Pub Date : 2016-05-01DOI: 10.1109/WODES.2016.7497827
Fredrik Hagebring, Oskar Wigström, B. Lennartson, S. Ware, R. Su
This paper describes an optimisation model for the scheduling of a system consisting of three stacker cranes that are restricted to the same track. To improve the efficiency of the solution methods, a novel simplification of the model is presented, which has a low impact on the quality of the solution but greatly decreases its complexity. This model is then used to benchmark several popular solution methods, including both optimal and approximate methods. Some are based on monolithic models, whereas others solve the problem in phases by using sub-problem formulations. The result presented in this paper shows that evaluated solution methods have complementary strengths and weaknesses. Constraint Programming (CP) is very efficient on small scale problems, while Mixed Integer Linear Programming (MILP) scales much better when the number of movement orders increases. However, none of these methods are able to solve large instances of the problem to optimality. To handle the complexity of the problem, approximate solution methods are the only viable option. In this paper we show that promising results can be obtained even with simple methods using well known search algorithms such as A* and Tabu-search. However, preliminary results on more advanced search algorithms show that further improvements may be achieved, allowing the solution of very large problem instances.
{"title":"Comparing MILP, CP, and A* for multiple stacker crane scheduling","authors":"Fredrik Hagebring, Oskar Wigström, B. Lennartson, S. Ware, R. Su","doi":"10.1109/WODES.2016.7497827","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497827","url":null,"abstract":"This paper describes an optimisation model for the scheduling of a system consisting of three stacker cranes that are restricted to the same track. To improve the efficiency of the solution methods, a novel simplification of the model is presented, which has a low impact on the quality of the solution but greatly decreases its complexity. This model is then used to benchmark several popular solution methods, including both optimal and approximate methods. Some are based on monolithic models, whereas others solve the problem in phases by using sub-problem formulations. The result presented in this paper shows that evaluated solution methods have complementary strengths and weaknesses. Constraint Programming (CP) is very efficient on small scale problems, while Mixed Integer Linear Programming (MILP) scales much better when the number of movement orders increases. However, none of these methods are able to solve large instances of the problem to optimality. To handle the complexity of the problem, approximate solution methods are the only viable option. In this paper we show that promising results can be obtained even with simple methods using well known search algorithms such as A* and Tabu-search. However, preliminary results on more advanced search algorithms show that further improvements may be achieved, allowing the solution of very large problem instances.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127514791","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497880
Y. Shang, L. Hardouin, M. Lhommeau, C. Maia
This paper presents robust controllers solving the disturbance decoupling problem(DDP) of a class of uncertain max-plus linear systems, whose system matrices vary between intervals with known lower and upper bounds. The DDP for such uncertain max-plus linear systems is defined as finding a control interval such that the output trajectory interval for the disturbed controlled system belongs to the output trajectory interval for the undisturbed controlled system. In other words, the controls are able to absorb the effects of disturbances robustly for such systems. Both of the open-loop control intervals and the output feedback control intervals solving the DDP are constructed using the residuation theory and proved to be optimal for the just-in-time control criterion. The main results of this paper are illustrated by a high throughput screening system for drug discovery.
{"title":"Robust controllers in disturbance decoupling of uncertain max-plus linear systems: an application to a high throughput screening system for drug discovery","authors":"Y. Shang, L. Hardouin, M. Lhommeau, C. Maia","doi":"10.1109/WODES.2016.7497880","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497880","url":null,"abstract":"This paper presents robust controllers solving the disturbance decoupling problem(DDP) of a class of uncertain max-plus linear systems, whose system matrices vary between intervals with known lower and upper bounds. The DDP for such uncertain max-plus linear systems is defined as finding a control interval such that the output trajectory interval for the disturbed controlled system belongs to the output trajectory interval for the undisturbed controlled system. In other words, the controls are able to absorb the effects of disturbances robustly for such systems. Both of the open-loop control intervals and the output feedback control intervals solving the DDP are constructed using the residuation theory and proved to be optimal for the just-in-time control criterion. The main results of this paper are illustrated by a high throughput screening system for drug discovery.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125082412","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497826
Ming Liu, Lujun Xu, Shijin Wang, C. Chu
This paper investigates quay crane scheduling problem at container ports, subject to arbitrary precedence constraint. Differing from traditional machine scheduling problems, non-crossing constraint must be satisfied because parallel quay cranes mount on a same rail to unload or load containers. Precedence relation in an arbitrary form is rarely investigated in the literature, however it may be originated from (i) reefers or dangerous cargo which requires high priority of processing, and (ii) yard stacking plan. We present computational complexity for several problem variations. We show the problem, even without precedence constraint, is strongly NP-hard, which improves the state-of-the-art. A genetic algorithm is proposed to obtain near-optimal solutions. Computational experiments demonstrate the efficiency.
{"title":"Efficient algorithm for quay crane scheduling with arbitrary precedence constraint","authors":"Ming Liu, Lujun Xu, Shijin Wang, C. Chu","doi":"10.1109/WODES.2016.7497826","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497826","url":null,"abstract":"This paper investigates quay crane scheduling problem at container ports, subject to arbitrary precedence constraint. Differing from traditional machine scheduling problems, non-crossing constraint must be satisfied because parallel quay cranes mount on a same rail to unload or load containers. Precedence relation in an arbitrary form is rarely investigated in the literature, however it may be originated from (i) reefers or dangerous cargo which requires high priority of processing, and (ii) yard stacking plan. We present computational complexity for several problem variations. We show the problem, even without precedence constraint, is strongly NP-hard, which improves the state-of-the-art. A genetic algorithm is proposed to obtain near-optimal solutions. Computational experiments demonstrate the efficiency.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123483447","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497856
M. Schuh, J. Lunze
A method for the active fault-tolerant control of discrete event systems modeled by deterministic Input/Output automata is proposed that can be applied if the diagnostic result consists of a set of fault candidates rather than a single fault. Based on the ambiguous diagnostic result a common model of the faulty plant is constructed that describes the identical part of the behavior of the plant under all fault candidates. Then the reconfiguration of the controller is performed based on this common model. It is proved that the resulting reconfigured tracking controller steers the faulty plant into the desired final state, no matter which fault actually occurred.
{"title":"Fault-tolerant control of deterministic I/O automata with ambiguous diagnostic result","authors":"M. Schuh, J. Lunze","doi":"10.1109/WODES.2016.7497856","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497856","url":null,"abstract":"A method for the active fault-tolerant control of discrete event systems modeled by deterministic Input/Output automata is proposed that can be applied if the diagnostic result consists of a set of fault candidates rather than a single fault. Based on the ambiguous diagnostic result a common model of the faulty plant is constructed that describes the identical part of the behavior of the plant under all fault candidates. Then the reconfiguration of the controller is performed based on this common model. It is proved that the resulting reconfigured tracking controller steers the faulty plant into the desired final state, no matter which fault actually occurred.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115519022","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497889
D. Lefebvre
This paper proposes algorithms that incrementally compute control sequences driving the marking of timed Petri nets from an initial value to a reference one, avoiding forbidden and dangerous states with a duration that approaches the minimal value. The proposed algorithms are applicable to a large class of discrete event systems in particular in the domain of flexible manufacturing, communication and computer science or transportation and traffic. To overcome the most burdensome part of the computations, only the sequences encoded in a small area of the reachability graph are worked out. The main contributions are to propose an estimation of the minimal duration of the remaining sequences to the reference based on the computation of the firing count vectors and a progressive search of the forbidden and dangerous states according to a backtracking phase. The approach is suitable for deadlock-free scheduling problems.
{"title":"Deadlock-free scheduling for timed Petri net models combined with MPC and backtracking","authors":"D. Lefebvre","doi":"10.1109/WODES.2016.7497889","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497889","url":null,"abstract":"This paper proposes algorithms that incrementally compute control sequences driving the marking of timed Petri nets from an initial value to a reference one, avoiding forbidden and dangerous states with a duration that approaches the minimal value. The proposed algorithms are applicable to a large class of discrete event systems in particular in the domain of flexible manufacturing, communication and computer science or transportation and traffic. To overcome the most burdensome part of the computations, only the sequences encoded in a small area of the reachability graph are worked out. The main contributions are to propose an estimation of the minimal duration of the remaining sequences to the reference based on the computation of the firing count vectors and a progressive search of the forbidden and dangerous states according to a backtracking phase. The approach is suitable for deadlock-free scheduling problems.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129773137","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497872
Zicheng Liu, N. Wu, Fajun Yang, Yan Qiao
It is very difficult to schedule a single-arm cluster tool with wafer revisiting such that wafer residency time constraints are satisfied. This paper conducts a study on this challenging problem for a single-arm cluster tool with atomic layer deposition (ALD) process. With a so called p-backward strategy being applied, a Petri net model is developed to describe the dynamic behavior of the system. Based on the model, existence of a feasible schedule is analyzed, schedulability conditions are derived, and a scheduling algorithm is presented if there is a schedule. A schedule is obtained by simply setting the robot waiting time and it is very computationally efficient. The obtained schedule is shown to be optimal. Illustrative examples are given to demonstrate the proposed approach.
{"title":"Optimal scheduling of time-constrained single-arm cluster tools with wafer revisiting","authors":"Zicheng Liu, N. Wu, Fajun Yang, Yan Qiao","doi":"10.1109/WODES.2016.7497872","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497872","url":null,"abstract":"It is very difficult to schedule a single-arm cluster tool with wafer revisiting such that wafer residency time constraints are satisfied. This paper conducts a study on this challenging problem for a single-arm cluster tool with atomic layer deposition (ALD) process. With a so called p-backward strategy being applied, a Petri net model is developed to describe the dynamic behavior of the system. Based on the model, existence of a feasible schedule is analyzed, schedulability conditions are derived, and a scheduling algorithm is presented if there is a schedule. A schedule is obtained by simply setting the robot waiting time and it is very computationally efficient. The obtained schedule is shown to be optimal. Illustrative examples are given to demonstrate the proposed approach.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"161 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114630210","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497822
Francis Atampore, J. Dingel, K. Rudie
Web services play a major role in electronic businesses and allow organizations to perform certain business activities in a distributed fashion. In some circumstances, a single service is not able to perform certain tasks and it becomes imperative to compose two or more services in order to complete a task. While approaches to tackle such a problem are known, the task of generating provably correct Web service compositions still remain challenging and complex. In this paper, we develop a supervisory control framework for automated composition of Web services. Labelled Transition Systems augmented with guards and data variables are used to represent a given set of Web service specifications. We model the interactions of services asynchronously and we use guards and data variables to allow us to express certain preconditions which are then propagated from the system requirements through the overall composite service. The objective of our framework is to synthesize a controller, which interacts with a given set of Web services through messages to guarantee that a given specification is satisfied. A key novelty of this work is the application of control theory to service-oriented computing and the incorporation of run-time input into the supervisor generation process.
{"title":"Automated service composition via supervisory control theory","authors":"Francis Atampore, J. Dingel, K. Rudie","doi":"10.1109/WODES.2016.7497822","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497822","url":null,"abstract":"Web services play a major role in electronic businesses and allow organizations to perform certain business activities in a distributed fashion. In some circumstances, a single service is not able to perform certain tasks and it becomes imperative to compose two or more services in order to complete a task. While approaches to tackle such a problem are known, the task of generating provably correct Web service compositions still remain challenging and complex. In this paper, we develop a supervisory control framework for automated composition of Web services. Labelled Transition Systems augmented with guards and data variables are used to represent a given set of Web service specifications. We model the interactions of services asynchronously and we use guards and data variables to allow us to express certain preconditions which are then propagated from the system requirements through the overall composite service. The objective of our framework is to synthesize a controller, which interacts with a given set of Web services through messages to guarantee that a given specification is satisfied. A key novelty of this work is the application of control theory to service-oriented computing and the incorporation of run-time input into the supervisor generation process.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125640450","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497834
Jeremie Benhamron, J. G. Thistle
To make the techniques of supervisory control theory more accessible to non-experts, an intuitive and user-friendly modelling approach is needed to dissociate the modeller from the abstract automaton models used within the theory. This paper attempts to resolve this issue by presenting a modelling framework based upon graph rewriting, in which so-called implicit automaton models are used to generate automata that can be used as input to supervisory synthesis algorithms. It is demonstrated how the proposed modelling approach can be supported by a graph transformation tool such as GROOVE which implements the graph rewriting modelling paradigm.
{"title":"Graph transformation as a modelling framework for supervisory control","authors":"Jeremie Benhamron, J. G. Thistle","doi":"10.1109/WODES.2016.7497834","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497834","url":null,"abstract":"To make the techniques of supervisory control theory more accessible to non-experts, an intuitive and user-friendly modelling approach is needed to dissociate the modeller from the abstract automaton models used within the theory. This paper attempts to resolve this issue by presenting a modelling framework based upon graph rewriting, in which so-called implicit automaton models are used to generate automata that can be used as input to supervisory synthesis algorithms. It is demonstrated how the proposed modelling approach can be supported by a graph transformation tool such as GROOVE which implements the graph rewriting modelling paradigm.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132898011","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497879
Jia Xu, L. Buşoniu, T. Boom, B. Schutter
This paper addresses the infinite-horizon optimal control problem for max-plus linear systems where the considered objective function is a sum of discounted stage costs over an infinite horizon. The minimization problem of the cost function is equivalently transformed into a maximization problem of a reward function. The resulting optimal control problem is solved based on an optimistic planning algorithm. The control variables are the increments of system inputs and the action space is discretized as a finite set. Given a finite computational budget, a control sequence is returned by the optimistic planning algorithm. The first control action or a subsequence of the returned control sequence is applied to the system and then a receding-horizon scheme is adopted. The proposed optimistic planning approach allows us to limit the computational budget and also yields a characterization of the level of near-optimality of the resulting solution. The effectiveness of the approach is illustrated with a numerical example. The results show that the optimistic planning approach results in a lower tracking error compared with a finite-horizon approach when a subsequence of the returned control sequence is applied.
{"title":"Receding-horizon control for max-plus linear systems with discrete actions using optimistic planning","authors":"Jia Xu, L. Buşoniu, T. Boom, B. Schutter","doi":"10.1109/WODES.2016.7497879","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497879","url":null,"abstract":"This paper addresses the infinite-horizon optimal control problem for max-plus linear systems where the considered objective function is a sum of discounted stage costs over an infinite horizon. The minimization problem of the cost function is equivalently transformed into a maximization problem of a reward function. The resulting optimal control problem is solved based on an optimistic planning algorithm. The control variables are the increments of system inputs and the action space is discretized as a finite set. Given a finite computational budget, a control sequence is returned by the optimistic planning algorithm. The first control action or a subsequence of the returned control sequence is applied to the system and then a receding-horizon scheme is adopted. The proposed optimistic planning approach allows us to limit the computational budget and also yields a characterization of the level of near-optimality of the resulting solution. The effectiveness of the approach is illustrated with a numerical example. The results show that the optimistic planning approach results in a lower tracking error compared with a finite-horizon approach when a subsequence of the returned control sequence is applied.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114321616","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497857
Dan You, Shouguang Wang, C. Seatzu
This work focuses on the problem of providing a linear algebraic characterization of the admissible marking set relative to a Petri net with uncontrollable transitions, subject to a linear constraint. More specifically, given a linear constraint that limits the number of tokens in one place, an algorithm is proposed to provide an approximation of the admissible marking set in terms of a disjunction of transformed linear constraints. The optimality of the solution is guaranteed provided that certain conditions are satisfied during the intermediate steps of the iterative approach.
{"title":"A new linear constraint transformation approach for Petri nets with uncontrollable transitions","authors":"Dan You, Shouguang Wang, C. Seatzu","doi":"10.1109/WODES.2016.7497857","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497857","url":null,"abstract":"This work focuses on the problem of providing a linear algebraic characterization of the admissible marking set relative to a Petri net with uncontrollable transitions, subject to a linear constraint. More specifically, given a linear constraint that limits the number of tokens in one place, an algorithm is proposed to provide an approximation of the admissible marking set in terms of a disjunction of transformed linear constraints. The optimality of the solution is guaranteed provided that certain conditions are satisfied during the intermediate steps of the iterative approach.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123760874","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}
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