Mekatronik Mühendisliği Bölümü

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Citation - WoS: 9
Citation - Scopus: 10
Computation of Supervisors for Reconfigurable Machine Tools
(Springer, 2015) Schmidt, Klaus Werner
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 - WoS: 5
Citation - Scopus: 5
Optimal Supervisory Control of Discrete Event Systems: Cyclicity and Interleaving of Tasks
(Siam Publications, 2015) Schmidt, Klaus Werner
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 - WoS: 8
Citation - Scopus: 8
Reconfigurability of Behavioural Specifications for Manufacturing Systems
(Taylor & Francis Ltd, 2017) Schmidt, Klaus Werner
Reconfigurable manufacturing systems (RMS) support flexibility in the product variety and the configuration of the manufacturing system itself in order to enable quick adjustments to new products and production requirements. As a consequence, an essential feature of RMS is their ability to rapidly modify the control strategy during run-time. In this paper, the particular problem of changing the specified operation of a RMS, whose logical behaviour is modelled as a finite state automaton, is addressed. The notion of reconfigurability of specifications (RoS) is introduced and it is shown that the stated reconfiguration problem can be formulated as a controlled language convergence problem. In addition, algorithms for the verification of RoS and the construction of a reconfiguration supervisor are proposed. The supervisor is realised in a modular way which facilitates the extension by new configurations. Finally, it is shown that a supremal nonblocking and controllable strict subautomaton of the plant automaton that fulfils RoS exists in case RoS is violated for the plant automaton itself and an algorithm for the computation of this strict subautomaton is presented. The developed concepts and results are illustrated by a manufacturing cell example.
Citation - WoS: 20
Citation - Scopus: 20
Robust Priority Assignments for Extending Existing Controller Area Network Applications
(Ieee-inst Electrical Electronics Engineers inc, 2014) Schmidt, Klaus Werner
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 - WoS: 16
Citation - Scopus: 18
Verification of Modular Diagnosability With Local Specifications for Discrete-Event Systems
(Ieee-inst Electrical Electronics Engineers inc, 2013) Schmidt, Klaus Werner
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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