Nonlinear dynamics of magnetorheological whole-satellite with variable parameters under small amplitude and medium-high frequency vibration

2021 ◽  
Author(s):  
Xiong Deng ◽  
Xiaomin Dong ◽  
Jianwei Xing ◽  
Wenfeng Li ◽  
Jun Xi
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Mr Damper ◽  
Variable Stiffness ◽  
Satellite System ◽  
Analysis Method ◽  
Variable Parameters ◽  
Fixed Parameter ◽  
Time Histories ◽  
Parameter Varying

Abstract Whole-satellite vibration isolation system with magneto-rheological (MR) damper is a new idea to solve the problem of small amplitude and medium-high frequency vibration. However, it also brings challenges to MR technology, wherein the super hysteresis and variable stiffness properties of MR damper are lack of research. Considering the particularity of MR damper under small amplitude and medium-high frequency conditions, the MR damper is identified by employing an improved Bingham model, then dynamic characteristics of the whole-satellite system are analyzed by nonlinear bifurcation theory, and then the nonlinear analysis method of MR whole-satellite system with variable parameters is proposed. To verify the effectiveness of the nonlinear analysis method of MR whole-satellite system with variable parameters, the influence of bifurcation parameters on the system parameters is analyzed qualitatively and quantitatively, then time histories and phase diagrams of fixed-parameter and parameter-varying MR whole-satellite system are compared. The analysis suggests that the improved Bingham model adequately characterizes the strong nonlinear hysteretic and variable stiffness behavior of the MR damper. Moreover, the comparison results illustrate that the time histories and phase portraits of the parameter-varying system are in good agreement with those of different fixed-parameter system, and the parameter-varying system has good adaptability in the selected range of bifurcation parameters. This study provides a basis for the design of structural parameters and the optimization of control strategy for MR whole-satellite system.

Analytical Solution for Rotational Rub-Impact Plate Under Thermal Shock

2016 ◽  
Vol 32 (3) ◽  
pp. 297-311
Author(s):  
T.-Y. Zhao ◽  
H.-Q. Yuan ◽  
B.-B. Li ◽  
Z.-J. Li ◽  
L.-M. Liu
Keyword(s):  
Thermal Shock ◽  
High Frequency ◽  
Equations Of Motion ◽  
Low Frequency ◽  
Cantilever Plate ◽  
Analysis Method ◽  
Multiple Frequency ◽  
Width Direction ◽  
Blade Tip ◽  
High Frequency Vibrations

AbstractThe analysis method is developed to obtain dynamic characteristics of the rotating cantilever plate with thermal shock and tip-rub. Based on the variational principle, equations of motion are derived considering the differences between rubbing forces in the width direction of the plate. The transverse deformation is decomposed into quasi-static deformation of the cantilever plate with thermal shock and dynamic deformation of the rubbing plate under thermal shock. Then deformations are obtained through the calculation of modal characteristics of rotating cantilever plate and temperature distribution function. Special attention is paid to the influence of tip-rub and thermal shock on the plate. The results show that tip-rub has the characteristics of multiple frequency vibrations, and high frequency vibrations are significant. On the contrary, thermal shock shows the low frequency vibrations. The thermal shock makes the rubbing plate gradually change into low frequency vibrations. Because rub-induced vibrations are more complicated than those caused by thermal shock, tip-rub is easier to result in the destruction of the blade. The increasing friction coefficient intensifies vibrations of the rubbing plate. Minimizing friction coefficients can be an effective way to reduce rub-induced damage through reducing the surface roughness between the blade tip and the inner surface of the casing.

A Geometric Parametric Analysis of a Magnetorheological Engine Mount

2010 ◽  
Author(s):  
Walter Anderson ◽  
Constantine Ciocanel ◽  
Mohammad Elahinia
Keyword(s):  
High Frequency ◽  
New Technology ◽  
Low Frequency ◽  
Variable Stiffness ◽  
Small Displacement ◽  
Element Analysis ◽  
Mr Fluid ◽  
Wide Range ◽  
Engine Mount ◽  
Vehicle Technology

Engine vibration has caused a great deal of research for isolation to be performed. Traditionally, isolation was achieved through the use of pure elastomeric (rubber) mounts. However, with advances in vehicle technology, these types of mounts have become inadequate. The inadequacy stems from the vibration profile associated with the engine, i.e. high displacement at low frequency and small displacement at high frequency. Ideal isolation would be achieved through a stiff mount for low frequency and a soft mount for high frequency. This is contradictory to the performance of the elastomeric mounts. Hydraulic mounts were then developed to address this problem. A hydraulic mount has variable stiffness and damping due to the use of a decoupler and an inertia track. However, further advances in vehicle technology have rendered these mounts inadequate as well. Examples of these advances are hybridization (electric and hydraulic) and cylinder on demand (VCM, MDS & ACC). With these technologies, the vibration excitation has a significantly different profile, occurs over a wide range of frequencies, and calls for a new technology that can address this need. Magnetorheological (MR) fluid is a smart material that is able to change viscosity in the presence of a magnetic field. With the use of MR fluid, variable damping and stiffness can be achieved. An MR mount has been developed and tested. The performance of the mount depends on the geometry of the rubber part as well as the behavior of the MR fluid. The rubber top of the mount is the topic of this study due to its major impact on the isolation characteristics of the MR mount. To develop a design methodology to address the isolation needs of different hybrid vehicles, a geometric parametric finite element analysis has been completed and presented in this paper.

The effects of pH on force and stiffness development in mouse muscles

1987 ◽  
Vol 65 (8) ◽  
pp. 1798-1801 ◽  
Author(s):  
J. M. Renaud ◽  
R. B. Stein ◽  
T. Gordon
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Force Production ◽  
Muscle Length ◽  
Low Ph ◽  
Muscle Stiffness ◽  
Average Force ◽  
Cross Bridge ◽  
Effects Of Ph ◽  
Cross Bridges

Changes in force and stiffness during contractions of mouse extensor digitorum longus and soleus muscles were measured over a range of extracellular pH from 6.4 to 7.4. Muscle stiffness was measured using small amplitude (<0.1% of muscle length), high frequency (1.5 kHz) oscillations in length. Twitch force was not significantly affected by changes in pH, but the peak force during repetitive stimulation (2, 3, and 20 pulses) was decreased significantly as the pH was reduced. Changes in muscle stiffness with pH were in the same direction, but smaller in extent. If the number of attached cross-bridges in the muscle can be determined from the measurement of small amplitude, high frequency muscle stiffness, then these findings suggest that (a) the number of cross-bridges between thick and thin filaments declines in low pH and (b) the average force per cross-bridge also declines in low pH. The decline in force per cross-bridge could arise from a reduction in the ability of cross-bridges to generate force during their state of active force production and (or) in an increased percentage of bonds in a low force, "rigor" state.

scholarly journals Design and Analysis of a Novel Variable Stiffness Joint for Robot

2018 ◽  
Vol 249 ◽  
pp. 03005
Author(s):  
Xiang Zhang ◽  
Twan Capehart ◽  
Carl A. Moore
Keyword(s):  
High Frequency ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Robotic Systems ◽  
Compliant Joint ◽  
Variable Transmission ◽  
Application Requirements ◽  
Base Application ◽  
Robotic Applications ◽  
Human Robotic Interaction

As people pay more attention to the safety of human-robotic interaction, the flexibility of machine joints is becoming more and more important. To address the needs of future robotic applications, many kinds of variable stiffness mechanisms have been designed by scientists. But most of the structures are complex. By studying and comparing many different mechanism designs of variable stiffness joint, we recognize the need to miniaturization and reduce weight of variable stiffness joints with high frequency operation. To address this, need a continuously Variable Compliant Joint (CVCJ) was designed. The core of the joint is based on the structure of the spherical continuously variable transmission (SCVT) which is the catalyst to change the stiffness continuously and smoothly. In this paper, we present a compact variable stiffness joint structure to meet the volume and weight requirements of the future robotic systems. We show the connection between the joint stiffness coefficient and the structure parameters by making mathematical analysis, modelling and simulation for the system to verify the ability to satisfy the base application requirements of the compliant joint.

scholarly journals Intravaginal Devices and GNSS Collars with Satellite Communication to Detect Calving Events in Extensive Beef Production in Northern Australia

2020 ◽  
Vol 12 (23) ◽  
pp. 3963
Author(s):  
Christie Pearson ◽  
Lucy Lush ◽  
Luciano A. González
Keyword(s):  
High Frequency ◽  
Satellite Communication ◽  
Satellite System ◽  
Behavioral Changes ◽  
Very High Frequency ◽  
Average Activity ◽  
Newborn Calves ◽  
Global Navigation Satellite ◽  
Further Development ◽  
Very High

Observing calves at birth may help to identify risk factors for, and reduce, calf loss in extensive beef systems. The objectives of this study were to: (1) evaluate two commercial satellite birth alert systems to enable the observation of newborn calves and (2) assess behavioral changes of cows around calving. Vaginal Implant Transmitters (VIT) paired with Global Navigation Satellite System (GNSS) collars were worn by 20 cows in Trial 1 and 10 cows in Trial 2 to identify birthing events. The VIT and GNSS collars contained a temperature sensor, accelerometer, and very high frequency (VHF) to communicate with a handheld tracker, and ultra-high frequency (UHF) for communication between the VIT and GNSS collar, which had two-way communication using Iridium satellites. A change (Brand 1) or drop (Brand 2) in temperature of more than 3 °C and inactivity triggered the VIT to communicate an expelled alert to the collar, which transmitted the birth alert information via Iridium (device ID, date, time and geolocation of the GNSS collar at expulsion). Cows and calves were tracked in the paddock following a birth alert to assess their health and status. Overall, true birth alerts occurred in only 27.6% of devices. Cows remained active on the day of calving travelling 5.54 ± 4.11 and 5.00 ± 2.80 km/day compared to 6.45 ± 2.79 and 6.12 ± 2.30 km/d on days when calving did not occur for Trial 1 and 2, respectively (mean ± SD). Average activity of the accelerometer X- and Y-axis on calving day was reduced by 15%–20% compared to other days in Trial 1 (p < 0.05) but not in Trial 2 (p > 0.05). Results suggest that these two birth alert systems are not suitable for use in extensive systems and the further development of the technology is required. Cows in the current trials remained active on the day of, and after, calving, indicating that a faster, real-time alert system and communication protocol would be required to achieve the aim of finding newborn calves.

scholarly journals Variability and Performance of Short to Long-Range Single Baseline RTK GNSS Positioning in Indonesia

2019 ◽  
Vol 94 ◽  
pp. 01012 ◽  
Author(s):  
Irwan Gumilar ◽  
Brian Bramanto ◽  
Fuad F. Rahman ◽  
I Made D. A. Hermawan
Keyword(s):  
Long Range ◽  
High Frequency ◽  
Carrier Phase ◽  
Satellite System ◽  
High Accuracy ◽  
Gnss Positioning ◽  
And Performance ◽  
Gnss Network ◽  
Single Baseline ◽  
Global Navigation Satellite

As the modernized Global Navigation Satellite System (GNSS) method, Real Time Kinematic (RTK) ensures high accuracy of position (within several centimeters). This method uses Ultra High Frequency (UHF) radio to transmit the correction data, however, due to gain and power issues, Networked Transport of RTCM via Internet Protocol (RTCM) is used to transmit the correction data for a longer baseline. This Research aims to investigate the performance of short to long-range single baseline RTK GNSS (Up to 80 KM) by applying modified LAMBDA method to resolve the ambiguity in carrier phase. The RTK solution then compared with the differential GNSS network solution. The results indicate that the differences are within RTK accuracy up to 80 km are several centimeter for horizontal solution and three times higher for vertical solution.

Study of Flow-Induced Vibration Phenomena in Automotive Shock Absorbers

2016 ◽  
Vol 248 ◽  
pp. 204-210 ◽  
Author(s):  
Marian Sikora
Keyword(s):  
High Frequency ◽  
Shock Absorber ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Flow Induced Vibration ◽  
Shock Absorbers ◽  
Time Histories ◽  
Valve Stiction ◽  
High Frequency Excitation ◽  
Frequency Excitation

The purpose of this study was to develop a model of the dynamic behavior of a hydraulic vehicle double-tube shock absorber. The model accounts for the effects of compressibility, valve stiction, inertia, etc. and can be suitable for use in the analyses on flow-induced pressure fluctuations in the device. The author highlights all major variables to influence the output of the shock absorber, and then proceeds by performing a series of simulations using the developed model. The model is demonstrated to operate well in the large amplitude and low frequency range as well as the small amplitude and high frequency excitation operation regimes. The results are presented in the form of time histories of pressures in each fluid volume of the damper, flow rates through the valves, piston rod acceleration and force. Fast Fourier Transform (FFT) graphs are presented, too, in order to identify major components of the pressure fluctuation phenomena in frequency domain.

New Variable Stiffness Damper with Magnetorheological-Based Accumulator Control

2018 ◽  
Vol 775 ◽  
pp. 204-209
Author(s):  
Lim Jian Hong ◽  
Fitrian Imaduddin ◽  
Saiful Amri Mazlan ◽  
Muhammad Hafiz Idris ◽  
Irfan Bahiuddin
Keyword(s):  
Direct Effect ◽  
Mr Damper ◽  
Variable Stiffness ◽  
Experimental Results ◽  
Compression Force ◽  
Control Zone ◽  
Hydraulic Oil ◽  
Compensation Control ◽  
Mr Fluids ◽  
Compression Stiffness

This paper introduces a new design of variable stiffness damper using controlled accumulator filled with Magnetorheological (MR) fluids. The originality of the new design is in its capability to offer less consumption of MR fluids than the conventional design of MR damper. The new design does not fill the whole cylinder with MR fluids but only use the accumulator space as the volume compensation control zone with MR fluids. The MR fluids control the compressive movement of the accumulator piston which alter the flow of the hydraulic oil to the accumulator chamber. As a result, the regulated flow of oil to the accumulator chamber will only have a direct effect to the compression stiffness of the damper. The experimental results show that the proposed design is capable to adjust the compression force while maintaining the rebound force of the damper.

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