Contact mechanics for soft robotic fingers: modeling and experimentation

Human fingers possess mechanical characteristics, which enable them to manipulate objects. In robotics, the study of soft fingertip materials for manipulation has been going on for a while; however, almost all previous researches have been carried on hemispherical shapes whereas this study concentrates on the use of hemicylindrical shapes. These shapes were found to be more resistant to elastic deformations for the same materials. The purpose of this work is to generate a modified nonlinear contact-mechanics theory for modeling soft fingertips, which is proposed as a power-law equation. The contact area of a hemicylindrical soft fingertip is proportional to the normal force raised to the power of γcy, which ranges from 0 to 1/2. Subsuming the Timoshenko and Goodier (S. P. Timoshenko and J. N. Goodier, Theory of Elasticity, 3rd ed. (McGraw-Hill, New York, 1970) pp. 414-420) linear contact theory for cylinders confirms the proposed power equation. We applied a weighted least-squares curve fitting to analyze the experimental data for different types of silicone (RTV 23, RTV 1701, and RTV 240). Our experimental results supported the proposed theoretical prediction. Results for human fingers and hemispherical soft fingers were also compare

Optimal Design of Three-Phalanx Prosthesis Underactuated Fingers Using Genetic Algorithm

This research is interested to investigate the optimum design procedure for a finger driving mechanism to have a proper configuration of the finger for its utilization in hand prosthesis. To get this goal, a Genetic Algorithm (G.A) was used. Three criteria were selected to find the optimal solution. The most important of them was the percentage of the grasping stability. This criterion was evaluated as must type by using Kepner-tregos method. When the optimal solution was found, this one was modified to facilitate the fabrication of a prototype. The modifications consist of mostly rounding the parameters and uniforming the rollers dimensions. Those changes did not affect too much the forces characteristics. The prosthetic hand prototype was built of hard ABS (Acrylonitrile Butadiene Styrene) plastic using rapid prototyping. Testing results indicate that the proposed Genetic Algorithm gives reasonable -quality results in short computation time

Free Vibration Analysis of Composite Cylindrical Shell Reinforced with Silicon Nano-Particles: Analytical and FEM Approach

Previous research presented the effect of nanomaterials on the mechanical properties of composite materials with various volume fraction effects; in addition, their research presented the effect of nanomaterials on the same mechanical characteristics for a composite plate structure, such as vibration and thermal buckling behavior. Therefore, since the use of shell structures is for large applications, it is necessary to investigate the modification of the vibration characteristics of its design with the effect of nanomaterials and study the influence of other reinforced nanoparticle types on its features. Therefore, in this work, silicon nanoparticles were selected to investigate their effect on the vibration behavior of a shell structure. As a result, this work included studying the vibration behavior by testing the shell structure with a vibration test machine. In addition, after manufacturing the composite material shell with various silicon volume fractions, the mechanical properties were evaluated. In addition, the finite element technique with the Ansys program was used to assess and compare the vibration behavior of the shell structure using the numerical technique. The comparison of the results gave an acceptable percentage error not exceeding 10.93%. Finally, the results evaluated showed that the modification with silicon nanomaterials gave very good results since the nanomaterials improved about 65% of the shell's mechanical properties and vibration characteristics

Chemical composition and antimicrobial activity of essential oils from Cuminum cyminum L. collected in different areas of Morocco

Essential oils from 8 Cuminum cyminum local populations collected in Morocco were investigated for their chemical composition and antimicrobial activity. The chemical composition, investigated by gas chromatographic technique, revealed a common fingerprint in all Moroccan samples: twenty-five compounds were identified with γ-terpinen-7-al being the major component in all samples studied. The antimicrobial activity of cumin essential oils were tested against 10 bacterial strains, belonging to 8 different species, and 6 yeast strains, belonging to 4 species. Lactic acid bacteria showed a good resistance to all essential oil tested while overall the cumin essential oils showed a strong antifungal activity that affected both maximum specific growth rate and lag tim

Analytical and numerical flexural properties of polymeric porous functionally graded (PFGM) sandwich beams

Purpose: Materials with porosity gradient functionally gradient properties reflect changes in the material's position spatially in response to changes in porosity. One porous metal comprised the FGM core and had not previously been considered in bending analyses. Design/methodology/approach: Analytical formulations were derived based on the classical beam theory (CBT). According to the power-law scheme, the material properties of FG beams are supposed to vary along the thickness direction of the constituents. Findings: The results show that the porosity and power gradient parameters significantly influence flexural bending characteristics. It is found that there is a fair agreement between the analytical and numerical results, with a maximum error percentage not exceeding 5%. Research limitations/implications: The accuracy of analytical solutions is verified by employing the finite elements method (FEM) with commercial ANSYS 2021 R1 software. Practical implications: FGM beams' elastic properties with an even porosity distribution through-beam core and bonded with two thin solid skins at the upper and lower surfaces were carried out. Originality/value: This paper develops an analytical study to investigate the flexural problem of a functionally graded simply supported sandwich beam with porosities widely used in aircraft structures and biomedical engineering. The objective of the current work is to examine the effects of some key parameters, such as porous ratio, power-law index, and core metal type, on the flexural properties such as bending load, total deformation, and strain energy

Contact mechanics for soft robotic fingers: modeling and experimentation

Human fingers possess mechanical characteristics, which enable them to manipulate objects. In robotics, the study of soft fingertip materials for manipulation has been going on for a while; however, almost all previous researches have been carried on hemispherical shapes whereas this study concentrates on the use of hemicylindrical shapes. These shapes were found to be more resistant to elastic deformations for the same materials. The purpose of this work is to generate a modified nonlinear contact-mechanics theory for modeling soft fingertips, which is proposed as a power-law equation. The contact area of a hemicylindrical soft fingertip is proportional to the normal force raised to the power of γcy, which ranges from 0 to 1/2. Subsuming the Timoshenko and Goodier (S. P. Timoshenko and J. N. Goodier, Theory of Elasticity, 3rd ed. (McGraw-Hill, New York, 1970) pp. 414-420) linear contact theory for cylinders confirms the proposed power equation. We applied a weighted least-squares curve fitting to analyze the experimental data for different types of silicone (RTV 23, RTV 1701, and RTV 240). Our experimental results supported the proposed theoretical prediction. Results for human fingers and hemispherical soft fingers were also compare

Phytochemical composition of Moroccan saffron accessions by headspace solid-phase microextraction

The phytochemical composition of 19 saffron samples collected under different Moroccan environments is evaluated by Headspace Solid-Phase Micro-extraction coupled with gas chromatography–mass spectrometry. The aim is to categorize Moroccan saffron volatiles and to highlight the impact of the environment on the chemical composition of the spice. This is the first research conducted on Moroccan saffron volatiles according to their geographical origin. A total of 57 volatile components have been identified. Differences in compound proportion and composition among the accessions were observed. The main chemical classes of volatiles identified were monoterpene hydrocarbons (6 to 42%), oxygenated monoterpenes (3 to 29%) and non-terpene derivatives. Only 14 compounds were found in common to all the accessions. The most important, in decreasing proportions, are safranal, 1, 8-cineole, 4-keto-isophorone, isophorone and α-pinene. 70% of the accessions analyzed contain β-isophorone, an isomere of isophorone which is a criterion of saffron high quality. Other components are identified in very few accessions, in lower amount, e.g., rose oxide (26% of accessions), allo-ocimene (13%) and piperitone (4%). A difference in the volatiles composition has been noticed consequently to accessions origin and drying mode. The cluster analysis based on Jaccard similarity and complete link method has identified five groups, at 75% of similarity. This study highlights the impact of the environment on saffron volatiles composition when the drying is done naturally, and this could be used as chemical fingerprinting for the authenticity of the product, according to its origin