scholarly journals Parametric Vibration Analysis of a Six-Degree-of-Freedom Electro-Hydraulic Stewart Platform

2021 ◽  
Vol 2021 ◽  
pp. 1-27
Author(s):  
Xiaoming Yuan ◽  
Yue Tang ◽  
Weiqi Wang ◽  
Lijie Zhang
Keyword(s):  
Natural Frequency ◽  
Vibration Analysis ◽  
Dominant Frequency ◽  
Stewart Platform ◽  
Sixth Order ◽  
Equivalent Stiffness ◽  
Main Resonance ◽  
Hydraulic Oil ◽  
Coupling Parameters ◽  
Vibration Time

Electro-hydraulic Stewart 6-DOF platform is a 6-DOF parallel mechanism combined with the electro-hydraulic servo control system, which is widely used in the field of construction machinery. In actual working conditions, the flow and pressure pulsation of the hydraulic oil output from the hydraulic leg of the electro-hydraulic Stewart platform are inevitable, so the equivalent stiffness of the platform leg will change, and the stiffness parameters of the transmission system will change, resulting in vibration, which will affect the accuracy of the platform. This paper considering the fluid unit equivalent stiffness cyclical fluctuations and leg, on the basis of the relationship between hydraulic stiffness, constructs the electric hydraulic Stewart platform machine vibration dynamics equation, fluid coupling parameters of vibration parameters using the method of the multiscale approximate analytic formula of the main resonance and combination resonance are derived, and the system parameters vibration time-domain response and frequency response under two different poses are discussed. Results show that the system first to six order natural frequency and the first to the sixth order natural frequency and frequency of hydraulic oil equivalent stiffness of the combination of frequency will have an effect on the parameters of the system vibration. In the main resonance, the dominant frequency is mainly the first to sixth order natural frequency of the system; in the combined resonance, the dominant frequency is the combined frequency. Through the parameter vibration analysis of two different positions of the platform, it is concluded that when the platform is in an asymmetric position, each leg of the system is more involved in vibration. This study can provide the reference for the subsequent dynamic optimization and reliability analysis of the electro-hydraulic Stewart platform.

Weakfish sonic muscle: influence of size, temperature and season

2002 ◽  
Vol 205 (15) ◽  
pp. 2183-2188 ◽  
Author(s):  
M. A. Connaughton ◽  
M. L. Fine ◽  
M. H. Taylor
Keyword(s):  
Natural Frequency ◽  
Pulse Duration ◽  
Dominant Frequency ◽  
Forced Response ◽  
Acoustic Energy ◽  
Honest Signal ◽  
Muscle Twitch ◽  
Cross Sectional ◽  
Fish Size ◽  
Sonic Muscle

SUMMARYThe influence of temperature, size and season on the sounds produced by the sonic muscles of the weakfish Cynoscion regalis are categorized and used to formulate a hypothesis about the mechanism of sound generation by the sonic muscle and swimbladder. Sounds produced by male weakfish occur at the time and location of spawning and have been observed in courtship in captivity. Each call includes a series of 6-10 sound pulses, and each pulse expresses a damped, 2-3 cycle acoustic waveform generated by single simultaneous twitches of the bilateral sonic muscles. The sonic muscles triple in mass during the spawning season, and this hypertrophy is initiated by rising testosterone levels that trigger increases in myofibrillar and sarcoplasmic cross-sectional area of sonic muscle fibers. In response to increasing temperature, sound pressure level (SPL), dominant frequency and repetition rate increase, and pulse duration decreases. Likewise, SPL and pulse duration increase and dominant frequency decreases with fish size. Changes in acoustic parameters with fish size suggest the possibility that drumming sounds act as an `honest' signal of male fitness during courtship. These parameters also correlate with seasonally increasing sonic muscle mass. We hypothesize that sonic muscle twitch duration rather than the resonant frequency of the swimbladder determines dominant frequency. The brief (3.5 ms), rapidly decaying acoustic pulses reflect a low-Q, broadly tuned resonator, suggesting that dominant frequency is determined by the forced response of the swimbladder to sonic muscle contractions. The changing dominant frequency with temperature in fish of the same size further suggests that frequency is not determined by the natural frequency of the bladder because temperature is unlikely to affect resonance. Finally, dominant frequency correlates with pulse duration (reflecting muscle twitch duration),and the inverse of the period of the second cycle of acoustic energy approximates the recorded frequency. This paper demonstrates for the first time that the dominant frequency of a fish sound produced by a single muscle twitch is apparently determined by the velocity of the muscle twitch rather than the natural frequency of the swimbladder.

Experimental Investigations on the Contour Generation of a Reconfigurable Stewart Platform

2013 ◽  
pp. 291-301
Author(s):  
G. Satheesh Kumar ◽  
T. Nagarajan
Keyword(s):  
Error Analysis ◽  
Natural Frequency ◽  
Vibration Isolation ◽  
Stewart Platform ◽  
Design Tool ◽  
Experimental Investigations ◽  
Variable Geometry ◽  
Optimum Geometry ◽  
Complete Set

Reconfiguration of Stewart platform for varying tasks accentuates the importance for determination of optimum geometry catering to the specified task. The authors in their earlier work (Satheesh et al., 2008) have indicated the non availability of an efficient holistic methodology for determining the optimum geometry. Further, they have proposed a solution using the variable geometry approach through the formulation of dimensionless parameters in combination with generic parameters like configuration and joint vector. The methodology proposed provides an approach to develop a complete set of design tool for any new reconfigurable Stewart platform for two identified applications viz., contour generation and vibration isolation. This paper details the experimental investigations carried out to validate the analytical results obtained on a developed Stewart platform test rig and error analysis is performed for contour generation. The experimental natural frequency of the developed Stewart platform has also been obtained.

Investigation of stiffness of small wind turbine blade based on vibration analysis technique

2019 ◽  
Vol 44 (1) ◽  
pp. 49-59
Author(s):  
Nilesh Chandgude ◽  
Nitin Gadhave ◽  
Ganesh Taware ◽  
Nitin Patil
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Natural Frequency ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Element Analysis ◽  
Finite Element Software ◽  
Small Wind Turbine

In this article, three small wind turbine blades of different materials were manufactured. Finite element analysis was carried out using finite element software ANSYS 14.5 on modeled blades of National Advisory Committee for Aeronautics 4412 airfoil profile. From finite element analysis, first, two flap-wise natural frequencies and mode shapes of three different blades are obtained. Experimental vibration analysis of manufactured blades was carried out using fast Fourier transform analyzer to find the first two flap-wise natural frequencies. Finally, the results obtained from the finite element analysis and experimental test of three blades are compared. Based on vibration analysis, we found that the natural frequency of glass fiber reinforced plastic blade reinforced with aluminum sheet metal (small) strips increases compared with the remaining blades. An increase in the natural frequency indicates an increase in the stiffness of blade.

Dynamic stability index and vibration analysis of a flexible Stewart platform

2007 ◽  
Vol 307 (3-5) ◽  
pp. 495-512 ◽  
Author(s):  
Parthajit Mukherjee ◽  
Bhaskar Dasgupta ◽  
A.K. Mallik
Keyword(s):  
Dynamic Stability ◽  
Vibration Analysis ◽  
Stability Index ◽  
Stewart Platform

Vibration Characteristics Analysis of Large Dismountable Out-Moving Jaw Crusher

2014 ◽  
Vol 472 ◽  
pp. 27-30
Author(s):  
Yong Jiang
Keyword(s):  
Natural Frequency ◽  
Experimental Analysis ◽  
Vibration Analysis ◽  
Large Scale ◽  
Vibration Characteristics ◽  
Vibration System ◽  
Working Process ◽  
Jaw Crusher ◽  
Characteristics Analysis ◽  
Working Frequency

The working process of the out-moving jaw crusher is complex vibration system with multeity freedoms, it is vibration Characteristics directly affect the performance of the machine. The thesis put PWD120150 as research target, experimental analysis was conduct to the typical vibration Characteristics, the natural frequency and the working frequency of the machine and key components was obtained, which provided references for the design of avoiding mechanical resonance, and provided technical reference to the vibration analysis of the large scale equipment.

scholarly journals Nonlinear Resonance Responses of Electromechanical Integrated Magnetic Gear System

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Xiu-hong Hao ◽  
Hong-qian Zhu ◽  
Deng Pan
Keyword(s):  
Natural Frequency ◽  
Magnetic Force ◽  
Nonlinear Differential Equations ◽  
Nonlinear Resonance ◽  
Magnetic Coupling ◽  
Dominant Frequency ◽  
Electromechanical Integrated ◽  
Coupling Stiffness ◽  
Magnetic Gear ◽  
Stiffness And Damping

Nonlinear differential equations for an electromechanical integrated magnetic gear (EIMG) system are developed by considering the nonlinearity in the magnetic force of the system components. Expressions for the main resonances and superharmonic resonances are obtained for output wave frequencies close to the natural frequency and half the natural frequency of the derived EIMG system. The response laws are discussed in detail. The magnetic coupling stiffness among the components is found to exhibit distinct nonlinearity, leading to strong main resonances and superharmonic resonances. Smaller values of the magnetic coupling stiffness and damping result in larger response amplitudes and transient responses that slowly decay to zero. When the main resonances and superharmonic resonances occur, the dominant frequency of the response is the natural frequency of the derived EIMG system, and the amplitudes of different components of the resonance display large differences.

Coupling Vibration Analysis of Blood Vessels

2001 ◽  
Author(s):  
Jingliang Miao ◽  
Haixiang Liu
Keyword(s):  
Blood Flow ◽  
Blood Vessel ◽  
Blood Vessels ◽  
Dynamic Model ◽  
Natural Frequency ◽  
Vibration Analysis ◽  
Vessel Wall ◽  
Blood Vessel Wall ◽  
Coupled Vibration ◽  
Coupling Vibration

Abstract This paper proposes and analyzes a simple dynamic model of blood vessel wall. By studying the coupled vibration of blood flow and vessel wall, one can get the natural frequency of a blood vessel. The method used here is generalized calculus of variations. The results show that the flexibility of blood vessels has a greater influence on the fundamental frequency of the coupled vibration and the viscosity of blood vessel has little effect on the frequency of the coupled vibration but has a greater effect on the amplitude of the vibration. Therefore it is important to control both the viscosity and flexibility of blood vessels.

Transversal Vibration Analysis of Vehicle Track System

2019 ◽  
Author(s):  
Pingxin Wang ◽  
Xiaoting Rui ◽  
Jianshu Zhang ◽  
Hailong Yu
Keyword(s):  
Natural Frequency ◽  
Vibration Analysis ◽  
Stability Control ◽  
Axially Moving Beam ◽  
Natural State ◽  
Beam Model ◽  
Tracked Vehicle ◽  
Transversal Vibration ◽  
Rubber Bushing ◽  
Axially Moving

Abstract The track is mainly composed of track shoes, track pins and rubber bushing elements. In order to suppress the transversal vibration of the upper track during the smooth running process of the tracked vehicle, it is necessary to study the important factors affecting the frequency characteristics of the kinematic chain and their interaction. Unlike the conventional chain drive system, the track in the natural state has a bending rigidity due to the action of the rubber bushing. Based on the dynamic theory of axially moving beam, the differential equation of transversal vibration of a beam element is established. The entire upper track is assumed to be a continuous multi-span axially moving Euler-Bernoulli beam with an axial tension. Based on the Transfer Matrix Method of Multibody System, the transfer equation is obtained. According to the boundary conditions, the natural frequency of the system is solved. The correctness of the beam model hypothesis is verified by experiments. The results show that the first-order natural frequency of the upper track increases with the increase of the tension and the decrease of the vehicle speed. Through frequency analysis, the main excitation source for the transversal vibration of the track is the polygon effect produced by the meshing of the track and the sprocket. This study provides a theoretical basis for the vibration analysis and stability control of the upper track on the tracked vehicle.

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.

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