PETRI NET BASED APPROACHES TO MANUFACTURING SYSTEMS

This paper describes the planning in manufacturing systems. The skeleton and the functionality of a Petri Net Toolbox, embedded in the Matlab environment, are briefly presented, as offering a collection of instruments devoted to simulation, analysis and synthesis of discrete event systems. Timed Petri Nets are used to model operational and routing in production systems. A generalized multi productive machine modules is defined, adapter to system feature, repeated and connected to compose the TPN models of production systems with different levels of routing and operation. The present paper approaches the stochastic medium considered to be fundamental in describing the changes and the aleatory variations during the desertion process of machines and blocking times in the processing activity. We intend to present a simulated model according to which we can establish the time variation and the outputs process in a simple production system.Petri Nets, discrete event, manufacturing systems

A Petri Nets-based Scheduling Methodology forMultipurpose Batch Plants.

This article presents an optimization methodology of batch production processes assembled by shared resources which rely on a mapping of state-events into time-events allowing in this way the straightforward use of a well consolidated scheduling policies developed for manufacturing systems. A technique to generate the timed Petri net representation from a continuous dynamic representation (Differential-Algebraic Equations systems (DAEs)) of the production system is presented together with the main characteristics of a Petri nets-based tool implemented for optimization purposes. This paper describes also how the implemented tool generates the coverability tree and how it can be pruned by a general purpose heuristic. An example of a distillation process with two shared batch resources is used to illustrate the optimization methodology proposed

Performance Analysis of an Assembly System: a Case Study

International audiencePetri nets are well suited for modelling production systems and analysis of their performance. In this paper we study a flowshop system driven by a set of local command units and a central controller, modelled with Timed Coloured Petri nets by means of CPN Tools. We show that Petri nets can be applied not only to improve its production rate by comparing various algorithms for the controller policy service, but also to analyse the significance of parameters as conveying and mechanical delays, maximum work-in-process or to understand problems appeared in the real syste

Automating the transformation-based analysis of visual languages

The final publication is available at Springer via http://dx.doi.org/10.1007/s00165-009-0114-yWe present a novel approach for the automatic generation of model-to-model transformations given a description of the operational semantics of the source language in the form of graph transformation rules. The approach is geared to the generation of transformations from Domain-Specific Visual Languages (DSVLs) into semantic domains with an explicit notion of transition, like for example Petri nets. The generated transformation is expressed in the form of operational triple graph grammar rules that transform the static information (initial model) and the dynamics (source rules and their execution control structure). We illustrate these techniques with a DSVL in the domain of production systems, for which we generate a transformation into Petri nets. We also tackle the description of timing aspects in graph transformation rules, and its analysis through their automatic translation into Time Petri netsWork sponsored by the Spanish Ministry of Science and Innovation, project METEORIC (TIN2008-02081/TIN) and by the Canadian Natural Sciences and Engineering Research Council (NSERC)

MODELING DYNAMICS OF DATABASES WITH RELATIONAL DISCRETE EVENT SYSTEMS AND MODELS

Behavior of relational databases is studied within the framework of Relational Discrete Event Systems (RDESes) and Models (RDEMs). Three behavior specification methods based on production systems, recurrence equations, and Petri nets are defined and their expressive powers are compared. Production system RDEM is extended to support non-determinism, and various deterministic and non-deterministic production system interpreters are introduced and formally compared in terms of their expressive power. It is shown that the parallel deterministic interpreter has more expressive power than other interpreters including an OPS5-like interpreter. Since it is also parallel, this makes the parallel deterministic interpreter a very attractive interpreter for production systems.Information Systems Working Papers Serie

Commercial bumble bee (Bombus impatiens) hives under exclusion netting systems for apple pollination in orchards

Exclusion netting systems are effective in various contexts and are increasingly used to control crop pests. However, factors affecting pollination management under nets are poorly known. The pollination effectiveness of commercial bumble bee hives of Bombus impatiens Cresson (Hymenoptera: Apidae) was studied for apple production under exclusion netting systems in a research orchard located in Quebec, Canada during 2016–2017. Sixteen single-row plots of apple trees (plot length: 18.5 m, cultivar GingerGold) were subjected to one of the following four treatments during bloom: (1) introduction of a bumble bee hive placed at the end of the row, under nets; (2) introduction of a bumble bee hive placed in the middle of the row, under nets; (3) negative control with no pollinators, under nets and (4) agronomic control with nearby bee hives (<50 m), without nets. Resulting post-harvest fruit quality (e.g., fruit weight, size, number and distribution of seeds) was evaluated, as well as correlations between bumble bee visitation rates and fruit quality parameters were evaluated. Results suggest that bumble bees provided adequate pollination under exclusion netting systems and that resulting fruit quality was equivalent to that of apple fruit conventionally pollinated by honey bees and wild bees community (bumble bees and other bees) in the orchard environment. Positioning bumble bee hives in the middle of the row provided better fruit load homogeneity in pollinated trees. Additional discussion on bumble bees as apple pollinators and on pollen distribution methods is also included

Economic performance of cage fish farming

Mariculture has the potential to augment production and incomes through coastal as well as open sea farming. The global aquaculture production increased by about 25 times in the last 30 years when compared to only seven times increase in capture fisheries production during the corresponding period. Mariculture systems include in-shore and off-shore and maintain a constant high saline water conditions. In-shore mariculture systems include clams, oysters and other molluscs, which are wild-caught or hatcheryreared seed grown on the sea floor or on suspended nets, ropes, or other structures. Off-shore mariculture refers to large intensive fisheries in off-shore fish pens