Mekatronik Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/255

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Citation Count: Schmidt, K.W., Breindl, C. (2014). A framework for state attraction of discrete event systems under partial observation. Information Sciences, 281, 265-280. http://dx.doi.org/10.1016/j.ins.2014.05.026
A framework for state attraction of discrete event systems under partial observation
(Elsevier Science Inc., 2014) Schmidt, Klaus Werner; Breindl, Christian; 17337
State attraction for discrete event systems (DES) addresses the problem of reaching a desired subset of the plant state space after a bounded number of event occurrences. The problem of state attraction arises for example in fault-tolerant supervisory control or in the control of reconfigurable manufacturing systems, and is also applicable to systems biological problems such as the control of gene regulatory networks. State attraction is investigated with the assumption of full event observation in the existing literature. This paper extends the concept of state attraction to the case of partial observation. The notion of weak attraction under partial observation (WAPO) is introduced and necessary and sufficient conditions for the existence of a supervisor under partial observation that achieves WAPO are derived. Furthermore, a solution algorithm is proposed that finds such supervisor whenever it exists. It is shown that such supervisor can always be realized as a subautomaton of the observer automaton of the DES plant. An application example from systems biology illustrates the obtained results.
Citation Count: Schmidt, Klaus Werner; Schmidt, E.G, "A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet", 2010 International Symposium On Industrial Embedded Systems, Sies 2010 - Conference Proceedings, pp. 205-208, (2010).
A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet
(2010) Schmidt, Klaus Werner; Schmidt, E. G.; 17337
In the recent years, the use of real-time Ethernet protocols becomes more and more relevant for time-critical networked industrial applications. In this context, this paper presents a method to compute the worst-case packet delays on switched Ethernet. Based on an evaluation of the packet delays at each switch port and the network topology, we construct a weighted directed graph that allows to find the worst-case end-toend packet delay by solving a conventional longest-path problem
Citation Count: Hazir, Ö.; Schmidt, K.W.; Eryilmaz, U.,"An Optimization Model to Coordinate Scheduling and Controling in Projects: Case With İnstantaneous Control Constraints", Opt-I 2014 - 1St International Conference On Engineering and Applied Sciences Optimization, Proceedings, pp. 2095-2110, (2014).
An Optimization Model to Coordinate Scheduling and Controling in Projects: Case With İnstantaneous Control Constraints
(National Technical University of Athens, 2014) Hazır, Öncü; Schmidt, Klaus Werner; Eryılmaz, Utkan; 17337
Today, many enterprises in different industries take part in various projects, and organizational performances depend more and more on project performances. In order to maximize performance, effective management of project functions is crucial. In this regard, we focus on scheduling and control functions and their relation. Characteristics of data sharing among them and possible integration strategies are theoretically investigated. A model base for a decision support framework that accounts for these interdependencies and supports managers is developed. To solve the formulated integrated project scheduling and control problem, a tabu search algorithm is combined with optimal control techniques. As a result, a project schedule as well as the means and timing of interventions are determined such that the project cost is minimized. The obtained results are supported by computational experiments. Integrated models and algorithms to be developed aim to fill an important theoretical gap in project management.
Citation Count: Sülek, A.N.; Schmidt, K.W.,"Computation of Fault-Tolerant Supervisors for Discrete Event Systems ?",Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 4, No. 1, pp. 115-120, (2013).
Computation of Fault-Tolerant Supervisors for Discrete Event Systems ?
(2013) Sülek, A. N.; Schmidt, Klaus Werner; 17337
Fault-tolerance addresses the problem of operating a system even in case of faults. In this paper, we study fault-tolerance in the supervisory control framework for discrete event systems (DES). We consider DES, where certain events might no longer be possible in case a fault happens. In this setting, we first identify necessary and suficient conditions for the existence of a supervisor that realizes a given behavioral specification both in the non-faulty and in the faulty case. We further show that it is possible to determine a supremal fault-tolerant sublanguage in case the existence condition is violated. Finally, we propose an algorithm for the computation of this sublanguage and prove its correctness. Different from existing work, our fault-tolerant supervisor allows fault occurrences and system repairs at any time. The concepts and results developed in this paper are illustrated by a manufacturing system example.
Citation Count: Sülek, A.N., Schmidt, K.W.,"Computation of Supervisors for Fault-Recovery and Repair for Discrete Event Systems",Advances in the Astronautical Sciences, Vol. 9, No. 3, pp. 428-433, (2014).
Computation of Supervisors for Fault-Recovery and Repair for Discrete Event Systems
(IFAC Secretariat, 2014) Sülek, Ayşe Nur; Schmidt, Klaus Werner; 17337; 107424
In this paper, we study the fault-recovery and repair of discrete event systems (DES). To this end, we first develop a new method for the fault-recovery of DES. In particular, we compute a fault-recovery supervisor that follows the specified nominal system behavior until a fault-occurrence, that continues its operation according to a degraded specification after a fault and that finally converges to a desired behavior after fault. We next show that our method is also applicable to system repair and we propose an iterative procedure that determines a supervisor for an arbitrary number of fault occurrences and system repairs. We demonstrate our method with a manufacturing system example.
Citation Count: Schmidt, K.W. (2015). Computation of supervisors for reconfigurable machine tools. Discrete Event Dynamic Systems-Theory And Applications, 25(1-2), 125-158. http://dx.doi.org/10.1007/s10626-014-0183-9
Computation of supervisors for reconfigurable machine tools
(Springer, 2015) Schmidt, Klaus Werner; 17337
The rapid reconfiguration of manufacturing systems is an important issue in today's manufacturing technology in order to adjust the production to varying product demands and types. In this paper, we study the control of reconfigurable machine tools (RMTs) with the aim of fast reconfiguration and an easy controller implementation. We first formulate a particular reconfiguration problem for RMTs in a discrete event system setting, and then provide a necessary and sufficient condition for its solution. Moreover, we propose a polynomial-time algorithm for the construction of a reconfiguration supervisor as the composition of one modular supervisor for each separate RMT configuration. Each modular supervisor operates in three modes. In the first mode, it tracks the plant state if its corresponding configuration is inactive. In the second mode, it performs a configuration change if its corresponding configuration becomes active and in the third mode, it follows the specified behavior of its corresponding configuration if the configuration is active. An important property of the proposed reconfiguration supervisor is that it performs reconfigurations in a bounded number of event occurrences. In addition, the modular realization of our reconfiguration supervisor enables controller modifications such as adding or removing configurations during run-time. All results presented in the paper are illustrated by an RMT example.
Citation Count: Schmidt, K.W...et al. (2016). Controller area network with priority queues and FIFO queues: improved schedulability analysis and message set extension. International Journal Of Vehicle Design, 71(1-4), 335-357. http://dx.doi.org/10.1504/IJVD.2016.078786
Controller area network with priority queues and FIFO queues: improved schedulability analysis and message set extension
(Inderscience Enterprises LTD, 2016) Schmidt, Klaus Werner; Alkan, Burak; Schmidt, Ece Güran; Karani, Duygu Culum; Karakaya, Utku; 17337
Controller area network (CAN) enables communication of electronic control units (ECUs) via messages using priority-based arbitration, which requires the implementation of priority queues (PQs) in the ECU device driver. Nevertheless, it is possible that not all ECUs on a CAN support PQs but use FIFO queues (FQs) instead. In this case, the classical CAN scheduling model with PQs is not suitable for the computation of message worst-case responsetimes (WCRTs) that are essential for verifying the correct vehicle operation. This paper considers an existing scheduling model for CAN with both PQs and FQs. First, an improved algorithm for speeding up the WCRT computation is proposed. Second, the practical case where an existing CAN message set is extended by new messages is addressed. An original algorithm for assigning priorities to new messages while keeping the priority order of existing messages is developed. Both algorithms are evaluated by computational experiments.
Citation Count: Schmidt, K.W., Schmidt, E.G. (2012). Distributed real-time protocols for industrial control systems: framework and examples. IEEE Transactions on Parallel And Distributed Systems, 23(10), 1856-1866. http://dx.doi.org/ 10.1109/TPDS.2011.300
Distributed real-time protocols for industrial control systems: framework and examples
(IEEE-Computer Soc, 2012) Schmidt, Klaus Werner; Schmidt, Ece Güran; 17337
The automation of today's large-scale industrial systems relies on the operation of distributed controller devices that perform local computations and exchange information via communication networks. The subject of this paper is the development of a family of shared-medium industrial communication protocols that support the transmission of real-time (RT) and nonreal-time (nRT) data among distributed controller devices. Different from existing protocols, we suggest to incorporate information that is available from the control application in the protocol definition. As a result, our protocols dynamically change the bandwidth allocation on the shared medium according to the instantaneous communication requirements while ensuring hard RT guarantees. Following the recent developments in industrial automation, our protocols can be realized as software layers on top of low-cost conventional Ethernet
Citation Count: Schmidt, K.W., Ribeiro Cury, J.E. (2012). Efficient abstractions for the supervisory control of modular discrete event systems. IEEE Transactions On Automatic Control, 57(12), 3224-3229. http://dx.doi.org/10.1109/TAC.2012.2200373
Efficient abstractions for the supervisory control of modular discrete event systems
(IEEE-Inst Electrical Electronics Engineers Inc, 2012) Schmidt, Klaus Werner; Ribeiro Cury, Jose Eduardo; 17337
The topic of this technical note is the nonblocking and maximally permissive abstraction-based supervisory control for modular discrete event systems (DES). It is shown, that an efficient abstraction technique, that was developed for the nonconflict verification of modular DES, is also suitable for the nonblocking supervisory control. Moreover, it is proved that this abstraction technique can be extended by the condition of local control consistency, in order to achieve maximally permissive supervision. Different from existing approaches, the presented abstraction does not require to preserve the shared events among the system components in the respective abstraction alphabets, and hence leads to potentially smaller system abstractions. The obtained results are illustrated by a flexible manufacturing system example.
Citation Count: Kartal, Y.B., Schmidt, E.G., Schmidt, K.W. (2016). Modeling distributed real-time systems in TIOA and UPPAAL. ACM Transactions On Embedded Computing Systems, 16(1). http://dx.doi.org/10.1145/2964202
Modeling distributed real-time systems in TIOA and UPPAAL
(Assoc Computing Machinery, 2016) Kartal, Yusuf Bora; Schmidt, Ece Güran; Schmidt, Klaus Werner; 17337
The mission- and life-critical properties of distributed real-time systems require concurrent modeling, analysis, and formal verification in the design stage. The timed input/output automata (TIOA) framework and the UPPAAL software package are two widely used modeling and verification tools for this purpose. To this end, we develop the algorithm TUConvert for converting distributed TIOA models to UPPAAL behavioral models and formally prove its correctness. We demonstrate the applicability of our algorithm by the formal verification of a distributed real-time industrial communication protocol that is modeled by TIOA
Citation Count: Schmidt, K.W. (2015). Optimal supervisory control of discrete event systems: cyclicity and interleaving of tasks. Siam Journal On Control And Optimization, 53(3), 1425-1439. http://dx.doi.org/10.1137/120892908
Optimal supervisory control of discrete event systems: cyclicity and interleaving of tasks
(Siam Publications, 2015) Schmidt, Klaus Werner; 17337
A substantial number of tasks in production systems are executed in a repetitive, cyclic fashion. Specifically, production systems run different production cycles of different products as well as different instances of the same production cycle. In this paper, we consider the optimal control and interleaving of such production cycles in a supervisory control framework for discrete event systems (DESs). That is, different from other approaches, our work is based on a behavioral specification of each production cycle. First, we adapt an optimal control approach for DESs, in order to optimize the operation of individual production cycles. Second, we employ the interleaving composition to design a supervisor that enables the simultaneous execution of different production cycles. Combining both results, we can further determine the maximum number of production cycles that can be executed simultaneously on a given production system.
Citation Count: Schmidt, K.W. (2014). Robust Priority Assignments for Extending Existing Controller Area Network Applications. IEEE Transactions on Industrial Informatics, 10(1), 578-585. http://dx.doi.org/10.1109/TII.2013.2266636
Robust priority assignments for extending existing controller area network applications
(IEEE-Inst Electrical Electronics Engineers Inc, 2014) Schmidt, Klaus Werner; 17337
The usage of the controller area network (CAN) as an in-vehicle communication bus requires finding feasible and robust priority orders such that each message transmitted on the bus meets its specified deadline and tolerates potential transmission errors. Although such priority orders can be determined by available algorithms whenever they exist, it is always assumed that a CAN priority order is computed from scratch. In practical applications, it is frequently necessary to extend an existing message set by new messages. In this case, a feasible priority order that retains the standardized IDs of the existing messages and assigns suitable priorities to the new messages needs to be found. This paper proposes an algorithm for the computation of robust priority orders that solves the stated problem of extending existing message sets. First, bounds for the priorities of new messages are determined and then the most robust priority order that keeps the IDs of the existing messages is computed. The obtained algorithms are proved to yield correct results and are illustrated by detailed scheduling examples.
Citation Count: Nooruldeen, A., Schmidt, K.W. (2015). State Attraction Under Language Specification for the Reconfiguration of Discrete Event Systems. IEEE Transactions On Automatic Control, 60(6), 1630-1634. http://dx.doi.org/ 10.1109/TAC.2014.2358811
State Attraction Under Language Specification for the Reconfiguration of Discrete Event Systems
(IEEE-Inst Electrical Electronics Engineers Inc, 2015) Nooruldeen, Anas; Schmidt, Klaus Werner; 17337
In this note, we study a particular setting for the reconfiguration of discrete event systems (DES) that is applicable to the control of reconfigurable manufacturing systems (RMS). We consider DES that can operate in different configurations and we are interested in the realization of configuration changes. Different from previous work, we intend to reach a set of plant states where a new configuration can be started in a bounded number of transitions and at the same time fulfill a behavioral specification before starting the new configuration. To this end, we introduce the concept of weak attraction under language specification (WALS) and derive necessary and sufficient conditions for its verification. Using WALS, we propose a polynomial-time algorithm for computing a supervisor that performs the described configuration changes. We demonstrate the applicability of our method using a workcell of an RMS.
Citation Count: Schmidt, K.W. (2013). Verification of modular diagnosability with local specifications for discrete-event systems. IEEE Transactions on Systems Man Cybernetics Systems, 43(5), 1130-1140. http://dx.doi.org/10.1109/TSMCA.2012.2227251
Verification of modular diagnosability with local specifications for discrete-event systems
(IEEE-Inst Electrical Electronics Engineers Inc, 2013) Schmidt, Klaus Werner; 17337
In this paper, we study the diagnosability verification for modular discrete-event systems (DESs), i.e., DESs that are composed of multiple components. We focus on a particular modular architecture, where each fault in the system must be uniquely identified by the modular component where it occurs and solely based on event observations of that component. Hence, all diagnostic computations for faults to be detected in this architecture can be performed locally on the respective modular component, and the obtained diagnosis information is only relevant for that component. We define the condition of modular language diagnosability with local specifications (MDLS) in order to capture that each fault can indeed be detected in this modular architecture. Then, we show that MDLS can be formulated as a specific language-diagnosability problem. As the main contribution of this paper, we develop an incremental abstraction-based approach for the verification of MDLS, which is based on projections that fulfill the loop-preserving observer condition. In particular, our approach efficiently avoids the construction of a global system model, which is infeasible for systems of realistic size. Furthermore, we do not rely on the assumption of a live global plant, which is prevalent in previous diagnosability methods for modular DESs. We illustrate our approach and its computational savings by a manufacturing system example.

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