Leveraging Flow Regeneration in Individual Energy-Efficient Hydraulic Drives

2021 ◽  
Author(s):  
Damiano Padovani
Keyword(s):  
Natural Frequency ◽  
Dynamic Properties ◽  
Poor Performance ◽  
Control Techniques ◽  
Lower Natural Frequency ◽  
Operating Region ◽  
Depth Analysis ◽  
Study Case ◽  
Boom Crane ◽  
Circuit Configuration

Abstract The current demand for energy efficiency in hydraulics directs towards the replacement of centralized, valve-controlled actuators with individual, throttleless drives. The resulting solutions often require an undesirable sizing of the key components to expand the system’s operating region. Using flow regeneration (i.e., shortcutting the actuator’s chambers) mitigates this issue. Such an option, already stated for individual drives, lacks an in-depth analysis from the control perspective since the dynamic properties are changed (e.g., the natural frequency is decreased to about 60% of the original value). Therefore, this research paper studies a representative single-pump architecture arranged in a closed-circuit configuration. Linear control techniques are used to understand the system dynamics and design a PI-control algorithm that also adds active damping. The outcomes are validated via high-fidelity simulations referring to a single-boom crane as the study case. The results encompassing diverse scenarios indicate that flow regeneration is only interesting in those applications where the dynamic response is not demanding. In fact, the lower natural frequency reduces the system’s bandwidth to about 69% of the original value and affects the closed-loop position tracking drastically. This poor performance becomes evident when medium-to-high actuation velocity is commanded with respect to the maximum value.

Dynamic Property Evaluation of a Long-Span Cable-Stayed Bridge (Sutong Bridge) by a Bayesian Method

2018 ◽  
Vol 19 (01) ◽  
pp. 1940010 ◽  
Author(s):  
Yan-Chun Ni ◽  
Qi-Wei Zhang ◽  
Jian-Feng Liu
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Structural Damage ◽  
Dynamic Properties ◽  
Modal Identification ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Sutong Bridge

Modal identification aims at identifying the dynamic properties including natural frequency, damping ratio, and mode shape, which is an important step in further structural damage detection, finite element model updating, and condition assessment. This paper presents the work on the investigation of the dynamic characteristics of a long-span cable-stayed bridge-Sutong Bridge by a Bayesian modal identification method. Sutong Bridge is the second longest cable-stayed bridge in the world, situated on the Yangtze River in Jiangsu Province, China, with a total length of 2 088[Formula: see text]m. A short-term nondestructive on-site vibration test was conducted to collect the structural response and determine the actual dynamic characteristics of the bridge before it was opened to traffic. Due to the limited number of sensors, multiple setups were designed to complete the whole measurement. Based on the data collected in the field tests, modal parameters were identified by a fast Bayesian FFT method. The first three modes in both vertical and transverse directions were identified and studied. In order to obtain modal parameter variation with temperature and vibration levels, long-term tests have also been performed in different seasons. The variation of natural frequency and damping ratios with temperature and vibration level were investigated. The future distribution of the modal parameters was also predicted using these data.

scholarly journals Laser and the Tuber: Thermal Dynamic and Volumetric Factors Influencing Seizure Outcomes in Pediatric Subjects With Tuberous Sclerosis Undergoing Stereoencephalography-Directed Laser Ablation of Tubers

Neurosurgery ◽  
2019 ◽  
Vol 66 (Supplement_1) ◽  
Author(s):  
Michael A Stellon ◽  
Kelsey Diva Cobourn ◽  
Matthew Whitehead ◽  
Nancy Elling ◽  
William McClintock ◽  
...  
Keyword(s):  
Tuberous Sclerosis ◽  
Surgical Management ◽  
Pediatric Patients ◽  
Dynamic Properties ◽  
Invasive Technique ◽  
Tuber Tissue ◽  
Ablation Volume ◽  
Depth Analysis ◽  
Cortical Tubers

Abstract INTRODUCTION Tuberous Sclerosis (TSC) is a well-known cause of Medically Refractory Epilepsy (MRE). It is well documented that early surgical management can improve patient outcomes. Stereoencephalography-directed Magnetic Resonance guided Laser Interstitial Thermal Therapy (SEEG-directed MRgLITT) is an emerging minimally invasive technique that appears aptly suited for the surgical management of this condition. Our aims are to present our experiences with patients who had undergone prior SEEG-directed MRgLITT to identify and treat cortical tubers responsible for clinical seizures and to perform an in-depth analysis of volumetric and thermal dynamic factors that may be related to seizure outcomes. METHODS We studied all pediatric patients with MRE due to TSC who underwent SEEG-directed MRgLITT, investigating seizure outcomes in relationship to thermal dynamic and volumetric factors of MRgLITT when applied to cortical tubers. RESULTS About 8 cortical tubers from 3 pediatric patients were analyzed. About 2 out of 3 patients had Engel I outcomes at last follow-up. Median follow-up was 15 mo. Average A/T (ablation volume/tuber volume) ratio for Engel I outcomes was 1.28 (variance, 0.16) and 0.84 (variance < 0.01) for all other outcomes (P = .035). When assessing thermal dynamic properties of cortical tuber tissue, there was a moderate positive correlation when comparing ablation energy to ablation volume (R2 = 0.65). When the calcified tuber is excluded from regression analysis, the correlation is stronger (R2 = 0.77). Thus, the calculated volume to ablate 1 cm3 of cortical tuber tissue is 1263.6 J (calcified tuber) or 1089.5 J (noncalcified tuber). CONCLUSION SEEG-directed MRgLITT is a safe and effective technique in the management of pediatric patients with MRE due to TSC. It appears that the A/T ratio is a useful indicator in predicting seizure outcomes.

scholarly journals Effects of Tree Crown Structure on Dynamic Properties of Acer rubrum L. ‘Florida Flame’

2014 ◽  
Vol 40 (4) ◽  
Author(s):  
Jason Miesbauer ◽  
Edward Gilman ◽  
Mihai Giurcanu
Keyword(s):  
Natural Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Acer Rubrum ◽  
Tree Crown ◽  
Tree Form ◽  
Induced Stress ◽  
Crown Structure ◽  
Before And After ◽  
One Year

Knowledge of tree dynamic properties is important to improve one’s ability to assess tree risk. Pull-and-release tests were performed on 16 Acer rubrum L. ‘Florida Flame’ trees in summer and winter over a two-year period, and natural frequency and damping ratios were calculated. One year prior to testing, trees were designated as either excurrent or decurrent and pruned to impose that form. During summer tests, trees were pruned to maintain designated form, and tests were performed before and after pruning. Trees were then systematically dissected to measure morphological and allometric characteristics. Excurrent trees had a higher natural frequency than decurrent trees in summer and winter, and pruning in summer increased the frequency of excurrent trees more than decurrent trees. Tree form and pruning had little effect on damping ratio. Decurrent trees had a larger percent of their branch mass in the top half of the crown than excurrent trees, which would subject them to larger wind-induced stress on their trunks and increase the risk of failure.

Dynamic Properties of Delaminated Braided Textile Composite Beams

2008 ◽  
Author(s):  
Benjamin Dauda ◽  
S. Olutunde Oyadiji ◽  
Prasad Potluri
Keyword(s):  
Natural Frequency ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Testing ◽  
Composite Beams ◽  
Textile Composite ◽  
Element Analysis ◽  
Frequency Shifts ◽  
Cantilevered Beams

In this paper, vibration analysis of through-width single- and multi-delaminated cantilevered composite beams is carried out using Finite Element Analysis (FEA) approach. Different configurations of multiple delaminations are considered. The FEA results for single delaminations are validated via experimental testing. It is found that changes in the natural frequencies of delaminated cantilevered beams are related to the number, type and distributions of delaminations within a beam. Also, the natural frequency shifts due to single or multiple delaminations are influenced by the thickness-wise locations of the delaminations. As the delamination is moved from the outermost inter-laminar layer towards the mid-plane of the beam, the natural frequency decreases and reaches a minimum value when the delamination is located at the midplane. Single delaminations have a more significant effect on natural frequencies than multiple delaminations of the same overall dimension as the single delamination. Furthermore, it is found that there is a greater reduction in natural frequency when multiple delaminations are close together than when they are spread out. However, where the locations of multiple delaminations coincide with nodal or antinodal vibration points, the effect is significantly altered.

Nonlinear Dynamic Modeling of Smart Composite With Peizoelectric Nitinol and MMC

2009 ◽  
Author(s):  
Abbas Amini ◽  
Hamid Mehdigholi ◽  
Mohammad Elahinia
Keyword(s):  
Natural Frequency ◽  
Numerical Approximation ◽  
Order Equation ◽  
Advanced Materials ◽  
Smart Composite ◽  
Dynamic Motion ◽  
Lower Natural Frequency ◽  
Linear Behavior ◽  
The Relationship ◽  
Nonlinear Dynamic Modeling

In this paper, one smart composite involving nitinol, piezoelectric and MMC is modeled. This simulation covers all criteria in these advanced materials and theoretically solves the five-order equation. Furthermore, numerical sample is investigated and results have been explored. The results represent the relationship between natural frequency of the structure, temperature, the lateral deflection and martensite ratio of shape memory alloy. The results show nonlinearity response in dynamic motion in lower natural frequency and linear behavior in higher frequency. In this simulation, numerical approximation has been avoided.

Vibrational Characteristics of Micro Beams

2005 ◽  
Author(s):  
Oladipo Onipede ◽  
Ilya Avdeev ◽  
Amir Khalilollahi ◽  
Lisa Buziewicz
Keyword(s):  
Natural Frequency ◽  
Applied Voltage ◽  
Dynamic Properties ◽  
Electrostatic Force ◽  
Elastic Stiffness ◽  
Critical Parameters ◽  
Driving Voltage ◽  
Mems Devices ◽  
Non Linear ◽  
Voltage Frequency

Several high frequency MEMS devices such as resonators and filters can be modeled as electrostatically driven micro-beams. While their static structural response depends solely on the magnitude of the applied voltage and their elastic stiffness, their dynamic response also depends on their mass, damping properties and the applied voltage frequency. In designing these devices, critical parameters must include the maximum voltage, voltage frequency and the natural frequency of the system. Even though the electrostatic force developed by the voltage is non-linear, the system can be modeled as a harmonic system due to the periodic nature of the response. Results from a non-linear structural-electrostatic dynamic model show the importance of the dynamic properties and the non-linear electrostatic force. The results show significantly lower limiting voltages, especially when the driving voltage is close to the natural frequency of the system. The effect of damping is also addressed.

Estimation of the dynamic properties of floors using Heel Drop Tests

2021 ◽  
Author(s):  
Mehdi Setareh ◽  
Jiang Li
Keyword(s):  
Dynamic Response ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Accurate Estimate ◽  
Inexpensive Method ◽  
Structure Interaction ◽  
Modal Damping ◽  
Drop Tests ◽  
Interaction Phenomenon

<p>To evaluate the dynamic response of floors, it is important to estimate their dynamic properties, in particular natural frequencies and modal damping ratios. Heel drop test is a simple and inexpensive method of floor excitation to measure its dynamic properties. Even though this test can result in a relatively accurate estimate of the floor natural frequency, this may not be the case for the modal damping ratios. With the help of a number of volunteers, heel drop tests were conducted on a force platform placed on a test floor. The tests were also repeated using an instrumented hammer. The results showed that the measured natural frequency using heel drops was close to that found using the instrumented hammer. However, the modal damping ratios found using the heel drop tests were higher, which can be attributed to the human-structure interaction phenomenon.</p>

Operational Modal Analysis of Broaching Machine

2012 ◽  
Vol 159 ◽  
pp. 170-175
Author(s):  
Lv Gao Lin ◽  
Shen Shun Ying ◽  
Shu Qiong Chen ◽  
Xiao Tian Lv
Keyword(s):  
Cutting Force ◽  
Natural Frequency ◽  
Fundamental Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Cutting Velocity

Modal parameters for LG51SH broaching machine from operational responses are studied to examine the dynamic properties of mechanical structure. The operational modal is analyzed using PolyMAX method with responsive data of key point in broaching machine, which is excited in practical broaching operation and tested by LMS SCADAIII-105 system. The identified steady state modal, representative modal shape, modal damping ratio and natural frequency in broaching are presented. The test and analysis result shows that there are natural frequency of 38Hz and 192Hz, which are close to multiple of the fundamental frequency of cutting force in broaching, 6Hz, therefore, reasonable cutting velocity should be adopted to void producing fundamental frequency of cutting force in broaching.

Blade-Shaft Coupled Resonance Vibration by Using Active Magnetic Bearing Excitation

2008 ◽  
Author(s):  
Norihisa Anegawa ◽  
Hiroyuki Fujiwara ◽  
Osami Matsushita
Keyword(s):  
Natural Frequency ◽  
Rotational Speed ◽  
Critical Speed ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Dynamic Vibration Absorber ◽  
Blade Vibration ◽  
Lower Natural Frequency ◽  
Damped System ◽  
Spring System

The turbine generator requires sufficient reliability as a major component of the power plant. The rotor dynamics calculates the critical speed of the shaft-bearing system for design to avoid appearance of the critical speed, while the blade dynamics calculates the natural frequency of the blade to avoid nX resonance. For longer blades, however, the lower natural frequency requires that the design of the shaft and blade takes into account the coupling of the blade vibration mode with nodal diameter k = 0 and k = 1 with the vibration of the shaft. The present work analyzes the coupling of the parallel motion of the shaft with the in-plane vibration of the blade within k = 1 modes. More specifically, the existence of an unstable region due to coupling and the coupled resonance in an eight-blade (N = 8) where each blade is assumed to be a 1-DOF mass-spring system were analyzed in detail. Analysis was also made on the forced vibration of a stable damped system. At a rotational speed Ω = |ωs − ωb|, the vibration of the shaft was limited to a relatively small amplitude due to anti-resonance points resulting from the dynamic vibration absorber effect, while the resonance of the blades was relatively big amplitude. A violent coupled resonance resulting from the dynamic absorber effect of the blades and shaft was observed at a rotational speed Ω = ωs + ωb. The resonance in blade vibration at Ω = |ωb − ωs| was experimentally confirmed.

A Theory Treatment of Pedestrian-Induced Lateral Vibration of Structure

2017 ◽  
Vol 140 (6) ◽  
Author(s):  
Qingshan Yang ◽  
Yanan Gao
Keyword(s):  
Natural Frequency ◽  
Dynamic Properties ◽  
Damping Capacity ◽  
Lateral Vibration ◽  
Structural Damping ◽  
Step Width ◽  
Step Frequency ◽  
Public Attention ◽  
Structural Dynamic ◽  
Dynamic Performances

The lateral excessive sway motion caused by pedestrian traffic has attracted great public attention in the past decades years. However, the theories about exploring the effect of pedestrian on the lateral dynamic properties of structure are scarce. The new contribution of this paper is that a new pedestrian-structure system is proposed for exploring the effect of human on structural dynamic properties based on a sway assumption. Study shows that pedestrian deteriorates the natural frequency of structure and improves structural damping. The influence tendencies of pedestrian on structure can be supported by measurements. The further parametric study shows that the changes of human dynamic parameters have some evident impacts on structural dynamic performances. For example, the increase of leg damping can trigger an improvement of structural damping capacity. In addition, the walking step frequency closing structural harmonic natural frequency can incur the worst response. The increase of step width deteriorates lateral vibration and structural frequency but can slightly improve structural damping. One of essential reasons influencing structural lateral dynamic properties is the dynamic human system including body mass, damping, stiffness, and its motion behavior such as step frequency. This theory is proposed to analyze how pedestrian alters the lateral dynamic performances on those sensitive structures such as the footbridges or stadium bleachers. For example, how the variation of step width influences the change of natural frequency of structure?

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