Four quadrant multi pump-motor
Digital pump/motors, broadly characterized as using discrete valves to control the fluid entering and leaving the displacement chamber in positive displacement machines, have been the subject of multiple research groups and industry over the past two decades. In general, the goals include improving the efficiency, particularly at reduced displacements in variable displacement units, and increased control capabilities. This presentation will provide a brief overview of digital pump/motors followed by the progression of research at Purdue University leading to a mechanically controlled pump/motor able to pump and motor each in a clockwise or counterclockwise rotation (four quadrant) and capable of pumping oil, water, and corrosive fluids. Similar to most digital pump/motor configurations the internal losses scale with displacement, and the pump/motor maintains its efficiency at low displacements relative to currently available units. The displacement can be controlled using simple mechanical motion and low forces, multiple fluids can be used (depends on piston sealing gap configuration), and the mechanically based fluid-control system is adaptable to radial, in‐line, and axial pump/motor configurations.

Dr. John Lumkes, Jr is the Assistant Dean & Associate Director, Office of Academic Programs, in the College of Agriculture, and Professor of Agricultural and Biological Engineering at Purdue University. Dr. Lumkes received his Ph.D. from the University of Wisconsin in 1997. His Ph.D. research was the design and implementation of a control system for a hydraulic hybrid vehicle. His current work focuses on agricultural automation, fluid power, innovation and design, multi-domain modeling of dynamic systems, and mechatronics. He has published over 80 journal and conference articles related to his research and educational activities; in 2002 he published a textbook titled “Control Strategies for Dynamic Systems.” Dr. Lumkes has facilitated international exchange activities in Africa, Brazil, and China for Purdue students, and since 2009 has mentored over 200 undergraduate students on international design projects. He has been internationally recognized for his research, teaching, mentoring, and service learning activities.

Numerical and experimental analyses of vane and piston pumps
The main sources of power loss in Fluid Power are related to leakage flows, incomplete filling of the pumping volume and not optimized geometry of components. With reference to the positive displacement machines (mainly axial piston, gerotor and vane units), the behavior of the flux inside the component affects overall performance causing the onset of unwanted issues such as vanes detachment due to a not well designed timing of the pump, a not complete filling of the variable chamber volume and cavitation phenomena. Even valves could be affected by some of those issues as example, a not optimized spool/body geometries could cause cavitation and undesired flow forces and torques with consequence on their performances. In order to study all above mentioned phenomena, accurate fluid-dynamic models are needed; for these reasons the Fluid Power Research Group (FPRG) of the University of Naples “Federico II” is born to create numerical simulation models of both pumps and valves. Details of those numerical approaches are shown, with some hints on the experimental efforts done for the validation of all the main assumptions made in the numerical models.

Dr. Emma Frosina is an Assistant Professor at the Department of Industrial Engineering of the University of Naples “Federico II” since July 2017. She received the Ph.D. at the same university on June 2016 with a research entitled: “A CFD Approach to the Optimization of Components in Fluid Power”. Her current works focus on the modeling and optimization of fluid power components (machines, valves, etc.) using numerical approaches both lumped parameter and three-dimensional CFD. Dr. Frosina is author of more than 30 journal and conference articles related to her research and educational activities. She and prof. Adolfo Senatore, full professor at the University of Naples, manage the Fluid Power Research Center mentoring many Ph.D., graduate and undergraduate students.

Modeling, improving, and scaling of lubricating interfaces in axial piston machines
Thanks to its superior power density, flexible connection, and dynamic controllability, the fluid power (FP) system is commonly used to transmit and control mechanical power. In modern FP systems (e.g. displacement control systems, hydrostatic transmissions, and electro-hydraulic actuators), the energy efficiency and the life expediency of pumps and motors are emphasized. Among different types of positive displacement units, axial piston machines (APMs) are ideal for aerospace, industrial, agricultural, and off-road vehicle applications due to their high-pressure operation capability, contact-free design, and fast displacement control. For each APM, the friction and leakage of its lubricating interfaces (LIs) determine its overall performance. In this presentation, an LI performance prediction tool will be discussed ― specifically, the presentation will focus on the numerical simulation of elasto-hydrodynamic (EHL) pressure distribution in the gap flow, the temperature distribution in the non-isothermal compressible fluid and its surrounding structure, and the interactions between pressure, temperature, deformations, and fluid properties. The validation of the model will also be discussed. Using the results of this sophisticated and accurate simulation tool, and the understanding of the fluid-structure interaction of the LIs that those results bring to light, design improvements are proposed to reduce the power loss of APM by smartly utilizing component deformation to allow the surfaces forming the LI to adapt to the operating condition. The simulation tool is also used to understand the scaling criteria of the LIs, and, to propose a scaling guideline for APM which allows the hydrostatic pump and motor manufacture to scale its existing unit to other sizes without an expensive redesigning process.

Dr. Lizhi Shang is a post-doctoral research assistant at Maha fluid power research center. He received this B.S. from Huazhong University of science and technology in June 2011. In fall of 2011, he began as a master student in New Jersey Institute of technology. In Summer of 2012, he joined Maha fluid power research center for two months as a visiting student. He officially became a graduate student at Maha fluid power research center at Purdue University since January 2013 under the supervision of Dr. Monika Ivantysynova. His research focus was studying the scaling of axial piston pumps and motors. He successfully defended his Ph.D. in November 2018.

Unusual aspects to be considered in the simulation of positive displacement machines
The simulation of positive displacement machines can be performed with very different levels of detail. The presentation reports real cases of pumps studied at the Politecnico di Torino over the years, where some phenomena, normally neglected in the simulation of those types of machine, have a strong importance on the results.More in details, the effect of the centrifugal force on the oil in the variable volume chambers and the influence of the elastic deformation of the components on the pump performances are described.
The first phenomenon can induce a worsening of the filling at high speed if the flow area of the variable chambers is increased. A validated CFD simulation has demonstrated that in some cases the feeding of the chambers from both sides or the radial feeding can be detrimental for the volumetric efficiency.
The deformation of the mechanical components, such as the port plate or even the cover in gerotor and vane pumps, is the main source of improvement or worsening of the volumetric efficiency, but even with an influence on the pressure ripple. Moreover the elastic deformation of the stator assembly can have an appreciable effect on the timing and on the displacement.
Although the presented studies refer to very specific units, the outcomes can represent an interesting food of thought for those who are involved in simulation of fluid power machines.

Massimo Rundo
Graduated in Mechanical Engineering at the Politecnico di Torino in 1996. After graduation he participated, as visiting researcher at the Fluid Power Research Laboratory of the Politecnico di Torino, to extensive research projects on lubricating pumps for internal combustion engines. In 2005 he joined the Faculty as assistant professor. He is currently lecturer of the M.Sc. courses of Fluid Power and Automotive Fluid Power Systems. His research activity is mainly focused on modelling, simulation and testing of fluid power components.

A model-based approach for the evaluation of noise emissions in external gear pumps
Noise emissions are one of the most known detrimental aspects of fluid power technology, and a limiting factor for many applications. The pump is a crucial element as concerns the generation of noise and vibration in a hydraulic system; moreover, it is now a common practice to consider port flow oscillations as main source of fluid borne noise. However, methods for simulating the transfer path from the fluid borne noise sources to the actual airborne noise, depending on the pump architecture, are still incomplete. Moreover, current literature often does not consider some important sources of noise, at both fluid-borne and structure-borne noise level. In this regard, taking the case of external gear pumps as reference, a simulation method to predict the actual airborne noise starting from the main noise sources is presented. A fluid dynamic model, HYGESim, previously developed at the Maha Fluid Power Research Center for the simulation of the main flow through external gear pumps is used to evaluate the instantaneous pressures within the internal fluid domain of the unit. These pressures are used as internal load functions applied to the internal parts of the pumps. A finite element model (FEM) and a boundary element model (BEM) are properly combined, to perform the vibro-acoustic analysis of the pump. In this way, all fluid-borne and structure-borne noise sources are properly considered for the estimation of the actual air-borne noise. The model is validated through comparisons between the simulated and the measured sound pressure levels (SPLs) and sound power levels (SWLs). For this purpose, a test campaign was performed by utilizing a semi-anechoic chamber. The results presented in the paper illustrate the potential of the proposed approach to predict the actual noise emissions of an external gear pump. Relevance is given to the important effect of the pump mounting on the overall emitted noise, as well as the features of noise directionality.

Sangbeom Woo is a Ph.D. student in the Mechanical Engineering department at Purdue University and working as a research assistant at the Maha Fluid Power Research Center. He received his B.S. in 2013 and M.S. in 2015 in mechanical engineering at Yonsei University, South Korea. During his master studies, he conducted the research on physical and engineering acoustics in relation to such areas as noise/vibration/harshness, acoustical holography, and active noise control. His current research focuses on reduction of noise and vibration in hydraulic pumps.

A review on axial piston pump technologies
In this talk, the author will identify the design parameters that have the greatest impact on the bandwidth frequency of a pressure controlled, axial-piston, swash-plate type pump. This study is motivated by the fact that a physical limitation for these machines has been observed in practice, as it has been difficult to increase the bandwidth frequency much beyond 25 Hz. Though much research has been done over the past thirty years to understand the dynamical behavior of these machines, the essential design-characteristics that determine the bandwidth frequency of the pump remain elusive. In part, this is due to the fact that the machine is complex and when coupled with a hydraulic control valve that is disturbed by steady and transient fluid-momentum effects this dynamical property becomes difficult to assess. In this presentation, a comprehensive model for the pressure controlled, axial piston machine will be presented including the dynamic components of the pump and the control valve. The pump model includes the effects of the discrete pumping-elements acting on the swash plate, while the valve model includes both steady and transient fluid-momentum forces. To identify the dominate features of the model, nondimensional analysis is employed and the complexity of the model is subsequently reduced by eliminating negligible terms. Furthermore, a closed-form expression for the bandwidth frequency is employed and perturbation analysis is used to identify the dominant set of parameters that impact the bandwidth frequency of the pump. In conclusion, it is shown that, by far, the greatest impact on the bandwidth frequency may be achieved by reducing the swept volume of the control actuator and by increasing the flow capacity of the control valve.

Noah D. Manring is the Glen A. Barton Professor of fluid power in the Mechanical and Aerospace Engineering Department at the University of Missouri. He holds 11 U.S. patents for innovations in the field of fluid power. As a professor, he has received research funding from Caterpillar Inc., Festo Corp. and the National Fluid Power Association, as well as from the Department of Education, the National Science Foundation and various private donors. He has additionally done consulting work for several industrial firms, including Moog Inc., FMC Wyoming Corp., Dennison Hydraulics and Parker Hannifin. Manring published two textbooks, Hydraulic Control Systems and Fluid Power Pumps and Motors. Before joining the MU faculty, Manring worked for eight years in the off-highway mobile equipment industry.

Energy efficiency and autonomy in off-road vehicles in future worksites
Innovative hydraulics and automation in Tampere University (TAU) has been studied energy efficiency and remote or autonomous off-road vehicles during the last three decades. This research is highly related to work for Professor Monika Ivantysynova.
Future worksites will be occupied by different level of automation work machines. How these machines are working individually and how a fleet of these machines cooperates is discussed. The ways of saving energy and how the autonomy in these machines is achievable is described and defined in the presentation.
The required control strategies, sensors, and algorithms for operating with autonomous wheel loader are studied and presented in the paper. The control strategy is consisting of e.g. static and dynamic mapping, path planning, obstacle observation and avoidance. In the autonomous machines and also in machines where operator assistance system is active the situational awareness is the key research field. How we are sensing the surroundings of the machine with the today’s sensors is presented in the paper.
Power management and energy efficiency in hydraulic work machines are still active fields of research. Multiple architectures and configurations have been suggested concerning this field. In addition, implemented solutions that consider an entire machine are rarely presented. This presentation introduces the research work of the control system which is minimizing the fuel consumption. Compared to traditional controls, the new methods both reduce the fuel consumption and extend the operating range of a machine.

Professor Kalevi Huhtala is leading the fluid power research in Tampere University. The Fluid power research team consists of five professors and total staff of 40. He is graduated from Tampere University of technology in 1996. Title of his doctor thesis is “Modelling of Hydrostatic Transmission - Steady-State, Linear and Non-Linear Models”. The nomination of professorship took place in 2003. The research field of the professorship is hydraulics in mobile machines. His main research interests are autonomous mobile machines. He has supervised over 10 doctoral theses and over 100 master theses. He has several scientific publications. He has been member of scientific program committees of conferences in Aachen, Dresden, Linz, Hangzhou, Linköping and Tampere.

Fully 3-D printed soft actuator characterization
Additive manufacturing is an enabling technology that is rapidly advancing with the development of new printers, materials, and processes. The purpose of this research was to design a part that could function similar to a pneumatic piston-cylinder producing small force outputs between 5 and 10 N. The research presented in this paper looks at various types of 3D printing methods to produce flexible linear bellows actuators to achieve this functionality. In particular, stereolithography, fused deposition modeling, digital light processing, and Polyjet printing were examined to produce a variety of test actuators. A successful flexible part was designed and produced using Polyjet printing, the steady state and dynamic responses of constructed actuators were measured and characterized at various loading conditions. The displacement trends at different load conditions followed a non-linear path, exhibiting highly elastic deformation typical of the flexible resins used in this project.

Jose Garcia is an assistant professor of the school of engineering technology at Purdue University in West Lafayette. Graduated from Universidad de los Andes with a B.S. in Mechanical engineering in 2002, completed his master and doctoral studies at Purdue University in 2006 and 2011 respectively. He worked as a post-doctoral researcher at the Illinois Institute of Technology from 2011 to 2012.

Simultaneous achievement of high control performance and energy efficiency of electro-hydraulic systems via parallel connection of pump and valve control units
There have been an ever increasingly stronger demand for electro-hydraulic systems of having both high control performance and high energy efficiency. Traditionally, high performance electro-hydraulic systems are achieved through the use of costly high-bandwidth servo-valve control units, in which inevitable throttling losses make the overall system very energy inefficient. For better energy efficiency, direct pump controlled systems have become the standard. Though significant efforts have been made during the past decades in improving the achievable bandwidth of the pump control units, in general, they are still far slower than those of the valves, leading to relatively poor overall system control performance, especially under large flows or large power conditions. This talk presents a novel idea of using parallel connection of pump and valve control units to achieve the two goals simultaneously. Specifically, the hardware consists of two main parts -- direct pump control unit and independent metering control unit through fast acting valves. Unlike existing pump-valve systems which are essentially of series connection and have the same throttling losses problem as the purely valve controlled system, the two parts in our study are of parallel connection. Such a hardware configuration leads to a dual-stage actuation system in which the lower bandwidth pump is used to provide the majority amount of flow to drive the overall system in an energy-efficient way, while the fast-acting valves are controlled precisely to generate the small amount of adjusting flow for high control performance. In addition, our previously proposed high-performance adaptive robust control approach is employed to synthesize controllers that seamlessly coordinate the pump control unit and the valve control unit in dealing with the unavoidable uncertainties and nonlinearities of the overall system and the different dynamic properties of the pump and the valve. Comparative experimental results obtained show that the proposed system not only achieves better control performance than the valve controlled system due to the reduced valve control flow needed, but also about 50%-70% reduction in energy consumption at the same time.

Dr. Yao received his PhD degree in Mechanical Engineering from the University of California at Berkeley in February 1996 after obtaining M.Eng. degree in Electrical Engineering from Nanyang Technological University of Singapore in 1992, and B.Eng. in Applied Mechanics from Beijing University of Aeronautics and Astronautics of China in 1987. Since 1996, he has been with the School of Mechanical Engineering at Purdue University, where he was promoted to the rank of Professor in 2007. He was also honored as a Kuang-piu Professor in 2005, a Changjiang Chair Professor at Zhejiang University by the Ministry of Education of China in 2010.
Dr. Yao received a Faculty Early Career Development (CAREER) Award by National Science Foundation (NSF) in 1998 and a Joint Research Fund for Outstanding Overseas Chinese Young Scholars from National Natural Science Foundation of China (NSFC) in 2005. His research interests include the design and control of intelligent high performance coordinated control of electro-mechanical/hydraulic systems, optimal adaptive and robust control, nonlinear observer design and neural networks for virtual sensing, modeling, fault detection, diagnostics, and adaptive fault-tolerant control, and data fusion. He has published significantly on the subjects with well over 300 technical papers while enjoying the application of the theory through industrial consulting. He is the recipient of the O. Hugo Schuck Best Paper (Theory) Award from the American Automatic Control Council in 2004 and the Outstanding Young Investigator Award of ASME Dynamic Systems and Control Division (DSCD) in 2007, the Best Conference Paper Awards on Mechatronics of ASME DSCD in 2012, and a winner of the 4th Nagamori Awards by Nagamori Foundation, Kyoto, Japan, in 2018. Dr. Yao is a Fellow of ASME and a senior member of IEEE and has chaired numerous sessions and served in a number of International Program Committee of various IEEE, ASME, and IFAC conferences including the General Chair of the 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics and the International Program Committee Chair of the 6th IFAC Symposium on Mechatronic Systems in 2013. From 2000 to 2002, he was the Chair of the Adaptive and Optimal Control Panel and, from 2001 to 2003, the Chair of the Fluid Control Panel of the ASME Dynamic Systems and Control Division (DSCD). He was the founding member to the ASME DSCD Mechatronics Technical Committee in 2005 and served in various roles including TC Chair. He was a Technical Editor of the IEEE/ASME Transactions on Mechatronics from 2001 to 2005 and Associate Editor of the ASME Journal of Dynamic Systems, Measurement, and Control from 2006 to 2009. Additional details are referred to https://engineering.purdue.edu/~byao.

How mixing Hydraulics and New Sensors can win more challenges than expected
Sensors are playing a more relevant role in Hydraulic and Electro-Hydraulic applications. More performing controls, need for diagnostics, prognostics and efficient use of systems, ask for sensors integration in components and systems. Also "smart components" are one of the new frontiers for more compact and efficient architectures in Hydraulics. On the other hand sensors are costly and also the installation and connection is a cost that, in many application, isn't compatible with the target. In recent years MEMS sensors are offering a wide choice of possible sensorization solutions, year by year increasing reliability and options for sensorisation solutions. The presentation deals on a special sensor designed and made in National Research Council in Italy. called DETF (Dual Ended Twin Force), which offers more than one connection and sensing solution in the hydraulic applications field. The sensor is a strain sensor with very high sensitivity, and the presentation will show how to successfully apply it to hydraulic components, acquiring internal pressure, gear teeth diagnosis in gear pumps, and how to create a flow sensor with very low pressure drop. The same sensor can be applied and tuned for different purposes and could represent an enhancement in hydraulic components sensorisation.

Massimiliano Ruggeri, PhD in Management Engineering, MSC in Electronic Engineering in Italy. Researcher at National research Council of Italy since 2001, previously employed in FCA Group. Vice president of Italian IEC, Contract professor for Microprocessor Systems and Computer Architecture courses at Engineering Department of Ferrara University in Italy. Research interests are in electro-hydraulic applications, sensors and actuators, mechatronics, Functional Safety and its applications in machines, hybrid and electric systems, automated machines and mobile robotics. Author of more than 100 papers in the field of electro-hydraulic applications for heavy-duty and Agricultural vehicles.

How Industry and University Collaboration Can Lead to a Robust and Reliable Product
As the fluid power industry strives to follow design for six sigma principles to provide robust and reliable components and products, a solid understanding of the underlying physics of the product is required. The advantages of utilizing the understanding obtained through the work done at Universities and incorporating this in design for six sigma principles will be shown. An industry and University collaboration project will be presented to show the increased understanding of the physics of operation of a gerotor orbit motor.

Kyle Merrill received a PhD from Purdue University in 2012 with an emphasis in Fluid Power. He has worked in research and development for Parker Hannifin for more than 13 years, supporting the development of products at three different divisions. His experience is in piston pump design, electro-hydraulic control of pumps and motors, hydraulic hybrid design, and gerotor orbit motor design.

Prospective on Systems Engineering and Electrification in Fluid Power
The current state of the art of Hydraulic Systems design is presented through some actual examples. These focus on the combination of electronic controls with traditional hydraulics, experimental test and simulation used to support machine design. Finally, an overview on electrification of mobile equipment is given, presenting the solutions that Parker Hannifin is currently developing for specific equipment.

Germano Franzoni holds a PhD in Mechanical Engineering from University of Parma, Italy. During his international studies he worked with Monika Ivantysynova at the Maha Research Center. He has been employed since 2007 in the Mobile Systems Engineering team at Parker Hannifin where he covered several responsibilities pertaining System Design, R&D and Global Business Development for specific markets.

Individual Electro-Hydraulic Drives for Off-Road Vehicles
This presentation summarizes the first period of activities performed within the project “Individual Electro-Hydraulic Drives for Off-Road Vehicles” supported by the US Dept of Energy, which has as team members the Maha Fluid Power Research Center, Dr. Sudhoff’s team at Purdue Electrical and Computer Engineering , Bosch Rexroth and Case New Holland. The project focuses on the study and the design of novel electro-hydraulic-actuators suitable for off-road applications. Elements of novelty are represented by the design of a four-quadrant electro-hydraulic machine, which combines a permanent magnet electric machine with a positive displacement hydraulic gear machine, as well as the hydraulic circuit that performs the hydraulic actuation. The design of the four quadrant electro-hydraulic machine optimizes performance in terms of efficiency and power density. The reference off-road vehicle is a compact wheel loader, and a commercial unit representative of the current state of the art was instrumented to measure the energy efficiency of the hydraulic actuation system which normally implements an open center hydraulic control architecture. Experiments were performed also to determine representative drive cycles and to validate a simulation model of the hydraulic system implemented within this research. The simulation model allowed estimating the benefit of the proposed technology, which allows reaching increases in energy efficiency of the hydraulic system up to 70%, depending on the drive cycle.

Dr. Vacca is Professor of Fluid Power System at Purdue University, with a joint appointment between the Department of Agricultural and Biological Engineering and the School of Mechanical Engineering. He currently leads the Maha Fluid Power Research Center established in 2004 by Prof. Monika Ivantysynova. Dr. Vacca completed his studies in Italy (Ph.D. from the University of Florence in 2005) and he joined Purdue in 2010 after being an Assistant Professor of Fluid Machinery at the University of Parma (Italy). Fluid power technology has been Dr. Vacca's major research interest since 2002. Goals of his research are the improvement of energy efficiency and controllability of fluid power systems and the reduction of noise emissions of fluid power components. To accomplish these goals, his research team has developed original numerical and experimental techniques for hydraulic systems and components. Prof. Vacca's interests also include the modeling of the properties of hydraulic fluids, with focus to the effects of aeration and cavitation, as well as the use of low viscous fluids (such as water) in fluid power systems. Dr. Vacca is the author of more than 100 papers, most of them published in international journals or conferences. He is also very active in the fluid power research community. He is a faculty member of the Center for Compact and Efficient Fluid Power (CCEFP), co-chair of Fluid Power Systems and Technology Division (FPST) of ASME, and a former chair of the SAE Fluid Power division. Dr. Vacca is also Treasurer and Secretary of the Board of the Global Fluid Power Society (GFPS). Furthermore, he is also Editor in Chief of the International Journal of Fluid Power and Guest Editor of the Special Issue of Energies "Energy Efficiency and Controllability of Fluid Power Systems."

Efficient, Compact, and Smooth Variable Propulsion Motor
Low speed high torque (LSHT) motors are used to propel a variety of off-highway vehicles. A variable displacement traction motor is desirable for several reasons, including enabling hybridization, increasing ground speed, and the ability to downsize the pump. Existing variable LSHT motors are either discretely variable or high-speed motors with a planetary gearbox. The Variable Displacement Linkage Motor (VDLM) is a LSHT motor that is continuously variable and can reach zero displacement. The VDLM offers several benefits over current LSHT motors in that it is highly efficiency over its operating range, has low torque ripple, and is displacement dense due to its multi-lobed cam and radial packaging. This talk will present a comprehensive dynamic model of the VDLM that captures the mechanism kinematics and kinetics, friction in the bearings and piston-cylinder interface, and pressure dynamics in the cylinders as a function of valve timing and piston trajectory. This model has been implemented in an automated motor design routine for rapid exploration of the solution space. An example multi-objective optimization of the motor parameters is presented for a specific application.

Hybrid Hydraulic-Electric Architecture for Off-Road Mobile Machines
Two recent trends in off-road mobile machines are improving energy efficiency and electrification. This presentation will describe a current DOE-funded project in which these two trends are merged. Specifically, the project is studying a system architecture in which hydraulic actuation and electric actuation are combined in an opportune way so as to simultaneously achieve efficiency improvement and control performance while keeping the electrical motor and drives small enough to be affordable.

Perry Y. Li is Professor of Mechanical Engineering at the University of Minnesota. He received his Ph.D. in Mechanical Engineering from the University of California, Berkeley in 1995. He joined the University of Minnesota in 1997 and served as the Deputy Director for the CCEFP from 2006-2013. His research interests are in control and design of mechatronic and fluid power systems, including on- and off-road hydraulic hybrid powertrains, compressed air energy systems, wave energy, human interactive robots, underwater vehicles, hydraulic transformers, and hydraulic components and systems that utilize on/off valves for control.

A 20 Years Research Journey in Fluid Power along with Deep Respect and Friendship with Monika
soon to appear

Liquid Piston Gas Compressor/Expander for Compressed Air Energy Storage (CAES) and CO2 Sequestration
This project is developing a high pressure, high-efficiency gas compressor/expander for applications such as grid scaled, long duration, compressed air energy storage (CAES) and for carbon dioxide sequestration. The compressor/expander overcomes the intrinsic tradeoff between efficiency and power in high-pressure gas compression/expansion with the use of a liquid piston and an augmented heat transfer medium. The design process towards a cost-optimized prototype will be presented.

Perry Y. Li is Professor of Mechanical Engineering at the University of Minnesota. He received his Ph.D. in Mechanical Engineering from the University of California, Berkeley in 1995. He joined the University of Minnesota in 1997 and served as the Deputy Director for the CCEFP from 2006-2013. His research interests are in control and design of mechatronic and fluid power systems, including on- and off-road hydraulic hybrid powertrains, compressed air energy systems, wave energy, human interactive robots, underwater vehicles, hydraulic transformers, and hydraulic components and systems that utilize on/off valves for control.

Enhancing energy capture in wind turbines using a hydrostatic transmission and dynamic pitching
Efforts have been made to improve energy capture of wind turbines. Conventional wind turbines use heavy, multi-stage fixed-ratio gearboxes and doubly fed induction generators. Unlike a fixed-ratio gearbox, a hydrostatic transmission (HST) is a variable-ratio transmission allowing the generator to run at rated speed regardless of wind speed. HST drivetrains are lighter, cheaper, and reliable and eliminate power electronics. A novel power regenerative research platform has been developed to validate the performance of an HST for wind turbine. Results from the test bed will be presented. Studies show that dynamic pitching under specific conditions can almost double the maximum lift on airfoils. Integrating a dynamic pitching control strategy with the traditional control in region 2, will potentially enhance energy harvesting.

Biswaranjan Mohanty is a PhD candidate in Kim Stelson’s research group in the Department of Mechanical Engineering at the University of Minnesota. He is working on dynamics and control of hydrostatic transmissions for wind turbine application. His research interest include dynamic systems and control, mechatronics and fluid power. He received his M.S degree in Electrical Engineering from University of Minnesota, in 2019 and B.Tech degree in Mechanical Engineering from NIT- Rourkela, India in 2009. He worked as Design and Development Engineer at Tata-Hitachi Construction Equipment, India

Modeling and Optimization of Trajectory-Based HCCI Combustion
The authors have previously demonstrated that trajectory-based HCCI combustion control enabled by free piston engine can provide considerable improvement in the fuel economy and significant reduction in the emissions compared to conventional engines. In this work, using simulation results generated from a physics based thermo-kinetic combustion model and experimental data from the newly developed controlled trajectory rapid compression and expansion machine (CT-RCEM) at the University of Minnesota, a framework is presented to study the effect of piston trajectory on the power and efficiency of HCCI combustion and using it for combustion optimization. Using a high-speed electrohydraulic actuator driven by a high bandwidth controller, the CT-RCEM provides the unique ability of complete and precise control of the piston trajectory inside the combustion chamber. This combined with the ability to precisely set the initial and boundary conditions (temperature, pressure, etc.), as desired, a wide range of operating conditions such as different compression ratios, operating speeds, and different trajectories for same compression ratio and speed, can be experimentally explored using the CT-RCEM to further understand the dynamic relationship between the piston trajectory and HCCI combustion.

Abhinav Tripathi (Ph.D. student in Dr.Sun's research group)
received his B.Tech. degree from NIT –Warangal, India, in 2011 and M.S. degree from University of Minnesota – Twin Cities in 2017, in Mechanical Engineering. He is currently a PhD candidate in the Department of Mechanical Engineering at the University of Minnesota where he has been working on the development of the CT-RCEM since 2014. His research interests include dynamic systems and control, mechatronics, dynamics of combustion, and fluid power. He worked as an Operations and Maintenance Engineer (2011-2014) at Indian Oil Corporation, Rajkot, India

Seamless Electric to Hydraulic Conversion
Current electric-to-hydraulic conversion systems use modularized components (electric motor, mechanical transmission, and piston pump), which include redundant bearings, interfaces, shafts, and seals. This inherently results in a system with a modest energy efficiency due to losses at each power conversion stage and large rotational inertia resulting in poor dynamic response. As an alternative, this study proposes the use of an integrated linear electric motor-piston pump to eliminate multiple energy conversions and redundant components. Two ends of the linear motor mover serve as pistons of a double acting pump. Check valves control the fluid flow from a low-pressure tank to the chambers and then to a high-pressure outlet. For the electric machine design, an axisymmetric permanent magnet linear motor topology is modeled and analyzed. A multi-objective optimization algorithm is linked to FEA models of the motor to investigate the optimal machine design. For the mechanical design, dynamic models of the mechanical and fluid mechanics were created and parameters were optimized. As the project progresses, our goal is to integrate these electric models with mechanical models to perform multi-physics optimization for use as a charge pump in a hydrostatic transmission and experimentally validate the models with a physical prototype system.

HEV research on commercial vehicles
soon to appear

Analysis of the Power Distribution in the Hydraulic Circuit of a Mid-Size Agricultural Tractor
Agricultural tractors make a massive use of hydraulic control technology. Being fuel consumption a big concern in agricultural applications, tractors typically use the latest state-of-the-art technology to allow efficient fluid power actuations. Nevertheless, the quantification of the energy loss within the hydraulic system of such applications represents an important step to drive development of the current technology through cost-effective solutions.
This presentation describes an analysis carried at the Maha Fluid Power Research center on the load sensing (LS) circuit of a New Holland T8 tractor taken as reference. A simulation model has been developed within the AMESim software with the aim of accurately predict the operation of the system including the energy flow from the hydraulic supply to the hydraulic users. Within the research, experimental tests on the reference tractor were designed and executed to allow the model validation. The comparison between the experimental results and the simulation data shows the validity of the model. Furthermore, the model allows highlighting the energy losses in the different components of the system as well as identifying the most favorable operating conditions of the system with respect to energy efficiency. The model can be used in support of future research aimed at formulating more efficient solution for the hydraulic circuit of agricultural tractors.

Xin Tian, born in November, 1994 in China, joined Maha fluid power lab as a direct PhD in 2017 Fall after receiving her bachelor degree in Mechanical Engineering. Her work has been focused on simulation, modeling and control of hydraulic systems.

Hydrostatic Development Directions
The presentation will cover key development directions in hydrostatics, which have significantly contributed to the competitive standing in the offroad market. It will be shown how those developments have led to customer success as well as value, and which directions need to be taken to be prepared for the approaching mega trends.

Dr. Robert Rahmfeld is the Senior Director Engineering for Hydrostatics at Danfoss Power Solutions, being technically responsible for all axial piston units (swash plate and bent-axis principle) in low, medium and high power duty. He is with Danfoss over 10 years in various engineering positions, holds several patents, and is author or co-author of more than 40 scientific journal and conference papers. Before joining Danfoss, Dr. Rahmfeld completed his PhD on new displacement controlled hydraulic linear actuators at the Technical University of Hamburg in 2002 under supervision of Professor Monika Ivantysynova, and his MSc in mechanical engineering at Duisburg University in 1996.

Polymer-Enhanced Fluid Effects on Mechanical Efficiency of Hydraulic Pumps
Viscosity modifiers are believed to reduce viscous friction through beneficial shear thinning and use of lower molecular weight base oils. In this investigation the effects of polymer shear thinning and base oil viscosity on pump torque are examined. Mixtures of low traction synthetic poly(alphaolefin) base oils and poly(isobutylene) viscosity modifiers were evaluated in a pump dynamometer. Dynamometer tests were conducted under steady-state conditions per the ISO 4409 standard method. Correlations between pump performance, rheological properties, and molecular dynamic simulations were probed. Molecular dynamics simulations provided insights into the relationship between polymer conformation and temporary shear thinning. Pump and high shear rate viscosity data suggested that moderate shear thinning slightly decreased pump torque at idle conditions. These findings help provide a basis for the rational formulation of polymer enhanced hydraulic fluids.

Paul Michael is the Manager of Tribology Research at the Milwaukee School of Engineering Fluid Power Institute. He has 40 years of experience formulating and testing lubricants. Paul is active in ASTM, ISO, and NFPA standards committees and serves as a lubrication subject matter expert for the US Military. He has more than 40 publications on the topics of energy efficient fluids, hydraulic fluid compatibility, filtration, particle characterization, and machinery lubrication.

Science of Pattern Coating onto Heterogeneous Surfaces Using a Hybrid Tool
Slot coating has been increasingly adapted in recent years toward deposition of patterned films, particularly narrow stripes and patches. These efforts represent significant progress toward a unique and highly scalable additive-only manufacturing approach. However, for various emerging technologies such as flexible electronics, display devices, sensors, and wearables, the feature size capability of patterned slot coating remains a persistent challenge. In this talk, we present a novel technique for slot coating of narrow features at or below 50 µm. Our approach features simultaneous deposition of two miscible coating fluids as a single heterogeneous film, in order to overcome some of the wetting behaviors that otherwise limit the patterned slot coating process. We describe the operational principles and material requirements for this process, and provide a simple process model validated by experimental results. In our discussion, we address the minimum feature size that can be expected, as well as the sensitivity of the output pattern geometry to process conditions and physical properties of the coating fluids.

Tequila Harris
Dr. Tequila A. L. Harris is an Associate Professor in the George W. Woodruff School of Mechanical Engineering, at Georgia Institute of Technology and the Deputy Director of Manufacturing for the Center on Compact and Efficient Fluid Power. Prior to joining Georgia Tech, she earned her Masters and Doctorate degrees from Rensselaer Polytechnic Institute and a Bachelors in Physics from Lane College. Dr. Harris’ research is focused on exploring the connectivity between thin film quality and its functionality, durability and performance, based on its manufacture. Her aim is to elucidate mechanisms that cause system failure, which may have initiated at the manufacturing stage. With the use of numerical simulations and experimentation, she has introduced unique models and approaches to predict and control the quality of thin films, processed on permeable and impermeable substrates. By addressing the associated complex fundamental problems, she aims to impact a plethora of industries and fields such as energy, electronics and environmental. Dr. Harris has received several awards and honors, of note, the L. E. Scriven Young Investigator Award and the National Science Foundation CAREER Award.

High Efficiency Hydraulic Pump-Motors Employing Partial Stroke Piston Pressurization
A novel variable displacement piston-type pump-motor technology is described. High efficiency is obtained by varying the portion of the piston stroke over which the piston is subjected to high pressure, which is termed “partial stroke piston pressurization”, or PSPP. The innovation consists of implementing PSPP using novel high efficiency, low power hydro-mechanical valves. Previous implementations of PSPP have instead used electro-hydraulic valves or cam-operated valves. PSPP pump-motors are intrinsically more efficient and smaller than conventional variable displacement piston-type pump-motors. Additional benefits of the hydro-mechanical PSPP technology described here include simplicity, reliability, and lower cost. Experimental performance data is presented for the first prototype operating in pumping mode that demonstrates that PSPP pumps maintain high efficiency at low displacements. Potential applications include off-road equipment, such as excavators and fork lifts, aircraft wing and landing gear articulation, industrial presses, elevators and automotive power steering.

Alissa Montzka received her B.S. in Applied Physics with mechanics and computational emphases and B.A. in Mathematics from Bethel University in 2017. She had three engineering internship positions in the Twin Cities while studying at Bethel: two at medical device companies, and one in kinetic architecture. Her graduate research at the University of Minnesota-Twin Cities is focused on testing the performance of a prototype pump/motor employing partial stroke piston pressurization.

Thomas Chase received his BSME and MSME degrees in mechanical engineering from the Rochester Institute of Technology in 1977 and 1983, respectively. He received his Ph.D. in mechanical engineering at the University of Minnesota in 1984. He was an Assistant Professor at the University of Rhode Island from 1983-1985. He has been at the University of Minnesota since, where he is currently a Professor and Morse-Alumni Distinguished Teaching Professor of Mechanical Engineering. His current research interests are in the areas of fluid power, mechanism design, computer aided engineering and the design of apparatus for high energy physics experiments. He is a Fellow of the ASME.

Pushing the Performance Limits of the Lubricating Interfaces in Axial Piston Machines
Since its inception, the Maha Fluid Power Research Center has pursued the design of more efficient and versatile axial piston machines of swash plate type. With applications from agriculture to construction and aerospace, the power loss incurred by these positive displacement machines affects a wide variety of systems. In striving to diminish these losses, the Center has, through the development and implementation of a powerful multi-physics simulation tool, investigated the impact of design changes at the very source of the efficiency problem in such pumps: their three main lubricating interfaces. Through numerous design studies and optimization routines, it was found that the leakage and torque loss due to viscous flow in these lubricating gaps could be significantly reduced using certain forms of micro surface shaping--- i.e. via imposing a shape, on the order of microns in height, on the surfaces abutting the interface fluid film. Furthermore, looking towards a more environmentally friendly future, micro surface shaping is currently being investigated as a means for pushing the performance bounds of axial piston machines whose working fluid is water. This fluid is especially challenging on account of its low viscosity, which lessens the load-carrying capacity of lubricating interfaces by reducing hydrodynamic pressure buildup within the fluid film. However, simulation studies of surface shaping at the piston-cylinder lubricating interface in axial piston machines show promising results for increasing the sustainable load. The virtual prototyping approach taken by the Center, where the behavior of new interface surface shapes can be tested in simulation, rather than on the test bench, not only enables the time and cost-effective development of suitable surface shaping for a wide variety of pumps, but also produces valuable insight into the behavior of the interfaces in axial piston machines--- insight that can be used to set the stage for future design ideas.

Meike Ernst is a Ph.D. candidate in the Mechanical Engineering department at Purdue University, and a research assistant working at the Maha Fluid Power Research Center. Her work centers on improving the performance of the piston-cylinder lubricating interface in axial piston machines of swash plate type when water is used as the hydraulic fluid.

Mechano-Chemical Surface Modification with Cu2S: Inducing Superior Lubricity
Advances toward low friction surfaces are in growing demand from many economic sectors for energy efficiency and environmental safety. However, the traditional approach of multi-grade oil formulation is limited by its inability to induce pollution-free generation of uniform oil-retaining films needed to improve surface lubricity. Here, a direct route to the formation of a surface layer of superior lubricity is presented as an alternative to the use of oil additives for friction reduction. The deformation-induced generation of a surface film consisting of low-shear strength oil-retaining compounds is obtained via supplying chemically beneficial elements during a widely used surface finishing mechanical treatment. An ultra-low friction coefficient of about 0.01 is obtained with base oil lubrication after tailoring the surface chemistry by shot peening using a mixture of Cu2S and Al2O3; this result opens new horizons for surface engineering.

Dr. Michael Varenberg is an Assistant Professor and the head of Tribology & Surface Engineering Lab in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. His research areas cover friction and wear of engineering surfaces, micro/nano tribology, bionic tribology, tribological instrumentation, and contact mechanics.

Hydraulic Systems Digitalization
For several years, research and academic institutes have focused on the advantages of complementing fluid power systems with electronic systems. Over time, industry has progressively adopted such efforts including electronic controls and electronic devices to exploit the potential of fluid power systems thereby optimizing efficiency, productivity and reliability. For several years, Bosch-Rexroth has focused on the development of functional bundles that couple robust and highly efficient fluid power components with scalable, open and modular software to fit any machine manufacturer requirement. One such example is the electronic load-sensing (eLS) functional bundle for multi-actuator systems. This functional bundle enables the digitalization of one of the most well established hydraulic systems, load-sensing (LS), allowing for an increase in efficiency, improvement on the machine dynamics and ensures the stability of the overall system with minimal commissioning effort. This presentation will focus on the eLS concept and well as a technical example that illustrates the system functionality.

Digital Displacement pump technology
Outline of presentation:

• Introduction to Digital Displacement technology and Artemis Intelligent Power
• Efficiency and control characteristics
• Evolution of system architectures
• Application examples and results achieved
• Market Launch of Products
• Current R&D activities at Artemis

Niall joined Artemis in 1999, where he demonstrated the first vehicle propel transmission with Digital Displacement® technology – and wrote a PhD on the subject. As Technical Director, he led the team designing electronics, software and system simulation models, and inventing control systems for applications from hybrid vehicles to offshore wind turbines. Niall became Managing Director in 2013, and still retains a keen interest in technical matters.