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

Digitaalihydraulisen monipainejärjestelmän hyötysuhteen määrittäminen kuormaa nostaviin sovelluksiin

The purpose of this thesis is to determine the energy efficiency of the digital hydraulic multi-pressure actuator (DHMPA) for use in load-lifting applications. In order to accomplish this, three different characteristic efficiencies are defined; traditional, total, and regeneration efficiency. The traditional efficiency represents a comparable figure to that in traditional hydraulic systems. However, it does not consider energy regeneration, and thus, does not reflect the true efficiency of the DHMPA. Therefore, the total efficiency considering the regeneration, is defined. Furthermore, the regeneration efficiency describes how efficiently load-mass potential energy can be restored to the system. In addition, novel digital hydraulic technologies are reviewed and the operation of the DHMPA unit is studied. The efficiency figures are determined based on experimental measurement results. The test setup consists of pump unit, load-lifting test rig and the DHMPA. Measurements are done with a separate data acquisition system and the data acquired is analysed in MATLAB. Measured quantities are pressures, flow rates, positions, and temperatures of the system during the 500-cycle lifting-lowering test of the 1180 kg load-mass. The collected data is used for calculating the energy balance of the system, which can then be used for determining the three characteristic efficiencies of the system. In addition, the system performance is evaluated based on this data. The results show that the DHMPA is feasible for use in load-lifting applications. However, some unexpected errors occurred in the positioning of the load-mass. Nevertheless, the performance can be improved by careful tuning and dimensioning of the DHMPA components. Although the system performance requires further investigation, the energy-efficiency is highly competitive to that of conventional hydraulic systems. The traditional efficiency was 128%, yielding approximately 3-4 times lower energy consumption than the traditional systems. The total efficiency exceeded 63%, which is remarkably higher than that of traditional systems. Furthermore, the potential energy from the load-mass could be regenerated with efficiency of 80%. Therefore, this study showed that the DHMPA has a significant energy-saving potential in load-lifting applications. However, in order to optimize the system performance and efficiency, a further study will be needed.Tämän diplomityön tarkoituksena on määrittää digitaalihydraulisen monipainejärjestelmän (DHMPA) hyötysuhde kuormaa nostavia sovelluksia varten. Tämän tavoitteen saavuttamiseksi, kolme ominaista hyötysuhdelukua määritetään: perinteinen, kokonais- ja talteenottohyötysuhde. Perinteinen hyötysuhde antaa vertailukelpoisen luvun perinteisten hydraulijärjestelmien kanssa. Se ei kuitenkaan ota huomioon talteenotettua energiaa, eikä siten kuvasta järjestelmän todellista hyötysuhdetta. Tämän vuoksi määritetään kokonaishyötysuhde, joka huomioi energian talteenoton. Talteenottohyötysuhde puolestaan kuvaa, kuinka tehokkaasti massan nostoon sidottu potentiaalienergia voidaan ottaa takaisin järjestelmään. Lisäksi esitellään muita uusia digitaalihydrauliikan sovelluksia sekä perehdytään tarkemmin DHMPA:n toimintaan. Hyötysuhdeluvut määritetään kokeellisten mittaustulosten avulla. Testijärjestelmä koostuu hydraulikoneikosta, massaa nostavasta testipenkistä sekä DHMPA-yksiköstä. Mittausdata kerätään erillisellä tiedonkeruujärjestelmällä ja se analysoidaan MATLAB-ohjelmistolla. Mitattavia suureita ovat järjestelmän paineet, tilavuusvirrat, asemat sekä lämpötilat 500-askelisen, 1180 kg:n massaa nostavan ja laskevan testiohjelman aikana. Näiden tietojen avulla määritetään järjestelmän energiatase, josta puolestaan voidaan johtaa halutut hyötysuhdeluvut. Lisäksi näiden tietojen avulla voidaan arvioida järjestelmän toimintaa ja suorituskykyä. Tulokset näyttävät, että DHMPA-yksikköä voidaan soveltaa kuormaa nostavissa sovelluksissa. Testiajon aikana esiintyi kuitenkin odottamattomia asemavirheitä. Näitä virheitä voidaan minimoida virittämällä ja mitoittamalla järjestelmä huolellisesti. Vaikka tämä vaatiikin lisätutkimusta, voidaan todeta, että DHMPA:n hyötysuhde on hyvin kilpailukykyinen perinteisiin järjestelmiin verrattuna. Perinteinen hyötysuhde oli 128%, mikä tarkoittaa noin 3-4 kertaa pienempää energian kulutusta tavanomaisiin järjestelmiin verrattuna. Kokonaishyötysuhteeksi saatiin yli 63%, joka on merkittävästi parempi kuin perinteisten järjestelmien. Massan potentiaalienergia kyettiin ottamaan talteen 80% hyötysuhteella. Tutkimuksen avulla osoitettiin, että DHMPA voi tarjota huomattavan energiansäästöpotentiaalin massaa nostaviin järjestelmiin. Lisätutkimusta kuitenkin tarvitaan suorituskyvyn ja hyötysuhteen optimoimiseksi

Improved modelling and driving of hydraulic asymmetric cylinders systems

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

modelling and energy comparison of system layouts for a hydraulic excavator

Abstract For decades the improvement of energy efficiency in mobile hydraulics has forced the research world to develop energy saving solutions and to redesign existing hydraulic circuits. This paper presents an overview about the state of the art of excavator valve systems based on open centre flow control (OFC) and a load sensing principle (LS). The purpose of this study is to compare different hydraulic systems on a middle size (9ton) excavator and to analyse the differences in term of energy saving and fuel consumption. Starting from a validate mathematical model of the considered hydraulic excavator whose functioning is in LS logic, many alternatives are proposed as flow on demand system, positive and negative flow control. Systems comparison has been done on typical excavator working cycles as trench digging and levelling referring to the JCMAS standard. An optimization tool, based on genetic algorithm, has been exploited for the definition of the optimal spool areas to reduce the pressure losses and by-pass flow rate maintaining identical controllability and performance

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

System and Thermal Modeling of Hydraulic Hybrids: Thermal Characteristics Analysis

Hybrid vehicles have become a popular alternative to conventional powertrain architectures by offering improved fuel efficiency along with various other environmental benefits. Among them, hydraulic hybrid vehicles (HHVs) have several benefits, which make it the superior technology for certain applications over other types of hybrid vehicles, such as lower component costs, more environmentally friendly construction materials, higher power densities, and more regenerative energy available from braking. There have been various studies on HHVs, such as energy management optimization, control strategies for various system configurations, the effect of system parameters on the hybrid system, and proposals for novel hybrid architectures. One area not been thoroughly covered in the past is a detailed modeling and examination of the thermal characteristics for HHVs due to a difficulty of describing the rapid thermal transients in the unsteady state systems. In this dissertation, a comprehensive system and thermal modeling has been studied for hydraulic hybrid transmissions (HHTs). The main motivation behind developing a thermal model of HHTs is to gain a deeper understanding of the system’s thermal performance, and key influencing factors, without relying on experimental data. This will enable HHVs to be designed more efficiently by identifying and addressing potential issues with transmission’s thermal performance prior to hardware testing. Since there exists no thermal study on HHVs in the past, a thermal modeling method has been introduced, which can be applicable to hydraulic hybrid architectures. A thermal modeling methodology based on a novel numerical scheme and accurate theoretical description has been developed in order to capture the rapid thermal transient in the hydraulic system under unsteady state conditions. The model has been applied to a series HHT and validated with measured data from the hardware-in-the-loop (HIL) test rig with a standard driving cycle, FTP-72. In addition, the proposed thermal modeling methodology has been used to analyze and optimize the cooling system of a novel HHV architecture, which is implemented in a sport utility vehicle (SUV) in Maha Fluid Power Research Center. The modeling results have been compared with the measured data while driving the vehicle. In both studies, the simulation results have shown a good correlation with the experimental data in terms of the overall trends and variation ranges. The goal of the developed model is the application to the system and thermal issues in HHVs, such as thermal stability analysis, management of the cooling system, packaging and hydraulic component optimization, and evaluation of thermal characteristics of different architectures. As an advanced topic of this research, thermal management of an open and a closed circuit hydraulic hybrid systems has been studied by simulation. The comparison results show a potential to a better thermal management for the open circuit systems with smaller heat exchangers, as well as less power consumption with incorporation of smaller charge pumps compared to the closed circuit systems. In the future, the developed comprehensive system and thermal modeling method can be applied to different advanced topics, such as analysis of performance and thermal characteristics, systems and components optimization, and systems evaluation with different external conditions, for different hydraulic hybrid systems

Volume 3 – Conference

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

Hydraulic Hybrid Excavator: Layout Definition, Experimental Activity, Mathematical Model Validation and Fuel Consumption Evaluation

Energy saving and fuel consumption reduction techniques are among the principal interests for both academic institutions and industries, in particular, system optimization and hybridization. This paper presents a new hydraulic hybrid system layout for mobile machinery implemented on a middle size excavator. The hybridization procedure took advantage of a dynamic programming (DP) algorithm, which was also utilized for the hybrid components dimensioning and control strategy definition. A dedicated experimental activity on test bench was performed on the main components of the energy recovery system (ERS). The JCMAS working cycle was considered as the reference test for a fuel consumption comparison between the standard and the hybrid excavator. A fuel saving up to 8% on the JCMAS cycle, and up to 11% during the digging cycle, has been allowed by the proposed hybrid system

Efficiency Improved Load Sensing System - Reduction of System Inherent Pressure Losses

Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different pressure levels. This paper introduces a novel hydraulic LS system architecture with reduced SIPL. In the new circuit, each actuator section is automatically connected either to the tank or to a hydraulic accumulator in dependence of its individual and the systems load situation via an additional valve. When connected to the accumulator, the additional pressure potential in the return line increases the load on the actuator and thus reduces the pressure difference to be throttled at the pressure compensator. The new circuit was developed and analyzed in simulation. For this, the hydraulic simulation model of a hydraulic excavator was used. To validate the sub-models of both machine and new circuit, two separate test rigs were developed and used. Both valid sub-models then were combined to the model of the optimized system. The final simulation results showed, that under the applied conditions, the novel hydraulic circuit was able to decrease SIPL of the examined system by approximately 44% and thus increasing the machines’ total energy efficiency. With the successful completion of the project, the gathered knowledge will be used to further develop the proposed circuit and its components