Petri Net Models Optimized for Simulation

Petri nets and simulation are a modeling paradigm and a tool, respectively, which may be successfully combined for diverse applications, such as performance evaluation, decision support, or training on complex systems. Simulation may require significant computer resources; hence, in this chapter, two Petri net-based formalisms are analyzed for profiting from their respective advantages for modeling, simulation, and decision-making support: a set of alternative Petri nets and a compound Petri net. These formalisms, as well as the transformation algorithms between them, are detailed and an illustrative example is provided. Among the main advantages of these formalisms, their intuitive application for modeling discrete event systems in the process of being designed, as well as the compactness that may present the resulting model, in the case of a compound Petri net, leading to efficient decision making, can be mentioned

Influence of geometry in the behavior of disc-shaped mechanical energy absorbers for agricultural tractors

Disc-shaped mechanical energy absorbers (MEAs), in combination with rollover protection structures (ROPSs), may contribute to the prevention of the infringement of the safety zone and the collapse of the ROPS in case of the overturn of an agricultural tractor. An MEA can absorb a significant amount of potential energy of an overturning tractor and its deformation produces a rotation of the ROPS around the safety zone. In this research, MEAs with two different geometries have been developed. Both geometries present common features, such as disc dimensions, number of rings, and number of arms, but the distribution of the arms differs. Additionally, these MEA were manufactured in steel discs of four different thicknesses, ranging from 2 to 6 mm. The manufactured MEAs were tested in a universal testing machine, and their behavior characterized. From this data, linear models of the MEAs were developed. As a consequence, a number of characteristic parameters were selected and calculated, such as the activation load and the strain energy absorbed in a safe range of applied loads. Some patterns and trends were analyzed from the tested MEAs, which enables a better description of their behavior and the extrapolation of this behavior to other non-tested thicknesses and geometries.This research was funded by the Public University of Navarre, grant number PJUPNA1912

Equivalent and efficient optimization models for an industrial discrete event system with alternative structural configurations

Discrete event systems in applications, such as industry and supply chain,may show a very complex behavior. For this reason, their design and operation may be carried out by the application of optimization techniques for decision making in order to obtain their highest performance. In a general approach, it is possible to implement these optimization techniques by means of the simulation of a Petri net model, which may require an intensive use of computational resources. One key factor in the computational cost of simulation-based optimization is the size of the model of the system; hence, it may be useful to apply techniques to reduce it. This paper analyzes the relationship between two Petri net formalisms, currently used in the design of discrete event systems, where it is usual to count on a set of alternative structural configurations.These formalisms are a particular type of parametric Petri nets, called compound Petri nets, and a set of alternative Petri nets. The development of equivalent models under these formalisms and the formal proof of this equivalence are the main topics of the paper.The basis for this formal approach is the graph of reachable markings, a powerful tool able to represent the behavior of a discrete event system and, hence, to show the equivalence between two different Petri net models. One immediate application of this equivalence is the substitution of a large model of a system by a more compact one, whose simulation may be less demanding in the use of computational resources

Analysis of product shrinkage and waste in a potato bagging plant

Nowadays, an average of 2 kg of waste per person are generated in Spain. Furthermore, the household consumption is rising and, as a consequence, the waste production is also increasing. This trend presents a direct impact in the environment. Moreover, after two years of COVID-19 pandemic, it has been detected a stronger rise in consumption per person, while consumption through professional commercial channels for hospitality industry has been lower. This paper analizes the waste generation and product shrinkage in a potato bagging plant, which addresses its production to both final consumers and retailers. The raw materials washing line, as well as the production line, are taken into consideration in the analysis, while new uses to the produced waste are proposed, aiming at providing new useful life, such as the production of bioplastics or the production of biodiesel. As a consequence, the environment impact is minimized and new products are obtained

Design, Manufacturing, Validation of a Multi-Orientation Tilt Test Bench for Testing Vehicles Rollover and Tests of ATV-Quad for Agricultural Applications

A rollover test bench has been designed, manufactured, and validated for analyzing the all-terrain vehicle (ATV)-Quad overturn of diverse vehicles in different configurations, such as installing a rollover protection system (ROPS), considering drivers of different physical constitutions, the appropriate use of safety belts, or having a full or empty fuel tank. The main purpose of this research is to determine the tilt angle of the vehicle that triggers the ATV-Quad overturn. The scope of the design and development of the newly conceived bench include the mechanical structure, the electronics and the control. It can simulate static and dynamic rollover in different directions. As a main conclusion, it can be stated that the performance of the test bench was successful, since it allowed for the development of several ATV models, equipped with different dummies, in a variety of configurations. In particular, it was possible to assess the effectivity of the AD-ROPS system (automatically deployed ROPS), regarding the protection of the driver of the vehicle. Moreover, multiple tests, performed with diverse ATV-Quads in the developed bench and in different configurations, have been reported and their results discussed

Enriching Simheuristics with Petri net models: potential applications to logistics and supply chain management

Some classic and complex problems in Operations Research consist of simplified versions of real logistic and supply chain management applications. One common and successful, but approximated approach for coping with these problems considers the system of interest isolated from its environment. In such a case, the links to the real world may be reduced to a set of parameters associated with probabilistic distributions. Simheuristics is a solving methodology able to provide efficiently near-optimal solutions for these constrained problems. This paper presents a methodology combining Simheuristics with a Petri net model, describing the environment of a logistic system. An extended version of the capacitated vehicle routing problem with stochastic demands is stated adding a Petri net model. Petri nets are widely used for modeling parallelism and concurrency, providing a realistic description of this environment, which may change the behavior of the isolated system and the scope of the decision-making

Enriching Simheuristics with Petri net models: potential applications to logistics and supply chain management

Some classic and complex problems in Operations Research consist of simplified versions of real logistic and supply chain management applications. One common and successful, but approximated approach for coping with these problems considers the system of interest isolated from its environment. In such a case, the links to the real world may be reduced to a set of parameters associated with probabilistic distributions. Simheuristics is a solving methodology able to provide efficiently near-optimal solutions for these constrained problems. This paper presents a methodology combining Simheuristics with a Petri net model, describing the environment of a logistic system. An extended version of the capacitated vehicle routing problem with stochastic demands is stated adding a Petri net model. Petri nets are widely used for modeling parallelism and concurrency, providing a realistic description of this environment, which may change the behavior of the isolated system and the scope of the decision-making