A well-known challenge in vehicle dynamics is to design a vehicle that will not only keep the occupants comfortable, but will also ensure safe and stable operation during various manoeuvres over multiple driving surfaces. A soft and compliant suspension is generally required for good ride comfort, while a stiff suspension with a low centre of mass is required for improved handling. These contradicting factors in the design process is commonly referred to as the ride comfort versus handling compromise. A newly developed semi-active hydropneumatic suspension system is proposed to reduce or negate this compromise by being able to change its characteristics according to the dynamic state of the vehicle. The unit is equipped with two proportional solenoid valves that can provide continuously variable damping. In addition, the valves are able to completely close off flow to compressible gas volumes to provide four discrete stiffness characteristics. This suspension system is based on a previously developed suspension that had only two state (open or closed) valves, which provided discrete damping characteristics. A thorough investigation of the older system proved that the system was capable of addressing the ride comfort versus handling compromise. The purpose of this study was to investigate whether the updated design could deliver improved performance and to recommend focus areas for future research initiatives. The suspension system’s characteristics were determined experimentally by actuating the unit on a test bench. Results indicated that the unit produced the desired stiffness, low damping and response time characteristics. A mathematical model of the suspension unit was developed and validated against experimental data. The model was used in single degree of freedom simulations to investigate both passive and semi-active controlled performance. Results indicated that the suspension could be semi-actively controlled for improve ride comfort. However, the magnitude of improvements with semi-active control, which includes a suitable response time, proved to be rather insignificant compared to the optimum passive suspension. / Dissertation (MEng)--University of Pretora, 2019. / Mechanical and Aeronautical Engineering / MEng (Mechanical) / Unrestricted

Le développement croissant de systèmes de stockages connectés au réseau électrique se voit stimulé par les problématiques de gestion de réseau liés entre autres à l'intégration croissante de technologies de production renouvelables. L'accumulation hydropneumatique d'énergie apparait comme une solution propre et économiquement intéressante dans le panel des technologies existantes. Cette étude analyse une configuration d'accumulation air-eau sans séparation, en cycle fermé et utilisant une pompe/turbine rotodynamique. Les principales problématiques en relation à ces choix techniques sont : les phénomènes de transfert de masse et de chaleur à l'interface air-eau, les caractéristiques de fonctionnement d'une machine hydraulique rotodynamique en régime d'opération variable et le rendement d'accumulation du système. Ces aspects sont traités ici par des approches locales dans certains cas, puis globales afin de pouvoir proposer un modèle de comportement dynamique du système de stockage pouvant faire l'objet de simulations rapides. Les aspects de modélisation ont été élaborés en parallèle au développement d'un banc d'essais de 45 kW réalisé dans le cadre de ce travail. Les observations expérimentales obtenues sur ce banc sont comparées aux résultats du modèle qui rend bien compte de la dynamique et de l'état énergétique du système. Des études d'amélioration du système sont engagées à la fin du document. Elles concernent d'une part la question de la flexibilité de fourniture de puissance et d'autre part le rendement d'accumulation du réservoir de stockage. / The present increasing development of storage systems connected to electrical network is stimulated by network management issues related to recent energetic landscape evolutions such as the increasing integration of renewable production sources. The hydro-pneumatic system seems to offer a clean and cheap energy storage solution among the set of existing storage technics. The present study analyses an air-water direct contact accumulation configuration, in closed cycle and using a rotodynamic pump/turbine. The main points of interest related to these technical choices are: the air-water interface mass and heat phenomena, variable operating point performances of a rotodynamic hydraulic machine and the overall efficiency of the storage device. These aspects are studied by, in some cases, a local approach, and then a global one in order to propose a dynamic behaviour model of the storage system suitable for rapid simulations. The modelling aspects were treated in parallel to the development of a 45 kW test rig built during this project. The experimental observations made on this test rig are compared to the modelling results that represent correctly the dynamics and energetic state of the system. At the end of this document, some studies for the improving of the power delivery flexibility and efficiency increasing of the accumulation element are engaged.

Este trabalho se propõe a apresentar uma nova solução para o problema da dissolução de ar em reservatório hidropneumático. No capítulo introdutório são apresentadas informações e características sobre reservatório hidropneumático, sobretudo relacionadas ao seu funcionamento. Neste capítulo comenta-se sobre as principais soluções utilizadas para superar o problema da dissolução de ar. No segundo capítulo enumeram-se com detalhes os objetivos do trabalho. Na revisão da literatura são apresentadas diversas referências, relativas aos estudos do regime transitório e do comportamento do reservatório hidropneumático. No capítulo seguinte apresenta-se com detalhes a nova solução, que é o tema central desta tese. No capítulo 5 é feito o desenvolvimento do modelo matemático de cálculo de transitório, empregando o método das características, e estabelecendo as condições de contorno associadas a um reservatório hidropneumático convencional. No capítulo 6, estuda-se o fenômeno da dissolução de ar num reservatório hidropneumático. Através da elaboração de um equacionamento teórico e exemplos ilustrativos, a intenção é obter as equações que traduzam o mais próximo possível o que efetivamente ocorre dentro do reservatório em termos de transferência de massa de ar. O desenvolvimento dos capítulos 5 e 6 é importante, pois estabelecem as equações referentes a um reservatório hidropneumático convencional, que servirão de base para o desenvolvimento das equações correspondentes a um reservatório empregando a nova solução proposta. Isto é feito no capítulo 7. O capítulo 8 é referente aos testes realizados, onde são apresentados os resultados e as análises dos mesmos. Finalmente, entre muitas conclusões obtidas, há a clara constatação de que a solução proposta é viável, mas que, porém, o assunto não se esgotou, de forma que são feitas recomendações para trabalhos futuros. / This work proposes to present a new solution for the problem of the air dissolution in hydropneumatic reservoir. In the introductory chapter are presented information and characteristics about hydropneumatic reservoir, mainly the ones related to his operation. In this chapter it is commented about the main solutions used to overcome the problem of the air dissolution. In the second chapter the objectives of this work are presented. In the literature review several references are presented related to the studies of transitory regime and of the behavior of the hydropneumatic reservoir. In the following chapter it is presented with details the new solution, that is the central theme of this thesis. In chapter 5 the development of a mathematical model for calculation of transitory was made using the method of the characteristics, establishing the boundary conditions associated to a conventional hydropneumatic reservoir. In the chapter 6, the air dissolution phenomenon in a hydropneumatic reservoir is studied. Through the elaboration of theoretical equations and illustrative examples, the intention is to obtain the equations that translate the closest possible what occurs inside of the reservoir in terms of mass transfer of air. The development of the chapters 5 and 6 is important, because they establish the referring equations to a conventional hydropneumatic reservoir, which will serve as base for the development of equations corresponding to a reservoir using the new proposed solution. That is done in the chapter 7. Chapter 8 regards the tests accomplished, where the results and analyses of the same ones are presented. Finally, among many obtained conclusions, there is the clear verification that the proposed solution is viable, but that, however, the subject didn\'t become exhausted, so that there are made recommendations for future works.

Este trabalho se propõe a apresentar uma nova solução para o problema da dissolução de ar em reservatório hidropneumático. No capítulo introdutório são apresentadas informações e características sobre reservatório hidropneumático, sobretudo relacionadas ao seu funcionamento. Neste capítulo comenta-se sobre as principais soluções utilizadas para superar o problema da dissolução de ar. No segundo capítulo enumeram-se com detalhes os objetivos do trabalho. Na revisão da literatura são apresentadas diversas referências, relativas aos estudos do regime transitório e do comportamento do reservatório hidropneumático. No capítulo seguinte apresenta-se com detalhes a nova solução, que é o tema central desta tese. No capítulo 5 é feito o desenvolvimento do modelo matemático de cálculo de transitório, empregando o método das características, e estabelecendo as condições de contorno associadas a um reservatório hidropneumático convencional. No capítulo 6, estuda-se o fenômeno da dissolução de ar num reservatório hidropneumático. Através da elaboração de um equacionamento teórico e exemplos ilustrativos, a intenção é obter as equações que traduzam o mais próximo possível o que efetivamente ocorre dentro do reservatório em termos de transferência de massa de ar. O desenvolvimento dos capítulos 5 e 6 é importante, pois estabelecem as equações referentes a um reservatório hidropneumático convencional, que servirão de base para o desenvolvimento das equações correspondentes a um reservatório empregando a nova solução proposta. Isto é feito no capítulo 7. O capítulo 8 é referente aos testes realizados, onde são apresentados os resultados e as análises dos mesmos. Finalmente, entre muitas conclusões obtidas, há a clara constatação de que a solução proposta é viável, mas que, porém, o assunto não se esgotou, de forma que são feitas recomendações para trabalhos futuros. / This work proposes to present a new solution for the problem of the air dissolution in hydropneumatic reservoir. In the introductory chapter are presented information and characteristics about hydropneumatic reservoir, mainly the ones related to his operation. In this chapter it is commented about the main solutions used to overcome the problem of the air dissolution. In the second chapter the objectives of this work are presented. In the literature review several references are presented related to the studies of transitory regime and of the behavior of the hydropneumatic reservoir. In the following chapter it is presented with details the new solution, that is the central theme of this thesis. In chapter 5 the development of a mathematical model for calculation of transitory was made using the method of the characteristics, establishing the boundary conditions associated to a conventional hydropneumatic reservoir. In the chapter 6, the air dissolution phenomenon in a hydropneumatic reservoir is studied. Through the elaboration of theoretical equations and illustrative examples, the intention is to obtain the equations that translate the closest possible what occurs inside of the reservoir in terms of mass transfer of air. The development of the chapters 5 and 6 is important, because they establish the referring equations to a conventional hydropneumatic reservoir, which will serve as base for the development of equations corresponding to a reservoir using the new proposed solution. That is done in the chapter 7. Chapter 8 regards the tests accomplished, where the results and analyses of the same ones are presented. Finally, among many obtained conclusions, there is the clear verification that the proposed solution is viable, but that, however, the subject didn\'t become exhausted, so that there are made recommendations for future works.

Orientador: Pablo Siqueira Meirelles / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-07T01:26:23Z (GMT). No. of bitstreams: 1 Sa_RobertoLuisde_M.pdf: 2111156 bytes, checksum: 0673c52c0192cecc5142208203b6adfb (MD5) Previous issue date: 2006 / Resumo: Este trabalho apresenta o desenvolvimento de um sistema de controle para um modelo de suspensão hidropneumática concebido para carretas agrícolas. A partir de um modelo não­ linear de um quarto de veículo com dois graus de liberdade foram implementados dois sis­temas de controle, um ativo e outro semi-ativo, ambos baseados na estratégia de controle Skyhook. Considerando-se duas excitações, uma do tipo degrau com amplitude de 40[mm]e outra do tipo variável com amplitudes contidas numa faixa de variação de +/- 30[mm], foram realizadas simulações para três situações diferentes: Com a massa suspensa na condição de carga mínima, na condição de carga média e na condição de carga máxima. Com desempenho próximo ao obtido para o sistema ativo no quesito isolação de vibrações, quando comparado com o caso passivo, o sistema semi-ativo não apresentou deteriorações significativas no mo­ vimento da massa não-suspensa. Foi mostrado que para a aplicação considerada o sistema semi-ativo mostrou ser a melhor opção, uma vez que é mais confiável e apresenta um custo de implementação mais baixo do que um sistema ativo / Abstract: This study deals with the development of a control system suited for a Hydropneumatic Suspension System designed for use in Agricultural Devices. Using the Skyhook Control methodology, two control systems are designed for a quarter car non-linear model, an active and a semi-active one. For performance measurement, two kinds of road excitation sources are considered: a 40[mm] amplitude bump and a variable road profile with amplitude range from -30 to +30[mm]. The simulations take into account three different situations: maximum sprung mass loading, minimum sprung mass loading and medium sprung mass loading. The resulting performance of the semi-active system was almost as good as the performance achieved by the active system and much better than the performance of the passive one. Since the semi-active system is more reliable and has a smaller implementation cost than the active one, for the application concerned it resulted to be the best solution / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

This diploma thesis deals with the design of the front landing gear with steering nose leg and hydropneumatic shock absorber, designed for aircraft PS - 28 Cruiser. In the thesis there was created design of basic types of front landing gear and the best option was selected. The work is further elaborated design of hydropneumatic shock absorber and comparise with the measured load. At the end of the work it was created the structural design of the front landing gear.

Investigation and testing of hydropneumatic suspension systems has previously been done at Scania between the year 1992 and 2000. Interest has aroused at Scania CV AB to further test a hydropneumatic suspension. The reason being the new ventures of decarbonised, clean, electrified, automatized and digitalised vehicles. If electrified trucks are to be adopted in the market as an alternative to trucks with combustion engines, solutions for this type of vehicle’s capacity need to be presented. The vehicle’s weight needs to be reduced; the effectiveness of the components needs to be increased and alternatives to increase battery storage needs to arise if it’s going match the traveling distance of a combustion engine. The mission of the project is to present an installation solution of a hydropneumatic suspension that retains the performance of the current air suspension. The presented material will contain CAD-models of all the brackets that will be designed to fit the suspension, as well as the placement in the vehicle assembly for said brackets. The results show that as for the front suspension the best solution is a placement of the hydraulic cylinders in front of the vehicles front axle. Furthermore the rear suspension is best suited for a placement of the hydraulic cylinders behind the vehicles rear axle. However it was concluded that the rear suspension will not be able to retain the current stroke of the vehicle without sacrificing its ground clearance. Parts of the suspension could however be terminated when the air suspension system was replaced by the hydropneumatic system namely: The front suspension anti-roll bar, shock absorbers, air springs and their coexisting brackets.

Rollover prevention in Sports Utility Vehicles (SUV‟s) offers a great challenge in vehicle safety. By reducing the body roll angle of the vehicle the load transfer will increase and thus decrease the lateral force that can be generated by the tires. This decrease in the lateral force can cause the vehicle to slide rather than to roll over. This study presents the possibility of using slow active suspension control to reduce the body roll and thus reduce the rollover propensity of a vehicle fitted with a hydro-pneumatic suspension system. The slow active control is obtained by pumping oil into and draining oil out of each hydro-pneumatic suspension unit individually. A real gas model for the suspension units as well as for the accumulator that supplies the oil is incorporated in a validated full vehicle Adams model. This model is then used to simulate a double lane change manoeuvre performed by a SUV at 60 km/h and it is shown that a significant improvement in body roll can be obtained with relatively low energy requirements. The proposed control is successfully implemented on a Land Rover Defender test vehicle. A Proportional-Derivative (PD) controller is used to control on-off solenoid operated valves and the flow is adjusted using the lateral acceleration as a parameter. Experimental results confirm that a significant improvement in body roll is possible. AFRIKAANS : Omrolvoorkoming in Sportnutsvoertuie bied geweldige uitdagings in terme van voertuigveiligheid. Deur die rolhoek van die voertuig te verminder word die laterale lasoordrag verhoog en word die laterale krag wat die bande kan genereer minder. As die laterale krag genoeg verminder sal die voertuig eerder gly as omrol. Die studie ondersoek die moontlikheid om stadig-aktiewe suspensiebeheer op 'n voertuig met 'n hidropneumatiese suspensie te gebruik om bakrol te verminder en dus die omrolgeneigdheid van die voertuig te verlaag. Die beheer word toegepas deur olie in elke hidropneumaties suspensie-eenheid individueel in te pomp of te dreineer. 'n Werklike gas model word gebruik om die supensie-eenhede asook die akkumulator, wat die olie aan die suspensie voorsien, te modeleer. Hierdie modelle word in 'n gevalideerde volvoertuig ADAMS model geïnkorporeer en 'n dubbel laanverwisseling word gesimuleer teen 60 km/h. Die resultate toon dat 'n beduidende verbetering in die rolhoek moontlik is met relatiewe lae energievereistes. Die voorgestelde beheer is suksesvol op 'n Land Rover Defender geïmplimenteer en 'n Proportioneele-Differensiaal (PD) beheerder word gebruik om die aan-af solenoїde kleppe te beheer terwyl die vloei aangepas word na gelang van die laterale versnelling. Eksperimentele resultate bevestig dat 'n beduidende verbetering in bakrol moontlik is. / Dissertation (MEng)--University of Pretoria, 2012. / Mechanical and Aeronautical Engineering / unrestricted

Standardized parts like hydraulic accumulators are used in nearly every hydraulic system, in many cases even several. Therefore, even small changes in size and weight of accumulators can save considerable material costs. In mobile applications, hydraulic accumulators are used among others in hydro-pneumatic suspension systems. There is a strong focus on miniaturization and weight reduction, as the components always have to be transported with the vehicle. Energy density and energy content of conventional hydraulic accumulators cannot be maximized at the same time. This limitation can be overcome by adding a heat capacity with large surface into the gas volume of the accumulator. The heat capacity enlarges the isothermal frequency range and therefore enlarges the energy density of the accumulator at the given frequency and the given size. In this paper an experimental comparison of conventional hydraulic accumulators and accumulators with foam inserts shows, that at a specific frequency band, the stiffness of foam filled accumulators is significantly lower than of conventional accumulators. The energy density is about 11 % higher than in conventional accumulators. Consequently, a space reduction of about 18 % is possible.

All-wheel suspensions are generally challenging, particularly if they are equipped with an automatic level control. In mobile machines, the special application conditions make their use even more demanding regarding layout and control. A high center of gravity, load variations, off-road-conditions etc. require special measures to reduce roll and pitch movements. Additionally the uneven ground along with the mechanical suspension setup often create a need to measure and optimize tyre-to-ground forces in order to provide best traction and suspension properties. Hydropneumatic suspensions have all the potential to meet all these requirements and provide a comfortable, safe and efficient suspension setup.