817 research outputs found

    Improving Energy Efficiency and Motion Control in Load-Carrying Applications using Self-Contained Cylinders

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    Because of an increasing focus on environmental impact, including CO2 emissions and fluid spill pollution, inefficient hydraulic systems are being replaced by more environmentally friendly alternatives in several industries. For instance, in some offshore applications that have multiple diesel generators continuously running to produce electricity, all hydraulic rotating actuators supplied from a central hydraulic power unit have been replaced with AC induction motors containing a variable frequency drive and gearbox. However, hydraulic linear actuators are still needed in most load-carrying applications mainly because of their high reliability associated with external impact shocks. Moreover, their force capacity is higher than that of their linear electromechanical counterparts. Valve-controlled linear actuators (cylinders) supplied from a centralized hydraulic power unit are standard in offshore load-carrying applications. In addition to the advantages mentioned above of hydraulic linear actuators, they have, nevertheless, a number of important drawbacks, which include: 1) a high level of energy consumption due to significant power losses caused by flow throttling in both the pipelines and valves, 2) reduced motion performance due to the influence of load-holding valves, 3) high CO2 emissions and fuel costs related to the diesel generator that supplies electricity to the hydraulic power unit, 4) significant potential for hydraulic fluid leakage because of many leakage points, 5) demanding efforts with respect to installation and maintenance, as well as 6) costly piping due to the centralized hydraulic power supply. The work presented in this dissertation and the appended papers are devoted to replacing inefficient hydraulic linear actuation systems traditionally used in offshore load-carrying applications with more environmentally friendly solutions. Two alternative technologies are identified, namely electro-mechanical and electro-hydraulic self-contained cylinders. The feasibility of replacing conventional valve-controlled cylinders with self-contained cylinder concepts is investigated in two relevant case studies.publishedVersio

    Improved modelling and driving of hydraulic asymmetric cylinders systems

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    Asymmetric and symmetric cylinder drives are the major actuators for hydraulic linear motion control applications. The asymmetric type is the most popular one and can be found in various areas, industrial, civil and even aerospace. Its compact design in structure and high power to weight ratio are highlighted, but nonlinear behaviours are found in these applications. An asymmetric cylinder is usually controlled by a symmetric ported control valve, which introduces difficulty in the motion control of the cylinder. To avoid such issue, symmetric cylinder drives are typically chosen for high-performance dynamic response applications. This thesis focusses at improving the modelling and driving of the asymmetric cylinder drive system.The major nonlinearities in asymmetric cylinder systems occur when the control valve crosses its null position, causing pressure jumps, and system parameters switching to new values. In this scenario, the system is usually operating at low speed, in which the friction influence is an important factor. In addition, energy efficiency is always a concern in hydraulic applications, a valve-controlled asymmetric cylinder drive can have better controllability than a pump-controlled system, but its energy efficiency is worse than the latter. The aims of this research are to:•Improve modelling of asymmetric cylinder drive systems.•Improve the driving of asymmetric cylinder systems at low speed and velocity reversal with friction consideration.•Combine the advantages of a valve-controlled and a pump-controlled asymmetric cylinder drive system for energy efficiency purpose.A detailed analysis of a valve-controlled asymmetric cylinder system is carried out, and the nonlinearities behaviours are investigated in structure and theory aspects. The simulation modelling in this thesis reveals the system performances when the control valve travels across its null position, and this process is simulated with a numerical solution. An analytical solution is developed, showing that the new analytical solution runs 200 times faster than the original numerical method in simulation. Friction is inevitable in any device and it plays an important role in hydraulic nonlinearities, especially when the system runs at low speed and velocity reversal. Existing friction models are investigated and reviewed, but limited friction models considered the pressure influence in hydraulics. A new friction model for hydraulic system is developed on current LuGre model. This new friction model includes pressure term, acceleration term and velocity term. The new friction model is validated by experimental results and improvements are demonstrated.Under the consideration of energy efficiency, functionality, cost and feasibilities, a hybrid pump-controlled asymmetric cylinder system that combines the merits of a valve-controlled system and a pump-controlled system is implemented. Its pros and cons are investigated and analysed. Its simulation model is built to aid further analysis of the existing nonlinearities.Comparing the simulation results of the hybrid pump-controlled asymmetric cylinder system with the valve-controlled asymmetric cylinder system, the energy efficiency of the hybrid pump-controlled system is 20% better and can be further optimised. The various experimental results validate the simulation model of the hybrid system. Therefore, the functionality and feasibility of the energy efficient design of the hybrid pump-controlled system are validated.The design circuit of the hybrid pump-controlled asymmetric cylinder system is not fully optimised, and improvements can be achieved in future works including replacing the pilot shifted four-way valve with a solenoid valve, adding accumulators to stabilise the pressure in the service line and adding a controller to optimise the system performance.</div

    Robust Control Design of an Electro-Hydraulic Actuator

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    A Self-Contained Cylinder Drive with Indirectly Controlled Hydraulic Lock

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    This paper presents a self-contained pump-controlled hydraulic linear drive including an innovative load holding sub-circuit. For safety critical applications such as crane manipulators, locking valves or load holding valves are enforced by legislation, but the load holding functionality may also be used actively to decrease the energy consumption for applications where the load is kept stationary for longer periods of time. The system proposed in this paper is based on a simple hydraulic architecture using two variable-speed electric motors each connected to a fixed-displacement pump. This architecture is well-known in academic literature, but in this paper a novel load holding sub-circuit has been included. To control this load holding functionality, the low chamber pressure needs to be controlled accurately, while still being able to control the motion of the cylinder piston as well. Due to strong cross-couplings between cylinder piston motion and chamber pressures this task is non-trivial. The control for opening the locking valves is indirect in the sense that it is controlled via the chamber pressures, which are actively controlled. The fundamental control strategy presented in this paper is based on transforming the highly coupled physical states to virtual states, significantly reducing cross-couplings.publishedVersio

    Volume 3 – Conference

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    We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit

    An electro-hydraulic servo with intelligent control strategy

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    Versatile engineering applications have been developed to assist, reduce, and avoid human being from any heavy or harmful manufacturing processes. The gradually increased demand in force and position controls have simultaneously increased the usage of Electro-Hydraulic Servo (EHS) system. However, the time varying characteristics such as high-speed, outburst starting and stopping dynamic have led the EHS system to suffer from uncertainties and nonlinearities effects. Therefore, in order to enhance the performance of an EHS to surmount the uncertain and nonlinear effects, a hybrid Fuzzy-PID control strategy is developed which particularly improve the accuracy of the system by enhancing the control performance during the positioning tracking. By measuring the performance of the proposed control approach, the transient response and steady-state analysis will be performed which taking linear and intelligent control strategies as the references in the assessment process. The finding indicates the capability of a hybrid Fuzzy-PID controller in reducing the control effort applied to the EHS system

    Volume 2 – Conference: Wednesday, March 9

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    10. Internationales Fluidtechnisches Kolloquium:Group 1 | 2: Novel System Structures Group 3 | 5: Pumps Group 4: Thermal Behaviour Group 6: Industrial Hydraulic

    Volume 1 – Symposium

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    We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group A: Materials Group B: System design & integration Group C: Novel system solutions Group D: Additive manufacturing Group E: Components Group F: Intelligent control Group G: Fluids Group H | K: Pumps Group I | L: Mobile applications Group J: Fundamental
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