Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167697
Haining Yu, C. Cassandras
We use Stochastic Fluid Models (SFM) to capture the operation of threshold-based flow control policies in manufacturing systems without resorting to detailed discrete event models. By applying Infinitesimal Perturbation Analysis (IPA) to a SFM of a workcenter we derive gradient estimators of throughput and buffer overflow metrics with respect to flow control parameters. It is shown that these gradient estimators are unbiased and independent of distributional information of supply and service processes involved. Moreover, they can be implemented using actual system data, which enables us to develop simple iterative schemes for adjusting thresholds (hedging points) on line so as to optimize an objective function that trades off throughput and buffer overflow costs.
{"title":"Perturbation analysis and optimization of a flow controlled manufacturing system","authors":"Haining Yu, C. Cassandras","doi":"10.1109/WODES.2002.1167697","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167697","url":null,"abstract":"We use Stochastic Fluid Models (SFM) to capture the operation of threshold-based flow control policies in manufacturing systems without resorting to detailed discrete event models. By applying Infinitesimal Perturbation Analysis (IPA) to a SFM of a workcenter we derive gradient estimators of throughput and buffer overflow metrics with respect to flow control parameters. It is shown that these gradient estimators are unbiased and independent of distributional information of supply and service processes involved. Moreover, they can be implemented using actual system data, which enables us to develop simple iterative schemes for adjusting thresholds (hedging points) on line so as to optimize an objective function that trades off throughput and buffer overflow costs.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130713717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167681
J. Rosell
The automatic synthesis of a plan to perform a robotized assembly task from a high level description of the product to be assembled is a difficult issue which involves assembly planning and task planning. One of the main scopes of task planning is the planning of contact motions, which usually relies on a graph representation of contact space. This paper deals with the automatic computation of the local contact space using colored Petri nets (CPN). The presented CPN model is to be integrated into a Petri net based system that copes with both planning issues, making use of the hierarchical nature of high level Petri nets.
{"title":"Local contact state space generation using colored Petri nets","authors":"J. Rosell","doi":"10.1109/WODES.2002.1167681","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167681","url":null,"abstract":"The automatic synthesis of a plan to perform a robotized assembly task from a high level description of the product to be assembled is a difficult issue which involves assembly planning and task planning. One of the main scopes of task planning is the planning of contact motions, which usually relies on a graph representation of contact space. This paper deals with the automatic computation of the local contact space using colored Petri nets (CPN). The presented CPN model is to be integrated into a Petri net based system that copes with both planning issues, making use of the hierarchical nature of high level Petri nets.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124894218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167710
M. Giordano, F. Martinelli, P. Valigi
In this paper we consider a single part-type, single unreliable machine production system under a fluid approximation to describe the part flow through the system. We will assume that only a finite space is available for waiting demand and customers arriving when the backlog buffer is full are rejected, incurring in a penalty. The problem is to determine a production control which minimizes an infinite horizon average loss/backlog/surplus cost. In the infinite buffer capacity case, this problem is solved by a hedging point policy. In this paper we consider the finite capacity case, and based on an equation presented in a previous paper we discuss the effect of some meaningful parameters on the computed hedging point and the effect of finite buffers on the optimality of Just In Time (JIT) policies. An adaptive control algorithm is realized to determine the optimal hedging point when the system parameters are not known and must be estimated through the observation of the system.
{"title":"The effect of finite buffers on the optimal safety stock for unreliable systems","authors":"M. Giordano, F. Martinelli, P. Valigi","doi":"10.1109/WODES.2002.1167710","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167710","url":null,"abstract":"In this paper we consider a single part-type, single unreliable machine production system under a fluid approximation to describe the part flow through the system. We will assume that only a finite space is available for waiting demand and customers arriving when the backlog buffer is full are rejected, incurring in a penalty. The problem is to determine a production control which minimizes an infinite horizon average loss/backlog/surplus cost. In the infinite buffer capacity case, this problem is solved by a hedging point policy. In this paper we consider the finite capacity case, and based on an equation presented in a previous paper we discuss the effect of some meaningful parameters on the computed hedging point and the effect of finite buffers on the optimality of Just In Time (JIT) policies. An adaptive control algorithm is realized to determine the optimal hedging point when the system parameters are not known and must be estimated through the observation of the system.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127998371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167709
B. de Schutter, T. van den Boom
In previous work we have introduced model predictive control (MPC) for max-plus-linear and max-min-plus(-scaling) discrete-event systems. For max-plus-linear systems there are efficient algorithms to solve the corresponding MPC optimization problems. However, previously, for max-min-plus(-scaling) systems the only approach was to consider a limited subclass of decoupled max-min-plus systems or to use nonlinear nonconvex optimization algorithms, which are not efficient if the size of the system or the MPC optimization problem is large. In this paper we present a more efficient approach that is based on canonical forms for max-min-plus-scaling functions and in which the MPC optimization problem is reduced to a set of linear programming problems.
{"title":"Model predictive control for max-min-plus-scaling systems - efficient implementation","authors":"B. de Schutter, T. van den Boom","doi":"10.1109/WODES.2002.1167709","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167709","url":null,"abstract":"In previous work we have introduced model predictive control (MPC) for max-plus-linear and max-min-plus(-scaling) discrete-event systems. For max-plus-linear systems there are efficient algorithms to solve the corresponding MPC optimization problems. However, previously, for max-min-plus(-scaling) systems the only approach was to consider a limited subclass of decoupled max-min-plus systems or to use nonlinear nonconvex optimization algorithms, which are not efficient if the size of the system or the MPC optimization problem is large. In this paper we present a more efficient approach that is based on canonical forms for max-min-plus-scaling functions and in which the MPC optimization problem is reduced to a set of linear programming problems.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114890016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167662
C. Cassandras
Hybrid systems have emerged as a result of combining conventional time-driven dynamics with event-driven dynamics. This provides an opportunity for frameworks and methodologies developed for discrete event systems to enlarge their scope, driven by applications that range from manufacturing to command-control systems. The goal of this paper is to explore this transition from the point of view of discrete event system theory. Many hybrid systems may be viewed as consisting of a lower-level component that corresponds to time-driven physical processes, which a higher-level component with event-driven dynamics is called upon to coordinate by switching between different process operating modes. We concentrate on the formulation of optimization problems that arise in this "hybrid" setting, where the control variables affect both higher and lower level components. We also discuss a natural evolution of perturbation analysis techniques for discrete event systems into similar methodologies for a class of hybrid systems, known as stochastic fluid models, that find wide applicability in the control of communication networks.
{"title":"From discrete event to hybrid systems","authors":"C. Cassandras","doi":"10.1109/WODES.2002.1167662","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167662","url":null,"abstract":"Hybrid systems have emerged as a result of combining conventional time-driven dynamics with event-driven dynamics. This provides an opportunity for frameworks and methodologies developed for discrete event systems to enlarge their scope, driven by applications that range from manufacturing to command-control systems. The goal of this paper is to explore this transition from the point of view of discrete event system theory. Many hybrid systems may be viewed as consisting of a lower-level component that corresponds to time-driven physical processes, which a higher-level component with event-driven dynamics is called upon to coordinate by switching between different process operating modes. We concentrate on the formulation of optimization problems that arise in this \"hybrid\" setting, where the control variables affect both higher and lower level components. We also discuss a natural evolution of perturbation analysis techniques for discrete event systems into similar methodologies for a class of hybrid systems, known as stochastic fluid models, that find wide applicability in the control of communication networks.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129572128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167669
A. Giua, C. Seatzu
In this paper we consider a high-level description of a railway network using a skeleton net that belongs to the class of ES/sup 2/PR nets. The resource places of this model correspond to the action of a safeness enforcing supervisor. Liveness constraints may also be enforced for this class by adding appropriate monitor places designed using siphon analysis. We show how this can be done without an exhaustive computation of all siphons and characterize the cases in which this procedure can be recursively applied, giving a simple test for the closed loop net to remain an ES/sup 2/PR net.
{"title":"Liveness enforcing supervisors for railway networks using ES/sup 2/PR Petri nets","authors":"A. Giua, C. Seatzu","doi":"10.1109/WODES.2002.1167669","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167669","url":null,"abstract":"In this paper we consider a high-level description of a railway network using a skeleton net that belongs to the class of ES/sup 2/PR nets. The resource places of this model correspond to the action of a safeness enforcing supervisor. Liveness constraints may also be enforced for this class by adding appropriate monitor places designed using siphon analysis. We show how this can be done without an exhaustive computation of all siphons and characterize the cases in which this procedure can be recursively applied, giving a simple test for the closed loop net to remain an ES/sup 2/PR net.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125819439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167678
S. Haar, L. Kaiser, F. Simonot-Lion, J. Toussaint
We show that an important subclass of timed automata (Alur and Dill, 1994), called timed state machines, is weakly time equivalent to safe non-zero time Petri nets (TPNs) in the sense of Merlin and Farber (1976). We present an explicit construction for two-way translation between 1-safe TPNs and TSMs. The translation improves on the efficiency of other methods: the TSM obtained for a given net is polynomial in the size of the reachability graph, and a given TSM is translated into a net whose size grows linearly with that of the automaton model.
{"title":"Equivalence of timed state machines and safe TPN","authors":"S. Haar, L. Kaiser, F. Simonot-Lion, J. Toussaint","doi":"10.1109/WODES.2002.1167678","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167678","url":null,"abstract":"We show that an important subclass of timed automata (Alur and Dill, 1994), called timed state machines, is weakly time equivalent to safe non-zero time Petri nets (TPNs) in the sense of Merlin and Farber (1976). We present an explicit construction for two-way translation between 1-safe TPNs and TSMs. The translation improves on the efficiency of other methods: the TSM obtained for a given net is polynomial in the size of the reachability graph, and a given TSM is translated into a net whose size grows linearly with that of the automaton model.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122155224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167686
A. Benveniste, É. Fabre, S. Haar, C. Jard
This paper studies the diagnosis of asynchronous discrete event systems. We follow a so-called true concurrency approach, in which neither the global state nor global time are available. Instead, we use only local states in combination with a partial order model of time; our basic mathematical tool is that of Petri net unfoldings. This study was motivated by the problem of event correlation in telecommunications network management.
{"title":"Diagnosis of asynchronous discrete event systems, a net unfolding approach","authors":"A. Benveniste, É. Fabre, S. Haar, C. Jard","doi":"10.1109/WODES.2002.1167686","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167686","url":null,"abstract":"This paper studies the diagnosis of asynchronous discrete event systems. We follow a so-called true concurrency approach, in which neither the global state nor global time are available. Instead, we use only local states in combination with a partial order model of time; our basic mathematical tool is that of Petri net unfoldings. This study was motivated by the problem of event correlation in telecommunications network management.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123074961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167679
Bo Lindstrøm, Lisa Wells
This paper presents a framework for tools for monitoring discrete-event system models. Monitoring is any activity related to observing, inspecting, controlling or modifying a simulation of the model. We identify general patterns in how ad-hoc monitoring is done, and generalise these patterns to a uniform and flexible framework. A coloured Petri net model and simulator are used to illustrate how the framework can be used to create various types of monitoring tools. The framework is presented in general terms that are not specific to any particular formalism. The framework can serve as a reference for implementing different types of monitors in discrete-event system simulators.
{"title":"Towards a monitoring framework for discrete-event system simulations","authors":"Bo Lindstrøm, Lisa Wells","doi":"10.1109/WODES.2002.1167679","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167679","url":null,"abstract":"This paper presents a framework for tools for monitoring discrete-event system models. Monitoring is any activity related to observing, inspecting, controlling or modifying a simulation of the model. We identify general patterns in how ad-hoc monitoring is done, and generalise these patterns to a uniform and flexible framework. A coloured Petri net model and simulator are used to illustrate how the framework can be used to create various types of monitoring tools. The framework is presented in general terms that are not specific to any particular formalism. The framework can serve as a reference for implementing different types of monitors in discrete-event system simulators.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"263 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122907968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-02DOI: 10.1109/WODES.2002.1167663
T. Yoo, S. Lafortune
We consider a decentralized control architecture for discrete-event systems where local supervisors are allowed to change dynamically the manner in which their local decisions are combined globally. This is done by changing the default decisions regarding the enablement of common controllable events. In previous work, this default was fixed a priori and remained constant throughout the operation of the system. We show that under dynamic decision fusion rules, a larger class of languages can be achieved as compared with architectures with static fusion rules. A dynamic version of the notion of co-observability appears in the necessary and sufficient conditions for the existence of supervisors in the new architecture. The dynamic co-observability relaxes (static) co-observability. The existence of a set of local dynamic default decision rules that ensures dynamic co-observability can be decided in polynomial time.
{"title":"Decentralized supervisory control: a new architecture with a dynamic decision fusion rule","authors":"T. Yoo, S. Lafortune","doi":"10.1109/WODES.2002.1167663","DOIUrl":"https://doi.org/10.1109/WODES.2002.1167663","url":null,"abstract":"We consider a decentralized control architecture for discrete-event systems where local supervisors are allowed to change dynamically the manner in which their local decisions are combined globally. This is done by changing the default decisions regarding the enablement of common controllable events. In previous work, this default was fixed a priori and remained constant throughout the operation of the system. We show that under dynamic decision fusion rules, a larger class of languages can be achieved as compared with architectures with static fusion rules. A dynamic version of the notion of co-observability appears in the necessary and sufficient conditions for the existence of supervisors in the new architecture. The dynamic co-observability relaxes (static) co-observability. The existence of a set of local dynamic default decision rules that ensures dynamic co-observability can be decided in polynomial time.","PeriodicalId":435263,"journal":{"name":"Sixth International Workshop on Discrete Event Systems, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128016464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：