hierarchically: partitioning recipes in a set of tasks, allocated to machines' manufacturing services and expressed as a sequence of elementary actions. Then, we propose a run-time scheduling algorithm able to exploit the novel structure given to knowledge by the proposed modeling approach. The algorithm aims at minimizing the makes pan while maximizing machines utilization. We validate the contributions of this paper on a full-fledged production line. The modeling strategy has been implemented in SysML: a well-known systems modeling language. The experiments show the presented model and the proposed scheduling approach enabling a more precise and more performing control over the manufacturing process
- …
