This paper focuses on thermal analysis of a direct driven hydraulic setup (DDH). DDH combines the benefits of electric with hydraulic technology in compact package with high power density, high performance and good controllability. DDH enables for reduction of parasitic losses for better fuel efficiency and lower operating costs. This one-piece housing design delivers system simplicity and lowers both installation and maintenance costs. Advantages of the presented architecture are the reduced hydraulic tubing and the amount of potential leakage points. The prediction of the thermal behavior and its management represents an open challenge for the system as temperature is a determinant parameter in terms of performance, lifespan and safety. Therefore, the electro-hydraulic model of a DDH involving a variable motor speed, fixed-displacement internal gear pump/motors was developed at system level for thermal analysis. In addition, a generic model was proposed for the electric machine, energy losses dependent on velocity, torque and temperature was validated by measurements under various operative conditions. Results of model investigation predict ricing of temperature during lifting cycle, and flattened during lowering in pimp/motor. Conclusions are drawn concerning the DDH thermal behavior.

<p dir="ltr">In recent years increasingly stringent regulations regarding the pollution emissions and greenhouse gasses (GHG) of off-highway vehicles have emerged. However, recent studies underscores that off-highway vehicles have an average efficiency of 30%. In response, researchers are exploring the possibility of electrifying these vehicles with electric machines (EMs) potentially undertaking one, multiple, or all the vehicular functions previously reliant on internal combustion engines (ICEs).</p><p dir="ltr">Contemporary off-highway vehicle technology revolves around hydraulic systems tailored for diesel engines, tuned to specific torque characteristics and operating at a single speed. While replacing the prime mover with electric machines, the proper hydraulic supply capable of matching the same torque speed characteristics must be found. Furthermore, it must be determined whether an integration capable of reducing the mass, cost, and volume can be implemented, and if energy recuperation is possible. </p><p dir="ltr">In essence, achieving the desired transformation in off-highway vehicle technology necessitates a comprehensive reevaluation of both hydraulic systems and power sources, with electrification emerging as a promising strategy for harmonizing efficiency, emission standards, and performance expectations. </p><p><br></p><p dir="ltr">This work proposes guidelines to systematically design EMs and positive displacement hydraulic gear machines (HMs), along with their integration in an electro-hydraulic unit (EHU). To do so, three different variants of EHU are produced. The first variant features an external gear machine (EGM) integrated in a permanent magnet synchronous electric machine (PMSEM). The second and third variants integrate an internal gear machine (IGM) and a PMSEM, wherein the final variant introduces features endowing its operation at high rotational velocities.</p><p dir="ltr">The EM and HM constituting all variants of EHU are designed using a genetic algorithm-based optimization framework. This optimization framework encapsulates dedicated models for the EM and the HM that allow the calculation of the EHU performance. The first optimization objectives are the minimization of power consumption over the duty cycle of the selected reference machine, the minimization of the pressure and flow ripple, and maximization of the power density of the EHU. The optimization of the second and third variants instead only aims to maximize the total efficiency and power density of the EHU. </p><p dir="ltr">After having determined the parameters of the EHU through the optimization procedure the designs are refined with thorough simulations focusing on the fluid-dynamic features and the design of the axial balance system of the HMs. </p><p dir="ltr">The three variants present an increasing level of HM and EM integration and component reduction. While in the first variant HM and EM have a dedicated housing, and the HM is only positioned in the inert region of the EM, in the latest variants the HM and the EM also share the same casing. The first variant of EHU is air cooled by a radial fan system attached to the EM rotor and openings machined in the casing. The second variant takes advantage of the extreme integration and the differential pressure generated across the HM to liquid cooling the EM. The third variant necessitates the use of an external system to cool the EM. </p><p dir="ltr">To prove the effectiveness of the design process the first two EHU variants are prototyped and tested. The first EHU variant is tested both in a standalone configuration and on the reference machine showing total efficiency values up to 69%, proving its functionality and proving the capability of recuperating energy. The tests conducted on the second variant EHU show a volumetric efficiency that ranges between 81% and above 96% for a pinion rotation velocity of 6000 rpm proving the value of the presented design process. Despite the good quality of the volumetric efficiency values, this EHU variant present morphological limitations that negatively impact its mechanical efficiency. Finally, the third EHU concept is presented not only to remedy the morphological limitations of the second variant but also to address the challenges raised by high rotational velocity operation. </p>

This paper focuses on thermal analysis of a direct driven hydraulic setup (DDH). DDH combines the benefits of electric with hydraulic technology in compact package with high power density, high performance and good controllability. DDH enables for reduction of parasitic losses for better fuel efficiency and lower operating costs. This one-piece housing design delivers system simplicity and lowers both installation and maintenance costs. Advantages of the presented architecture are the reduced hydraulic tubing and the amount of potential leakage points. The prediction of the thermal behavior and its management represents an open challenge for the system as temperature is a determinant parameter in terms of performance, lifespan and safety. Therefore, the electro-hydraulic model of a DDH involving a variable motor speed, fixed-displacement internal gear pump/motors was developed at system level for thermal analysis. In addition, a generic model was proposed for the electric machine, energy losses dependent on velocity, torque and temperature was validated by measurements under various operative conditions. Results of model investigation predict ricing of temperature during lifting cycle, and flattened during lowering in pimp/motor. Conclusions are drawn concerning the DDH thermal behavior.

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Made available in DSpace on 2014-12-17T14:58:24Z (GMT). No. of bitstreams: 1 JoaoDBS_DISSERT.pdf: 2950294 bytes, checksum: b123f316a60d2e367696c4d97c359a71 (MD5) Previous issue date: 2013-11-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The development of non-linear controllers gained space in the theoretical ambit and of practical applications on the moment that the arising of digital computers enabled the implementation of these methodologies. In comparison with the linear controllers more utilized, the non -linear controllers present the advantage of not requiring the linearity of the system to determine the parameters of control, which permits a more efficient control especially when the system presents a high level of non-linearity. Another additional advantage is the reduction of costs, since to obtain the efficient control through linear controllers it is necessary the utilization of sensors and more refined actuators than when it is utilized a non-linear controller. Among the non-linear theories of control, the method of control by gliding ways is detached for being a method that presents more robustness, before uncertainties. It is already confirmed that the adoption of compensation on the region of residual error permits to improve better the performance of these controllers. So, in this work it is described the development of a non-linear controller that looks for an association of strategy of control by gliding ways, with the fuzzy compensation technique. Through the implementation of some strategies of fuzzy compensation, it was searched the one which provided the biggest efficiency before a system with high level of nonlinearities and uncertainties. The electrohydraulic actuator was utilized as an example of research, and the results appoint to two configurations of compensation that permit a bigger reduction of the residual error / O desenvolvimento de controladores n?o lineares ganharam espa?o nos ?mbitos te?rico e de aplica??es pr?ticas no momento que o surgimento de computadores digitais possibilitou a implementa??o destas metodologias. Em compara??o aos controladores lineares mais utilizados, os controladores n?o lineares apresentam a vantagem de n?o necessitarem da lineariza??o do sistema para determinar os par?metros de controle, o que permite um controle mais eficiente principalmente quando o sistema apresenta elevado grau de n?o linearidade. Outra vantagem adicional ? a redu??o dos custos, uma vez que para obter o controle eficiente atrav?s dos controladores lineares ? necess?ria a utiliza??o de sensores e atuadores mais refinados do que quando se utiliza um controlador n?o linear. Dentre as teorias de controle n?o linear, o m?todo de controle por modos deslizantes se destaca por ser um m?todo que apresenta maior robustez frente ?s incertezas. J? ? comprovado que a ado??o de t?cnicas de compensa??o na regi?o do erro residual permite melhorar ainda mais o desempenho desses controladores. Assim, neste trabalho ? descrito o desenvolvimento de um controlador n?o linear que busca a associa??o da estrat?gia de controle por modos deslizantes com a t?cnica de compensa??o fuzzy. Mediante a implementa??o de algumas estrat?gias de compensa??o fuzzy, buscou-se aquela que proporcionasse maior efici?ncia frente a um sistema com elevado grau de n?o linearidades e incertezas. O atuador eletrohidr?ulico foi utilizado como exemplo de estudo, e os resultados apontam para duas configura??es de compensa??o que permitem uma maior redu??o do erro residual

<p>The electrification trend affecting off-road vehicles is paving the way toward dedicated electrified hydraulic actuation systems. Although traditional centralized fluid power architectures are still utilized in many applications for low cost, power density, and reliability, nowadays emission policy results in an increasing interest in developing electro-hydraulic actuator (EHA) solutions. EHAs enable non-throttling actuation and energy recuperation during overrunning loads, leading to higher transmission efficiency and lower fuel consumption. These features in energy efficiency make EHAs competitive in meeting emission regulations compared to conventional hydraulic solutions.</p> <p>The key challenge in developing the EHA solution comes from the high cost and space requirements, especially for the adoption of self-contained EHAs in mobile applications. In this study, two architectures for the EHA are proposed, a closed-circuit architecture and an open-circuit one, to determine the most practical and efficient configuration. The most effective open-circuit architecture with distributed concepts is further investigated for implementation, which requires less modification of the mechanical structures and performs more efficiently than the closed-circuit alternative. The proposed EHA is driven by an electro-hydraulic unit (EHU) consisting of a variable-speed electric motor and a fixed-displacement hydraulic pump, which is relatively cost-effective. A novel hydraulic configuration is proposed, which allows the EHA to cover full-speed operating ranges in four quadrants. </p> <p>To verify the EHA design, the behavior of the proposed system should be predicted prior to costly experiments and demonstrations. For this purpose, an integrated simulation model is developed based on the lumped parameter approach in the Amesim environment. The model includes the electric system, the hydraulic system, and the mechanism to be implemented, which are capable of flexible analysis of functionality, efficiency, and thermal performance.</p> <p>In this work, a dedicated test rig for EHA testing is developed. The test rig can help verify EHA performance, test the control algorithm, and diagnose errors before implementing the system on real applications. The experimental results from the test rig also validate the simulation model. An independent load drive of the test rig allows testing all possible  loading conditions of the proposed EHA, thus demonstrating the energy performance in four quadrants. Thermal behavior is investigated with long duty cycles to determine the need for additional cooling equipment. After the validation of the hydraulic configuration, a power electronics setup is added to the test rig, which allows to drive the EHA system with the novel designed EHUs. Validation on the test platform paves the way for implementation in a vehicle. </p> <p>As a final step, the proposed EHA system is implemented in a reference vehicle, a Case New Holland TV380 skid steer loader. A novel designed EHU is adopted to drive the system for technology demonstration. The energy savings capacity of the EHA is investigated in comparison to the baseline measurements of the traditional open-center hydraulic architecture. The impressive savings from the reduction of throttling losses and energy recovery guide the possible commercialization of such EHAs in mobile hydraulic applications. The controller design of the implemented EHA system is investigated with the aim of improving the dynamic performance, e.g., reducing damping oscillation. Basic power management strategies are also studied to integrate EHA with the power train of current hydraulic machines. Regarding future work, based on this research but not within the scope of this study, the proposed EHA system can be adopted with different types of prime movers, such as axial piston machines as the hydraulic part of an EHU. Furthermore, the design approach proposed in this study can help resize the EHA system for other applications with different loading conditions and power requirements, and the energy savings capability can be further investigated. With this, a comprehensive market analysis will be performed for the commercialization of EHA. </p>

The recent electrification trend in the off-road market has incentivized research towards the proposal of compact, cost-effective and energy-efficient solutions for hydraulic actuators. As a result, increased attention has been given to electro-hydraulic actuator (EHA) architectures. The paper offers a study performed on a novel closed-circuit EHA architecture with the goal to maximize the overall system efficiency while meeting or exceeding traditional off-road applications performance, thereby enabling further electrification of off-road applications. Both numerical and experimental approaches are utilized to validate the functionality of the proposed EHA circuital configuration in four quadrants. Moreover, the actuator functionality at both high and low velocities are considered, which has never been explored in the past due to the limitations on the hydraulic machine driving speed. The good match between the experimental data and the simulation results confirms the potential of the simulation model for sizing such EHA architecture for different actuator sizes, duty cycles, and performance levels.