Exploring the path of the variable resistance

Science ◽  
2021 ◽  
Vol 373 (6557) ◽  
pp. 854-855
Author(s):  
Hans Hilgenkamp ◽  
Xing Gao
Keyword(s):  
2021 ◽  
Vol 92 (1) ◽  
pp. 014904
Author(s):  
A. V. Talanov ◽  
J. Waissman ◽  
T. Taniguchi ◽  
K. Watanabe ◽  
P. Kim

2009 ◽  
Vol 31 (1) ◽  
pp. 50-64 ◽  
Author(s):  
D Travis McMaster ◽  
John Cronin ◽  
Michael McGuigan

1975 ◽  
Vol 38 (2) ◽  
pp. 247-251 ◽  
Author(s):  
R. W. J. BARKER ◽  
B. L. HART
Keyword(s):  

Author(s):  
Dennis A. Siginer ◽  
Mario Letelier ◽  
Juan Sebastián Stockle Henríquez

Abstract A predetermined flow pattern in a magnetorheological damper providing continuously variable resistance to flow is required for efficient damping of a given load. The required predetermined flow pattern rests on the a priori determination of the constitutive properties of the magnetorheological (MR) fluid determined to generate variable resistance to flow. The inverse problem of constructing the predetermined response of the damper with a specific displacement pattern of the piston in the damper for efficient damping of a given load is solved. The magnetorheological (MR) fluid in the damper is modeled as a Bingham phase change material with time dependent yield stress offering continuously variable resistance to the flow in the piston to achieve the required specific displacement pattern. The governing equations are solved for any time history of the dimensionless yield stress of the fluid which in turn is determined from the imposed response of the damper. Analytical tools developed can be used in optimizing damper performance. The application of the method to resonance mitigation is illustrated.


Author(s):  
Jiajia Zheng ◽  
Yancheng Li ◽  
Jiong Wang

This paper presents the design and multi-physics optimization of a novel multi-coil magnetorheological (MR) damper with a variable resistance gap (VRG-MMD). Enabling four electromagnetic coils (EMs) with individual exciting currents, a simplified magnetic equivalent circuit was presented and the magnetic flux generated by each voltage source passing through each active gap was calculated as vector operations. To design the optimal geometry of the VRG-MMD, the multi-physics optimization problem including electromagnetics and fluid dynamics has been formulated as a multi-objective function with weighting ratios among total damping force, dynamic range, and inductive time constant. Based on the selected design variables (DVs), six cases with different weighting ratios were optimized using Bound Optimization BY Quadratic Approximation (BOBYQA) technique. Finally, the vibration performance of the optimal VRG-MMD subjected to sinusoidal and triangle displacement excitations was compared to that of the typical multi-coil MR damper.


1971 ◽  
Vol 59 (5) ◽  
pp. 805-807
Author(s):  
A.N. Morgan ◽  
W.G. Townsend

2021 ◽  
Vol 77 (1) ◽  
pp. 235-244
Author(s):  
Darío Martínez-García ◽  
Ángela Rodríguez-Perea ◽  
Álvaro Huerta-Ojeda ◽  
Daniel Jerez-Mayorga ◽  
Daniel Aguilar-Martínez ◽  
...  

Abstract The purpose of this study was to investigate the acute effect of pre-activation with Variable Intra-Repetition Resistance and isometry on the overhead throwing velocity in handball players. Fourteen female handball players took part in the study (age: 21.2 ± 2.7 years, experience: 10.9 ± 3.5 years). For Post-Activation Potentiation, two pre-activation methods were used: (I) Variable Intra-Repetition Resistance: 1 x 5 maximum repetitions at an initial velocity of 0.6 m·s-1 and a final velocity of 0.9 m·s-1; (II) Isometry: 1 x 5 s of maximum voluntary isometric contraction. Both methods were "standing unilateral bench presses" with the dominant arm, using a functional electromechanical dynamometer. The variable analysed was the mean of the three overhead throws. Ball velocity was measured with a radar (Stalker ATS). The statistical analysis was performed using ANOVA with repeated measures. No significant differences were found for either method (variable resistance intra-repetition: p = 0.194, isometry: p = 0.596). Regarding the individual responses, the analysis showed that 86% of the sample increased throwing velocity with the variable resistance intra-repetition method, while 93% of the sample increased throwing velocity with the isometric method. Both the variable intra-repetition resistance and isometric methods show improvements in ball velocity in female handball players. However, the authors recommend checking individual responses, since the results obtained were influenced by the short rest interval between the pre-activation and the experimental sets.


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