scholarly journals Electro-Hydraulic Drive of the Variable Ratio Lifting Device under Active Load

2021 ◽  
pp. 599-610
Author(s):  
Andrzej Kosucki ◽  
Łukasz Stawiński ◽  
Adrian Morawiec ◽  
Jarosław Goszczak
Keyword(s):  
Asynchronous Motor ◽  
Experimental Studies ◽  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Open Loop ◽  
Control Mode ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Energy Recuperation ◽  
Hydraulic Cylinders

Hydraulic systems fed by fixed displacement pumps driven by frequency-controlled electric motors can replace conventional throttling systems due to their ability to control the speed of hydraulic cylinders regardless of the value and direction of the load. These systems can improve the energy efficiency of the drive or even provide the possibility of energy recuperation during lowering. This paper presents experimental studies of the new drive system with volumetric control of the speed of the lifted/lowered payload using the example of a scissor lift. The system uses a reversible gear pump driven by an asynchronous motor fed by a frequency inverter operating in field-oriented control mode. Comparative studies of the mapping of the assumed speed of the hydraulic cylinder and platform are presented, as well as studies of the influence of the load change on the speed and positioning of the mechanism driven by the open-loop controlled system.

scholarly journals Volumetric hydraulic drive with series connection of hydraulic actuators

2020 ◽  
Vol 1 (4) ◽  
pp. 61-69
Author(s):  
V.N. Pil'gunov ◽  
◽  
K.D. Yefremova ◽  
Keyword(s):  
Single Channel ◽  
Production Systems ◽  
Experimental Studies ◽  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Series Connection ◽  
Power Characteristics ◽  
Serial Number ◽  
Piston Speed ◽  
Hydraulic Cylinders

The aim of the proposed work is theoretical and experimental studies of the performance of a single-channel hydraulic drive with a series connection of executive hydraulic cylinders and the de-velopment of recommendations for predicting their characteristics. The authors of the paper carried out a set of experimental studies and obtained the numerical kinematic, speed and power characteristics of a single-channel hydraulic drive with five hydraulic cylinders connected in series. It is shown that the nature of the kinematic connection is determined by the differentiation of the hydraulic cylinders. The speed of advancement of the piston of an indi-vidual hydraulic cylinder is determined by its serial number in the chain of hydraulic cylinders, while the highest speed of the piston movement is developed by the first hydraulic cylinder. The relative unevenness of the piston movement in comparison with the speed of the piston movement of the first hydraulic cylinder is determined by the differentiation of the hydraulic cylinder, while the hydraulic drive with the differentiation D = 2 has the greatest unevenness. It is shown that by the selection of the differentiation of the hydraulic cylinders, their stepwise arrangement and the displacement of the location of the bottom of the hydraulic cylinder, that it is possible to realize complex forms of the total trajectory of the points of attachment of the hydraulic cylinder rods. In the hydrostatic (power) hydraulic drive in the rod cavities of the hydraulic cylinders, depend-ing on the serial number of the hydraulic cylinder, the thrust on its rod and the differentiation set different pressure levels, and the lowest pressure will be in the piston cavity of the last hydraulic cylinder. With uniformly loaded hydraulic cylinders, the pressure in the piston cavities depends only on the number of the hydraulic cylinder and its differentiation. In a hydraulic drive with hydraulic cylinders of equal power, the last hydraulic cylinder will develop the greatest force at the lowest piston speed. In addition, the work also shows that the reproducibility of the positions of unloaded rods of hy-draulic cylinders of equal differentiation is not less than 1%. As a result of the experimental studies, a method was developed for the design of a volumetric hydraulic drive with sequential switching on of executive hydraulic cylinders, which can be used to solve the problems of hydrofication of me-chanical engineering production (bending presses, sheet stamping), in shipbuilding (ship slipways), in flexible production systems, industrial and warehouse logistics.

scholarly journals Psychoacoustic Evaluation of Hydraulic Pumps

2021 ◽  
Vol 13 (13) ◽  
pp. 7320
Author(s):  
Tobias Pietrzyk ◽  
Markus Georgi ◽  
Sabine Schlittmeier ◽  
Katharina Schmitz
Keyword(s):  
Sound Pressure ◽  
Paired Comparison ◽  
Hydraulic Drive ◽  
Operating Parameter ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Hydraulic Pump ◽  
Listening Tests ◽  
Internal Gear ◽  
Axial Piston

In this study, sound measurements of an axial piston pump and an internal gear pump were performed and subjective pleasantness judgements were collected in listening tests (to analyze the subjective pleasantness), which could be seen as the inverse of the subjective annoyance of hydraulic drives. Pumps are the dominant sound source in hydraulic systems. The noise generation of displacement machines is subject of current research. However, in this research only the sound pressure level (SPL) was considered. Psychoacoustic metrics give new possibilities to analyze the sound of hydraulic drive technology and to improve the sound quality. For this purpose, instrumental measurements of the acoustic and psychoacoustic parameters are evaluated for both pump types. The recorded sounds are played back to the participants in listening tests. Participants evaluate them regarding the subjective pleasantness by means of paired comparison, which is an indirect scaling method. The dependence of the subjective pleasantness on speed and pressure was analyzed for both pump types. Different regression analyses were carried out to predict the subjectively perceived pleasantness or annoyance of the pumps. Results show that a lower speed is the decisive operating parameter for reducing both the SPL and the annoyance of a hydraulic pump.

Development of hydraulic cylinder diagnostic methods by modeling methods

2021 ◽  
pp. 41-45
Author(s):  
Keyword(s):  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Technical Condition ◽  
Diagnostic Methods ◽  
Technical Diagnostics ◽  
Remaining Service Life ◽  
Construction Machine ◽  
Piston Speed ◽  
Variable Nature ◽  
Hydraulic Cylinders

The hydraulic drive of a construction machine is a complex dynamic system that is subjected to many dynamic loads of a variable nature and operates under conditions of variable external influences caused by various factors. During operation, these loads cause failure of the hydraulic transmission elements. To prevent these malfunctions, technical diagnostics should be applied by determining their current technical condition and remaining service life. The article assesses the working condition of hydraulic cylinders using a mathematical model. Using matlab/simulink software to simulate the hydraulic cylinder and hydraulic piston speed when changing the hydraulic cylinder clearance. The simulation results are presented. Keywords: diagnostic, hydraulic cylinder, simulation, development

scholarly journals A Self-Contained Electro-Hydraulic Cylinder with Passive Load-Holding Capability

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 292 ◽  
Author(s):  
Damiano Padovani ◽  
Søren Ketelsen ◽  
Daniel Hagen ◽  
Lasse Schmidt
Keyword(s):  
Energy Efficiency ◽  
Cost Efficiency ◽  
Tracking Error ◽  
Hydraulic Cylinder ◽  
Position Tracking ◽  
Hydraulic Systems ◽  
Practical Applications ◽  
Hydraulic Cylinders ◽  
External Loads ◽  
Boom Crane

Self-contained electro-hydraulic cylinders have the potential to replace both conventional hydraulic systems and the electro-mechanical counterparts enhancing energy efficiency, plug-and-play installation, and reduced maintenance. Current commercial solutions of this technology are limited and typically tailor-made, whereas the research emphasis is primarily on cost efficiency and power applications below five [kW]. Therefore, there is the need of developing more flexible systems adaptable to multiple applications. This research paper offers a contribution in this regard. It presents an electro-hydraulic self-contained single-rod cylinder with passive load-holding capability, sealed tank, capable of recovering energy, and scalable up to about eighty [kW]. The system implementation on a single-boom crane confirms its feasibility: The position tracking error remains well within ±2 [mm], oscillations are limited, and the overall energy efficiency is about 60 [%] during actuation. Concerning the passive load-holding devices, it is shown that both vented and non-vented pilot-operated check valves achieve the desired functioning and can hold the actuator position without consuming energy. Additional observations about the size and the arrangement of the load-holding valves are also provided. In conclusion, this paper demonstrates that the proposed self-contained cylinder can be successfully extended to several practical applications, especially to those characterized by overrunning external loads and the need of securing the actuator position.

Internal leakage identification of hydraulic cylinder based on intrinsic mode functions with random forest

2019 ◽  
Vol 233 (15) ◽  
pp. 5532-5544 ◽  
Author(s):  
Lin Li ◽  
Yixiang Huang ◽  
Jianfeng Tao ◽  
Chengliang Liu
Keyword(s):  
Random Forest ◽  
Hydraulic Cylinder ◽  
Support Vector ◽  
Hydraulic Systems ◽  
Intrinsic Mode Functions ◽  
Random Forest Algorithm ◽  
Mode Decomposition ◽  
Empirical Mode Decomposition Method ◽  
Hydraulic Cylinders ◽  
Experimental Pressure

Monitoring for internal leakage of hydraulic cylinders is vital to maintain the efficiency and safety of hydraulic systems. An intelligent classifier is proposed to automatically evaluate internal leakage levels based on the newly extracted features and random forest algorithm. The inlet and outlet pressures as well as the pressure differences of two chambers are chosen as the monitoring parameters for leakage identification. The empirical mode decomposition method is used to decompose the raw pressure signals into a series of intrinsic mode functions to obtain the essence in experimental signals. Then, the features extracted from intrinsic mode functions in terms of statistical analysis are formed the input vector to train the leakage detector. The classifier based on random forest is established to categorize internal leakage into proper levels. The accuracy of the internal leakage evaluator is verified by the experimental pressure signals. Moreover, an internal leakage evaluator is established based on the support vector machine algorithm, in which the wavelet transform is applied for feature extraction. The accuracy and efficiency of different classifiers are compared based on leakage experiments. The results show that the classifier trained by the intrinsic mode function features in terms of random forest algorithm may more effectively and accurately identify internal leakage levels of hydraulic cylinders. The leakage evaluator provides probability for online monitoring of the internal leakage of hydraulic cylinders based on the inherent sensors.

Experimentally Validated Models of O-Ring Seals for Tiny Hydraulic Cylinders

2014 ◽  
Author(s):  
Jicheng Xia ◽  
William K. Durfee
Keyword(s):  
Simulation Models ◽  
Hydraulic Cylinder ◽  
Operating Conditions ◽  
System Level ◽  
Needle Valve ◽  
Hydraulic Systems ◽  
System Level Simulation ◽  
Piston Seal ◽  
Cylinder Piston ◽  
Hydraulic Cylinders

To enable simulation of tiny hydraulic systems, including predicting system efficiency, it is necessary to determine the effect of the hydraulic cylinder piston seal. For tiny cylinders whose bore is less than 10 mm, O-ring seals are convenient. Simplified models for the O-ring were used to describe piston leakage and friction and based on the models, the force and volumetric efficiencies for tiny cylinders were predicted for a range of steady state operating conditions. To validate the models, a test stand was constructed to collect experimental data for 4, 6 and 9 mm bore cylinders, which were in the form of a vertical ram with a single O-ring seal. The ram was fully extended and put under load. A needle valve was then cracked to cause the ram to descend at different speeds. Pressure, load and velocity were recorded and the data used to calculate cylinder efficiencies, which were then compared to model predictions. The model and the experiment showed essentially zero leakage. The experimental force efficiency had good agreement with the model over a range of operating conditions. The study showed that simple O-ring models for tiny hydraulic cylinders suffice for building system level simulation models.

scholarly journals SELF-CLEANING FILTER FOR CLOSED HYDROSYSTEMS OF AGRICULTURAL EQUIPMENT

2021 ◽  
Vol 295 (2) ◽  
pp. 130-138
Author(s):  
M. STADNIK ◽  
◽  
А. VIDMYSH ◽  
S. SHARGORODSKIY ◽  
V. RUTKEVYCH ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Pressure Pulsation ◽  
Experimental Studies ◽  
Hydraulic Drive ◽  
Operating Mode ◽  
Working Fluid ◽  
Hydraulic Systems ◽  
Agricultural Equipment ◽  
Self Cleaning ◽  
Special Stand

The issue of increasing the reliability and durability of hydraulic units of closed hydraulic systems of agricultural equipment is considered, due to better cleaning of the working fluid by filtration units. The design of a self-cleaning filter with hydraulic automatic control of backwashing of slotted filtration elements with a counterflow of the working fluid is proposed. A special stand has been developed for simulating the operation of a self-cleaning filter of closed hydraulic systems of agricultural equipment. Experimental studies on a special stand confirmed the efficiency of the proposed design and made it possible to identify its main advantages in comparison with domestic and foreign counterparts. Based on the analysis of transient processes with increased pressure pulsation of agricultural equipment of a closed hydraulic drive, the actual pressure drop at which automatic flushing is triggered was established, compared with the calculated one, in which it was impossible to take into account such real factors as friction in the sealing units, the characteristics of the springs, distortions, tightness of valve pairs, fluctuations in dimensional chains. The most optimal operating mode of auto-washing equipment with a choke diameter of 1.0 mm has been determined. The auto-washing equipment was switched on at a pressure drop of 1.5 MPa (15 atm) and in an improved mode – pressure pulsations with an amplitude of 2 MPa (20 atm) when the auto-wash was turned off decreased in time to 0.12 s. It is noted that the developed self-cleaning filter for closed hydraulic systems of agricultural equipment will improve the reliability and increase the service life of the elements of hydraulic units and the machine itself as a whole.

scholarly journals Analysis of the Throttle Speed Control Efficiency in Volumetric Hydraulic Drives

2019 ◽  
pp. 13-33
Author(s):  
K. D. Efremova ◽  
V. N. Pilgunov
Keyword(s):  
Control Method ◽  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Movement Speed ◽  
Working Fluid ◽  
Total Efficiency ◽  
Control Methods ◽  
Output Link ◽  
Hydraulic Cylinders ◽  
Load Characteristics

To control a movement speed of the output link of an executive hydraulic engine (hydraulic cylinder or hydraulic motor), volumetric hydraulic drives traditionally use volumetric and throttle control methods. Under volumetric control, a supply unit employs a pressure-regulated positive displacement pump, as a result of which it is impossible or difficult to separate and independently control the movement speed of the output links of the hydraulic cylinders. In case of throttle control, there is a significant dependence of the speed of the output link on the load it overcomes, a low efficiency of the hydraulic drive and hereto related active heating of the working fluid, as well as large energy losses. However, in embodiment, due to lack of an expensive variable pump, this method of control is much cheaper and can be used in a multi-channel hydraulic drive with a centralized supply unit.Depending on the throttling device localization in the hydraulic drive circuit, there are series (primary or secondary control) and parallel (working fluid bypass adjustment) throttle connection schemes. The secondary control scheme, which generates a pressure in the outlet of the executive hydraulic engine, is preferable due to the fact that it provides an increased pressure in both cavities of the executive hydraulic engine and, accordingly, a lack of combined air bubbles in the working fluid. Heat released in the throttle is discharged directly into the tank, and the pressure in the outlet reduces the danger level of the emergency situation consequences in the event of an unauthorized change in the sign of the load to be overcome. The quality of control is, mainly, assessed by the type of load characteristics, i.e. dependences of the output link speed and its developed power on the load to be overcome, as well as by the control efficiency (the total efficiency value of the regulating and executive subsystems of the hydraulic drive). The dependence of the dynamics and kinematics of the hydraulic drive on the control methods are of particular interest.The proposed paper, based on the developed mathematical models and their testing for specific sizes of hydraulic cylinders presents the numerical values of the load characteristics and dependences of the total efficiency on the load value to be overcome. Shows that the speed load characteristic steepness of an executive hydraulic cylinder and the sign of its derivative are determined by the throttle control method. The greatest power developed by the output link of the hydraulic engine is shifted to the loads that are 50 ... 70% of their maximum value.As a result of theoretical studies using numerical calculation methods, a technique has been developed for selecting a throttle control method with an assessment of its quality and efficiency. The results of the conducted studies expand the capabilities to forecast the dynamics and kinematics of the output link of the hydraulic drive at the stage of its engineering design.

A Novel Design Concept of Digital Hydraulic Drive for Knee Exoskeleton

2021 ◽  
Author(s):  
Rituraj Rituraj ◽  
Rudolf Scheidl ◽  
Peter Ladner ◽  
Martin Lauber
Keyword(s):  
Gait Cycle ◽  
Hydraulic Drive ◽  
Cost Effective ◽  
Peak Torque ◽  
Energy Recuperation ◽  
Moderate Power ◽  
Hydraulic Cylinders ◽  
Exoskeleton Design ◽  
Novel Design ◽  
Unique Mechanism

Abstract Hydraulic actuation of exoskeletons has gained interest among researchers due the potentials of high power density and energy recuperation allowing the reduction of mass and space used by the device (when compared to the traditional electrically actuated exoskeletons). However, developing a light and cost-effective design of such exoskeleton remains a key challenge. In this work, a novel design of digitally driven knee exoskeleton is presented. The design uses simple hydraulic cylinders instead of multi-chamber cylinders (which are typically used in digital actuations and are expensive). The design also includes a unique mechanism that is able to satisfy the peak torque requirements during a typical gait cycle with a smaller hydraulic force. This ensures small size of hydraulic components and a moderate power demand from the energy source. To study this exoskeleton design, a numerical model of the exoskeleton and the lower limb is developed in this work. The simulation results show that the design is able to track the motion of the knee in a typical gait cycle as well as satisfy the necessary torque requirements.

Efficiency Analysis of an Electro-Hydraulic Drive for Mobile Lifting Machines

2020 ◽  
Author(s):  
Serena Morselli ◽  
Pietro Marani ◽  
Cesare Dolcin ◽  
Mattia Scolari ◽  
Cristian Ferrari
Keyword(s):  
Cooling System ◽  
Large Body ◽  
Hydraulic Drive ◽  
Environmental Issues ◽  
Hydraulic Cylinder ◽  
System Size ◽  
Operating Conditions ◽  
Gear Pump ◽  
Variable Speed ◽  
Low Speed

Abstract Environmental issues have become a critical topic at all levels and the Fluid Power industry is no exception. One of the most important research trends is aimed at improving efficiency through electrification, the availability of new electric motors and drive solutions is expected to promote the introduction of speed-controlled pump systems in mobile applications, nowadays dominated by conventional valve-controlled solutions. The paper will firstly present a collection of tests carried out on a lifting application, powered by an inverter-controlled electric motor moving a reversible gear pump/motor. The lowering phase is carried out in two alternative modes, the first one is the electric regenerative mode, the second one is the throttle-controlled mode. The analysis of the results will highlight different energy efficiencies of the system at different operating conditions. In particular the losses of volumetric unit, piping, throttle elements, hydraulic cylinder and electric components can change dramatically depending on operating conditions. In the second part of the paper, a lumped parameters model will be presented, using a commercial software. Firstly, the model will be able to catch the behavior of the test bench and secondarily it will be used to predict the expected performances of alternative design choices. Particular attention will be focused on low speed operation. In fact, there is more uncertainty and much less well-established knowledge on the behavior of the volumetric units at low speed, concerning the large body of work available for the nominal speed conditions. Finally an outlook will be drawn of expected advantages and limitations arising from the implementation of variable speed pumps on mobile machines. Such benefits will be presented with practical figures of merit such as the energy recovery performance, the increase of cycles and the cooling system size reduction.

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