Abstract
An optimal single DOF dynamic absorber is presented. A tremor has a random nature and then the system is subjected to a random excitation instead of a sinusoidal one; so the H 2 optimization criterion is probably more desirable than the popular H ∞ optimization method and was implemented in this research. The objective of H 2 optimization criterion is to reduce the total vibration energy of the system for overall frequencies. An objective function, considering the elbow joint angle, θ 2, tremor suppression as the main goal, was selected. The optimization was done by minimization of this objective function. The optimal system, including the absorber, performance was analyzed in both time and frequency domains. Implementing the optimal absorber, the frequency response amplitude of θ 2 was reduced by more than 98% and 80% at the first and second natural frequencies of the primary system, respectively. A reduction of more than 94% and 78%, was observed for the shoulder joint angle, θ 1. The objective function also decreased by more than 46%. Then, two types of random inputs were considered. For the first type, θ 1 and θ 2 revealed 60% and 39% reduction in their rms values, whereas for the second type, 33% and 50% decrease was observed.
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Farzam Farahmand is Professor of Mechanical Engineering and the head of the Biomechanics Section at Sharif Univ. of Technology, Tehran, Iran. His Ph.D. is from Imperial College, Department of Mechanical Engineering (Biomechanics), London, UK, 1996. His M.Sc. is from University of Tehran, Department of Mechanical Engineering (Applied Mechanics), Tehran, Iran, 1991. And his B.Sc. is from University of Tehran, Department of Mechanical Engineering (Solid Mechanics), Tehran, Iran, 1989. His research interests include musculoskeletal dynamics, orthopedic biomechanics, and robotic surgery and rehabilitation.
Mostafa Rahnavard received the B.S. and the M.S. (with the best honors) both in Mechanical Engineering-Dynamic system and control from K. Nasir Toosi Univ. of Technology and Sharif Univ. of Technology, Tehran, Iran in 2008 and 2010, respectively. He is currently a Ph.D. student of Mechanical Engineering in Tehran University.
Mojtaba Hashemi received the B.S. in Mechanical Engineering-Dynamic system and control from K. Nasir Toosi Univ. of Technology, Tehran, Iran in 2008 and the M.S. in Biomechanics from Sharif Univ. of Technology, Tehran, Iran in 2011. He is currently a Ph.D. student of Mechanical Engineering in Amirkabir Univ. of Technology.
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Rahnavard, M., Hashemi, M., Farahmand, F. et al. Designing a hand rest tremor dynamic vibration absorber using H 2 optimization method. J Mech Sci Technol 28, 1609–1614 (2014). https://doi.org/10.1007/s12206-014-0104-8
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DOI: https://doi.org/10.1007/s12206-014-0104-8