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

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

System Configuration and Control Using Hydraulic Transformer

University of Minnesota Ph.D. dissertation. May 2018. Major: Mechanical Engineering. Advisor: Perry Li. 1 computer file (PDF); xii, 294 pages.Hydraulic power transmission offers multiple benefits over competing technologies including an order of magnitude higher power density than electric systems, relatively low cost, fast response, and flexible packaging. Hydraulics are often used in high-performance mobile robots that demand power, precision, and compactness. However, typical hydraulic systems suffer from low system efficiency from the wide usage of throttle valves. The research described in this dissertation focuses on developing hydraulic transformers that transforms hydraulic power from one set of pressure and flow to the other set of pressure and flow to replace throttle valves such that a compact and efficient fluid power system can be realized. A dynamic model capable of capturing operating characteristics and losses is developed to establish a quantitative comparison between two major designs of the hydraulic transformer. A traditional design where a pump and motor are coupled together in a single package is chosen for the research. This design has three possible configurations with unique operating characteristics, and if these configuration modes can be switched, the resulting transformer is shown to be more compact and efficient. A trajectory tracking controller for a cylinder and force controller for a hydraulic human power amplifier is developed to demonstrate potential applications for the hydraulic transformer. The controller developed proves that utilizing hydraulic transformer need not sacrifice the control performance. Control methodologies ensuring efficiency of the transformer driven system are developed. Transformer operating speed is optimized to minimize the power loss through the transformer. Transformer configuration is switched actively to operate the transformer in its most optimal mode. These methods further improve the efficiency benefit of using the transformer. A hydraulic transformer system utilizing developed controllers compared against a throttle valve system tracking a trajectory with various loading conditions reveals that transformer system can achieve an efficiency of 81.2% which is more than threefold increase over the throttling system with an efficiency of 26.2%. This efficiency improvement is possible with the ability of a transformer to capture regenerative energy to reduce the net energy consumption. This dissertation successfully presents the controller development for a hydraulic transformer that captures both precision and efficiency

Volume 1 – Symposium: Tuesday, March 8

Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Components:Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Component

Inlet metering pump analysis and experimental evaluation with application for flow control

Dr. Roger Fales, Dissertation Supervisor.Field of study: Mechanical and aerospace engineering.Includes vita."December 2017."Axial piston pumps with variable volumetric displacement are often used to control flow and pressure in hydraulic systems. The displacement control mechanism in these pumps occupies significant space and accounts for significant cost in the pump design. Fixed displacement pumps have lower cost and a more compact design but suffer from significant energy consumption disadvantage due to the need for flow and pressure control by throttling flow and bypassing unused flow to pressures below the discharge pressure. An inlet metering valve (IMV) controlled pump marks a recent development in pumping technology for hydraulic systems. In this design, an inlet metering valve restricts inlet flow reducing inlet pressure so that the specific volume of the fluid is increased as it enters a fixed displacement pump. By altering the specific volume of the working fluid, the inlet metering valve permits precise control over the pump discharge flow. This study presents a theoretical model for inlet metering pump efficiency. The work considers additional sources of energy loss unique to the inlet metering system. Experimental results associated with inlet metering pump efficiency are presented. A comparison of the theoretical model and the experimental results is also included. It is determined that the current efficiency model accurately predicts efficiencies determined using experimental data. In addition, a velocity control system is considered which utilizes the inlet metering valve controlled pump. The stability and the performance of the velocity control system were studied for the open-loop and the closed-loop with a PID, H[infinity symbol], and a two degrees of freedom controllers. The simulation showed that the velocity control system is stable and has good performance characteristics.Includes bibliographical references (pages 112-122)

Using Digital Hydraulics in Secondary Control of Motor Drive

Due to the increased focus on pollution and global warming, there is a demand for energy efficient systems. This also applies to the offshore oil and gas industry. Normally used hydraulic systems tend to suffer from low energy efficiency, especially when operating with part loads. In the last decades, a new pump and motor technology has experienced increased interest due to the potential of high energy efficiency in a wide range of operation conditions. This new technology is called digital displacement machine technology. Nowadays, there is a desire from the offshore oil and gas industry to use this digital displacement machine technology to design highly efficient hydraulic winch drive systems. The main objectives of the work presented in this thesis are to design a controller for a digital displacement winch drive system and evaluate its control performance. The design of a controller is one part of the work needed to realizing a winch drive system with digital displacement machines. A winch with a lifting capacity of 20000 kg and a drum capacity of 3600 m of wire rope is used as a case study. Digital displacement machines have strict requirements for the on/off valves used to control each cylinder chamber. It is important to activate the valves at optimal times to ensure operation with high energy efficiency and low pressure and flow peaks. Only a small mistiming of the valves will affect the performance of the digital displacement machine significantly. One of the first contributions presented in this thesis is a method for defining how early or late the valves can be timed without reducing the energy efficiency significantly. The control of digital displacement machines is complicated and non-conventional. Each cylinder can be controlled individually and multiple displacement strategies can be used to achieve the same displacement. Each displacement strategy has its dynamic response characteristics and energy efficiency characteristics. The dynamic response characteristics of the drive system are highly relevant when designing control systems. Therefore, in addition to the conventional classical controller, also a suitable displacement strategy must be designed. Designing controllers for digital displacement machines are therefore more complex than designing controllers for conventional hydraulic machines. One of the main focuses of this project has been to analyze the transient and steady state response characteristics of different displacement strategies. In all, three displacement strategies are examined: full stroke displacement strategy, partial stroke displacement strategy and sequential partial stroke displacement strategy. Also, during this work, a new version of the partial stroke displacement strategy has been developed and included in the dynamic response analysis. The dynamic response analysis is a simulation study, where the simulation model is experimentally validated. The experimental work is conducted on a prototype of a single cylinder digital displacement machine. The prototype consists of a five cylinder radial piston motor where one cylinder is modified to operate with the digital displacement technology. The rest of the cylinders are not changed and not used. In addition to validating the simulation model, the prototype is used to test all of the analyzed displacement strategies in low speed operation. The results from the dynamic response analysis are used to select the displacement strategy that is most suited for use in a winch drive system. Then, controllers for the digital displacement winch drive system are developed. The main focus in the control design phase is not to design a new type of controller but to examine already developed controllers and fit them to a winch system driven by digital displacement machines. In the end, the simulation results of the designed controllers are shown and the results are discussed. The simulation results show that digital displacement machines can be used in winch drive systems and achieve both high motion control performance and wire tension control performance.publishedVersio

Volume 1 – Symposium

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

Smart Flow Control Processes in Micro Scale

In recent years, microfluidic devices with a large surface-to-volume ratio have witnessed rapid development, allowing them to be successfully utilized in many engineering applications. A smart control process has been proposed for many years, while many new innovations and enabling technologies have been developed for smart flow control, especially concerning “smart flow control” at the microscale. This Special Issue aims to highlight the current research trends related to this topic, presenting a collection of 33 papers from leading scholars in this field. Among these include studies and demonstrations of flow characteristics in pumps or valves as well as dynamic performance in roiling mill systems or jet systems to the optimal design of special components in smart control systems

Volume 2 – Conference: Wednesday, March 9

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