Suspension systems and wheels play a critical role in vehicle dynamics performance of a car in areas such as ride comfort and handling. Lumped parameter models (LPMs) are commonly used for assessing the performance of vehicle suspension systems. However, there is a lack of clarity with regard to the relative capabilities of different LPM configurations. A comprehensive comparative study of three most commonly used LPMs of increasing complexity has been carried out in the current work. The study reported here has yielded insights into the capabilities of the considered LPMs in predicting response time histories which may be used for assessing ride comfort. A shortcoming of available suspension system models appears to be in representation of harsh situations such as jounce movement which cause full compression of springs leading to ‘jerks’ manifested as high values of rate of change of acceleration of sprung mass riding on a wheel. In the current research work, a modified nonlinear quarter-car model is proposed to account for the contact force that results in jerk-type response. The numerical solution algorithm is validated through the simulation of an impact test on a car McPherson strut in a Drop Weight Impact Testing Tower developed in CAR Laboratory, CPDM. This is followed by a detailed comparison of HCM and QCM to examine their suitability for such analysis. For decades, wheel bearings in vehicles have been designed using simplified analytical approaches based on Hertz contact theory and test data. In the present work, a hybrid approach has been developed for assessing the load bearing capacity of a wheel ball bearing set. According to this approach, the amplitude of dynamic wheel load can be obtained from a lumped parameter analysis of a suspension system, which can then be used for detailed static finite element analysis of a wheel bearing system. The finite element modelling approach has been validated by successfully predicting the load bearing capacity of an SKF ball bearing set for an acceptable fatigue life. For the first time, using a powerful commercial explicit finite element analysis tool, a detailed dynamic analysis has been carried of a deep groove ball bearing with a rotating inner race. The analysis has led to a consistent representation of complex motions consisting of rotations and revolutions of rolling elements, and generated insights into the stresses developed in the various components such as balls and races. In conclusion, a simple yet effective fuzzy logic-based yaw control algorithm has been presented in the current research. According to this algorithm, two inputs i.e. a yaw rate error and a driver steering angle are used for generating an output in the form of an additive steering angle which potentially can aid a driver in avoiding straying from an intended path.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Transportable Range Augmentation and Control System (TRACS), Mobile Telemetry System (MTS), is a versatile system capable of supporting anywhere when called upon. The MTS is designed to operate anywhere on land. It is unknown how the system will perform on a floating platform without a stabilizing gimbal. The operation of a tracking system at sea generally require the use of a three-axis pedestal. The MTS is a two-axis pedestal. This paper is a report on how the MTS responds to simulated ocean-motion. Testing the system on a body of water is very expensive, especially out in the desert. The MTS was tested in the desert area of Las Cruces, New Mexico in the parking lot of EMI Technologies, prime contractor, using two forklifts to simulate ship motion in the pitch and yaw planes. The location is perfect for crossover dynamics tests. The tests conducted were for the purpose of determining if the MTS could auto-track a moving signal in space while it also moves due to “simulated ocean swells” that increase the generated tracking error signal levels in an opposite or in addition to the ones generated from the space vehicle. There is no gyroscopic correction. Successful results of the tests could preclude the use of a gyroscopically stabilized gimbaled platform necessary to keep the tracking system steady for auto-tracking a target during “6 degrees of freedom” disturbances. Several thousand dollars can be saved if the concept can be proven.

The main aim of this research project is to extend theories of four-wheel-steering as developed by J. Ackermann to include an individually steered four-wheel steering system for passenger vehicles. Ackermann’s theories, including theories available in this subject area, dwell much on vehicle system dynamics developed from what is called single track model and some call it a bicycle model. In the bicycle model, the front two wheels are bundled together. Similarly, the rear wheels are bundled together. The problem with this is that it assumes two front wheels or two rear wheels to be under the same road, vehicle and operating conditions. The reality on the ground and experiments that are conducted are to the contrary. Therefore this study discusses vehicle disturbance rejection through robust decoupling of yaw and lateral motions of the passenger vehicle. A mathematical model was developed and simulated using Matlab R2008b. The model was developed in such a way that conditions can be easily changed and simulated. The model responded well to variations in road and vehicle conditions. Focus was in the ability of the vehicle to reject external disturbances. To generate yaw moment during braking, the brake on the left front wheel was disconnected. This was done because lateral wind generators, as used by Ackermann, were not available. The results from both simulations and experiments show disturbance rejection in the steady state. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Mechanical and Aeronautical Engineering / unrestricted

[EN] This thesis aims to provide new knowledge and data regarding the relevance of angular vibration as a risk in freight transport. Also, a new test protocol is developed to allow in-lab freight transport risk simulation taking into account rotational modes (angular vibration). This could allow in one hand a better package optimization, and on the other hand a cost reduction in relation to the potential damages that the transported goods suffer in distribution circles. To achieve this, the considered starting point was a revision of the main transportation modes used in freight movement and their projected relevance in next years. This analysis highlights the advantages of intermodal goods transport against conventional transport, which compromises a transformation toward standard unit loads in transport and based on full semi-trailers and trailers. Also, road transport will continue being the most relevant, although ship transport for long-distance transport will be preferred over air transport, which is mainly used for high value goods. The analysis of existing works related to research in transport risks shows that even though ship transport is highly relevant in international good movements, studies related to the potential effect of this transport mode in goods are scarce. Also, in road transport there is a number of data already gathered by different authors, but more information related to the road typologies and geographical locations is needed. This will allow for a better adaptation of real-life effects in test protocols, which are based on mean values, and therefore a consequent reduction of packaging could be achieved alongside with minimization of material, costs and environmental impacts. This thesis will focus on acceleration, and therefore vibration, that occurs during transport in six different directions, tree lineal and three angular (rotational). Linear acceleration is considered at the moment in the industry as the most relevant one, and consequently tests protocols for freight simulation are designed using just lineal acceleration. The proposed work will cover full monitoring of terrestrial and intermodal transport, identifying and quantifying angular vibration (pitch, roll and yaw). This angular vibrations could have an important influence depending on their intensity, and produce important good damages in transport if not considered in the packaging design. This is especially relevant in road and ship transport, although it is true for any kind of transport mode. After analysing in detail the main references and test protocols used for transport simulation and the existing equipment, a new test protocol is designed which includes angular vibration. This is a first step towards development of an international recognised protocol which considers as a whole the main risks suffered by goods during transport and distribution. Finally, the achieved results allow to clearly identify future research lines for advancing the state of the art in relation to risk assessment of goods distribution, simulation of transport conditions, and development of new test protocols and related technologies. / [ES] La presente tesis tiene como objetivo principal aportar nuevos conocimientos y datos concretos sobre la relevancia de la vibración angular como riesgo durante el transporte de mercancías. Asimismo se desarrolla un protocolo de ensayo que permite la simulación en laboratorio de los riesgos en el transporte considerando los modos rotacionales (vibración angular), lo que puede permitir una mejor optimización de la cantidad de envases utilizados por un lado y por otro, la reducción de los costes asociados a la potencial pérdida o defecto en las mercancías derivadas de los múltiples riesgos a los que se ven sometidas en los circuitos de distribución. Así, se consideró como punto de partida una revisión de los principales modos de transporte utilizados para el transporte de las mercancías y su relevancia en los próximos años. De este análisis se destacan las ventajas del transporte intermodal para la distribución de mercancías con respecto al transporte convencional. Esto supone una transformación en la unitización de las cargas para el transporte más estándar y basada en contenedores para semitrailers y trailers completos. Además, el transporte por carretera sigue siendo el modo de transporte predominante, si bien en los transportes a largas distancias predomina claramente el transporte marítimo frente al transporte aéreo, que se utiliza principalmente para cargas de alto valor. Estudiados los principales trabajos existentes y riesgos en los distintos modos de transporte se concluye que, a pesar de la relevancia del transporte marítimo en el transporte internacional de mercancías, los estudios sobre los posibles efectos sobre la carga transportada son muy escasos. En el caso del transporte terrestre es donde más datos se aportan por distintos autores, pero es necesario conseguir más datos de inventario disponibles para la mayor tipología de carreteras y ubicaciones geográficas posibles. Esto permite una mejor adaptación a la realidad de los protocolos de ensayo que se basan en valores promedio, reduciendo los sobreembalajes y minimizando cantidad de material, costes e impactos ambientales. Se profundiza en la aceleración y por tanto, las vibraciones, que acontecen en seis direcciones; tres lineales y tres angulares (rotacionales), considerándose las lineales como las más importantes hasta el momento y por tanto, los protocolos actuales de simulación se construyen considerando únicamente estas tres direcciones. En el presente trabajo se lleva a cabo la monitorización completa de un circuito de transporte terrestre e intermodal que permite identificar y cuantificar las vibraciones angulares (pitch, roll y yaw) y que en función de su intensidad podrían tener, por tanto, una gran influencia y provocar daños en las mercancías durante el transporte si no se consideran en el diseño de los embalajes. Esto cobra especial relevancia en modos de transporte como el terrestre y el marítimo en concreto, si bien están presentes en cualquier modo de transporte. Tras el estudio en detalle de los actuales referentes y protocolos utilizados para la simulación del transporte, así como el equipamiento disponible, se diseña un protocolo de ensayos teórico que incorpora la vibración angular. Se trata este de un primer paso para disponer de un protocolo reconocido a nivel internacional que considere de forma integral los principales riesgos que acontecen sobre la mercancía transportada en su transporte y distribución. Con todo, los resultados obtenidos permiten identificar claramente futuras líneas de investigación que aporten nuevos avances en el conocimiento de los riesgos para las mercancías durante la distribución, la simulación y ensayos de los mismos así como de las tecnologías necesarias para llevar a cabo dicha simulación. / [CAT] Aquest treball te com a objectiu fonamental aportar nous coneixements i dades concretes sobre la rellevància de la vibració angular com a risc durant el transport de mercaderies. Amb aquest objectiu es dissenya un protocol d'assaig que permet la simulació en el laboratori dels riscs en el transport considerant les diferents maneres de vibració rotacionals (vibració angular); aconseguint una millor optimització de la quantitat d'envasos transportats i reduint el cost vinculat a les destrosses i defectes de producte produïts per els riscs de cicle de distribució. Com a punt de partida es va considerar una revisió dels més destacats modes de transport dirigits al transport de mercaderies i la rellevància de cada mode en els propers anys. D'aquest anàlisis és destaquen avantatges del transport intermodal davant del transport convencional per a la distribució de mercaderies. El transport intermodal requereix de una estandardització de les cargues basada en l'ús de contenidors per a semi tràilers i tràilers complets. A més, el transport per carretera segueix sent el mode de transport prevalent, mentre en els transports de llarga distancia predomina el transport marítim davant del transport aeri, dirigit a cargues amb un valor més alt. Analitzats els treballs existents més destacats i els riscs en els diferents modes de transport es conclou que malgrat la rellevància del transport marítim en el transport internacional de mercaderies, els estudis centrats en els possibles efectes sobre la càrrega transportada son escassos. En canvi, en el mode de transport terrestre és on més dades de diferents autors es poden trobar, encara que és necessari aconseguir més dades de inventari referents a la major tipologia de carreteres i ubicacions geogràfiques possible. La creació de un inventari més complet permet una millor adaptació a la realitat dels protocols d'assaig que es basen en termes mitjos (mitjana aritmètica), disminuint el excés d'embalatge i minimitzant la quantitat de material, els costos i l'impacte ambiental. En aquesta tesi s'aprofundeix en l'estudi de l'acceleració i per tant, les vibracions, que esdevenen en sis direccions; tres lineals i tres angulars (rotacionals), considerant les vibracions lineals com les més destacades i estudiades fins ara, de manera que els actuals protocols de simulació s'elaboren considerant únicament les tres direccions lineals. En canvi, el present treball duu a terme la monitorització completa d'un cicle de distribució terrestre e intermodal que permet identificar i quantificar les vibracions angulars (pich, roll i yaw); ja que en funció de la intensitat podrien tenir una gran influència i provocar danys en la mercaderia durant el transport si no estan considerades durant el disseny dels embalatges. Aquest fet obté especial rellevància en modes de transport com el terrestre i el marítim, encara que estan present en qualsevol mode de transport. Després del estudi en detall dels actuals referents i protocols utilitzats per a la simulació del transport, així com el equipament disponible, és dissenya un protocol d'assaig teòric que incorpora la vibració angular. Es tracta d'un primer pas per a disposar d'un protocol reconegut a nivell internacional que consideri de manera integral els principals riscs que han de suportar les mercaderies durant un cicle de distribució. En conseqüència, els resultats obtinguts permeten identificar clarament futures línies de investigació que aporten nous avanços en el coneixement dels riscs per a les mercaderies durant la distribució, la simulació i els assajos dels mateixos; així com de les tecnologies necessàries per dur a terme aquesta simulació. / Zabaleta Meri, FJ. (2016). Contribución al desarrollo de protocolos de simulación del transporte de cargas paletizadas en plataformas de vibración multiaxial, considerando la inclusión de los modos rotacionales (pitch and roll) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62219 / TESIS

This thesis presents the design, calibration, and performance evaluation of a type of two-hole pressure probe anemometer known as a Conrad probe, as well as its subsequent implementation on an autonomous, compact boundary layer measurement device and its first application for subsonic in-flight measurements of a swept wing boundary layer. Calibration of the Conrad probe was accomplished using two calibration functions and a non-nulling method for resolving in-plane flow velocity direction and magnitude over a range of ±30 degrees. This approach to calibration and application offered the advantages of rapid data acquisition with lower energy consumption than alternative methods for pressure probe anemometry in swept wing boundary layers. Following calibration, the probe was adapted for use on an autonomous boundary layer measurement device including development of revised software. Utilizing this setup, boundary layer measurements were obtained on both swept and unswept models in a wind tunnel with a maximum operational velocity of 110 mph corresponding to a dynamic pressure of 30 psf. The wind tunnel results showed that the Conrad probe could measure in-plane flow magnitude for both laminar and turbulent boundary layers with sufficient uncertainty and spatial resolution for its intended application in flight testing. The Conrad probe and boundary layer measurement system were then employed for flight tests of a 30 degree swept wing model carried beneath an aircraft at a flight Mach number of 0.52 and altitudes up to 44,000 ft. The flight test results from the Conrad probe allowed for the successful determination of overall boundary layer thickness, laminar/turbulent conditions, and degree of flow turning within the boundary layer. It is believed that the rapid data acquisition and low energy consumption of the Conrad probe implementation on the boundary layer measurement system make it a good alternative for future flight testing requiring measurements of in-plane flow velocity magnitude and direction.

It is possible to obtain information about the stability conditions of a vehicle by observing and comparing existing signals involved in the rotational motion of the vehicle around the vertical axis. Accurate information about the current state of a vehicle is critical for the development and function of new active safety features in a vehicle. Therefore, the goal of this thesis is to create a new signal based on already existing signals from the vehicle electronic control unit for detecting understeering and oversteering of a vehicle. The signal should consider all the factors that affect the evaluation of the vehicle´s stability conditions. The results show that the developed signal can, in certain conditions, detect understeering and oversteering. Issues arise in situations such as banked curves or low-mu surfaces. In those cases, the signal is not fully able to describe the vehicle behavior.

The earlier EU-sponsored project MEXICO (model experiments in controlled conditions) provided a huge database for flows past an experimental rotor in standard and yaw conditions. This study aims to determine the eligibility of different models under various conditions by using the MEXICO data. The main purpose of this project is to improve the BEM technique for yawed flows by using the new yaw model. Additionally, the BEM technique with new yaw model is compared with the CFD and measurement results. The Glauert’s yaw model is also applied in BEM model to compare the effectiveness of the new yaw model. It is proved that the CFD technique is still better than the BEM technique except at the high yaw and wind conditions. Furthermore, new yaw model is favored against Glauert’s yaw model. This project also aims to implement the new tip loss correction model in the BEM code and the results are validated with the CFD results.

No description available.

Aeroacoustic whistles are a significant source of customer complaints to automotive manufacturers. Whistles can occur on many such components, but the relative position and configuration of rearview mirrors means they are a more problematic source of tonal noise on vehicles. The low subsonic complex turbulent flow, combined with small cavity scales, determines the possible whistle mechanisms. The one considered to be most problematic, fluid-dynamic cavity resonance, is the topic of this research thesis. The research scope is limited to the automotive environment of external rearview mirrors and the fluid-dynamic resonance mechanism: low subsonic Mach number, M = 0.05 - 0.13; laminar boundary layers; and two-dimensional, acoustically compact cavities. The low unit-cost of rearview mirrors and the desire to have simple identification and prediction schemes, that could be used by production engineers, determined an empirical approach. A search of the existing literature revealed that there were some data on cavities of the above scale in low Mach number flow, but quoted errors in empirical descriptions were large and there was very little research on the effects of flow yaw angle on the chosen resonance mechanism. The research therefore aims to determine whether existing empirical descriptions of fluid-dynamic cavity resonance are suitable for the prediction of the resonance characteristics, with sufficient accuracy to enable unambiguous identification of the presence of the resonance and its mechanism. A second aim is to investigate the effects of a feature of the automotive flow environment, flow yaw angle, on the resonance. Flow yaw angle is determined by those components of the flow in the same plane as the surface in which the cavity is situated. An experimental program was undertaken using a purpose-built aeroacoustic wind tunnel and a simple cavity model. Testing with two types of cavity configurations, as well as flow visualisation, investigated the main features of the resonance in time-averaged yawed flow. Within the scope of this thesis, it is shown that fluid-dynamic cavity resonance characteristics can be accurately identified by a simple empirical model, even in yawed flow. Various descriptors allow identification of the resonance threshold, stage, frequency and relative amplitude in non-yawed flow, while the frequency and stage can also be identified in yawed flow. The relative decrease in resonance amplitude in yawed flow, although identified for these experiments, would depend on the degree of spanwise variation in the boundary layer characteristics for a given cavity configuration. The results also identify significant issues with testing in a free jet tunnel, due to the nature of fluid-dynamic cavity resonance and the fluctuation energy content in free shear layers. Despite this, the thesis aims are achieved, and appropriate design guidelines are produced for automotive designers.

Active vehicle safety systems for road vehicles play an important role in accident prevention. In recent years, rapid developments have been observed in this area with advancing technology and electronic control systems. Active yaw control is one of these subjects, which aims to control the vehicle in case of any impending spinning or plowing during rapid and/or sharp maneuver. In addition to the development of these systems, integration and cooperation of these independent control mechanisms constitutes the current trend in active vehicle safety systems design. In this thesis, design methodology and simulation results of an active yaw control system for two axle road vehicles have been presented. Main objective of the yaw control system is to estimate the desired yaw behavior of the vehicle according to the demand of the driver and track this desired behavior accurately. The design procedure follows a progressive method, which first aims to design the yaw control scheme without regarding any other stability parameters, followed by the development of the designed control scheme via taking other stability parameters such vehicle sideslip angle into consideration. A two degree of freedom vehicle model (commonly known as &ldquo / Bicycle Model&rdquo / ) is employed to model the desired vehicle behavior. The design of the controller is based on Fuzzy Logic Control, which has proved itself useful for complex nonlinear design problems. Afterwards, the proposed yaw controller has been modified in order to limit the vehicle sideslip angle as well. Integration of the designed active yaw control system with other safety systems such as Anti-Lock Braking System (ABS) and Traction Control System (TCS) is another subject of this study. A fuzzy logic based wheel slip controller has also been included in the study in order to integrate two different independent active systems to each other, which, in fact, is a general design approach for real life applications. This integration actually aims to initiate and develop the integration procedure of the active yaw control system with the (ABS). An eight degree of freedom detailed vehicle model with nonlinear tire model is utilized to represent the real vehicle in order to ensure the validity of the results. The simulation is held in MATLAB/Simulink environment, which has provided versatile design and simulation capabilities for this study. Wide-ranging simulations include various maneuvers with different road conditions have been performed in order to demonstrate the performance of the proposed controller.