Mekatronik Mühendisliği Bölümü

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Citation - WoS: 9
Citation - Scopus: 9
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
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 - WoS: 41
Citation - Scopus: 49
Fuzzy Discrete Event Systems for Multiobjective Control: Framework and Application To Mobile Robot Navigation
(Ieee-inst Electrical Electronics Engineers inc, 2012) Schmidt, Klaus Werner; Boutalis, Yiannis S.
Fuzzy discrete event systems (FDESs) have been introduced in recent years to model systems whose discrete states or discrete state transitions can be uncertain and are, hence, determined by a possibility degree. This paper develops an FDES framework for the control of sampled data systems that have to fulfill multiple objectives. The choice of a fuzzy system representation is justified by the assumption of a controller realization that depends on various potentially imprecise sensor measurements. The proposed framework consists of three basic steps that are performed at each sampling instant. First, the current fuzzy state of the system is determined by a sensor evaluation. Second, the fuzzy state in the future sampling instant is predicted for all possible control actions of the system. Finally, an original multiobjective weighting strategy is proposed to determine the control action to be applied in the current sampling instant. The features of the proposed approach are demonstrated by a detailed mobile robot example, which includes a simulation study.
Citation - WoS: 54
Citation - Scopus: 74
Maximally Permissive Hierarchical Control of Decentralized Discrete Event Systems
(Ieee-inst Electrical Electronics Engineers inc, 2011) Schmidt, Klaus; Breindl, Christian
The subject of this paper is the synthesis of natural projections that serve as nonblocking and maximally permissive abstractions for the hierarchical and decentralized control of large-scale discrete event systems. To this end, existing concepts for nonblocking abstractions such as natural observers and marked string accepting (msa)-observers are extended by local control consistency (LCC) as a novel sufficient condition for maximal permissiveness. Furthermore, it is shown that, similar to the natural observer condition and the msa-observer condition, also LCC can be formulated in terms of a quasi-congruence. Based on existing algorithms in the literature, this allows to algorithmically compute natural projections that are either natural observers or msa-observers and that additionally fulfill LCC. The obtained results are illustrated by the synthesis of nonblocking and maximally permissive supervisors for a manufacturing system.
Citation - WoS: 5
Citation - Scopus: 6
Multi-Objective Trajectory Planning for Slung-Load Quadrotor System
(Ieee-inst Electrical Electronics Engineers inc, 2021) Ergezer, Halit
In this article, multi-objective trajectory planning has been carried out for a quadrotor carrying a slung load. The goal is to obtain non-dominated solutions for path length, mission duration, and dissipated energy cost functions. These costs are optimized by imposing constraints on the slung-load quadrotor system's endpoints, borders, obstacles, and dynamical equations. The dynamic model of a slung-load quadrotor system is used in the Euler-Lagrange formulation. Although the differential flatness feature is mostly used in this system's trajectory planning, a fully dynamic model has been used in our study. A new multi-objective Genetic Algorithm has been developed to solve path planning, aiming to optimize trajectory length, mission time, and energy consumed during the mission. The solution process has a three-phase algorithm: Phase-1 is about randomly generating waypoints, Phase-2 is about constructing the initial non-dominated pool, and the final phase, Phase-3, is obtaining the solution. In addition to conventional genetic operators, simple genetic operators are proposed to improve the trajectories locally. Pareto Fronts have been obtained corresponding to exciting scenarios. The method has been tested, and results have been presented at the end. A comparison of the solutions obtained with MOGA operators and MOPSO over hypervolume values is also presented.
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: 17
Citation - Scopus: 19
State Attraction Under Language Specification for the Reconfiguration of Discrete Event Systems
(Ieee-inst Electrical Electronics Engineers inc, 2015) Nooruldeen, Anas; Schmidt, Klaus Werner
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 - WoS: 4
Citation - Scopus: 4
String Stability Under Actuator Saturation on Straight Level Roads: Sufficient Conditions and Optimal Trajectory Generation
(Ieee-inst Electrical Electronics Engineers inc, 2022) Bingol, Hilal; Schmidt, Klaus Werner
The heterogeneity of vehicles is an important factor when realizing cooperative adaptive cruise control (CACC) in practice. Specifically, it has to be considered that platoons generally consist of vehicles with both different dynamic properties and actuator limits on the engine and braking force, which is expected to have a negative impact on important properties such as string stability. Accordingly, the subject of this paper is the preservation of string stability for CACC in heterogeneous vehicle strings with potential actuator saturation. To this end, the paper formulates a velocity-dependent force bound that enables the derivation of sufficient conditions for preserving string stability during velocity changes of heterogeneous platoons. These conditions are then used for the analytical computation of trajectories for time-optimal velocity changes. The formal results of the paper are supported by an illustrative simulation study.
Citation - WoS: 15
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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