scholarly journals Distributed variable stiffness joint assist mechanism based on laminated structure

2021 ◽  
Vol 18 (6) ◽  
pp. 172988142110606
Author(s):  
Zhenquan Fan ◽  
Xiaoyu Wang ◽  
Zijin Wang ◽  
Sijia Gao ◽  
Sheng Lin
Keyword(s):  
Magnetic Field ◽  
Stiffness Matrix ◽  
Variable Stiffness ◽  
Drive Unit ◽  
Joint Power ◽  
Laminated Structure ◽  
Giant Magnetostrictive Material ◽  
In Series ◽  
Field Excitation ◽  
The Magnetic Field

Exoskeleton technology is more and more widely used in military, human rehabilitation, and other fields, but exoskeleton assisting mechanisms have problems such as high quality, concentrated driving sources, and poor flexibility. This article proposes a distributed variable stiffness joint power-assisted mechanism based on a laminated structure, which uses a giant magnetostrictive material as the driving source and the variable stiffness source of the structure. The distributed driving is realized by multiple driving units connected in series and parallel. Firstly, the drive unit stiffness matrix is deduced, and the expression equations of the cascaded total stiffness matrix of the drive module are obtained. After the simulation study, the curve of the stiffness of a single drive unit with a magnetic field and the stiffness of multiple drive units connected in series and parallel are in the absence of the magnetic field. The change curve of the stiffness of the booster module with the number of drive units under the excitation and saturation magnetic field excitation conditions is to achieve the effect of dynamically controlling the structural stiffness of the drive unit by controlling the size of the magnetic field and to obtain a general formula through data fitting. The number of drive units required under a fixed magnetic field excitation can ensure that the error is within 5%. The research results lay the foundation for further analysis of the distributed variable stiffness joint assist technology.

scholarly journals Finite Element Analysis of Magnetic Field Exciter for Direct Testing of Magnetocaloric Materials’ Properties

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2792
Author(s):  
Wieslaw Lyskawinski ◽  
Wojciech Szelag ◽  
Cezary Jedryczka ◽  
Tomasz Tolinski
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Circuit ◽  
Homogeneous Magnetic Field ◽  
Element Analysis ◽  
Mcm Testing ◽  
Testing Region ◽  
Magnetocaloric Materials ◽  
Field Excitation ◽  
The Magnetic Field

The paper presents research on magnetic field exciters dedicated to testing magnetocaloric materials (MCMs) as well as used in the design process of magnetic refrigeration systems. An important element of the proposed test stand is the system of magnetic field excitation. It should provide a homogeneous magnetic field with a controllable value of its intensity in the MCM testing region. Several concepts of a magnetic circuit when designing the field exciters have been proposed and evaluated. In the MCM testing region of the proposed exciters, the magnetic field is controlled by changing the structure of the magnetic circuit. A precise 3D field model of electromagnetic phenomena has been developed in the professional finite element method (FEM) package and used to design and analyze the exciters. The obtained results of the calculations of the magnetic field distribution in the working area were compared with the results of the measurements carried out on the exciter prototype. The conclusions resulting from the conducted research are presented and discussed.

scholarly journals Magnetorheological Elastomer-Based Variable Stiffness Flexible Coupling for Vibration Isolation.

2021 ◽  
Author(s):  
Thaer Mahmoud Syam ◽  
Ahmed Hegazi ◽  
Asan Muthalif ◽  
Yousif Badri
Keyword(s):  
Magnetic Field ◽  
Torsional Vibration ◽  
Vibration Isolation ◽  
Volume Fraction ◽  
Torsional Rigidity ◽  
Magnetic Field Effect ◽  
Variable Stiffness ◽  
Torsional Stiffness ◽  
Smart Composite Materials ◽  
The Magnetic Field

Magnetorheological elastomers (MRE) are smart composite materials by which their mechanical properties, such as stiffness, are changed under a magnetic field. In this article, the introduction of a variable stiffness coupling (VSC) fitted within a shaft for torsional vibration isolation that would adapt and change its attenuation frequency range is presented. The VSC concept on torsional vibration isolation is tested experimentally. MRE samples with 40% volume fraction are fabricated and manufactured using a 3D mold design and fixed within a coupling in a shaft to investigate the magnetic field effect on the torsional rigidity. Impact hammer test is conducted along with an accelerometer to obtain the transmissibility factor analysis. Results show that the vibration level decreases when the magnetic field increases. The 1st natural frequency of the system happened at 26 Hz and moved to 28 Hz when the applied current increases from 0 mT to 12.38 mT. MRE torsional stiffness increased from 37.4 N.m/rad to 61.6 N.m/rad when the current increased from 0 mT to 12.38 mT. The torsional damping coefficient showed a fluctuation in its variation as the damping effect of MR elastomer is ignored

Modeling of strain kinetics of damping viscoelastic magnetically controlled materials in creep mode

2019 ◽  
Vol 31 (2) ◽  
pp. 243-252
Author(s):  
Evguenia V Korobko ◽  
Mikalai A Zhurauski ◽  
Buhe Bateer ◽  
Zoya A Novikova ◽  
Vladimir A Kuzmin
Keyword(s):  
Magnetic Field ◽  
Experimental Studies ◽  
Magnetic Field Induction ◽  
The Other ◽  
Model Parameters ◽  
Field Induction ◽  
In Series ◽  
Maxwell Models ◽  
Kinetics Of ◽  
The Magnetic Field

The results of experimental studies of strain kinetics of composite magnetically controlled materials in the creep mode with preliminary exposure and without exposure are described by the Burgers model with two elastic and two viscous parameters, which is a combination of viscoelastic Kelvin–Voigt and Maxwell models connected in series. The dependence of the model parameters on the magnetic field induction is determined. The values of elastic and viscous parameters increase with increasing magnetic field induction in the range up to 500 mT by one or two orders of magnitude. It was determined that the value of the viscous Maxwell parameter does not change after preliminary exposure in the field. The values of the other two elastic and viscous Kelvin–Voigt parameters increase with exposure in a magnetic field.

Battery Powered Electromagnetic Flow Meter with Locally Shrunk Measurement Pipe

2014 ◽  
Vol 568-570 ◽  
pp. 315-319
Author(s):  
Tie Jun Liu ◽  
Min Zhou
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Flow Meter ◽  
Flow Transducer ◽  
Electromagnetic Flow ◽  
Transducer Design ◽  
Field Excitation ◽  
Electromagnetic Flow Meter ◽  
The Magnetic Field ◽  
Excitation Circuit

Based on computer simulation, a new measurement pipe design with locally shrunk cross section is proposed for electromagnetic flow transducer. The efficiency of the magnetic field excitation circuit is effectively enhanced. The sensitivity of the transducer is increased. The transducer design is adopted in a battery powered electromagnetic flow meter prototype to reduce the power consumption. The prototype was tested. The feasibility of the proposed design was proved.

scholarly journals Design and Analysis of Variable Flexible Actuator for Human-Robot Interaction

2019 ◽  
Vol 37 (2) ◽  
pp. 242-248
Author(s):  
Wendong Wang ◽  
Tongsen Sun ◽  
Xiaoqing Yuan ◽  
Jinzhe Li ◽  
Xing Ming
Keyword(s):  
Magnetic Field ◽  
Variable Stiffness ◽  
Mechanical Analysis ◽  
Simulation Software ◽  
Human Robot Interaction ◽  
Field Analysis ◽  
Robot Interaction ◽  
Magnetic Field Analysis ◽  
Mr Effect ◽  
The Magnetic Field

In view of the shortcomings of the traditional high-rigidity robots that can't ensure safety of human-robot interaction and the adaptability of complex environment, a variable stiffness flexible actuator is proposed for the robot joint based on the magnetorheological (MR) effect of MR Fluids. In this paper, the principle of flexible joint drive is detailed, and design the structure of the drive and perform mechanical analysis is designed. At the same time, the magnetic field analysis of the actuator is carried out by using the magnetic field simulation software Maxwell. Finally, the actuator is simulated and verified. Comparing the analysis of the results, the actuator has the characteristics of simple structure, easy control and wider active variable stiffness adjustment range, and can absorb the vibration or shock energy, and improve the robot joint output ability.

Influence of magnetic field, magnetic particle percentages, and particle diameters on the stiffness of magnetorheological fluids

2020 ◽  
Vol 31 (20) ◽  
pp. 2312-2325
Author(s):  
Wei Sun ◽  
Jingjun Yu ◽  
Yueri Cai
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Particle ◽  
Random Distribution ◽  
Magnetic Field Intensity ◽  
Variable Stiffness ◽  
Magnetorheological Fluid ◽  
Physical Transformation ◽  
Change State ◽  
The Magnetic Field

Generally, variable stiffness joints of soft robots are generally fabricated using thermoplastics and elastomers due to their ability to change state from rigid to flexible and vice versa. However, these materials require a considerable amount of time to change states and are associated with other technical drawbacks. We demonstrate the instantaneous physical transformation of a Ga-based magnetorheological fluid called Gallistan from a liquid to a viscoelastic solid, and precisely controlled within milliseconds under an applied magnetic field. We studied the magnetic properties of a magnetorheological fluid by dispersing Fe particles in a Ga–In–Sn eutectic alloy. Theoretical analysis of the movement of two particles under magnetic field and typical defects in dipolar chains is studied. The experimental results showed a reversible change in Young’s modulus depending not only on the magnetic field intensity but also the percentage of magnetic particles. Thus, we confirm that the arrangement of magnetic particles transition from random distribution to stable chain structures in the magnetic field. Based on the bi-material nested cantilever beam, the variable stiffness joints can also be precisely adjusted under a magnetic field. In future, this property of the magnetorheological fluid will help develop a variable stiffness joint for soft robotics.

scholarly journals A new magnetorheological elastomer torsional vibration absorber: structural design and performance test

2021 ◽  
Vol 12 (1) ◽  
pp. 321-332
Author(s):  
Pu Gao ◽  
Hui Liu ◽  
Changle Xiang ◽  
Pengfei Yan ◽  
Taha Mahmoud
Keyword(s):  
Magnetic Field ◽  
Torsional Vibration ◽  
Performance Test ◽  
Magnetic Circuit ◽  
Circuit Simulation ◽  
Variable Stiffness ◽  
Vibration Absorber ◽  
Vibration Exciter ◽  
Magnetorheological Elastomer ◽  
The Magnetic Field

Abstract. The semi-active torsional vibration absorber can effectively reduce the torsional vibration of the power-train system. In this paper, a new type of variable stiffness torsional vibration absorber with a magnetorheological elastomer (MRE) as an intelligent controlling element is designed, and the modal analysis, frequency-tracking scheme, and damping effects have been studied. A transient dynamic simulation is utilized to validate the rationality of the mechanical structure, the magnetic field parameters of the absorber are matched, and the magnetic circuit simulation analysis and the magnetic field supply analysis are carried out to verify the closed magnetic circuit. The principle prototype of the innovative vibration absorber is manufactured, the magnetic field strength of the absorber is tested by a Gauss meter, and the results show the efficacy of magnetizing the vibration absorber with a conductive slip ring by solving the magnetizing problem of the rotating parts of the vibration absorber. A special-purpose test rig with a torsional vibration exciter as a power source has been implemented. A comparative experiment has been carried out to test the frequency shift characteristics and authenticate the vibration-reduction effect of the new MRE torsional vibration absorber.

scholarly journals A Numerical Approach to Dynamically Consistent Spherical Dynamo Models

1993 ◽  
Vol 157 ◽  
pp. 129-133
Author(s):  
H. Fuchs ◽  
K.-H. Rädler ◽  
M. Schüler
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Fluid Velocity ◽  
Mean Field ◽  
Numerical Approach ◽  
Decay Modes ◽  
First Results ◽  
Finite Set ◽  
In Series ◽  
The Magnetic Field

Models of spherical dynamos are considered which involve the full interaction between the magnetic field and the motion of an incompressible conducting fluid. In the basic equations magnetic field and fluid velocity are expanded in series of certain decay modes. In this way these equations are reduced to an infinite set of ordinary first-order differential equations for the coefficients of these expansions. The behaviour of dynamos can then be studied by integrating a finite set of these equations numerically. Some first results obtained in this way are presented for mean-field models in which the growth of the magnetic field due to the α–effect is limited by large-scale motions generated by Lorentz forces.

Sign in / Sign up

Export Citation Format

Share Document