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RISS 인기검색어
- 검색키워드
- 저자 : Farzam Farahmand (검색결과 2 건)
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Design and analysis of a novel parallel mechanism for prosthetic knee wear test simulators
Fatemeh S. Daeinejad,Farzam Farahmand,Mohammad Durali,Mohammad H. Abedinnasab 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2
Using a parallel mechanism in the wear test simulators of prosthetic knees provides an easy access to the femoral and tibial components during tests. Moreover, because of its higher accuracy and load capacity, in comparison with serial mechanisms, it allows simulation of heavier tasks, such as climbing stairs, to be performed. This paper describes a new 3 Degree of freedom (DoF) spatial 2T1R (T:Translational DoF; R: Rotational DoF) parallel mechanism, for reproducing the force and motion of the tibial component of the knee prostheses in a wear test simulator. Kinematics and dynamics analysis of the mechanism indicated that it can satisfy the required DoFs, workspace and load capacity prescribed in the standard. Also, evaluation of the performance of the mechanism using the simMechanics toolbox of MATLAB revealed that it can reproduce the prescribed forces/torques with relatively high accuracy. However, the mechanism’s force outcomes were found to be affected by inaccuracies in mounting the prosthesis components, although less than the previous serial simulators. In comparison of the different possible architectures, a lateral leg angulation of 45 degrees provided the best efficacy, considering the size of actuators, the overall size of the mechanism and the accessibility of the test sample.
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Designing a hand rest tremor dynamic vibration absorber using H₂optimization method
Mostafa Rahnavard,Mojtaba Hashemi,Farzam Farahmand,Ahmad F. Dizaji 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5
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 H₂optimization criterion is probably more desirable than the popular H∞ optimization method and was implemented in this research. The objective of H₂optimization criterion is to reduce the total vibration energy of the system for overall frequencies. An objective function, considering the elbow joint angle, θ₂ , 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 θ₂ 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, θ₁ . The objective function also decreased by more than 46%. Then, two types of random inputs were considered. For the first type, θ₁ and θ₂revealed 60% and 39% reduction in their rms values, whereas for the second type, 33% and 50% decrease was observed.
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