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Keijzer, D.M. (author), Simon Soria, C. (author), Arends, J.J. (author), Sarıgöl, B. (author), Scarano, F. (author), Castro, Saullo G.P. (author)As of present the Urban Air Mobility market has been dominated by fully electric aircraft. However, hydrogen vehicles have remained relatively undeveloped in this segment, also because hydrogen poses additional design complexities and uncertainties concerning crashworthiness, fuel cell cooling, and low volumetric density. Nevertheless, hydrogen...conference paper 2024
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Keijzer, T. (author)Without us realizing it, solutions for safety and security are present all around us. However, everyone has undoubtedly also experienced how inconvenient some safety and security measures can be. For example, think about security checks at the airport, the need to wear a bicycle helmet, or being asked to perform 2-factor authentication to log...doctoral thesis 2023
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Chanfreut, P. (author), Keijzer, T. (author), Maestre, J. M. (author), Ferrari, Riccardo M.G. (author)This work presents a coalitional model predictive controller for collaborative vehicle platoons. The overall system is modeled as a string of locally controlled vehicles that can share data through a wireless communication network. The vehicles can dynamically form disjoint groups that coordinate their actions, i.e., the so-called coalitions....journal article 2023
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Keijzer, T. (author), Ferrari, Riccardo M.G. (author), Sandberg, Henrik (author)Interconnections in modern systems make them vulnerable to adversarial attackers both by corrupting communication channels and compromising entire subsystems. The field of secure state estimation (SSE) aims to provide correct state estimation even when an unknown part of the measurement signals is corrupted. In this letter, we propose a...journal article 2023
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Keijzer, T. (author), Engelbrecht, J. A.A. (author), Goupil, P. (author), Ferrari, Riccardo M.G. (author)The Flight Control System (FCS) is one of the most important systems in all modern aircraft. For such systems it is required to have robust Fault Detection Isolation and Reconfiguration (FDIR) functionalities with high detection performance. In this work we specifically consider the Oscillatory Failure Cases (OFC), which, if not mitigated,...journal article 2023
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Caenen, Annette (author), Keijzer, Lana (author), Bézy, Stéphanie (author), Duchenne, Jürgen (author), Orlowska, Marta (author), van der Steen, A.F.W. (author), de Jong, N. (author), Bosch, Johan G. (author), Voigt, Jens Uwe (author), D’hooge, Jan (author), Vos, H.J. (author)Ultrasound-based shear wave elastography is a promising technique to non-invasively assess the dynamic stiffness variations of the heart. The technique is based on tracking the propagation of acoustically induced shear waves in the myocardium of which the propagation speed is linked to tissue stiffness. This measurement is repeated multiple...journal article 2023
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Keijzer, T. (author), Ferrari, Riccardo M.G. (author)Sliding Mode Observer (SMO) based methods have been extensively used for Fault Estimation (FE). However, the fault detection (FD) problem for these SMO based FE methods has not been completely solved. In this paper a robust threshold on the so-called Equivalent Output Injection (EOI) is presented which enables FD for systems with measurement...journal article 2022
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Hanse, I. (author), Wikkerink, D.P. (author), Keijzer, R. (author), Dhalle, M. (author), ten Kate, H.H.J. (author), ter Brake, H.J.M. (author)The magnetic modelling and experimental validation of a superconducting degaussing system for maritime vessels is discussed. Degaussing coils compensate for the distortion in the earths' magnetic field by the magnetized steel hull of a ship, thus rendering it 'invisible' for magnetic field sensors. Whereas typical power requirements with...journal article 2022
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Keijzer, T. (author), Gallo, A.J. (author), Ferrari, Riccardo M.G. (author)In this paper we present a hierarchical scheme to detect cyber-attacks in a hierarchical control architecture for large-scale interconnected systems (LSS). We consider the LSS as a network of physically coupled subsystems, equipped with a two-layer controller: on the local level, decentralized controllers guarantee overall stability and...conference paper 2022
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Stobbe, P.J. (author), Keijzer, T. (author), Ferrari, Riccardo M.G. (author)Fully Homomorphic Encryption (FHE) has made it possible to perform addition and multiplication operations on encrypted data. Using FHE in control thus has the advantage that control effort for a plant can be calculated remotely without ever decrypting the exchanged information. FHE in its current form is however not practically applicable for...conference paper 2022
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Voorneveld, J.D. (author), Keijzer, L.B.H. (author), Strachinaru, Mihai (author), Bowen, Daniel J. (author), Mutluer, Ferit O. (author), van der Steen, A.F.W. (author), Ten Cate, Folkert (author), de Jong, N. (author), Vos, H.J. (author), Van den Bosch, Annemien E. (author), Bosch, Johan G. (author)High-frame-rate (HFR) echo-particle image velocimetry (echoPIV) is a promising tool for measuring intracardiac blood flow dynamics. In this study, we investigate the optimal ultrasound contrast agent (UCA: SonoVue) infusion rate and acoustic output to use for HFR echoPIV (PRF = 4900 Hz) in the left ventricle (LV) of patients. Three infusion...journal article 2021
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Sabbadini, A. (author), Caenen, A.F.M. (author), Keijzer, L.B.H. (author), van Neer, P.L.M.J. (author), Vos, H.J. (author), de Jong, N. (author), Verweij, M.D. (author)Shear wave elastography (SWE) has the potential to determine cardiac tissue stiffness from non-invasive shear wave speed measurements, important, e.g., for predicting heart failure. Previous studies showed that waves traveling in the interventricular septum (IVS) may display Lamb-like dispersive behaviour, introducing a thickness-frequency...journal article 2021
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Keijzer, T. (author), Jarmolowitz, Fabian (author), Ferrari, Riccardo M.G. (author)Road intersections are widely recognized as a lead cause for accidents and traffic delays. In a future scenario with a significant adoption of Cooperative Autonomous Vehicles, solutions based on fully automatic, signage-less Intersection Control would become viable. Such a solution, however, requires communication between vehicles and, possibly,...conference paper 2021
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Keijzer, T. (author), Ferrari, Riccardo M.G. (author)Platoons of autonomous vehicles are being investigated as a way to increase road capacity and fuel efficiency. Cooperative Adaptive Cruise Control (CACC) is an approach to achieve such platoons, in which vehicles collaborate using wireless communication. While this collaboration improves performance, it also makes the vehicles vulnerable to...conference paper 2021
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Keijzer, Lana B.H. (author), Caenen, A.F.M. (author), Voorneveld, J.D. (author), Strachinaru, Mihai (author), Bowen, Daniel J. (author), van der Steen, A.F.W. (author), de Jong, N. (author), Bosch, Johan G. (author), Vos, H.J. (author)Natural and active shear wave elastography (SWE) are potential ultrasound-based techniques to non-invasively assess myocardial stiffness, which could improve current diagnosis of heart failure. This study aims to bridge the knowledge gap between both techniques and discuss their respective impacts on cardiac stiffness evaluation. We recorded...journal article 2020
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Chanfreut, Paula (author), Keijzer, T. (author), Ferrari, Riccardo M.G. (author), Maestre, Jose Maria (author)In this paper a coalitional control and observation scheme is presented in which the coalitions are changed online by enabling and disabling communication links. Transitions between coalitions are made to best balance overall system performance and communication costs. Linear Matrix Inequalities are used to design the controller and observer,...journal article 2020
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Sabbadini, A. (author), Keijzer, L.B.H. (author), Vos, H.J. (author), de Jong, N. (author), Verweij, M.D. (author)Shear wave elastography (SWE) might allow non-invasive assessment of cardiac stiffness by relating shear wave propagation speed to material properties. However, after aortic valve closure, when natural shear waves occur in the septal wall, the stiffness of the muscle decreases significantly, and the effects of such temporal variation of...journal article 2020
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Keijzer, T. (author), Ferrari, Riccardo M.G. (author)Platoons of autonomous vehicles are being investigated as a way to increase road capacity and fuel efficiency. Cooperative Adaptive Cruise Control (CACC) is one approach to controlling platoons longitudinal dynamics, which requires wireless communication between vehicles. In the present paper we use a sliding mode observer to detect and...conference paper 2019
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Keijzer, Twan (author), Looye, Gertjan (author), Chu, Q. P. (author), van Kampen, E. (author)This paper discusses the design, implementation and flight testing of an incremental Backstepping (IBS) based manual flight control law with angular accelerometer (AA) feedback. The main advantages of incremental control laws are that they only require a partial model of the system and are of low complexity. Incremental control laws for...conference paper 2019
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Keijzer, L.B.H. (author), Strachinaru, Mihai (author), Bowen, Dan J. (author), Geleijnse, Marcel L. (author), van der Steen, A.F.W. (author), Bosch, Johan G. (author), de Jong, N. (author), Vos, H.J. (author)For the quantification of myocardial function, myocardial stiffness can potentially be measured non-invasively using shear wave elastography. Clinical diagnosis requires high precision. In 10 healthy volunteers, we studied the reproducibility of the measurement of propagation speeds of shear waves induced by aortic and mitral valve closure ...journal article 2019
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