Analytical Coupled Modeling and Model Validation of Hydraulic On/Off Valves

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
John Mahrenholz ◽  
John Lumkes
Keyword(s):  
High Speed ◽  
Eddy Currents ◽  
Hydraulic Systems ◽  
Coupled Modeling ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fluid Transients ◽  
Pressure Ripple ◽  
Valve Dynamics ◽  
Fully Coupled

The goal of this paper is to describe a method for modeling high speed on/off valves. This model focuses on the nonlinearities of the electromagnetic, fluidic, and mechanical domains, specifically within solenoid driven poppet style valves. By including these nonlinearities, the model accurately predicts valve transition time for different driving voltages and valve strokes. The model also predicts fluid transients such as pressure ripple. Unique attributes of the model are the inclusion of the effect of eddy currents and fringing while still being fully coupled with the fluid and mechanical domains. A prototype was constructed and used to experimentally validate the model. By developing accurate lumped parameter models, valve dynamics can be applied to hydraulic systems to accurately capture their dynamics.

Soft Switching in Switched Inertance Hydraulic Circuits

2016 ◽  
Author(s):  
Alexander C. Yudell ◽  
James D. Van de Ven
Keyword(s):  
High Speed ◽  
Soft Switching ◽  
Power Delivery ◽  
Lumped Parameter Model ◽  
Energy Losses ◽  
Hydraulic Systems ◽  
Zero Voltage Switching ◽  
Lumped Parameter ◽  
Capacitive Element ◽  
Zero Voltage

Switched Inertance Hydraulic Systems (SIHS) use inductive, capacitive, and switching elements to boost or buck a pressure from a source to a load in an ideally lossless manner. Real SIHS circuits suffer a variety of energy losses, with throttling of flow during transitions of the high-speed valve resulting in 44% of overall losses. These throttling energy losses can be mitigated by applying the analog of zero-voltage-switching, a soft switching strategy, adopted from power electronics. In the soft switching circuit, the flow that would otherwise be throttled across the transitioning valve is stored in a capacitive element and bypassed through check valves in parallel with the switching valves. To evaluate the effectiveness of soft switching in a boost converter SIHS, a lumped parameter model was constructed. The model demonstrates that soft switching can improve the efficiency of the circuit up to 42% and extend the power delivery capabilities of the circuit by 76%.

A Method of Characteristics Based Coupled Pump/Line Model to Predict Noise Sources of Hydrostatic Transmissions

2009 ◽  
Author(s):  
Richard Klop ◽  
Andrea Vacca ◽  
Monika Ivantysynova
Keyword(s):  
Method Of Characteristics ◽  
Numerical Approach ◽  
Noise Sources ◽  
Line Model ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Pressure Ripple ◽  
Flow Oscillations ◽  
Hydrostatic Transmissions ◽  
Parameter Approach

This study is a part of a larger research project to predict noise sources of hydrostatic transmissions and investigating new methods for designing quieter systems. The aim of this study is to validate the developed model describing pump dynamics coupled with effects of a connecting line, thus validating a coupled pump-motor-line model for hydrostatic transmissions. This paper illustrates a numerical approach for evaluating pressure and flow oscillations generated by a hydraulic pump coupled with a connecting line. The presented model describes pump dynamics using a lumped parameter approach as well as one-dimensional unsteady compressible fluid flow by means of method of characteristics (MOC). Several lumped parameter models have been developed for hydraulic pumps and motors and the method of characteristics has been applied for many applications; however, the presented model uniquely utilizes both approaches and considers influence of pump dynamics and propagating pressure and flow pulsations throughout the line. Measurements of pressure ripple in the line at two different points were carried out at various loading conditions to validate the developed model. Comparisons between measurements, the developed model, and another more simplified model were conducted. Results indicate a reasonable match between the developed model and measurements as well as the importance of considering a line model based on method of characteristics.

Static and Dynamic Bending Responses of the Human Cervical Spine

1998 ◽  
Vol 120 (6) ◽  
pp. 693-696 ◽  
Author(s):  
L. M. Voo ◽  
F. A. Pintar ◽  
N. Yoganandan ◽  
Y. K. Liu
Keyword(s):  
Cervical Spine ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Bending Moment ◽  
Dynamic Tests ◽  
Validation Data ◽  
Static Tests ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Dynamic Bending

The quasi-static and dynamic bending responses of the human mid-lower cervical spine were determined using cadaver intervertebral joints fixed at the base to a six-axis load cell. Flexion bending moment was applied to the superior end of the specimen using an electrohydraulic piston. Each specimen was tested under three cycles of quasi-static load-unload and one high-speed dynamic load. A total of five specimens were included in this study. The maximum intervertebral rotation ranged from 11.0 to 15.4 deg for quasi-static tests and from 22.9 to 34.4 deg for dynamic tests. The resulting peak moments at the center of the intervertebral joint ranged from 3.8 to 6.9 Nm for quasi-static tests and from 14.0 to 31.8 Nm for dynamic tests. The quasi-static stiffness ranged from 0.80 to 1.35 Nm/deg with a mean of 1.03 Nm/deg (±0.11 Nm/deg). The dynamic stiffness ranged from 1.08 to 2.00 Nm/deg with a mean of 1.50 Nm/deg (±0.17 Nm/deg). The differences between the two stiffnesses were statistically significant (p < 0.01). Exponential functions were derived to describe the quasi-static and dynamic moment-rotation responses. These results provide input data for lumped-parameter models and validation data for finite element models to better investigate the biomechanics of the human cervical spine.

scholarly journals Modelling and Validation of Cavitating Orifice Flow in Hydraulic Systems

2021 ◽  
Vol 13 (13) ◽  
pp. 7239
Author(s):  
Paolo Casoli ◽  
Fabio Scolari ◽  
Massimo Rundo
Keyword(s):  
Lumped Parameter Model ◽  
Hydraulic Systems ◽  
Vena Contracta ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Orifice Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Cfd Method ◽  
Hydraulic Valves

Cavitation can occur at the inlet of hydraulic pumps or in hydraulic valves; this phenomenon should be always avoided because it can generate abnormal wear and noise in fluid power components. Numerical modeling of the cavitation is widely used in research, and it allows the regions where it occurs more to be predicted. For this reason, two different approaches to the study of gas and vapor cavitation were presented in this paper. In particular, a model was developed using the computational fluid dynamics (CFD) method with particular attention to the dynamic modeling of both gaseous and vapor cavitation. A further lumped parameter model was made, where the fluid density varies as the pressure decreases due to the release of air and the formation of vapor. Furthermore, the lumped parameter model highlights the need to also know the speed of sound in the vena contracta, since it is essential for the correct calculation of the mass flow during vaporization. A test bench for the study of cavitation with an orifice was set up; cavitation was induced by increasing the speed of the fluid on the restricted section thanks to a pump located downstream of the orifice. The experimental data were compared with those predicted by CFD and lumped parameter models.

Development of a Dual Supply H-Bridge Amplifier for High Speed Actuation of Digital Hydraulic Switching Valves

2019 ◽  
Author(s):  
Florian Messner ◽  
Rudolf Scheidl
Keyword(s):  
Power Electronics ◽  
Significant Influence ◽  
High Speed ◽  
Point Of View ◽  
Hydraulic Systems ◽  
Valve Design ◽  
Improve Efficiency ◽  
Valve Dynamics ◽  
And Performance ◽  
Valve Actuation

For many digital hydraulic systems, fast and precise valve actuation is a key to improve efficiency and performance. Such an actuation may be achieved by optimizing the valve design from a mechanical and hydraulically point of view. But additionally, power electronics for valve actuation has to be given also high attention since it can have significant influence on valve dynamics, particularly in case of high-speed actuation with switching times in the range of 1 ms or less. Such actuation poses requirements that are not met by standard power electronics. These requirements are analysed in this paper and a proper schematic for the power electronics is derived. Measurements with a corresponding prototype prove that a fast, precise and very repeatable valve actuation can be achieved if the power electronics is conceived according to the characteristics of high speed valves.

Modeling and Validation of a High Speed Rotary PWM On/Off Valve

2009 ◽  
Author(s):  
Haink C. Tu ◽  
Michael B. Rannow ◽  
Meng Wang ◽  
Perry Y. Li ◽  
Thomas R. Chase
Keyword(s):  
High Speed ◽  
Pulse Width Modulation ◽  
Hydraulic Systems ◽  
Rotary Valve ◽  
Flow Area ◽  
Output Pressure ◽  
Critical Technology ◽  
Variable Displacement ◽  
Pressure Ripple ◽  
Actuation Power

Efficient high-speed on/off valves are a critical technology for enabling digital control of hydraulic systems via pulse-width-modulation (PWM). High-speed valves, when used in virtually variable displacement pumps (VVDP), increase system bandwidth and reduce output pressure ripple by enabling higher PWM frequencies. Our approach to achieving high speed and large flow area with low actuation power is a unidirectional rotary valve designed specifically for PWM. In comparison to conventional valves, the rotary valve reduces valve actuation power from a cubic dependence on PWM frequency to a square dependence by eliminating motion reversals during transition. This paper presents experimental data that validates the rotary valve concept, valve design equations, and dynamic model of a rotary valve based VVDP. Our unoptimized prototype exhibits 65% efficiency at 50% displacement and 15Hz PWM frequency while the validated model projects that an optimized valve is capable of achieving 85% efficiency at 15Hz and 73% at 75Hz.

The Impact of Peak-and-Hold and Reverse Current Driving Strategies on the Dynamic Performance of Commercial Cartridge Valves

2014 ◽  
Author(s):  
Farid Breidi ◽  
Tyler Helmus ◽  
Michael Holland ◽  
John Lumkes
Keyword(s):  
Power Systems ◽  
Input Signal ◽  
High Speed ◽  
Energy Savings ◽  
Eddy Currents ◽  
Response Times ◽  
Dynamic Performance ◽  
Reverse Current ◽  
Hydraulic Systems ◽  
The Impact

High speed valves have an important role in many existing fluid power systems and are an enabler for many proposed digital hydraulic systems. One method commonly used to improve the dynamic performance of on-off valves involves modifying the electrical input signal to the solenoids to reduce the inductive lag and eddy current decay. This research examined two commercially available direct actuated and pilot-stage actuated cartridge poppet valves and the role of peak-and-hold voltage and reverse current input profiles on opening and closing switching times. A test stand was built to characterize the performance of these valves. The valves were placed between two high frequency pressure transducers and the pressure differential across the valves was recorded, allowing the calculation of transition and delay time. The peak and reverse voltage duration was tested over a range of zero to ten milliseconds and an optimum response was found at a peak duration of six to eight milliseconds. Peak voltages ranged from 50 to 55 volts, followed by a holding voltage of 12 volts. Reverse current profiles were used to turn off the valves with a maximum peak current of three amps. The reverse current was used to increase the decay rate of eddy currents thus improving the turning off performance of the valves. Commercial valves that had a range of 33 to 55 millisecond turn-on response without input signal modification; these same valves had response times reduced to a range of seven to nine milliseconds after applying the peak and hold method. The turn-off time was reduced from 130 milliseconds to a range of 16 to 50 milliseconds after adding reverse current inputs. This improvement in valve performance can lead to siginificant energy savings due to reduction of transition losses and can widen the useful application of the valves.

Soft Switching in Switched Inertance Hydraulic Circuits

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Alexander C. Yudell ◽  
James D. Van de Ven
Keyword(s):  
High Speed ◽  
Peak Load ◽  
Soft Switching ◽  
Power Delivery ◽  
Lumped Parameter Model ◽  
Energy Losses ◽  
Hydraulic Systems ◽  
Zero Voltage Switching ◽  
Lumped Parameter ◽  
Capacitive Element

Switched inertance hydraulic systems (SIHS) use inductive, capacitive, and switching elements to boost or “buck” (reduce) a pressure from a source to a load in an ideally lossless manner. Real SIHS circuits suffer a variety of energy losses, with throttling of flow during transitions of the high-speed valve resulting in as much as 44% of overall losses. These throttling energy losses can be mitigated by applying the analog of zero-voltage-switching, a soft switching strategy, adopted from power electronics. In the soft switching circuit, the flow that would otherwise be throttled across the transitioning valve is stored in a capacitive element and bypassed through check valves in parallel with the switching valves. To evaluate the effectiveness of soft switching in a boost converter SIHS, a lumped parameter model was constructed. Simulation demonstrates that soft switching improves the efficiency of the modeled circuit by 42% at peak load power and extends the power delivery capabilities by 77%.

Lumped parameter models for two-ventricle and healthy and failing extracardiac Fontan circulations

2021 ◽  
Author(s):  
Matthew G Doyle ◽  
Marina Chugunova ◽  
S Lucy Roche ◽  
James P Keener
Keyword(s):  
Single Ventricle ◽  
Left Ventricular ◽  
Sensitivity Analyses ◽  
Surgical Strategies ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fontan Failure ◽  
Existence Of Periodic Solutions ◽  
Mathematical Definitions ◽  
Extracardiac Fontan

Abstract Fontan circulations are surgical strategies to treat infants born with single ventricle physiology. Clinical and mathematical definitions of Fontan failure are lacking, and understanding is needed of parameters indicative of declining physiologies. Our objective is to develop lumped parameter models of two-ventricle and single-ventricle circulations. These models, their mathematical formulations and a proof of existence of periodic solutions are presented. Sensitivity analyses are performed to identify key parameters. Systemic venous and systolic left ventricular compliances and systemic capillary and pulmonary venous resistances are identified as key parameters. Our models serve as a framework to study the differences between two-ventricle and single-ventricle physiologies and healthy and failing Fontan circulations.

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