Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651

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Author: search.filters.author.Schmidt, Klaus WernerPublication Index: search.filters.publicationIndex.WoS

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Now showing 1 - 10 of 28
  • Article
    Outputs Bounds for Linear Systems with Repeated Input Signals: Existence, Computation and Application to Vehicle Platooning
    (Tubitak Scientific & Technological Research Council Turkey, 2018) Schmidt, Klaus Werner; Saglam, Harun Bugra
    This paper investigates the effect of repeated time-limited input signals on the output excursion of stable, linear time-invariant systems. It is first shown that the maximum norm of the output signal remains bounded if the repeated input signals are separated by a nonzero dwell time. Then a novel method for computing a tight bound on the output signal norm is proposed. The setting of the paper is motivated by a vehicle platooning application, where vehicles repeatedly open/close gaps in order to perform lane changes. The developed method analyzes driving safety by computing a bound on the spacing error between vehicles when performing repeated open/close gap maneuvers.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Order-Preserving Languages for the Supervisory Control of Automated Manufacturing Systems
    (Ieee-inst Electrical Electronics Engineers inc, 2020) Nooruldeen, Anas; Schmidt, Klaus Werner
    Automated manufacturing systems (AMSs) consist of computer-controlled interconnected manufacturing components (MCs) that are used to transport and process different product types. Each product type requires a certain sequence of processing steps in different MCs. Hereby, multiple product types can share processing steps on the same MC and the paths of different products types can overlap. In this paper we consider the modeling of AMSs in the scope of supervisory control for discrete event systems (DES). On the one hand, a suitable AMS model must allow the representation of sequential and concurrent processing steps in MCs. On the other hand, such model must be able to track different product types traveling through the AMS so as to process the products correctly. While previous work is commonly concerned with the first requirement, this paper identifies that the existing literature lacks a general treatment of the second requirement. Accordingly, we first introduce order-preserving (OP) languages that preserve the order of different product types in MCs and we propose a suitable finite state automaton model for OP languages. Then, we show that the composition of OP languages again leads to an OP language. That is, modeling MCs by OP languages, an OP model of a complete AMS that is suitable for supervisory control is obtained. In addition, it is possible to use both OP models and non-OP models for general AMSs, where MCs have different properties. We demonstrate the applicability of the proposed modeling technique by a flexible manufacturing system example.
  • Article
    Citation - WoS: 65
    Citation - Scopus: 70
    Feedforward Strategies for Cooperative Adaptive Cruise Control in Heterogeneous Vehicle Strings
    (Ieee-inst Electrical Electronics Engineers inc, 2018) Al-Jhayyish, Ahmed M. H.; Schmidt, Klaus Werner
    String stability is an essential property to ensure that the fluctuations are attenuated along vehicle strings. This paper focuses on the fulfillment of string stability in the practical case of heterogeneous vehicle strings that comprise vehicles with different dynamic properties. Using the idea of predecessor following, acceleration feedforward, predicted acceleration feedforward, and input signal feedforward are considered as different possible feedforward strategies. For all strategies, the parameter ranges of predecessor vehicles that ensure string stability of a given vehicle are characterized, computed, and validated by simulation.
  • Conference Object
    Controller Design for Cacc With Time-Varying Communication Delays
    (Ieee, 2023) Soysal, Gokhan; Schmidt, Klaus Werner; Bingol, Hilal
    Cooperative Adaptive Cruise Control (CACC) aims at the safe and comfortable travel of vehicles at short distances in the form of platoons. Hereby, it is generally desired to attenuate disturbances along vehicles in a platoon, which is captured by different string stability conditions. In this paper, we focus on L-infinity string stability. This condition ensures reducing the magnitude of the acceleration signal along the platoon, which helps to avoid actuator saturation and increases driving comfort. Since the performance of CACC is adversely affected by time-varying communication and actuator delays, we develop the first controller design method for L-infinity-string stability, combining the Lyapunov-Krasovskii method and our custom bisection algorithm. Simulation experiments demonstrate the effectiveness of our method.
  • Article
    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.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Improved Load Distribution for Controller Area Network
    (Ieee, 2017) Batur, Ahmet; Schmidt, Klaus Werner; Schmidt, Ece Guran
    The main requirement for the design of the controller are network (CAN) is to guarantee that each message response time is smaller than their specified deadline. In practical in-vehicle applications, messages on CAN are released with offsets in order to avoid message bursts that lead to undesirably large response times. In this paper, new algorithms for the choice of suitable message offsets are developed and it is shown that these algorithms outperform existing algorithms.
  • Conference Object
    Citation - WoS: 8
    Citation - Scopus: 8
    Optimal Configuration Changes for Reconfigurable Manufacturing Systems
    (Ieee, 2013) Schmidt, Klaus Werner
    Reconfigurable manufacturing systems (RMSs) are designed to quickly adapt to new products and production requirements. To this end, RMSs need to be able to perform fast changes between different configurations. This paper investigates the reconfiguration of RMSs in a supervisory control framework. Different from previous work, we formulate and solve a reconfiguration problem that allows to start a newly requested configuration before the previously active configuration has been completed. Our solution is optimal in the sense that there is no other solution that enables an earlier start of the new configuration. The practicability of the proposed solution is demonstrated by a small RMS example.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 23
    Voronoi Boundary Visibility for Efficient Path Planning
    (Ieee-inst Electrical Electronics Engineers inc, 2020) Al-Dahhan, Mohammed Rabeea Hashim; Schmidt, Klaus Werner
    The subject of this paper is the computation of paths for mobile robots that navigate from a start position to a goal position in environments with static obstacles. Specifically, we focus on paths that are represented by straight lines. Such paths can for example directly be followed by omni-directional robots or can be used as an initial solution for path smoothing. In this context, the most common performance metrics are the path length, the obstacle clearance and the computation time. In this paper, we develop a new path planning algorithm that addresses all the stated performance metrics. Our method first determines all possible connections between the start position and goal position along the edges of the generalized Voronoi diagram (GVD) of a given obstacle map. The shortest connections are then refined using a balanced method for creating shortcuts along existing waypoints and introducing new waypoints in order to cut corners. As an important feature, our method reduces the number of required waypoints by iteratively adding new waypoints and then removing unnecessary waypoints along solution paths. Moreover, our method takes into account multiple start-goal connections, since the shortest start-goal connection along the edges of the GVD might not lead to the shortest solution path. A comprehensive computational evaluation for a large number of maps with different properties shows that the proposed method outperforms sampling-based algorithms such as Probabilistic Roadmaps (PRM) and exact methods such as Visibility Graphs (VG) by computing close-to-optimal solution paths with a specified minimum obstacle clearance in less time.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 2
    Trajectory Generation for Vehicle Platoons With Input and State Constraints
    (Ieee, 2020) Schmidt, Klaus Werner; Bingol, Hilal
    The motion of vehicle platoons depends on the motion of the platoon leader. The subject of this paper is the computation of minimum-time leader trajectories for velocity changes in platoons. In contrast to the current literature, input restriction is defined due to the fact that the engine power is within certain limits and condition restriction is defined for safe travelling. Applying cooperative adaptive cruise control, we ensure driving safety and comfort, and we account for practical limits on the input signal of all platoon vehicles. We show that suitable trajectories can be computed analytically and we illustrate our findings by a simulation study.
  • Conference Object
    Citation - WoS: 5
    Citation - Scopus: 6
    Fault-Tolerant Control of Discrete-Event Systems With Lower-Bound Specifications
    (Elsevier, 2015) Moor, Thomas; Schmidt, Klaus Werner
    Fault-tolerant control addresses the control of dynamical systems such that they remain functional after the occurrence of a fault. To allow the controller to compensate for a fault, the system must exhibit certain redundancies. Alternatively, one may relax performance requirements for the closed loop behaviour after the occurrence of a fault. To achieve fault tolerance for a hierarchical control architecture, a combination of both options appears to be advisable: on each individual level of the hierarchy, the controller may compensate the fault as far as possible, and then pass on responsibility to the next upper level. This approach, when further elaborated for discrete-event systems represented by formal languages, turns out to impose a hard lower-bound inclusion specification on the closed-loop behaviour. The present paper discusses the corresponding synthesis problem and presents a solution. (C) 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.