Exploration within Spherical Mechanisms
References
[1] Clément Trotobas, et al. The Kinematic Synthesis of a Spherical Mechanism for Assisting in Wrist Pronation and Supination. 20 Aug. 2023, https://doi.org/10.1115/detc2023-114766. Accessed 8 Apr. 2024.
[2] Radmehr, A., Asgari, M., & Masouleh, M. (2021, October 31). Experimental Study on the Imitation of the Human Neck-and-Eye Pose Using the 3-DOF Agile Eye Parallel Robot Based on a Deep Neural Network Approach. Research Gate. https://www.researchgate.net/figure/Render-model-of-the-Agile-Eye_fig2_307551463
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Why Spherical Mechanisms?
A spherical mechanism may be able to provide support while still allowing full rotation of the wrist. Spherical mechanisms leave the middle area of the mechanism open. This specific mechanism has 3 degrees of freedom.
Designing Spherical Mechanisms, from Wrist Orthotics to Mechanical Novelties
Frank McClimans and John Hoover
Advisors: Andrew Murray, Ph.D & David Myszka, Ph.D
Department of Mechanical & Aerospace Engineering
Objective: To design a less obtrusive wrist orthotic while simultaneously creating an innovative and captivating mechanism.
Existing Orthotics
Wrist Orthotic Design Challenges
Unlike prosthetics, which replicate natural movement without the constraint of existing body parts, orthotic design must account for the interaction between the device and the wearer's anatomy, necessitating careful alignment and fit to minimize interference and maximize effectiveness.
Figure 10: Agile Eye [2]
Figure 3: Stacked Mechanism[1]
Figure 1: Existing Orthotics
Figure 6: Mechanism without interferences
Figure 8: Double Rocker
Figure 4: Calculations (a) and simulations (b) for motion of the mechanism. [1]
Figure 7: Crank Rocker
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Figure 5: Optimization tables and equations [1]
Figure 9: Central Point
Figure 2: Optimized Mechanism [1]
DOF = 6×(14−1)−5×(15)−3×(3) = −6.
(Eqn. 10) Spatial KMOGE
DOF = 6×(14-1)−5×(6)−4×(9)−3×(3) = 3. (Eqn. 11) KMOGE w/ Spherical Mechanisms
To conclude DOF = 3 is correct, the Fermat-Toricelli Point was considered. The F-T point is the unique point such that the sum of the distances from each of a triangle’s three vertices to this unique point is minimized.
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