Modiciency - Efficient industrial hydraulic drives through independent metering using optimal operating modes

Independent metering poses a possibility to improve energy efficiency of throttlecontrolled hydraulic single-rod cylinder drives. This paper deals with energetic potentials gained through variable circuitry that come along with independent metering. A method to assess energetic potentials is described, based on load specific, optimal operating modes. As a means of yielding maximum energy efficiency for a wide range of applications, a smooth mode switching algorithm that minimizes losses and allows good motion tracking is proposed. The mode switching algorithm is validated in simulation and on a test stand

Bootstrap reservoir concepts for electro-hydraulic compact cylinder drives

This paper presents a conceptual study aiming to improve the compactness of electro-hydraulic compact drives (ECD ). In most current ECD architectures, gas accumulators are used as volume compensators for the flow imbalance emerging whenever asymmetric single rod cylinders are used. To stay within a required reservoir pressure range typically from two to four bar, a large gas volume is required, compromising system compactness. Combining conventional ECD architectures with a bootstrap reservoir offers a greater degree of freedom in system design, which enables downsizing or avoidance of the gas volume. Another potential benefit by including a bootstrap reservoir is the possibility of elevating the backpressure of the ECD thus enhancing drive stiffness, expanding the application range and market acceptance. Based on an open analysis of the solution space occurring when introducing a bootstrap reservoir, three system architectures are selected for a conceptual study. The results show that the downsizing potential is strongly dependent on the maximum friction force and the area ratio of the bootstrap reservoir pistons, while a linear analysis reveals that for some system architectures the bootstrap reservoir may severely influence the system dynamics. Simulation results confirm the functionality of the proposed system architectures, and show that a potential for downsizing/avoiding the gas volume, as well as increasing the ECD stiffness is present

Novel System Architectures by Individual Drives

Measures of individualization and integration offer a great potential for further development and optimization in hydraulic drive technology. Advantages are seen especially for energy efficiency and functionality. These potentials motivate current research activities for displacement controlled systems and for valve controlled structures. For the latter, the focus lies on strategies of independent metering. Furthermore, expected challenges for the future are discussed

Elektrohydrostatische Kompaktantriebe mit adaptiver Übersetzung durch diskrete Strukturumschaltung

Hydrostatische Zylinderantriebe mit drehzahlvariablem Pumpenantrieb stellen modulare translatorische Antriebssysteme dar, die die Vorteile der elektrome-chanischen und hydraulischen Domänen verbinden. Zusätzlich bieten diese sog. elektrohydrostatischen Kompaktantriebe den Vorteil einer einfach umsetzbaren, diskret variablen Übersetzung. Diese erlaubt es, bei Arbeitsspielen mit dedizierten Eil- und Kraftphasen den elektrischen Antriebsmotor kleiner auszulegen als bei einer Referenz mit fester Übersetzung. Dadurch kann Downsizing-Potential in Bezug auf Größe und Masse des elektrischen Antriebsmotors und der Leistungselektronik erschlossen werden. In der vorliegenden Arbeit werden zunächst die möglichen Ersparnisse durch diese Technologie beleuchtet und die prinzipiellen Möglichkeiten einer schaltbaren Übersetzung dargestellt. Es wird eine Methodik erarbeitet, die es erlaubt, den gesamten Lösungsraum diskret umschaltbarer elektrohydrostatischer Kompaktantriebe systematisch zu erfassen und zu bewerten. Schließlich werden anhand von zwei Demonstratoren die Grenzen und Potentiale der Technologie experimentell untersucht und unterschiedliche, im Rahmen der Arbeit erarbeitete Strategien für den Umschaltvorgang zwischen zwei Übersetzungsstufen validiert.Hydrostatic cylinder drives with variable speed pumps pose a modern form of modular translational drive systems, which merge the benefits of both electro-mechanic and hydraulic domains. Beyond that, these so called electrohydrostatic compact drives feature a possibility of implementing a discrete variable trans-ission ratio in a cost-effective manner. In the case of work cycles with dedicated rapid and force strokes, this allows the electric drive motor to be designed smaller than in the case of a reference with a fixed transmission ratio. In this way, downsizing potential can be exploited in terms of the size and mass of the electric drive motor and power electronics. In this thesis, the possible gains through this technology are first examined and the fundamental possibilities of a variable transmission are presented. A methodology is developed that allows the entire solution space of discretely switchable electrohydrostatic compact drives to be systematically mapped and evaluated. Finally, the limits and potentials of the technology are investigated experimentally by means of two demonstrators, and different strategies for the switching process between two transmission stages developed in the course of the thesis are validated

Elektrohydrostatische Kompaktantriebe mit adaptiver Übersetzung durch diskrete Strukturumschaltung

Hydrostatische Zylinderantriebe mit drehzahlvariablem Pumpenantrieb stellen modulare translatorische Antriebssysteme dar, die die Vorteile der elektrome-chanischen und hydraulischen Domänen verbinden. Zusätzlich bieten diese sog. elektrohydrostatischen Kompaktantriebe den Vorteil einer einfach umsetzbaren, diskret variablen Übersetzung. Diese erlaubt es, bei Arbeitsspielen mit dedizierten Eil- und Kraftphasen den elektrischen Antriebsmotor kleiner auszulegen als bei einer Referenz mit fester Übersetzung. Dadurch kann Downsizing-Potential in Bezug auf Größe und Masse des elektrischen Antriebsmotors und der Leistungselektronik erschlossen werden. In der vorliegenden Arbeit werden zunächst die möglichen Ersparnisse durch diese Technologie beleuchtet und die prinzipiellen Möglichkeiten einer schaltbaren Übersetzung dargestellt. Es wird eine Methodik erarbeitet, die es erlaubt, den gesamten Lösungsraum diskret umschaltbarer elektrohydrostatischer Kompaktantriebe systematisch zu erfassen und zu bewerten. Schließlich werden anhand von zwei Demonstratoren die Grenzen und Potentiale der Technologie experimentell untersucht und unterschiedliche, im Rahmen der Arbeit erarbeitete Strategien für den Umschaltvorgang zwischen zwei Übersetzungsstufen validiert.Hydrostatic cylinder drives with variable speed pumps pose a modern form of modular translational drive systems, which merge the benefits of both electro-mechanic and hydraulic domains. Beyond that, these so called electrohydrostatic compact drives feature a possibility of implementing a discrete variable trans-ission ratio in a cost-effective manner. In the case of work cycles with dedicated rapid and force strokes, this allows the electric drive motor to be designed smaller than in the case of a reference with a fixed transmission ratio. In this way, downsizing potential can be exploited in terms of the size and mass of the electric drive motor and power electronics. In this thesis, the possible gains through this technology are first examined and the fundamental possibilities of a variable transmission are presented. A methodology is developed that allows the entire solution space of discretely switchable electrohydrostatic compact drives to be systematically mapped and evaluated. Finally, the limits and potentials of the technology are investigated experimentally by means of two demonstrators, and different strategies for the switching process between two transmission stages developed in the course of the thesis are validated

Electro-hydrostatic compact drives with variable transmission ratio

Electro-hydrostatic compact drives are an emerging technology within a range of industrially available translational drive solutions, combining the specific advantages of hydraulic and electromechanical screw drives. Compared to electromechanical screw drives, hydrostatic drives can vary their transmission ratio with comparably little effort, giving them the key advantage of downsizing the electric drive components for a given load cycle. This paper provides a guideline on how to calculate the downsizing potential of electric motors and inverters arising from variable transmission ratio based on the load regime of a given application. Furthermore, a comprehensive systematisation of the actual switching process is described for systems that are switched by means of switching valves. The presented set of methodology is applied to demonstrators in order to validate the general findings

Modiciency - Efficient industrial hydraulic drives through independent metering using optimal operating modes

Independent metering poses a possibility to improve energy efficiency of throttlecontrolled hydraulic single-rod cylinder drives. This paper deals with energetic potentials gained through variable circuitry that come along with independent metering. A method to assess energetic potentials is described, based on load specific, optimal operating modes. As a means of yielding maximum energy efficiency for a wide range of applications, a smooth mode switching algorithm that minimizes losses and allows good motion tracking is proposed. The mode switching algorithm is validated in simulation and on a test stand

Bootstrap Reservoir Concept for Electro-Hydraulic Compact Drives

This paper presents a conceptual study aiming to improve the compactness of electro-hydraulic compact drives (ECD ). In most current ECD architectures, gas accumulators are used as volume compensators for the flow imbalance emerging whenever asymmetric single rod cylinders are used. To stay within a required reservoir pressure range typically from two to four bar, a large gas volume is required, compromising system compactness. Combining conventional ECD architectures with a bootstrap reservoir offers a greater degree of freedom in system design, which enables downsizing or avoidance of the gas volume. Another potential benefit by including a bootstrap reservoir is the possibility of elevating the backpressure of the ECD thus enhancing drive stiffness, expanding the application range and market acceptance. Based on an open analysis of the solution space occurring when introducing a bootstrap reservoir, three system architectures are selected for a conceptual study. The results show that the downsizing potential is strongly dependent on the maximum friction force and the area ratio of the bootstrap reservoir pistons, while a linear analysis reveals that for some system architectures the bootstrap reservoir may severely influence the system dynamics. Simulation results confirm the functionality of the proposed system architectures, and show that a potential for downsizing/avoiding the gas volume, as well as increasing the ECD stiffness is present

Novel System Architectures by Individual Drives

Measures of individualization and integration offer a great potential for further development and optimization in hydraulic drive technology. Advantages are seen especially for energy efficiency and functionality. These potentials motivate current research activities for displacement controlled systems and for valve controlled structures. For the latter, the focus lies on strategies of independent metering. Furthermore, expected challenges for the future are discussed

Novel System Architectures by Individual Drives

Measures of individualization and integration offer a great potential for further development and optimization in hydraulic drive technology. Advantages are seen especially for energy efficiency and functionality. These potentials motivate current research activities for displacement controlled systems and for valve controlled structures. For the latter, the focus lies on strategies of independent metering. Furthermore, expected challenges for the future are discussed