Mekatronik Mühendisliği Bölümü Yayın Koleksiyonu

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

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Author: search.filters.author.Schmidt, Klaus Werner

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  • 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.
  • Article
    Clothoid-based Lane Change Trajectory Computation for Self-Driving Vehicles
    (2017) Mohammed Ali Kahya, Ardam Haseeb; Schmidt, Klaus Werner
    The subject of this paper is the efficient computation of lane change trajectories for self-driving vehicles. The paper first identifies that a certain type of clothoid-based bi-elementary paths can be used to represent lane change trajectories for vehicles. It is further highlighted that the curvature of such trajectories must be adjusted to the driving situation in order to obtain feasible lane change trajectories. Accordingly, the paper establishes an analytical relation between the maximum admissible curvature of the lane change trajectory and the velocity profile during a lane change. Using this relation, the paper proposes an efficient Newton iteration for computing the parameters of bi-elementary paths for lane changes. The resulting lane change trajectories are as short as possible, while meeting the constraint on the maximum curvature. Simulation experiments for various driving situations show that the computed bi-elementary paths can be computed efficiently and constitute suitable lane change trajectories.
  • 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.
  • Article
    Optimal Message Scheduling for the Static Segment of Flexray
    (IEEE, 2010) Schmidt, Klaus Werner; Schmidt, Ece G.
    In this paper, we study the scheduling of periodic messages in the static segment of the FlexRay protocol. Our approach is based on two performance metrics. Similar to previous work, we seek to allocate a minimum number of frame IDs (FIDs) in the static segment. In addition, different from existing work, we want to minimize the message jitter, i.e., the deviation of the message transmission from the required periodicity. To this end, we first derive analytical expressions that quantify the FID allocation and the jitter, and then formulate a linear integer programming problem whose solution is the desired message schedule. An example illustrates our schedule optimization.
  • Publication
    Schedulability Analysis and Message Schedule Computation for the Dynamic Segment of Flexray
    (IEEE, 2010) Schmidt, Klaus Werner; Schmidt, Ece G.
    In this paper, we perform the schedulability analysis and schedule computation for sporadic real-time messages in the dynamic segment of the FlexRay protocol. We first formulate a linear integer programming problem that allows to determine if a given message schedule is feasible, i.e., the worst-case delay of each message is smaller than its deadline. Then, we develop a heuristic algorithm that enables the efficient computation of feasible schedules. Our results are illustrated by an experimental setup with three FlexRay nodes.
  • Book Part
    A new multi-agent decision making structure and application to model-based fault diagnosis problem
    (IEEE, 2017) Leblebicioğlu, Kemal; Zengin, Yasin; Schmidt, Klaus Werner
    A new hierarchical multi-agent decision-making structure has been proposed. There are two phases of the structure. The first phase is the construction phase where the decision making structure consisting of switching and classification agents is built on the training data set generated by the system scenarios. In construction phase, switching and classification agents are trained and made ready for decision making. In the decision phase, which is the second phase, the class of the new data sample is decided. This process is carried out by the transmission of the data sample to the correct classifier agent by the switching agents and the classification by the classifier agent. The proposed structure is applied to a complex fault identification problem and a successful result is obtained. The structure is also adaptable to other big data decision making problems.
  • Book Part
    A configurable CAN FD controller: architecture and implementation
    (IEEE, 2017) Afşin, Mehmet Ertuğ; Schmidt, Klaus Werner; Schmidt, Ece Güran
    CAN FD is a new standard which provides fast. data rate while preserving the compatibility with CAN (controller area network). In this paper, a Configurable IP core architecture (A-CAN) which is compatible with the CAN FD standard, is proposed. Different than existing CAN/CAN FD controllers, the numbers and sizes of transmit and receive buffers of A-CAN can be configured in run time. To this end, A-CAN enables the best use of single controller hardware for different applications and enables improving the real time communication performance. A CAN communicates with the host device over SPI without any specific interface requirements. A-CAN is implemented on an FPGA Evaluation Board and its functionally is verified at a rate of 2 Mbps.
  • Article
    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.
  • Conference Object
    The Controllability Prefix for Supervisory Control Under Partial Observation With an Application To Fault-Tolerant Control
    (Elsevier, 2017) Moor, Thomas; Schmidt, Klaus Werner
    The controllability prefix is known as a useful concept for the discussion and solution of synthesis problems in supervisory control of cp-languages, i.e., formal languages of infinite-length words. There, the controllability prefix is defined as the set of all finite-length prefixes that can be controlled to satisfy prescribed liveness and safety properties. In this paper, we discuss a variation of the controllability prefix to address supervisory control under partial observation for regular *-languages, i.e., formal languages of finite-length words. We derive algebraic properties that are useful for a quantitative analysis on how an upper-bound language-inclusion specification affects achievable lower-bound specifications. Our study is motivated by the synthesis of fault-tolerant supervisory controllers, where the possible occurrence of a fault may restrict the achievable pre-fault behaviour so severe, that a relaxation of the upper-bound specification becomes a practical option. As our study shows, such a relaxation can be systematically constructed in terms of the controllability prefix. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.