Deadlock must be prevented via the shop controller during the flexible manufacturing system (FMS) performing. Various models have been tried for the analysis and design of shop controller. Petri net is suitable to d...Deadlock must be prevented via the shop controller during the flexible manufacturing system (FMS) performing. Various models have been tried for the analysis and design of shop controller. Petri net is suitable to describe the dynamic behavior of the discrete event system, such as concurrency, conflict and deadlock, however, the verification of the .system behavior needs structure analysis with complex theoretical proof method. Temporal logic model checking has important advantages over traditional theorem prover. It is flatly automatic and can produce possible counter-example which is particularly important in finding subtle error in complex transition systems. In this paper, a new method for the deadlock prevention based on Petri net and Temporal Logic model checking is presented. The specification in the Temporal Logic is expressed according to some result of structure analysis of the Petri net. The model checking is employed to execute the formal verification, which will conduct an exhaustive exploration of all possible behaviors. Finally, an example is presented to demonstrate how the method works.展开更多
In a flexible manufacturing system, both the productivity and the flexibility of the manufacturing processes are highly influenced by robot sequencing. In this paper a petri net based approach for sequencing of indust...In a flexible manufacturing system, both the productivity and the flexibility of the manufacturing processes are highly influenced by robot sequencing. In this paper a petri net based approach for sequencing of industrial robot in a flexible manufacturing cell is presented and a decision structure for robot sequencing based on different criteria is described.展开更多
Due to the development of advanced manufacturing technology and the introduction of Smart Manufacturing notion in the field of modern industrial production, welding flexible manufacturing using robot technology has b...Due to the development of advanced manufacturing technology and the introduction of Smart Manufacturing notion in the field of modern industrial production, welding flexible manufacturing using robot technology has become the inevitable developing direction on welding automation. Based on a new intelligent arc welding flexible manufacturing cell (WFMC), its system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. A discrete control model of WFMC has been constructed, in which the system's status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into Petri net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real time control on welding flexible manufacturing cell and system.展开更多
In few years only, the efficiency record of perovskite solar cells(PSCs) has raised quickly from 3.8% to over 22%. This emerging photovoltaic technology has primarily shown its great potential of industrialization. ...In few years only, the efficiency record of perovskite solar cells(PSCs) has raised quickly from 3.8% to over 22%. This emerging photovoltaic technology has primarily shown its great potential of industrialization. Flexible PSCs are thought to be one of the most priority options for mass production, related to the intrinsic advantage of perovskite thin films which could be deposited by facile solution processes at low temperature. Flexible PSCs have at least four advantages in comparison to the rigid counterpart:(1) it can generate higher power output at lighter weight,(2) it is easily portable,(3) it can be easily attached to architectures or textiles with diverse shapes, and(4) it is compatible with roll-to-roll fabrication in a large scale. In this review, we have summarized recent development of the key materials and technologies applied in flexible PSCs. The key materials including flexible substrates, transparent and conductive electrodes, and interfacial materials; some key technologies about roll-to-roll manufacture, encapsulation technology have been overviewed. Finally, a prospect on possible application directions of flexible PSCs has been discussed.展开更多
The design of a control system for the material transport as used in gear-box flexible manufacturing system is presented in this paper. The scope of investigation covers material transport control, automatic vehicle, ...The design of a control system for the material transport as used in gear-box flexible manufacturing system is presented in this paper. The scope of investigation covers material transport control, automatic vehicle, material exchange station, multi-storeyed warehouse system, NC and CNC machines and host computer etc. The paper describes the transport control system and its design, and briefly describes the communication among devices and warehouse access principles.展开更多
In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by th...In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by the method is carried byintensively using model's structural information, such as invariants, siphons, etc.. As aresult, the analysis leads us to draw the general conclusion that the model obtained isconservativeness and thus bound, and characterize its liveness in terms of zero-markingminimal siphons. It is based on model's structural information that distinguishes ourmethod from others. in line of this thought, a liveness guarantying policy for the obtainedmodel is proposed. Some control subnets are merged into the original model according tothe proposed synthesis rules in this paper to ensure that no minimal siphons are emptiedin any state, therefore the liveness is guaranteed. As a result, a live, conservative andrevertible Petri Nets is obtained. A practical example is also presented to demonstrate theeffectiveness of this method.展开更多
As the main component of computer integrated manufacturing system (CIMS), flexible manufacturing system (FMS) should be an open system with reusability and extenchaility. Moreover, as FMS is a complex asynchronous con...As the main component of computer integrated manufacturing system (CIMS), flexible manufacturing system (FMS) should be an open system with reusability and extenchaility. Moreover, as FMS is a complex asynchronous concurrent system, its model also should have the abilities to express the concurrency in the system and to analyze the behavior of the system. It is difficult to use any one method to model such a complex system as FMS. A modeling method using Object-oriented modeling language-unified modeling language (UML) and object-Oriented Petri nets (OPNs) is proposed. Class diagram in UML is used to represent the static relations among the objects in FMS. OPNs are used to model the dynamic behavior of the objects and conduct performance analysis. OPNs also can be used to identify the attributes and operations of the objects. The model can describe the system integrally and can be used to design FMS control software naturally.展开更多
This paper presents a study on the performance of flexible manufacturing systems (FMSs), by using discrete event system (DES) models, considering resource losses modelled by a parameter entitled coverage factor. W...This paper presents a study on the performance of flexible manufacturing systems (FMSs), by using discrete event system (DES) models, considering resource losses modelled by a parameter entitled coverage factor. We conclude that the resources cell loss distribution between the tasks of a FSM is a real function that cannot be integrated, in order to calculate its primitive, in the classical sense of Riemann or Lebesgue, but only in the sense of Henstock-Kurzweil integral. Our result allows one to study more general processes where highly oscillatory functions occur. The method used to deduce the functi6n describing the resources cell loss distribution is compared with a classical method related in the literature, respectively rational interpolants. An example has been constructed to emphasize what we believe to be, new approaches.展开更多
In several industrial fields like air transport,energy industry and military domain,maintenance actions are carried out during downtimes in order to maintain the reliability and availability of production system.In su...In several industrial fields like air transport,energy industry and military domain,maintenance actions are carried out during downtimes in order to maintain the reliability and availability of production system.In such a circumstance,selective maintenance strategy is considered the reliable solution for selecting the faulty components to achieve the next mission without stopping.In this paper,a novel multi-level decision making approach based on data mining techniques is investigated to determine an optimal selective maintenance scheduling.At the first-level,the age acceleration factor and its impact on the component nominal age are used to establish the local failures.This first decision making employed K-means clustering algorithm that exploited the historical maintenance actions.Based on the first-level intervention plan,the remaining-levels identify the stochastic dependence among components by relying upon Apriori association rules algorithm,which allows to discover of the failure occurrence order.In addition,at each decision making level,an optimization model combined to a set of exclusion rules are called to supply the optimal selective maintenance plan within a reasonable time,minimizing the total maintenance cost under a required reliability threshold.To illustrate the robustness of the proposed strategy,numerical examples and a FMS real study case have been solved.展开更多
In this paper, steady-state behaviors for a large class of flexible manufacturing cells are considered under two types of schedules, i.e., simple schedule and composite schedule. It is shown that each composite schedu...In this paper, steady-state behaviors for a large class of flexible manufacturing cells are considered under two types of schedules, i.e., simple schedule and composite schedule. It is shown that each composite schedule can be obtained by composition of simple ones. A systematic approach to modeling and analysis of schedules is proposed cycle times of timed petri net models of schedules are derived. A example of three-machine cell is given.展开更多
Elementary siphons are useful in the development of a deadlock prevention policy for a discrete event system modeled with Petri nets. This paper proposes an algorithm to iteratively extract a set of elementary siphons...Elementary siphons are useful in the development of a deadlock prevention policy for a discrete event system modeled with Petri nets. This paper proposes an algorithm to iteratively extract a set of elementary siphons in a class of Petri nets, called system of simple sequential processes with resources (S3pR). At each iteration, by a mixed-integer programming (MIP) method, the proposed algorithm finds a maximal unmarked siphon, classifies the places in it, extracts an elementary siphon from the classified places, and adds a new constraint in order to extract the next elementary siphon. This algorithm iteratively executes until no new unmarked siphons can be found. It finally obtains a unique set of elementary siphons and avoids a complete siphon enumeration. A theoretical analysis and examples are given to demonstrate its efficiency and practical potentials.展开更多
Due to the complexity of dynamic job shop scheduling in flexible manufacturing system(FMS), many heuristic rules are still used today. A dynamic scheduling approach based on Lagrangian relaxation is proposed to improv...Due to the complexity of dynamic job shop scheduling in flexible manufacturing system(FMS), many heuristic rules are still used today. A dynamic scheduling approach based on Lagrangian relaxation is proposed to improve the quality and guarantee the real time capability of dynamic scheduling. The proposed method makes use of the dynamic predictive optimal theory combined with Lagrangian relaxation to obtain a good solution that can be evaluated quantitatively. The Lagrangian multipliers introduced here are capable of describing machine predictive states and system capacity constraints. This approach can evaluate the suboptimality of the scheduling systems. It can also quickly obtain high quality feasible schedules, thus enabling Lagrangian relaxation to be better used in the dynamic scheduling of manufacturing system. The efficiency and effectiveness of this method are verified by numerical experiments.展开更多
文摘Deadlock must be prevented via the shop controller during the flexible manufacturing system (FMS) performing. Various models have been tried for the analysis and design of shop controller. Petri net is suitable to describe the dynamic behavior of the discrete event system, such as concurrency, conflict and deadlock, however, the verification of the .system behavior needs structure analysis with complex theoretical proof method. Temporal logic model checking has important advantages over traditional theorem prover. It is flatly automatic and can produce possible counter-example which is particularly important in finding subtle error in complex transition systems. In this paper, a new method for the deadlock prevention based on Petri net and Temporal Logic model checking is presented. The specification in the Temporal Logic is expressed according to some result of structure analysis of the Petri net. The model checking is employed to execute the formal verification, which will conduct an exhaustive exploration of all possible behaviors. Finally, an example is presented to demonstrate how the method works.
文摘In a flexible manufacturing system, both the productivity and the flexibility of the manufacturing processes are highly influenced by robot sequencing. In this paper a petri net based approach for sequencing of industrial robot in a flexible manufacturing cell is presented and a decision structure for robot sequencing based on different criteria is described.
基金SupportedbyNationalNaturalScienceFoundationofChina (No .5 96 35 16 0 )Pre ResearchingKeyProjectoNationalDefenseTechnology
文摘Due to the development of advanced manufacturing technology and the introduction of Smart Manufacturing notion in the field of modern industrial production, welding flexible manufacturing using robot technology has become the inevitable developing direction on welding automation. Based on a new intelligent arc welding flexible manufacturing cell (WFMC), its system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. A discrete control model of WFMC has been constructed, in which the system's status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into Petri net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real time control on welding flexible manufacturing cell and system.
基金financially supported by the National Natural Science Foundation of China(51672094,51661135023)the National Key R&D Program of China(2016YFC0205002)+1 种基金the Selfdetermined and Innovative Research Funds of HUST(2016JCTD111)the open research funds of Engineering Research Center of Nano-Geo Materials of Ministry of Education,China University of Geosciences(NGM2017KF013)
文摘In few years only, the efficiency record of perovskite solar cells(PSCs) has raised quickly from 3.8% to over 22%. This emerging photovoltaic technology has primarily shown its great potential of industrialization. Flexible PSCs are thought to be one of the most priority options for mass production, related to the intrinsic advantage of perovskite thin films which could be deposited by facile solution processes at low temperature. Flexible PSCs have at least four advantages in comparison to the rigid counterpart:(1) it can generate higher power output at lighter weight,(2) it is easily portable,(3) it can be easily attached to architectures or textiles with diverse shapes, and(4) it is compatible with roll-to-roll fabrication in a large scale. In this review, we have summarized recent development of the key materials and technologies applied in flexible PSCs. The key materials including flexible substrates, transparent and conductive electrodes, and interfacial materials; some key technologies about roll-to-roll manufacture, encapsulation technology have been overviewed. Finally, a prospect on possible application directions of flexible PSCs has been discussed.
文摘The design of a control system for the material transport as used in gear-box flexible manufacturing system is presented in this paper. The scope of investigation covers material transport control, automatic vehicle, material exchange station, multi-storeyed warehouse system, NC and CNC machines and host computer etc. The paper describes the transport control system and its design, and briefly describes the communication among devices and warehouse access principles.
文摘In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by the method is carried byintensively using model's structural information, such as invariants, siphons, etc.. As aresult, the analysis leads us to draw the general conclusion that the model obtained isconservativeness and thus bound, and characterize its liveness in terms of zero-markingminimal siphons. It is based on model's structural information that distinguishes ourmethod from others. in line of this thought, a liveness guarantying policy for the obtainedmodel is proposed. Some control subnets are merged into the original model according tothe proposed synthesis rules in this paper to ensure that no minimal siphons are emptiedin any state, therefore the liveness is guaranteed. As a result, a live, conservative andrevertible Petri Nets is obtained. A practical example is also presented to demonstrate theeffectiveness of this method.
基金This project is supported by National Natural Science Foundation of China !(59889505)
文摘As the main component of computer integrated manufacturing system (CIMS), flexible manufacturing system (FMS) should be an open system with reusability and extenchaility. Moreover, as FMS is a complex asynchronous concurrent system, its model also should have the abilities to express the concurrency in the system and to analyze the behavior of the system. It is difficult to use any one method to model such a complex system as FMS. A modeling method using Object-oriented modeling language-unified modeling language (UML) and object-Oriented Petri nets (OPNs) is proposed. Class diagram in UML is used to represent the static relations among the objects in FMS. OPNs are used to model the dynamic behavior of the objects and conduct performance analysis. OPNs also can be used to identify the attributes and operations of the objects. The model can describe the system integrally and can be used to design FMS control software naturally.
基金supported by MEdC-ANCS,Research Contract CEEX 5954/18.09.2006
文摘This paper presents a study on the performance of flexible manufacturing systems (FMSs), by using discrete event system (DES) models, considering resource losses modelled by a parameter entitled coverage factor. We conclude that the resources cell loss distribution between the tasks of a FSM is a real function that cannot be integrated, in order to calculate its primitive, in the classical sense of Riemann or Lebesgue, but only in the sense of Henstock-Kurzweil integral. Our result allows one to study more general processes where highly oscillatory functions occur. The method used to deduce the functi6n describing the resources cell loss distribution is compared with a classical method related in the literature, respectively rational interpolants. An example has been constructed to emphasize what we believe to be, new approaches.
文摘In several industrial fields like air transport,energy industry and military domain,maintenance actions are carried out during downtimes in order to maintain the reliability and availability of production system.In such a circumstance,selective maintenance strategy is considered the reliable solution for selecting the faulty components to achieve the next mission without stopping.In this paper,a novel multi-level decision making approach based on data mining techniques is investigated to determine an optimal selective maintenance scheduling.At the first-level,the age acceleration factor and its impact on the component nominal age are used to establish the local failures.This first decision making employed K-means clustering algorithm that exploited the historical maintenance actions.Based on the first-level intervention plan,the remaining-levels identify the stochastic dependence among components by relying upon Apriori association rules algorithm,which allows to discover of the failure occurrence order.In addition,at each decision making level,an optimization model combined to a set of exclusion rules are called to supply the optimal selective maintenance plan within a reasonable time,minimizing the total maintenance cost under a required reliability threshold.To illustrate the robustness of the proposed strategy,numerical examples and a FMS real study case have been solved.
文摘In this paper, steady-state behaviors for a large class of flexible manufacturing cells are considered under two types of schedules, i.e., simple schedule and composite schedule. It is shown that each composite schedule can be obtained by composition of simple ones. A systematic approach to modeling and analysis of schedules is proposed cycle times of timed petri net models of schedules are derived. A example of three-machine cell is given.
基金supported by the Natural Science Foundation of China under Grant No.60773001,61074035, 61064003,and 50978129the Fundamental Research Funds for the Central Universities under Grant No. JY 10000904001+2 种基金the National Research Foundation for the Doctoral Program of Higher Education,the Ministry of Education,P.R.China,under Grant No.20090203110009the"863"High-tech Research and Development Program of China under Grant No.2008AA04Z 109the Alexander von Humboldt Foundation
文摘Elementary siphons are useful in the development of a deadlock prevention policy for a discrete event system modeled with Petri nets. This paper proposes an algorithm to iteratively extract a set of elementary siphons in a class of Petri nets, called system of simple sequential processes with resources (S3pR). At each iteration, by a mixed-integer programming (MIP) method, the proposed algorithm finds a maximal unmarked siphon, classifies the places in it, extracts an elementary siphon from the classified places, and adds a new constraint in order to extract the next elementary siphon. This algorithm iteratively executes until no new unmarked siphons can be found. It finally obtains a unique set of elementary siphons and avoids a complete siphon enumeration. A theoretical analysis and examples are given to demonstrate its efficiency and practical potentials.
文摘Due to the complexity of dynamic job shop scheduling in flexible manufacturing system(FMS), many heuristic rules are still used today. A dynamic scheduling approach based on Lagrangian relaxation is proposed to improve the quality and guarantee the real time capability of dynamic scheduling. The proposed method makes use of the dynamic predictive optimal theory combined with Lagrangian relaxation to obtain a good solution that can be evaluated quantitatively. The Lagrangian multipliers introduced here are capable of describing machine predictive states and system capacity constraints. This approach can evaluate the suboptimality of the scheduling systems. It can also quickly obtain high quality feasible schedules, thus enabling Lagrangian relaxation to be better used in the dynamic scheduling of manufacturing system. The efficiency and effectiveness of this method are verified by numerical experiments.