Papers by Ernesto Lopez-mellado
Simulation, Jan 18, 2017
This paper presents a modeling methodology for designing networked agents systems. It focuses on ... more This paper presents a modeling methodology for designing networked agents systems. It focuses on the agent hybrid state representation, its dynamic behavior, and its interaction with neighbor agents. The agent's internal state as well as the communication interface between agents is modeled using timed hybrid Petri nets. The methodology is illustrated through the modeling of a case study related to energy interchange networks. The simulation of the case study model is included to illustrate the advantages the proposed methodology.
Acta Informatica, Sep 13, 2023
A novel and efficient method for discovering concurrent workflow processes is presented. It allow... more A novel and efficient method for discovering concurrent workflow processes is presented. It allows building a suitable workflow net (WFN) from a large event log λ, which represents the behaviour of complex iterative processes involving concurrency. First, the t-invariants are determined from λ; this allows computing the causal and concurrent relations between the events and the implicit causal relations between events that do not appear consecutively in λ. Then a 1-bounded WFN is built, which could be eventually adjusted if its t-invariants do not match with those computed from λ. The discovered model allows firing all the traces in λ. The procedures derived from the method are polynomial time on |λ|; they have been implemented and tested on artificial logs.
IGI Global eBooks, Jan 18, 2011
IGI Global eBooks, May 24, 2011
This paper presents a methodology for synthesizing real-time controllers of assembly systems. The... more This paper presents a methodology for synthesizing real-time controllers of assembly systems. The approach used is knowledge-based; it combines the use of frames and production rules to implement decision-making processes controlling the activities of the assembly system components according to asynchronous events which represent expected or unexpected (but predictable) situations. The method the author proposes gives the guidelines to construct modular and condensed knowledge bases from the specification of the assembly tasks
Distributed workflow processes automation is addressed using a multi mobile agent system based ap... more Distributed workflow processes automation is addressed using a multi mobile agent system based approach. A method for the specification and development of workflow processes controllers is proposed; it is based on the idea that a mobile agent executes the tasks of a process through the system. First the system architecture and workflow requirements are modeled using a multi-level Petri net
This paper deals with distributed fault diagnosis of discrete event systems (DES). The approach h... more This paper deals with distributed fault diagnosis of discrete event systems (DES). The approach held is model based: an interpreted Petri net (IPN) describes both the normal and faulty behaviour of DES in which both places and transitions may be non measurable. The diagnoser monitors the evolution of the DES outputs according to a model that describes the normal behaviour of the DES. A method for designing a set of distributed diagnosers is proposed; it is based on the decomposition of the DES model into reduced submodels which require low interaction among them; the diagnosability property is studied for the set of resulting sub-models.
IFAC Proceedings Volumes, Sep 1, 1988
On-line failure analysis plays an important role in a complete failure recovery system. In our ap... more On-line failure analysis plays an important role in a complete failure recovery system. In our approach, a failure analysis system performs four functions: confirmation of the failure, updating of the workcell state, failure diagnosis and operator interface. The proposed scheme combines procedural and declarative approaches for representing ~he knowledge of the system. Diagnosis and updating functions can be implemented by a Production Rules system. A guideline to build the rules base is provided.
IFAC Proceedings Volumes, 2007
ABSTRACT The IEC developed the 61499 standard based in function blocks allowing representing comp... more ABSTRACT The IEC developed the 61499 standard based in function blocks allowing representing components and their interaction in distributed systems. This paper presents a methodology to automate the design of distributed controllers of discrete manufacturing systems, from a simple description of the system. The method takes advantage of the IEC-61499 facilities for deriving a modular representation, which is processed for developing a distributed controller. A case study regarding an assembly system is used to illustrate the proposed methodology; the resulting model is simulated using the FBDK software tool.
The problem of refining a Petri net (PN) discovered from a single sequence S of events T generate... more The problem of refining a Petri net (PN) discovered from a single sequence S of events T generated by discrete event processes is addressed. The refinement aims to reduce a possible exceeding language in the discovered model. A technique that extends a t-invariant based discovery method is presented. Given a discovered PN and its set of minimal t-invariants Y, the technique analyses the execution of the t-components in S and determines a sequencing pattern S Y that schedules the execution of t-components in the initial PN. Then, S Y is used to discover a PN' that uses transitions in T and new places; PN' schedules representative transitions of each t-invariant in S Y. The refined model is obtained by merging the representative transitions of both PN and PN' if the pattern is discovered. A first result coping with a subclass of safe PN in which each t-component has at least a transition not shared with any other component is reported.
International journal of robotics applications and technologies, Jul 1, 2013
This paper deals with the qualitative modelling of multiple mobile robot systems. The approach he... more This paper deals with the qualitative modelling of multiple mobile robot systems. The approach held is Petri net based: a definition of a three level scheme of Petri nets in which the tokens can be Petri nets is presented. The upper level describes the robots environment, the next level models the general behaviour of the mobile robots, and the third level represents specific features of each robot namely mission, tasks, and roadmaps; at this level it is also described resources and robot interaction protocols. The modelling formalism is illustrated through a case study regarding a mobile robot community evolving into a structured environment.
Modelling and analysis tools are essential for design and evaluation of complex systems. This is ... more Modelling and analysis tools are essential for design and evaluation of complex systems. This is particularly true for cellular systems, where a variety of handoff processes have been proposed. In this paper, the capabilities of Petri nets (PN) are used as a novel approach in the analysis of handoff problems. First, the generalized stochastic Petri net (GSPN) models are obtained, then they are analyzed as continuous time Markov chains derived from the reachability trees. Solution of the Markov chain permits to obtain performance indicators. Also the flexibility of coloured PN is applied advantageously to model multiple cells environments
In cellular telecommunications systems the transfer of calls (handoff) and the efficient use of c... more In cellular telecommunications systems the transfer of calls (handoff) and the efficient use of channels are essential features to keep in mind during the design of algorithms, in order to provide a continuous service to mobile users. This paper address the modeling and analysis stages of the design process using Petri nets (PN). First a high level description of the algorithms is done using colored Petri nets (CPN), then the equivalent (unfolded) timed PN is analyzed in order to obtain measures of performance. The work focuses on high level modeling; several schemes of handoff and dynamic channel allocation are dealt and their CPN model are presented.
... If X(ti) # E, then ti is said to be manipulated transitions, otherwise non manipulated. Place... more ... If X(ti) # E, then ti is said to be manipulated transitions, otherwise non manipulated. Place pi is said to be measurable if the i - th column vector of 'p is not null, ie ip(-,i) # 0, otherwise non measurable. ... it is said that (S,,AJ0) is controllable wrt (It,,,, A&). ...
2021 18th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), Nov 10, 2021
Nowadays, models play a relevant role in the analysis and monitoring of processes carried out by ... more Nowadays, models play a relevant role in the analysis and monitoring of processes carried out by organizations. Process discovery deals with the automated building of models from logs of event traces, which represent the executions of actual processes. However, when the logs come from highly flexible environments, most of the discovery algorithms obtain excessively complex models, which makes difficult their analysis. Trace clustering is a suitable approach to deal with this problem; it consists of dividing the logs into subsets, such that the executions within the same set are consistent with each other and derive a model for each subset. However, many clustering methods are based on the semantics of the executions, which is not the necessary feature for simplifying the model. In this paper, we propose a vector-based trace clustering approach in which the event traces are encoded as vectors, with the aim to gather the traces generated by the same process variant. The idea behind the method is that the different variants of a process can be distinguished by the corresponding sequential model substructures. Therefore, the proposed encoding method strives to partition the log into the subsets of traces from which those substructures can be revealed. An experimental evaluation with actual event logs shows that the method discovers simpler workflow nets than other available techniques.
Advances in computer and electrical engineering book series, 2019
Recent application development in the wireless sensor networks (WSNs) area makes arise problems r... more Recent application development in the wireless sensor networks (WSNs) area makes arise problems regarding data aggregation and effective methods to collect data. For addressing these problems, effective procedures are required. A multi-sink sensor network application has been characterized by many-to-many communication, where multiple sources report their data to multiple sinks. This chapter presents recent techniques for distributed multi-sink environments. The reviewed proposals are classified according to the purpose of the application, such as routing, monitoring of a specific target, data aggregation applications, and others. Finally, the authors present a discussion on the analyzed works.
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Papers by Ernesto Lopez-mellado