Evaluation of scenario-based automotive radar testing in virtual environment using real driving data. - In: 2022 IEEE 25th International Conference on Intelligent Transportation Systems (ITSC), (2022), S. 2379-2384
Safety assurance of intended functionality through rigorous testing is a key to large-scale homologation and deployment of automated driving. It is therefore imperative to transfer real world tests into efficient and quantifiable virtual testing procedures and environments without compromising reliability. In earlier work, we presented a fully operational over-the-air vehicle-in-the-loop test system for automotive millimeter-wave radar, where we generated a virtual electromagnetic environment with physically realistic radar target echoes. We evaluated the performance of the implemented test system with an exemplary scenario parameterised with analytically pre-defined vehicle manoeuvres. In this work, we significantly proceed with the performance evaluation through re-simulation of scenarios based on real driving data and traffic manoeuvres. We have measured a standard Euro-NCAP scenario, namely, the Car-to-Pedestrian Longitudinal Adult on a proving ground and re-simulated the ground truth parameters in the test bed. We compare the consistency of the test results at several data abstraction levels using parameter trajectories. Additionally, we introduce and evaluate quality metrics such as difference and root mean square error. For a driving scenario approximately 20 seconds long, we achieved promisingly low root mean square errors in range, azimuth and RCS of 0.3 m, 0.5˚ and 2 dB, respectively.
https://doi.org/10.1109/ITSC55140.2022.9922366
Hysteresis associated with intrinsic-oxide traps in gate-tunable tetrahedral CVD-MoS2 memristor. - In: IEEE 22nd International Conference on Nanotechnology (NANO), (2022), S. 527-530
We introduce back gated memristor based on CVD-grown 30-40 nm thick MoS2 channel. The device demonstrates bipolar behaviour and the measurements are consistent with the simulations performed within the intrinsic-oxide traps model. This confirms the theory that the source of hysteresis in thin-film MoS2 memristors is charge trapping on MoS2/SiO2 interface and the grain boundaries. The impact of back gate voltage bias, voltage sweep range and channel area on memristive effect was studied and quantified using hysteresis area. Hysteresis in bipolar memristors can be tuned by back gate voltage, which makes these devices promising for neuromorphic computing.
https://doi.org/10.1109/NANO54668.2022.9928717
Influence of solidification rate on hot crack behavior in heat conduction laser beam welding of EN AW-6082. - In: 12th CIRP Conference on Photonic Technologies, (2022), S. 490-495
Joining of thin aluminum sheets (<1mm) is widely used in the industry for electronic housings or EMC shielding. Aluminum alloys of the 6xxx series are particularly relevant for such applications. However, their use is very challenging in welding processing due to the hot cracking phenomenon. Hot cracks are known to form during the solidification phase and are a major defect regarding mechanical properties and tightness of the weld. For this reason, the formation of hot cracks must be prevented and solidification rate is known to be a key parameter. In this paper, the solidification rate is specifically manipulated by means of pulse shaping. Metallographic analysis and high-speed recordings of welds carried out with different pulse shapes that allowed the determination of a threshold solidification rate to avoid hot cracks. A further pulse shape optimization considered the determined threshold solidification rate and minimized the required pulse energy to realize sound welds. On the one hand, the study proved which simplifications can be assumed for the modeling and optimization of the pulse shapes and that solidification rate can be used as sole parameter to control crack formation of bead on plate welds. On the other hand, the experimental procedure enabled the identification of critical properties of laser beam sources regarding stability, threshold and fast adaptability of beam power.
https://doi.org/10.1016/j.procir.2022.08.076
Effect of local pressure distribution on spatter formation for welding high alloy steel at high welding speeds. - In: 12th CIRP Conference on Photonic Technologies, (2022), S. 391-396
Laser beam welding with solid-state lasers leads to the formation of spatters at relevant processing speeds (≥ 8 m/min). The use of local gas flows proved to be adequate to avoid these phenomena. This publication examines the mechanical effect of a local supply of argon, nitrogen and helium to provide a deeper understanding of the local pressure distribution and its effect on the welding process. A dynamic pressure measurement was performed to quantify the two-dimensional pressure field in and around the keyhole aperture. By varying flow rate, nozzle distance and flow angle of the nozzle, the size of pressure field and the position of maximum pressure could be varied. In order to describe the separation of the dynamic pressure from the composition of the shielding gas on spatter formation, equal dynamic pressures were considered for different shielding gases. It was shown that the effect of local gas flows cannot be solely attributed to the influence of the dynamic pressure.
https://doi.org/10.1016/j.procir.2022.08.173
Redundante Temperatursensorik für das Batterien-Monitoring. - In: EASS, (2022), S. 42-46
Der Einsatz redundanter Temperaturmesssysteme erlaubt es, die Betriebssicherheit von Sensorsystemen deutlich zu erhöhen. Solche Systeme bestehen aus mindestens zwei Sensoren gleicher oder unterschiedlicher Technologie bzw. Kennlinie. Der erste Fall wird als homogene, der letzte als diversitäre Redundanz bezeichnet. Insbesondere der Ausfall eines einzelnen Sensors kann auf diese Weise zuverlässig detektiert werden. Darüber hinaus kann bei Berücksichtigung einer eingeschränkten Zuverlässigkeit auch weiterhin ein Messwert ermittelt werden. Vor diesem Hintergrund besteht u. a. im Bereich der Automobilindustrie zunehmend Bedarf an selbstvalidierender Sensorik dieser Art.
Energy storage for powering fine adjustment systems in hermetically sealed ultra-precision devices. - In: EASS, (2022), S. 47-49
Ultra-precision devices are often operated in hermetically sealed chambers to avoid external disturbances and maximize their performance. The remaining disturbing effects are mitigated through compensation or corrective methods. Compensation is frequently done in form of in-situ fine mechanical adjustments of highly sensitive units. Such adjustment systems utilize electromechanical drives to transform electrical energy into an intended motion. Electric cables are used as energy and signal carriers from an external control unit. The associated disturbing effects limit the adjustability. In particular, cable connections act as mechanical coupling elements, introducing indeterminate and time-varying forces. This paper deals with the conceptual design of a fine adjustment system for ultra-precision devices with an integrated energy storage. A spring-based mechanical energy storage system controlled by an optical signal is found to be the most suitable solution for the targeted field of application. The integration of an energy storage in the adjustment system to avoid electric cables and their disturbance effects will significantly improve the quality and stability of the adjustment and further increase the performance of precision devices.
Antifungal effect of cold atmospheric plasma in a 3D model of cutaneous candidiasis. - In: Mycoses, ISSN 1439-0507, Bd. 65 (2022), PI-10, S. 26-27
https://doi.org/10.1111/myc.13502
Effective re-identification of a multivariate process under model predictive control using information from plant-model mismatch detection. - In: Computer aided chemical engineering, ISSN 1570-7946, Bd. 49 (2022), S. 361-366
A process under model predictive control is required to be re-identified when plant-model mismatch (PMM) occurs. During data acquisition for re-identification, the process is excited to enable accurate re-identification. However, the excitation of the process worsens control performance. This research proposes a new method for re-identification that can deal with the problem. In the proposed method, only the inputs of the transfer functions that have significant PMM are excited, and, at the same time, the other inputs are manipulated to suppress the variations of the controlled variables. The usefulness of the proposed method was confirmed through a simulation case study of a 3-input, 3-output process. As a result, it was shown that the proposed method can reduce the mean absolute control error during data acquisition to 87% of that of an existing method without compromising model accuracy after re-identification.
https://doi.org/10.1016/B978-0-323-85159-6.50060-9
A PID-based active control of camber angles for vehicle ride comfort improvement. - In: Advances in Italian mechanism science, (2022), S. 397-404
In the automotive industry, one of the principal issues is to ensure the comfort of vehicles as much as possible. High vertical accelerations of the vehicle body transmit undesired vibration, causing malaise to passengers. Car vehicles are subjected to vibrations induced by the road roughness or, during a curve travelling, by the roll motion. These factors contribute to generating the total vertical acceleration. The vertical acceleration due to the first factor can be decreased by correctly dimensioning the stiffness and damping of the suspension. In this paper, the active control of the camber angle of the rear wheels is proposed to reduce the vertical acceleration due to the roll motion. The proposed technique has been applied to a validated vehicle model developed in the ADAMS Car environment. The trailing-arm type rear suspension has been modified to include actuators functional for the control system implementation. The tracking of the variable vehicle body roll angle by rear wheels is allowed exploiting two PID controllers to improve the contact of the tire with the road and, therefore, the ride comfort. Two manoeuvres called Sine Steer and Fish-hook have been employed to validate the designed controllers. The RMS and the maximum value of the vehicle body's vertical acceleration decrease, demonstrating the employability of the proposed control system to improve ride comfort.
Optimization for vibration analysis in rotating machines. - In: Renewable energy & power quality journal, ISSN 2172-038X, Bd. 20 (2022), 315, S. 369-373
A not stable mechanical movement transmission between systems produces equilibrium losses, such as a rotor of motors that are coupled in rotating machines. This can be studied as a disturbance “vibration” either as characteristic of the movement transmission due to controlled displacement over rotors, which transmits the movement. Therefore, in this research is presented an analysis for an optimal control of the rotor axis displacement that includes “vibration” as the part of the movement transmission. It implies mathematical modelling and specific sensors selections to correlate the vibration in this control task. Furthermore, in order to verify the proposed analysis, it was simulated and tested in a hybrid magnetic bearing system.
https://doi.org/10.24084/repqj20.315