International Journal of Fluid Power

Editorial

Adolfo Senatore, Emma Frosina — Tue, 30 Jul 2024 00:00:00 +0200

On behalf of the Organizing Committee, we wish to welcome you to the Special Issue of the 2022 IEEE Global Fluid Power Society PhD Symposium (GFPS2022). The Symposium is a bi-annual event organized by Global Fluid Power Society (GFPS) to showcase and brainstorm on research carried out by junior investigators in the field of fluid power. GFPS Society was created in 2016 to merge two long-lasting fluid power organizations: Fluid Power Net International (FPNI) and Network of Fluid Power Centres in Europe (FPCE). GFPS inherits the spirit of both FPNI and FPCE and currently represents the world’s largest scientific network of fluid power institutions.

Energy-Efficiency Comparison of Different Implement Powertrain Concepts to Each Other and Between Different Heavy-Duty Mobile Machines

David Fassbender, Christine Brach, Tatiana Minav — Tue, 30 Jul 2024 00:00:00 +0200

For the electrification of heavy-duty mobile machine, alternative power-train concepts that are more efficient than conventional valve-controlled systems can be an important key that extends the operation time by making better use of the limited amount of available battery energy. Since power-train concepts are universal and can be applied to various types of heavy-duty mobile machine with different application conditions, it is advisable to assess and compare concepts on multiple of those machines and on the basis of a standardized investigation method. For this purpose, simulations of a telehandler, a wheel loader, and an excavator are done in this study. Each hdmm type is simulated with different setups that each apply one of three concepts: pure conventional valve-control in a ls system, as the benchmark, or one of two alternative concepts that were previously presented by the authors. The two alternative concepts are namely an LS system with the option to replace the metering valves of single actuators with a hydraulic motor connected to an electric generator and secondly a system with an electric machine that drives an ls pump as well as displacement-controlled actuators. The simulations show that both alternative concepts perform equally well on the reference telehandler and the wheel loader with maximum primary energy savings in a work cycle mix of around 37% on both machines compared to the reference setups. For the excavator, on the other hand, the displacement-controlled concept performed even better and reached savings of up to 48%.

Parametric Stability Analysis of Pneumatic Valves Using Convex Optimization

Tue, 30 Jul 2024 00:00:00 +0200

This paper proposes a stability analysis procedure of fluid power components according to some early design parameters. It is based on the numerical determination of the existence of a Lyapunov function, which guarantees the required performance. This is formulated as an optimization problem under Linear Matrix Inequalities constraints (LMIs). The model-based procedure is illustrated with an application to a pneumatic two-stage pressure regulation valve. The results show the method capability to provide a better understanding of the possible causes of the valve’s instability and how it can be avoided at an early design stage by tuning the physical parameters in order to guarantee a desired dynamical behavior and improve system robustness.

Active Damping Control of the Large-scale Flexible Hydraulic Manipulators with Independent Metering System

Ruiheng Jia, Junhui Zhang, Ruqi Ding, Fu Zhang, Jun Shen, Bing Xu — Tue, 30 Jul 2024 00:00:00 +0200

The large-scale flexible hydraulic manipulator (FHM) is the key machinery for automation in construction. It generally works in a precise position and suffers from serious vibrations caused by external excitation. Thus, it requires both active damping control and position control, which are typically implemented by the single valve system (SVS) in the past. However, the SVS only has one signal input which cannot address the two controllers simultaneously. To solve the problem, a decoupling active damping controller utilizing the independent metering system (IMS) is presented. To reduce the influence between controls, the control degree of freedom is increased by breaking the mechanical coupling of the inlet and outlet. The relative gain array (RGA) method is then used to determine the best variable pair. Thus, the position and active damping controllers can be designed separately in two control loops to achieve control decoupling. To achieve active damping control, the dynamic pressure feedback (DPF) based on a high-pass filter is introduced to optimize system damping. The proposed method is verified on a concrete pump truck simulation model which is a typical large-scale flexible hydraulic manipulator. Simulation results show that the proposed method reduces interactions between different control loops and has a gentler vibration of the end-effector compared to the conventional SVS.

Design of a Lead-Free Slipper Bearing for Low Speed Axial Piston Pump Applications

Roman Ivantysyn, Svenja Horn, Jürgen Weber — Tue, 30 Jul 2024 00:00:00 +0200

New application areas for hydrostatic machines result in novel challenges for the fluid film performance of the lubrication interfaces. In the past hydrostatic machines were designed with a combustion engine or a constant speed electric motor in mind. Therefore, they typically have a minimal speed requirement and are optimized for a low variation in their operating speed range. Electrification and flow by demand change this requirement drastically, forcing the pumps often in both very high and very low operating speeds. Typically, lubricating gaps in positive displacement machines consist of a hard/soft material pairing, where the soft pairing usually is a yellow brass with variable lead content. The lead is added to allow for mix friction contact at low speeds and other critical conditions. New developments in surface structuring allow for precise manufacturing of the surface shaping in the sub micro-meter range. This paper combined this technology with state of the art numerical simulations to design a surface structure that is capable withstanding pump operations without significant wear and therefore allows for lead free materials – even steel/steel pairings. The different materials were tested in simulation, on a novel hydrostatic-tribometer test rig as well as on the pump test rig. The design process as well as the simulation and measurement results will be presented in this paper.

New Hydraulic Control Technologies for Improving the Energy Efficiency of the Hydraulic System of Agricultural Tractors and Their Implements

Tue, 30 Jul 2024 00:00:00 +0200

This paper describes two alternative methods to achieve the goal of reducing the fuel consumption of the high-pressure hydraulic control system of agricultural tractors and their implements. The first approach consists of a re-visitation of the basic load sensing (LS) technology used to power the hydraulic remotes. Namely, the metering regulations proper of a LS system is shifted from the tractor remote valves to the implement control valves. The second approach instead converts the hydraulic supply from a flow-based control logic (like in the LS system) to a pressure-based control. In different ways, both methods allow eliminating the conflicts existing between the tractor control valves and the implement ones, which cause excessive pressurization of the supply pumps and therefore high throttling losses.

The proposed methods are properly analyzed in simulation, and then tested considering reference of a 390 hp tractor and a 16-row planter. The results show a high improvement in energy performance for both the proposed solutions. With respect to the commercial system considered as the baseline, both solutions allow increasing the energy efficiency by more than 38%, with variations that depend on the operating conditions.

Thermal-fluid Optimization Model of Small-scale Hydraulic Conduits

Jeffrey Bies, William Durfee — Tue, 30 Jul 2024 00:00:00 +0200

Multiphysics topology optimization has applications in computer-aided design of products, including small-scale fluid power systems where flow efficiency, thermal management, and weight management matter. While algorithms exist that can optimize a single objective, there are no solutions that can simultaneously address all three of these factors. This study developed a multiphysics topology optimization process that uses a thermal-fluid-structure model to generate high-pressure hydraulic designs where passive cooling is built into the flow channels. Python was used with Open-Source Field Operation and Manipulation (OpenFOAM) for geometry creation, meshing, and finite volume and sensitivity analysis to implement the multi-objective optimization for small-scale fluid power systems. The process was performed iteratively to inform the next iteration’s geometry until an optimized design was reached.

The results show that pressure drop, fluid density, fluid velocity, and inlet diameter are positively correlated with capillary branching and that design space and viscosity are negatively correlated with capillary branching. Enhanced heat transfer came at the cost of pressure drop, where increasing the allowable pressure drop by 195% led to an increased temperature drop of 17%. Expanding the design space had the most significant impact on heat transfer, where extending the design space width by three times led to a 365% increase in temperature drop. Incorporating a curved exterior wall in the design space while holding the area and mesh node count constant led to a 3% increase in temperature drop while decreasing computational time by 68%. Lower viscosity of the working fluid leads to increased capillary branching with minimal impact on temperature drop (0.3%), while incorporating a temperature-dependent viscosity model led to a more prominent temperature drop (15%). Future work will expand the topology optimization method to incorporate structural optimization to handle load-bearing.

Experimental Investigation of the Suction Capabilities of an Innovative High Speed External Gear Pump for Electro-Hydraulic Actuated Automotive Transmissions

Massimo Milani, Luca Montorsi, Fabrizio Paltrinieri — Tue, 30 Jul 2024 00:00:00 +0200

In this paper, the suction capabilities of an innovative high speed external gear pump have been measured and analysed for verifying its potential use as a reliable and efficient power unit for electro-hydraulic actuated automotive transmissions. In particular, with the aim to face extremely challenging operating conditions, mainly in terms of rotational speed, this specific type of volumetric machine is designed with both two suction and delivery ports. All the experimental measurements have been performed by using a specifically tailored test bench, equipped with a double Cardan joint and an overdrive, designed for running the pump over a wide range of rotational speeds, spanning between 400 and 7000 rpm, and applying a delivery pressure of about 45 bar, very close to a typical actuation value of a high-performance automotive hydraulic transmission. Furthermore, with the aim to confirm the consistency of the experimental measurements, two identical prototypes of the high speed external gear pump have been tested and compared for two different values of the operating temperature, respectively equal to 40 and 60^oC. First of all, the higher efficiency of the pump primary suction port has been clearly highlighted and evaluated. Moreover, for rotational speed values higher than 4000 rpm, a significant increase of the volumetric flow rate delivered by the pump can be achieved using both the suction ports together and, thus, this particular hydraulic configuration can be considered as a very promising design solution for the entire actuation system.

Degradation Identification of an EHA Piston Pump by Analysis of Load-Holding States

Yannick Duensing, Amos Merkel, Katharina Schmitz — Tue, 30 Jul 2024 00:00:00 +0200

To achieve the goal of more electric aircrafts current research investigates the frontline capabilities of electro-hydrostatic actuators (EHA) as substitution for conventional hydraulic flight control systems. Due to durability limitations, EHAs are to date only utilized as backup. In this paper the design of EHAs and the impact of the challenging working condition on the health status are presented. A longevity test bench, as well as developed test profile to cover real world operation are explained. Lastly, measurements of load-holding modes are analyzed in detail and insight about run-ins, temperature dependencies and wear-related efficiency losses are gained.