1,721,469 research outputs found
Electroadhesion for Soft Robotics: advancements in Soft Gripper applications
Full text linkThis thesis advances the field of electroadhesion applied to soft robotics, with focus on electroadhesion soft grippers. The main contribution of my work regards novel insights into the influence of mechanics on electroadhesion. In the first part of the Thesis, I explored how mechanics plays a critical role in the performance of current designs of electroadhesion soft grippers. In the second and last part of Thesis, I investigated an alternative approach for the realization of a novel electroadhesion soft robotic gripper embedding hydrogel into its structure.
Despite extensive research on electroadhesion based devices has been conducted in the past, only recently the role of the mechanical features of the system has been discovered and outlined. This is particularly important for robotic devices such as electrostatic and electrohydraulic actuators, electrostatic clutches and electroadhesion grippers. In this Thesis, I focused mainly on grippers. First, I explored the relationship between mechanical and electrical parameters of the grasping system and how it influences the wrapping capabilities of an electroadhesion gripper. Despite some current designs involve the use of external actuators to ease the grasping of objects with complex shapes, passive wrapping around objects can be reached under certain conditions. In the latter case, the wrapping is based on the phenomenon of zipping, already exploited in soft electrostatic actuators. Our work allowed us to discover that the zipping of gripper’s fingers on a curved object is ruled by two voltage thresholds, depending on the characteristics of the system. We experimentally validated the theoretical model and observed that actual behavior is predicted by the model, even if further investigations are needed to clarify what happens under certain conditions. The outcomes of this investigation are the starting point for determining how even more complex shape influence the object wrapping and to design grippers able to reliably grasp even the most complicated objects. The results can be useful for the advancement of electrostatic and electrohydraulic actuators as well.
The shape of the object also influences the maximum holding force of an electroadhesion gripper. When it grasps curved objects, the geometry of the object produces an exponential increase in the adhesion force. The effect has been observed in previous works, but no theoretical or systematical experimental investigations were conducted. I produced a model that considers the shape of the object and dramatically reduces the error in force prediction if compared with previous models. We also conducted a preliminary validation of the model. The first results confirm the validity of our hypotheses. Further work is required to fully validate the model. The results of the study are valuable not only for determining the capabilities of an electroadhesion soft gripper. They can easily be employed to guide the design of novel soft robotic devices such as electrostatic clutches. We aim at producing electrostatic clutches able to reduce requirements in terms of applied voltage or increase the output force, being equal other parameters.
The final part of the thesis presents the preliminary results conducted on the modulation of hydrogel friction obtained by applying voltage to it. Previous works demonstrated that hydrogel friction and adhesion respond to the application of relatively low voltages. We aim at exploiting this effect to produce the first electroadhesion soft gripper made by hydrogels. I started by investigating methods to increase water retention of hydrogel and to obtain bonding to external surfaces. Fulfilling these requirements is crucial to integrate hydrogels into a soft robot. I then produced preliminary experiments on the modulation of friction of hydrogel with applied voltage, that confirmed the hypotheses. Finally, I produced some tests on archaic prototypes of soft gripper’s finger embedding hydrogel into their structure. The first experiments did not produce the expected results. The work will be carried on by improving the designs of the prototypes. Further investigations for the refinement of bonding and water retention methods will be also conducted
Coordinates at Small Energy and Refined Profiles for the Nonlinear Schrödinger Equation
Full text linkIn this paper we give a new and simplified proof of the theorem on selection of standing waves for small energy solutions of the nonlinear Schrödinger equations (NLS) that we gave in [6]. We consider a NLS with a Schrödinger operator with several eigenvalues, with corresponding families of small standing waves, and we show that any small energy solution converges to the orbit of a time periodic solution plus a scattering term. The novel idea is to consider the “refined profile”, a quasi–periodic function in time which almost solves the NLS and encodes the discrete modes of a solution. The refined profile, obtained by elementary means, gives us directly an optimal coordinate system, avoiding the normal form arguments in [6], giving us also a better understanding of the Fermi Golden Rule
On the asymptotic stability of ground states of the pure power NLS on the line at 3rd and 4th order Fermi Golden Rule
No full textAssuming as hypotheses the results proved numerically by Chang et al. (SIAM J Math Anal 39:1070–1111, 2007/08) for the exponent p∈(3,5), we prove that some of the ground states of the nonlinear Schrödinger equation (NLS) with pure power nonlinearity of exponent p in the line are asymptotically stable for a certain set of values of the exponent p where the FGR occurs by means of a discrete mode 3rd or 4th order power interaction with the continuous mode. For the 3rd the result is true for generic p while for the 4th order case we assume that there are p’s satisfying Fermi Golden rule and the non-resonance condition of the threshold of the continuous spectrum of the linearization. The argument is similar to our recent result valid for p near 3 contained in Cuccagna and Maeda (J Funct Anal 288(11):110861, 2025)
A note on the Fermi Golden Rule constant for the pure power NLS
Full text linkWe provide a detailed proof that the Nonlinear Fermi Golden Rule coefficient that appears in our recent proof of the asymptotic stability of ground states for the pure power Nonlinear Schrödinger equations in R with exponent 0 < |p − 3| ≪ 1 is nonzero
A survey on asymptotic stability of ground states of nonlinear Schrödinger equations II
Full text linkWe give short survey on the question of asymptotic stability of ground states of nonlinear Schrödinger equations, focusing primarily on the so called nonlinear Fermi Golden Rule
Asymptotic stability of kink with internal modes under odd perturbation
Full text linkWe give a sufficient condition, in the spirit of Kowalczyk–Martel–Munoz–Van Den Bosch (Ann PDE 7(1):Paper No. 10, 98, 2021), for the local asymptotic stability of kinks under odd perturbations. In particular, we allow the existence of quite general configuration of internal modes. The extension of our result to moving kinks remains an open problem
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Note on Small Data Soliton Selection for Nonlinear Schrödinger Equations with Potential
Full text linkIn this note, we give an alternative proof of the theorem on soliton selection for small-energy solutions of nonlinear Schrödinger equations (NLS) studied in (Cuccagna and Maeda, Anal PDE 8(6):1289–1349, 2015; Cuccagna and Maeda, Ann PDE 7:16, 2021). As in (Cuccagna and Maeda, Ann PDE 7:16, 2021), we use the notion of refined profile, but unlike in (Cuccagna and Maeda, Ann PDE 7:16, 2021), we do not modify the modulation coordinates and do not search for Darboux coordinates
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