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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Understanding effect and diagnosis of internal leakage in hydrostatic actuation systems

Thakur, Amit 27 January 2012 (has links)
This research presents implementation of the Wavelet transform for detecting internal leakages occurring within an Electro-Hydrostatic Actuation (EHA) system. Simulation studies are carried out in order to investigate the feasibility of a particular approach and to determine the level of accuracy that can be expected in the experimental system. The effect of friction, orifices and the dynamics of motor/pump are considered during the simulation study. Experimental analysis based on Wavelet transform is conducted for detecting internal leakage. The original pressure signals at either side of the cylinder are decomposed using Wavelet transform to detect internal leakage which is clearly identified. Results obtained through the use of Wavelet transform prove that this method is fast and easily-implementable for leakage detection in EHA on the basis of the pressure data obtained. Internal leakages as low as 0.0042 lit/min are shown to be detectable 85% of the time using a structured input signal.
2

Understanding effect and diagnosis of internal leakage in hydrostatic actuation systems

Thakur, Amit 27 January 2012 (has links)
This research presents implementation of the Wavelet transform for detecting internal leakages occurring within an Electro-Hydrostatic Actuation (EHA) system. Simulation studies are carried out in order to investigate the feasibility of a particular approach and to determine the level of accuracy that can be expected in the experimental system. The effect of friction, orifices and the dynamics of motor/pump are considered during the simulation study. Experimental analysis based on Wavelet transform is conducted for detecting internal leakage. The original pressure signals at either side of the cylinder are decomposed using Wavelet transform to detect internal leakage which is clearly identified. Results obtained through the use of Wavelet transform prove that this method is fast and easily-implementable for leakage detection in EHA on the basis of the pressure data obtained. Internal leakages as low as 0.0042 lit/min are shown to be detectable 85% of the time using a structured input signal.
3

Electro-Hydrostatic Actuator (EHA) Position Tracking and Correction

Hu, Xiang 06 1900 (has links)
The Electro-Hydrostatic Actuator (EHA) is a self-contained and modular hydraulic actuation system using feedback control. EHAs are being increasingly used in engineering and industrial systems that require high precision and efficiency such as aircrafts (Airbus 380), off-highway hydraulic hybrids and construction machineries. In this research, mathematical models (linear and nonlinear) with different control strategies (that include PID, PID with feedforward compensation, and Sliding Mode Control (SMC)) are developed and experimentally applied to an EHA prototype. These methods are then compared to a new control strategy that is a combination of Interacting Multiple Model concept, Sliding Mode Control (IMM-SMC) and the Smooth Variable Structure Filter (SVSF). The IMM and the SMC strategies are also applied with the Kalman Filter (KF) for comparison. The above mentioned control strategies were implemented on an EHA prototype for position control under a range of fault conditions that were physically simulated. Both simulation and experimental results showed that the new IMM-SMC with SVSF outperformed all the other control strategies in terms of robustness and precision in trajectory tracking. / Thesis / Master of Applied Science (MASc)
4

Actuation system design with electrically powered actuators

Meng, Fanliang 01 1900 (has links)
This project addresses the actuation system architecture of future All-electric aircraft (AEA) with electrically powered actuators (EPA). Firstly, the information of EPAs is reviewed, and then an electro-hydrostatic actuator (EHA) and electro-mechanical actuator (EMA) are selected for further system research. The actuation system architecture of Boeing and Airbus is then presented as a conventional design where the new design concepts are also researched and the distributed architecture was proposed as another design trend. To find out which one is better, both of them are selected for further research. The easily available data makes the Flying Crane a better choice for the case study. Stall load, maximum rate and power are the main elements for electric actuator requirements and power consumption, weight, cost and safety are the most important aspects for civil aircraft actuation systems. The conventional and distributed flight actuation system design considered the redundancy of systems and actuators, and also the relationship of the power, control channel and actuator work mode. But only primary flight actuation control system specifications are calculated since this data has better precision and also the limited time has to be taken into consideration. Brief comparisons of the two system specifications demonstrate that the higher power actuator have has higher efficiency and distributed actuators could reduce the system weight through reduce the system redundancy with a power efficiency decline. The electrically powered actuation system for future aircraft design is a balance between actuator number, system weight and power consumption.
5

Konstrukční optimalizace elektro-hydrostatického válce pro letadla v kategorii všeobecného letectví / Structure Optimization of Electro-Hydrostatic Actuator for General Aviation Aircraft

Kraus, Jan January 2016 (has links)
The use of only one primary sort of energy is the present trend of aircraft design and its force systens. There are designed electromagnetical force systems for control of ther moving parts of aircraft structure. Great demands are laid on energy and dynamic characteristics at some force systems, especially at aircraft control system, and therefore there are developed electro-hydrostatic actuators, suitable for aircraft for aircraft control system, which could graduallly replace commonly used hydraulic servo-controol system. Not only electric signals but also required electric outputs are led into these electro-hydraulic actuators. Using a hydrostatic converter it is changed into mechanical output controlling the aircraft control system. The goal of work is to set requirements for characteristic and conception of electro – hydrostatic actuators for aircraft control systems. Further, on the basis of theoretical analysis , computer modeling and experiment, the design optimisation of electro-ghydrostatic actuator should be done for small business aircraft from the point of view of dimmensions and dynamic characteristics.
6

Development Of A Smart Material Electrohydrostatic Actuator Considering Rectification Valve Dynamics And In Situ Valve Characterization

Walters, Thomas E. 05 September 2008 (has links)
No description available.
7

Vibration isolation for rotorcraft using electrical actuation

Henderson, Jean-Paul January 2012 (has links)
The Active Control of Structural Response (ACSR) vibration suppression system, where hydraulic actuators located between the gearbox and the fuselage are used to cancel vibration in large helicopters, has been used successfully for many years. However the power consumed by the actuators can be high, and using hydraulic actuation for smaller rotorcraft has not been seen as practical. In contrast to active vibration reduction systems, passive vibration isolation systems require no external power. Passive vibration isolation systems however have the disadvantage of being limited to working at one specific frequency which will not be acceptable as slowed rotor flight becomes more common for fuel efficiency and noise legislation reasons. In this thesis two electrically powered actuation concepts, one piezoelectric, and one electromagnetic were initially evaluated. An electrically powered actively augmented passive, or hybrid, vibration reduction system based on an electro hydrostatic actuator (EHA) concept was proposed to be developed further. This hybrid actuator will have a wider range of operating frequencies than a purely passive system, and have lower power consumption than a purely active system. The design is termed a “Resonant EHA”; in that the resonant frequency of the coupled fluid, pump and electric motor rotor inertia matches the fundamental vibration frequency. The hydraulic cylinder, fluid and pump act as a single stage gear ratio, and the. brushless electric motor’s inertia is the main resonating mass as in a Dynamic Antiresonant Vibration Isolator (DAVI) passive vibration reduction system. The electrical power is used to compensate for friction in the actuator and other losses, and if needed can shift the operating point away from the resonant frequency. Simulation results indicated that a hydraulic circuit in which the pump leakage is fed back into the low pressure line would introduce unacceptable disturbances in the flows to and from the cylinder. To eliminate the source of the disturbances, a fully integrated electric motor and pump circuit design was chosen in which the electric motor is immersed in hydraulic fluid. An EHA demonstrator was built sized for a 1.5 tonne rotorcraft. For sizing comparison purposes the frameless brushless D.C motor for each strut of 1.5 tonne rotorcraft has a rotor and stator mass of approximately 1 kg, and can produce a continuous stall torque of 2 Nm. The bidirectional pump has a displacement of 1.5 cm3/rev, the mean system pressure was taken as 90 bar, and the double ended hydraulic cylinder has a 32 mm diameter bore, and 18 mm rod. Initial test results for the proof of concept EHA showed highly significant free play with a reversal of torque direction, resulting in unacceptable loss in transmission stiffness. The free play was traced to the gear pump and a hypothesis for the origin of the free play was put forward. To avoid torque reversals the EHA was further tested with a constant offset torque bias which proved successful in restoring a sufficient stiffness to the transmission. The sizing of the electric motor and power consumed with a non-zero offset torque is greater than a torque reversing motor, which limits the immediate application of the device in the present form. Future research investigating the use of other transmission elements, such as a piston pump, to obtain a more linear stiffness is recommended. As a hybrid vibration isolation system a Root Mean Square (RMS) reduction by a factor of four and near elimination of the fundamental frequency vibrations was achieved for the frequency range of 10 to 20 hertz.
8

Elektrisch-hydrostatische Kompaktantriebe mit Differentialzylinder für die industrielle Anwendung

Michel, Sebastian 13 October 2021 (has links)
Elektrisch-hydrostatische Kompaktantriebe (EKA) stellen ein innovatives, neuar-tiges Antriebskonzept dar, welches – ausgeführt als funktionsfertige Baugruppe – die Anwenderfreundlichkeit bei der Maschinenintegration, Inbetriebnahme und Wartung signifikant steigert. Elektrisch-hydrostatische Kompaktantriebe verbinden die inhärenten Vorteile hydraulischer Antriebstechnik wie beispiels-weise Robustheit, hohe Leistungsdichte und Überlastschutz mit Energieeffizi-enz, Ressourceneffizienz, Anwenderfreundlichkeit und geringem Bauraum. Auf-grund seines kompakten und kostengünstigen Aufbaus ist der Differentialzylin-der der mit Abstand am häufigsten eingesetzte Aktor bei hydraulischen Anwen-dungen. Die Herausforderung beim Einsatz eines Differentialzylinders im hyd-rostatischen Getriebe ist die Steuerung der asymmetrischen Volumenströme, die durch die einseitige Kolbenstange hervorgerufen werden. Die vorliegende Arbeit widmet sich der systematischen Entwicklung und Unter-suchung von Schaltungskonzepten, die sich für elektrisch-hydrostatische Kom-paktantriebe mit Differentialzylinder für die industrielle Anwendung eignen. Vor dem Hintergrund eines ressourcenschonenden und wirtschaftlichen Einsatzes der Antriebe werden Vorzugsvarianten ermittelt, die sowohl energie- als auch kosteneffizient sind. Das statische und dynamische Übertragungsverhalten so-wie die Energieeffizienz der ausgewählten Schaltungen werden auf der Grund-lage von praxisnahen Demonstratoren bestimmt. Die analytische und experi-mentelle Untersuchung der Vorzugsvarianten zeigt das Potential und die Gren-zen der Schaltungskonzepte für den industriellen Einsatz auf. Darüber hinaus wird der Vergleich mit elektromechanischen Kompaktantrieben im gleichen Leistungsbereich geführt, um die erzielten Ergebnisse in der Gegenüberstellung einordnen zu können. Um die Notwendigkeit einer aktiven Kühlung für potentielle Einsatzgebiete ohne aufwendige Experimente abschätzen zu können, werden zudem die Methoden der thermo-energetischen Netzwerksimulation auf elektrisch-hydrostatische Kompaktantriebe angewendet. Anhand eines Beispielantriebs wird ermittelt, mit welcher Genauigkeit das thermo-energetische Verhalten und die sich einstel-lende Beharrungstemperatur berechnet werden können.:1 Einleitung 1 2 Zielstellung der Arbeit 6 3 Stand der Forschung 8 3.1 Grundlagen 8 3.2 Hydrostatische Getriebe mit Gleichgangzylinder 10 3.2.1 Elektrisch-hydrostatische Aktuatoren (EHA) 11 3.3 Hydrostatische Getriebe mit Differentialzylinder 13 3.4 Thermo-energetische Analyse und Modellierung 24 4 Systematisierung der Schaltungsmöglichkeiten 27 4.1 Analyse typischer Anwendungen für EKA 27 4.2 Systematisierung der Lastfälle 27 4.3 Schaltungssystematik 29 4.4 Auswahl von Vorzugsvarianten 35 5 Einpumpenkonzept mit Ausgleichsventil 40 5.1 Aufbau und Funktionsweise 40 5.2 Demonstrator 43 5.3 Statisches Betriebsverhalten 46 5.4 Dynamisches Übertragungsverhalten 47 5.4.1 Dynamische Streckenkennwerte 47 5.4.2 Lastfallspezifisches dynamisches Verhalten 57 5.4.3 Dynamisches Verhalten bei dominanten Massekräften 60 5.5 Energieeffizienz 89 5.5.1 Elektrischer Antrieb 91 5.5.2 Hydrostatisches Getriebe 93 5.5.3 Gesamtantrieb 96 5.6 Fazit und Einsatzempfehlungen 97 6 Tandempumpenkonzept im offenen Kreis 99 6.1 Aufbau und Funktionsweise 99 6.2 Demonstrator 101 6.3 Statisches Übertragungsverhalten 102 6.4 Dynamisches Übertragungsverhalten 103 6.4.1 Dynamische Streckenkennwerte 103 6.4.2 Lastfallspezifisches dynamisches Verhalten 106 6.5 Energieeffizienz 109 6.5.1 Hydrostatisches Getriebe 109 6.5.2 Gesamtantrieb 111 6.6 Fazit und Einsatzempfehlungen 112 7 Untersuchung eines elektromechanischen Referenzantriebs 114 7.1 Bauarten, Eigenschaften und Einsatzgebiete elektromechanischer Linearantriebe 114 7.1.1 Übersetzung 117 7.1.2 Maximale Hubgeschwindigkeit 117 7.1.3 Maximale Hubkraft 117 7.1.4 Lebensdauer und Verschleiß 118 7.1.5 Wirkungsgrad 120 7.1.6 Steifigkeit 120 7.1.7 Fail-safe 121 7.2 Referenzantrieb 121 7.3 Statisches Übertragungsverhalten 122 7.4 Dynamisches Übertragungsverhalten 122 7.5 Energieeffizienz 123 7.5.1 Kugelgewindetrieb 123 7.5.2 Gesamtantrieb 124 8 Vergleich und Bewertung der Antriebssysteme 126 8.1 Statisches Übertragungsverhalten 126 8.2 Dynamisches Übertragungsverhalten 127 8.3 Energieeffizienz 128 8.4 Weiterführender Vergleich und Bewertung 129 9 Thermo-hydraulische Netzwerksimulation 134 9.1 Methodik 134 9.2 Grundlagen der Thermodynamik und Wärmeübertragung 135 9.2.1 Wärmeleitung 136 9.2.2 Konvektion 136 9.2.3 Wärmestrahlung 138 9.2.4 Wärmeübergang an Fugen zwischen Bauteilen 139 9.3 Analyse der Verlustleistungen 142 9.4 Analyse der Wärmeströme und thermischen Widerstände 145 9.4.1 Erzwungene Konvektion zwischen Öl und Innenfläche 146 9.4.2 Wärmeleitung in Festkörpern (Gehäuse) 147 9.4.3 Wärmeübergang an Fugen zwischen Bauteilen 147 9.4.4 Freie Konvektion an den Außenflächen 148 9.4.5 Wärmestrahlung an den Außenflächen 150 9.4.6 Zusammenfassung 151 9.5 Zulässige Öltemperatur des Antriebs 152 9.6 Thermo-hydraulisches Simulationsmodell des Demonstrators 152 9.7 Validierung 155 9.7.1 Vorbetrachtungen an einer Modellgeometrie 155 9.7.2 Prüfstandsaufbau und Versuchsparameter 157 9.7.3 Gegenüberstellung von Simulation und Messung 159 9.8 Sensitivitätsanalyse 162 9.8.1 Variation der Verlustleistung 163 9.8.2 Variation der Umgebungstemperatur 164 9.8.3 Variation des Korrekturfaktors für Umgebungsströmungen 165 9.9 Simulationsstudie zur Verbesserung des Wärmeabgabevermögens 166 9.10 Zusammenfassung 166 10 Zusammenfassung und Ausblick 168 11 Literaturverzeichnis 172 12 Anhang 194
9

A Complete Analysis for Pump Controlled Single Rod Actuators

Çalışkan, Hakan, Balkan, Tuna, Platin, Bülent E. 02 May 2016 (has links) (PDF)
In the current study a variable speed pump controlled hydrostatic circuit where an underlapped shuttle valve is utilized to compensate the unequal flow rate of a single rod actuator is analyzed. Parameters of the shuttle valve are included in the system analysis, rather than treating it as an ideal switching element as handled in literature. A linearized model of the system is obtained. An inverse kinematic model, which calculates the required pump drive speed for a desired actuator speed and given pilot pressure input, is formed. A numerical stability analysis program is developed, and the stability of all possible shuttle valve spool positons is determined. The theoretical findings are validated by non-linear simulation model responses.
10

Prediction of the thermo-energetic behaviour of an electrohydraulic compact drive

Michel, Sebastian, Weber, Jürgen 02 May 2016 (has links) (PDF)
Due to good energy-efficiency of electrohydraulic compact drives a cooling aggregate often is not installed. The operating temperature is governed by the complex interaction between dissipative heat input and passive heat output. This paper targets the simulation of the thermo-energetic behaviour of an electrohydraulic compact drive by means of a lumped parameter model in order to predict the operating temperature. The developed thermo-hydraulic model is validated against measurements utilising thermocouples and a thermographic camera to capture temperatures. The results show, that the presented methodology enables a satisfying accurate prediction of the thermo-energetic behaviour of electrohydraulic compact drives. A further analysis of simulation results is given, highlighting the power losses and heat rejection capabilities of different components. Finally, measures for the improvement of the heat rejection capabilities are studied.

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