Estimation of the efficiency of two subsystems of the “Energy Towers”

In order to reduce CO2 emissions, it is necessary to change over to climate-neutral energies as quickly as possible. To achieve this, the use of climate-neutral technologies must be expanded on the one hand, and on the other hand, the efficiency of existing plants, even those that are not climate-neutral, must be increased. In this publication, a new type of plant is investigated, which is designed to enable efficient energy conversion on the basis of Archimedes principle. In this investigation, the conversion efficiencies of two subsystems were calculated. The analytically calculated results provide a first estimate for the efficiencies of the two subsystems and can be further specified when a more detailed model of the plant is availabl

Estimation of Soil Pressures Based on the Pressures in the Hydraulic System for a Legged Forestry Machine

Harvesting operations with wheeled forestry machines can bring great harm to wet soils due to the machine weight and wheel slip. Factors such as the reduction of wheel slip, machine weight and total area affected by forestry machines are crucial in protecting soils. The accurate measurement of the pressure introduced by forestry machines to the soil, without harming the structure of the ground nor making assumptions of the tire or ground behavior, poses a challenge. Within this article a method to calculate the contact soil pressure, of a portal advancing mechanism for sensitive soils is presented. The results are then further evaluated based on simulative results. B y using the kinematics of the legged machine, it becomes possible to determine the soil pressure without making rough assumptions of the legs or the ground. The kinematic allows to measure the forces of the hydraulic actuators that are holding the legs in position. Through this, a direct calculation of the force which is transferred to the ground can be made. To determine the forces of the hydraulic actuators in a movement cycle, a coupled simulation of the kinematic and hydraulic system is set up. Using the determined pressures in the cylinders the exerted force on the ground is calculated. The developed calculation method has been set up in such a manner that the results can easily be compared to real world test data in future studies. In addition, the effects of this particular legged forestry machine on the ground will be compared to other machine types under the consideration, that with this new concept no slip is expected. Using this approach, the soil pressure and the impact on the ground of a legged forestry machine can be evaluated in an early stage of development

Optimization of Axial Piston Units Based on Demand-driven Relief of Tribological Contacts

Markets show a clear trend towards an ever more extensive electronic networking in mobile and stationary applications. This requires a certain degree of electronic integration of hydraulic components such as axial piston pumps. Beside some wellknow approaches, the transmission of axial piston units still is relatively unexplored regarding electronification. Nonetheless there is a quite high potential to be optimized by electronic. In view of this fact, the present paper deals with the tribological contacts of pumps based on a demand driven hydrostatic relief. The contact areas at cylinder - distributor plate, cradle bearing and slipper - swash plate will be investigated in detail and it will be shown how the pump behavior can be improved considerably through a higher level of relief and a central remaining force ratio. The potential of optimization is to improve the efficiency, especially in partial loaded operation, power range, also for multi quadrant operation, precision and stability. A stable lubricating film for slow-speed running and for very high speeds at different pressures is ensured as well

On the frequency dependency of fatigue damage caused by viscous fluid-structure interaction in hydraulic components

Experimental fatigue tests have been conducted for decades to study the lifetime of hydraulic components. Nevertheless, predicting the lifetime of hydraulic components remains difficult. For a quick market entry, test periods have to be short, and tests are often done under constant cyclic loading at high frequencies. The damage accumulation of hydraulic components, however, depends on the temporal load profiles, as viscous fluids introduce a time dependency. As a result, high pulsation frequencies alter the damage accumulation, which can result in misleading and inapplicable lifetime results. Previous studies have shown a significant difference in crack growth and lifetime when specimens have been submerged in pressurized oil. Despite the similarities between these experiments and hydraulic systems, the frequency dependency of fatigue damage in hydraulic components and the corresponding fluid-structure interaction in fatigue cracks have not yet been quantified. A one-dimensional numeric flow model in connection with a finite-element structural analysis was used to simulate the fluid flow and the crack opening. Based on the resulting stress amplitudes, the expected crack growth was predicted and compared to experimental data. The experiments show that the temporal load profile is critical to ensure equivalent damage accumulation in fatigue experiments. Otherwise, premature component failures can occur, and a large safety margin has to be applied

Optimization of Operation Strategy for Primary Torque based hydrostatic Drivetrain using Artificial Intelligence

A new primary torque control concept for hydrostatics mobile machines was introduced in 2018. The mentioned concept controls the pressure in a closed circuit by changing the angle of the hydraulic pump to achieve the desired pressure based on a feedback system. Thanks to this concept, a series of advantages are expected. However, while working in a Y cycle, the primary torque-controlled wheel loader has worse performance in efficiency compared to secondary controlled earthmover due to lack of recuperation ability. Alternatively, we use deep learning algorithms to improve machines' regeneration performance. In this paper, we firstly make a potential analysis to show the benefit by utilizing the regeneration process, followed by proposing a series of CRDNNs, which combine CNN, RNN, and DNN, to precisely detect Y cycles. Compared to existing algorithms, the CRDNN with bi-directional LSTMs has the best accuracy, and the CRDNN with LSTMs has a comparable performance but much fewer training parameters. Based on our dataset including 119 truck loading cycles, our best neural network shows a 98.2% test accuracy. Therefore, even with a simple regeneration process, our algorithm can improve the holistic efficiency of mobile machines up to 9% during Y cycle processes if primary torque concept is used.Comment: 9 pages, 23 figure

Effiziente Fahrantriebe

Energieeffizienz erhöht ökologischen und ökonomischen Nutzen. Zukunftskonzepte von mobilen Arbeitsmaschinen präsentierte Prof. Dr.-Ing. Marcus Geimer, Inhaber des Lehrstuhls für Mobile Arbeitsmaschinen am Karlsruher Institut für Technologie (KIT), auf einem Fachpresse-Workshop der Schaeffler Gruppe Industrie. Im Artikel werden die wichtigsten Aussagen zusammengefass

Hybridantriebe für mobile Arbeitsmaschinen. 3. Fachtagung des VDMA und des Karlsruher Instituts für Technologie, 17. Februar 2011, Karlsruhe

Der Tagungsband "Hybridantriebe für mobile Arbeitsmaschinen" enthält die gesammelten Beiträge zu den Vorträgen der 3. Fachtagung am 17. Februar 2011. In 21 Artikeln wird über den Stand der Forschung und neue Entwicklungen auf dem Gebiet der Hybridantriebe für mobile Arbeitsmaschinen berichtet. Die Schwerpunkte liegen auf folgenden Themen: Simulation und Modellbildung, elektrische und hydraulische Hybridantriebe, Praxiserfahrung und Leistungsmanagement

An Approach to Combine an Independent Metering System with an Electro-Hydraulic Flow-on-Demand Hybrid-System

By combining an electro-hydraulic flow-on-demand system with an independent metering of the actuators in- and outlet, a higher efficiency and a better controllability compared to conventional hydraulic-mechanic load sensing systems can be reached. It also enables the integration of a hydraulic accumulator to recuperate energy due to active loads. This paper presents an alternative control strategy for this kind of hydraulic propulsion systems. Connected with the pump and during passive loads the meter-in flow controls the velocity of the actuator. Otherwise the velocity control is achieved by the meter-out flow while the oil flows into the accumulator or tank. Exemplary this system is simulated for a mobile forestry crane. Further steps are building up a test bench for optimization and validation as well as an implementation into a real machine for testing the suitability in use