Microphone windscreens are typically used to reduce the noise associated with wind flowing over a microphone diaphragm by reducing the velocity of the airflow. While most windscreens are effective at reducing this noise, they do not protect the microphone from many natural elements, such as moisture, sand, and other small particles. The focus of this research was to design a windscreen that protects an array of five microphones located around a 4.5-inch diameter cylinder from these natural elements. The design goals were to have a wind noise attenuation of at least 8 dB, an insertion loss of less than 1 dB from 5-1000 Hz, and a phase shift error of less than 3% over the same range. Computer simulations and experimental testing were used to select two basic designs. Four experimental tests consisting of wind noise attenuation, sand entrapment, insertion loss, and phase change measurements were used to optimize the geometry of these designs. The wind noise attenuation was tested by spinning the microphone array on a long boom and by setting the array in front of a fan. Sand was blown at the windscreen in order to test how well the windscreen protects the microphone array from small particles in the velocity stream. The insertion loss of the windscreen was tested by comparing an incoming signal traveling through the windscreen to the same signal without the windscreen. Finally, the phase shift between microphones was measured using a single frequency and comparing the microphone measurements with and without the windscreen. These four tests were performed on two designs. The first design consists of two foam filled concentric cones set around the microphone array. The second design consists of tubes that project outward from each microphone diaphragm, and then curve downwards. Both final windscreen designs meet the desired requirements. They both reduce wind noise attenuation by approximately 9 dB in a 13 mph wind and over 16 dB in a 20 mph wind. They also have negligible insertion loss, have a phase shift error of less than 3%, and are very efficient at blocking particles from entering the windscreen.

Pedestrian protection performance becomes more and more in focus for the car manufactures and systems to reduce injury risk are under development. A wider understanding of both the present and the future windscreen performance in free moving headform testing is needed to optimize these systems. The purpose of this thesis was therefore to learn and understand windscreen behaviour when subjected to head impact and to gain knowledge of CAE status for head impact in windscreens from a pedestrian point of view. A literature review concluded that there are different ways to model a windscreen. It was found that the computer material models for laminated windscreen glass were not capable of fully representing the behaviour of this material under all impact conditions, particularly the non-linear behaviour after fracture or failure. Experimental testing on three different windscreen models, with a free moving headform in a horizontal impactor, has been performed. Test set up was according to Euro NCAP pedestrian testing protocol and three different windscreen angles were tested. The parameter investigated was curvature and HIC and deformation depth on the windscreen were used as evaluation tools. Deformation was measured with a laser positioned behind the windscreen at impact. Film analysis and integration of headform accelerations were used as comparison. The testing concludes that different curvature alone will not have a big influence on HIC and deformation.   Keywords: PVB laminated windscreen, pedestrian, impact, free moving headform

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Zhongquan Zheng / Windscreens are widely used in outdoor microphone measurement for acoustic sensing systems. In many cases of outdoor microphone applications, wind noise interferes with the signals. The performance of measurement microphones thus heavily depends on correct designs of windscreens that are used to maximize the signal to noise ratio of the sensing system. The purpose of the study is to investigate the wind noise reduction between the unscreened microphone and the screened microphone under different frequencies of incoming wind turbulence. In this study, a modified immersed boundary method using the distributed forcing term has been applied to simulate the flow/acoustic interaction between air and the porous medium. Because of the high accuracy requirement in the vicinity of the interface between air and the porous medium, spatial derivatives of flux need to be discretized using high order schemes. In this study, several different schemes have been tested in the vicinity of the interface including a second-order upwind scheme, a third-order upwind scheme, and a fifth-order Weighted Essentially Non-Oscillatory (WENO) scheme. Based on the test results, the fifth-order WENO scheme is selected for most of the simulation cases. The model equations for flow outside the windscreen are the Navier-Stokes equations; flow inside the windscreen (porous medium) uses the modified Zwikker-Kosten equation. The wind turbulence in this study is generated by two different ways. The first is to place different sizes of solid cylinders and spheres in the upstream of the microphone under two-dimensional and three-dimensional conditions. The second is to use a Quasi-Wavelet method to generate the background atmospheric turbulence to simulate the real physical phenomena. Both two-dimensional and three-dimensional simulations for the flow over the unscreened and the screened microphone are presented and discussed under both low Reynolds number and high Reynolds number flow conditions. The results show that the windscreen effect is significant and the wind noise reduction level between the unscreened and the screened microphone can reach around 20dB either for low Reynolds number cases or for high Reynolds number cases. For low Reynolds number cases, Low flow resistivity windscreens are more effective for low frequency turbulence; high flow resistivity windscreens are more effective for high frequency turbulence. For high Reynolds number cases, the medium flow resistivity windscreens perform better compared to low flow resistivity windscreens and high flow resistivity windscreens.

Vulnerable road users (VRUs) are overrepresented in the statistics on severe and deadly injuries in traffic accidents, most commonly involving the head. The finite element (FE) method presents the possibility to model complex interactions between the human body and vehicles in order to better understand the injury mechanisms. While the rapid development of computer capacity has allowed for increasingly detailed FE-models, there is always a benefit of reducing the studied problem. Due to its material properties, the brain is more sensitive to rotational motion than to purely linear, resulting in complex injury causation. When studying brain injuries caused by a direct impact to the head, simulations using an isolated head model significantly increases efficiency compared to using a complete human body model. Also evaluation of head protective systems uses isolated mechanical head representations. It is not, however, established the extent to which the boundary conditions of the head determine the outcome of brain injuries. FE models of both the entire human body and the isolated head were used in this thesis to study the effect of the body, as well as active neck muscle tension, on brain injury outcome in VRU accidents. A pediatric neck model was also developed to enable the study of age-specific effects. A vehicle windscreen model was developed to evaluate the necessity of capturing the failure deformation during pedestrian head impacts. It was shown that the influence of the neck and body on brain injury prediction is greater in longer duration impacts, such as pedestrian head-to-windscreen impacts with an average difference of 21%. In accidents with shorter duration impacts, such as head-to-ground bicycle accidents, the average influence was between 3-12%. The influence did not consistently increase or limit the severity, and was dependent on the degree of rotation induced by the impact, as well as the mode of deformation induced in the neck. It was also shown that the predicted brain injury severity is dependent on capturing the large deformations of fractured windscreen, with the greatest effect near the windscreen frame. The pediatric neck model showed a large effect of age-dependent anatomical changes on inertial head loading, making it a promising tool to study the age-dependent effects in VRU accidents. / <p>QC 20171013</p>

För att kunna framföra ett fordon på ett säkert sätt är vindrutetorkning är en viktig del. Men, bara för att det är en viktig del i användandet innebär det inte att det är en viktig del i utvecklingen. Detta har visat sig genom att funktionen och designen av vindrutetorkare på lastbilar har varit densamma i årtionden. När hytten till Scanias senaste lastbilsmodell designades så minskades tjockleken på torpedväggen för att spara vikt. Detta minskade även styvheten i hytten, vilket fick de vibrationer som inducerades vid körning av vindrutetorkarna att nå en kritisk gräns. Problemställningen för detta exjobb var därför att förstå ursprunget till dessa vibrationer och hur delsystemen interagerar med varandra genom att utföra modellbaserad utveckling (MBD). Uppgiften var att undersöka vilka ändringar som behövde genomföras i styrningen av vindrutetorkarna och systemspecifikationen för den inbyggda styrenheten för att reducera vibrationerna och säkerställa Scanias position som premiummärke även i framtiden. Vindrutetorkarsystemet modellerades i Simulink, med både Simulink-block och Simscapemodeller. En strömberoende spänningskontroller för rörelsestyrning utvecklades för att sedan verifieras på nuvarande hårdvara. Rekommendationer för framtida arbete på ECU gällande systemfrekvens för mätning samt algoritmdesign gjordes, samt helhetstänket vid design av ett nytt system poängterades. Resultaten visar att styrning av en likströmsmotor med ström som ingångsparameter är komplicerat då strömmen varierar kraftigt på grund av störningar. Algoritmen som behandlar mätdatat måste därför vara väldigt robust eftersom filtrering påverkar systemet genom att lägga till fas i kontrollern, vilket ger eftersläpningar. Kommande arbetsinsatser bör fokusera på hur man väljer komponenter som matchar varandra gällande likströmsmotor och ECU. Desto mer logik som placeras i motorn, desto mindre datorkraft behövs i den inbyggda styrenheten. / Windscreen wiping is an important part of driving safety and vehicle maneuverability. However, importance does not automatically imply progression, and the wiping functionality for heavy commercial vehicles have remained roughly the same through decades. When redesigning the cab for the latest truck generation at Scania, the thickness of the firewall was reduced to save weight.This reduced the stiffness of the cab, which made the vibrations in the throttle pedal from actuating the windscreen wiper rise to a critical level.The problem definition in this thesis was to understand the root-cause and cooperation in the system by doing modelling and Model-Based Design (MBD), rather than starting with experimental verification. The task was to investigate what changes needed to be made in the controlling of the wiper motor and system specification of the ECU to reduce vibrations and ensure Scania's position as a premium brand in the future. The windscreen wiping system was modelled in Simulink, with both Simulink blocks and Simscape models. A current-measuring voltage-controller for motion-profiles was developed and verified on real production hardware. Recommendation for future development of next ECU generation regarding sampling time and controller design was made and the importance of considering the whole system design was emphasized. Results showed that controlling with current measurement of DC-motors as input parameter is avolatile approach due to disturbances. The algorithms depending on this measurement needs to be very robust, since filtering adds unwanted delay to the control loop. Further investigations should be made in the component selection when mapping motors with the correct driver. The more logic placed in the motor, the less need for a complex ECU and vice versa.