Overview of modern contributions in vehicle noise and vibration refinement with special emphasis on diagnostics

U ovom radu prikazana su određena razmatranja vezana za karakteristike buke i vibracija savremenih motornih vozila. Pored naučnog, problematika se razmatra i sa praktičnog aspekta u cilju struktuiranja potrebnih znanja, neophodnih za pravilnu dijagnostiku problema. Takođe se razmatraju napredne analize signala buke i vibracija. Ova sinergija naučnog i praktičnog pristupa predstavlja osnovu za dalja napredna istraživanja.This paper presents certain considerations related to noise, vibration and harshness issues on modern motor vehicles. The first, practical aspect was used toward structuring of the acquired knowledge and relationships, required for proper problem diagnosis. On the other hand, advanced signal analyses are considered. The influence on human body is processed and certain noise and vibration analyzers are presented. This synergy of scientific and applicative approach represents a basis for further research related to this important automotive branch

Acoustic Emission Characterization of Six Wind Turbines: A Diagnostic Tool to Isolate, Identify, and Quantify Point Source Contributors to a Wind Turbine’s Noise

The diagnostic tool developed in this study was designed to perform acoustic analyses to enhance the International Electrotechnical Commission’s (IEC) 61400-11, edition 2.1 Standard. The IEC Standard, which is the current international standard for collecting wind turbine acoustic data, describes a methodology for measuring, characterizing, and reporting wind turbine acoustic emissions. The developed diagnostic tool uses enhanced tonal analysis to allow for identification of peak frequencies and a more detailed characterization of a turbine’s acoustic emissions. In this study, the IEC Standard 61400-11 methodology was followed for acoustic and meteorological data acquisition for six wind turbines. Band pass filters isolated individual peak frequencies to identify and quantify individual point source contributors to a wind turbine’s acoustic emissions. Through specific mathematical conversions, a linear comparison of sound pressure levels was performed for relative quantification. Each identified sound pressure percentage was then associated with a point source contributor through application of a decision tree developed for this study. The diagnostic tool has shown to illustrate a process that presents concise acoustic information that may be useful to wind turbine manufacturers to target specific major component contributors for mitigation and subsequent reduction of their wind turbines’ acoustic emissions

Incidence and transfer behaviors of high-order hot judder in passenger cars

As one of the brake-induced noises and vibrations, hot judder is forced vibration, which is caused by unevenness of the brake disc due to the thermal mechanical interactions in wheel brakes. Brake disc unevenness is normally described and evaluated as the Disc Thickness Variation (DTV) and the disc’ Lateral Run-Out (LRO). DTV and LRO gener-ate Brake Pressure Variation (BPV) and Brake Torque Variation (BTV) in wheel brakes, which are transmitted to the driver and perceived by the driver as the brake pedal pulsa-tion, the steering wheel oscillation, the car body vibrations, and low-frequency drone noises inside a vehicle. Hot judder is characterized by hot spots on the disc surfaces. The frequency of hot judder is dependent on the wheel rotational speed, showing order behaviors. The num-ber of hot spots generally corresponds to the dominant order of hot judder. In the last decades, most of the hot judder tests have been carried out with brake dynamometers, and high numbers (typically around 10) of hot spots were found in the majority of the tests. The generation and development mechanisms of the high dominant order have been almost the exclusive focus of current hot judder researches. However, the influ-ences of the vibrations and noises (with higher frequencies compared with the low-order cold judder) caused by high-order hot judder on the driver’s subjective perception have been still not clarified. That is to say, it is still unknown in which form and under which conditions, the high-order hot judder can be transmitted to and perceived by the driver, and thus causing customer complaints. A top-down approach is used in order to investigate the influences of high-order judder on driver’s perception with respect to two aspects: the incidence of high-order hot jud-der in vehicle tests and the drivers’ perception of high-order hot judder. The first aspect is mainly investigated by studying the transferability of dynamometer tests to vehicle tests and by identifying the incidence of high-order hot judder in production brakes. Specifically, identical brakes from one front brake and one rear brake are separately tested with a brake dynamometer and through vehicle tests by means of road tests and chassis dynamometer tests, and all brakes of four production passengers are identified with accelerometers attached on the brake caliper and the caliper bracket. The perception of high-order hot judder is chiefly studied by investigating its transfer behaviors. Global transfer functions from BPV/BTV to the selected driver interface quantities (brake pedal pulsation, steering wheel oscillation, seat track vibrations, and vehicle interior drone noise) are defined, which establish the links between the hot judder intensity in the wheel brake and the intensity at the driver interface. In order to identify the transfer functions with a high signal-noise-ratio and better reproducibility, a novel testing method is adopted: vehicle tests with brake discs that are artificially modi-fied with the desired surface shapes simulating the high-order DTV/LRO. Altogether three vehicles with seven different modified discs are tested. Two critical levels of drone noise (60 and 80 dB(A)) are selected according to the general vehicle total noise level and the human’s perception characteristics of sound. The perception threshold values of the driver interface vibrations are obtained through regression analysis between their subjective ratings and objective measurements. Based on the critical drone noise levels and the threshold values of vibrations, as well as the global transfer functions, threshold values of BPV and BTV for perceiving the high-order judder are computed. Concerning the incidence of high-order judder, both the dominant order and the thermal increases of BTV and BPV for the dominant order showed great discrepancies in differ-ent test types (e.g. brake dynamometer or vehicle, drag braking application with con-stant velocity and constant pressure/torque or stop braking application with decreasing velocity and constant deceleration/pressure). Hot judder behaviors in the brake dyna-mometer test were not transferable to the vehicle tests. Besides, no evident high-order hot judder has been identified in all the brakes of the four passenger cars. Generally, hot judder seems to be more likely to be excited at the brake dynamometer than in the vehi-cles. Therefore, brake dynamometer test is still appropriate for detecting hot judder in the early phase of brake development, and thus preventing its occurrence in the vehicle. Regarding the driver’s perception, the drone noise is the most probable reason leading to customer complaints, since higher than 100 Hz less than 10 Nm BTV is required to perceive the drone noise and 50 Nm BTV can already result in unacceptable drone noise. The driver is less sensitive to the vibrations caused by high-order judder. Roughly at least 20 Nm BTV or 2.5 bar BPV is needed for perceiving the vibrations, and the perception is most possibly due to the steering wheel oscillation or the vertical vehicle vibration. Moreover, some resonances in the transfer paths play a significant role in the high-order judder transmission. Although the investigations in this work are limited to three vehicles, the practical significance of high-order hot judder on the driver’s percep-tion is revealed for the first time. With these results, the impact of the measured BTV and BPV of hot judder, e.g. in the brake dynamometer tests, can be assessed. Combining these results, the most effective and efficient way to mitigate the high-order hot judder would be reducing its occurrences in the wheel brakes and diminishing the prominent resonances in the transfer paths

Volume 1 – Symposium: Tuesday, March 8

Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Components:Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Component

Model-connected safety cases

Regulatory authorities require justification that safety-critical systems exhibit acceptable levels of safety. Safety cases are traditionally documents which allow the exchange of information between stakeholders and communicate the rationale of how safety is achieved via a clear, convincing and comprehensive argument and its supporting evidence. In the automotive and aviation industries, safety cases have a critical role in the certification process and their maintenance is required throughout a system’s lifecycle. Safety-case-based certification is typically handled manually and the increase in scale and complexity of modern systems renders it impractical and error prone.Several contemporary safety standards have adopted a safety-related framework that revolves around a concept of generic safety requirements, known as Safety Integrity Levels (SILs). Following these guidelines, safety can be justified through satisfaction of SILs. Careful examination of these standards suggests that despite the noticeable differences, there are converging aspects. This thesis elicits the common elements found in safety standards and defines a pattern for the development of safety cases for cross-sector application. It also establishes a metamodel that connects parts of the safety case with the target system architecture and model-based safety analysis methods. This enables the semi- automatic construction and maintenance of safety arguments that help mitigate problems related to manual approaches. Specifically, the proposed metamodel incorporates system modelling, failure information, model-based safety analysis and optimisation techniques to allocate requirements in the form of SILs. The system architecture and the allocated requirements along with a user-defined safety argument pattern, which describes the target argument structure, enable the instantiation algorithm to automatically generate the corresponding safety argument. The idea behind model-connected safety cases stemmed from a critical literature review on safety standards and practices related to safety cases. The thesis presents the method, and implemented framework, in detail and showcases the different phases and outcomes via a simple example. It then applies the method on a case study based on the Boeing 787’s brake system and evaluates the resulting argument against certain criteria, such as scalability. Finally, contributions compared to traditional approaches are laid out

Rehabilitation Engineering

Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device

The Berlin Brain-Computer Interface: Progress Beyond Communication and Control

The combined effect of fundamental results about neurocognitive processes and advancements in decoding mental states from ongoing brain signals has brought forth a whole range of potential neurotechnological applications. In this article, we review our developments in this area and put them into perspective. These examples cover a wide range of maturity levels with respect to their applicability. While we assume we are still a long way away from integrating Brain-Computer Interface (BCI) technology in general interaction with computers, or from implementing neurotechnological measures in safety-critical workplaces, results have already now been obtained involving a BCI as research tool. In this article, we discuss the reasons why, in some of the prospective application domains, considerable effort is still required to make the systems ready to deal with the full complexity of the real world.EC/FP7/611570/EU/Symbiotic Mind Computer Interaction for Information Seeking/MindSeeEC/FP7/625991/EU/Hyperscanning 2.0 Analyses of Multimodal Neuroimaging Data: Concept, Methods and Applications/HYPERSCANNING 2.0DFG, 103586207, GRK 1589: Verarbeitung sensorischer Informationen in neuronalen Systeme