189 research outputs found
Prehensile Pushing: In-hand Manipulation with Push-Primitives
No full textThis paper explores the manipulation of a grasped object by pushing it against its environment. Relying on precise arm motions and detailed models of frictional contact, prehensile pushing enables dexterous manipulation with simple manipulators, such as those currently available in industrial settings, and those likely affordable by service and field robots. This paper is concerned with the mechanics of the forceful interaction between a gripper, a grasped object, and its environment. In particular, we describe the quasi-dynamic motion of an object held by a set of point, line, or planar rigid frictional contacts and forced by an external pusher (the environment). Our model predicts the force required by the external pusher to “break” the equilibrium of the grasp and estimates the instantaneous motion of the object in the grasp. It also captures interesting behaviors such as the constraining effect of line or planar contacts and the guiding effect of the pusher’s motion on the objects’s motion. We evaluate the algorithm with three primitive prehensile pushing actions—straight sliding, pivoting, and rolling—with the potential to combine into a broader in-hand manipulation capability.National Science Foundation (U.S.). National Robotics Initiative (Award NSF-IIS-1427050)Karl Chang Innovation Fund Awar
Dexterous manipulation with simple grippers
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.Includes bibliographical references (pages 117-124).This thesis focuses on enabling robots, specially those with simple grippers, to dexterously manipulate an object in a grasp. The dexterity of a robot is not limited to the intrinsic capability of a gripper. The robot can roll the object in the gripper using gravity, or adjust the object's pose by pressing it against a surface, or it can even toss the object in the air and catch it in a different pose. All these techniques rely on resources extrinsic to the hand, either gravity, external contacts or dynamic arm motions. We refer to such techniques collectively as "extrinsic dexterity". We focus on empowering robots to autonomously reason about using extrinsic dexterity, particularly, pushes against external contacts. We develop mechanics and algorithms for simulating, planning, and controlling motions of an object pushed in a grasp. We show that the force-motion relationship at contacts can be captured well with complementarity constraints and the mechanics of prehensile pushing in a general setting can be formulated as a mixed nonlinear complementarity problem. For computational efficiency, we derive the abstraction of the mechanics in the form of motion cones. A motion cone defines the set of object motions a pusher can induce using frictional contact. Building upon these mechanics models, we develop a sampling-based planner and an MPC-based controller for in-hand manipulation. The planner generates a series of pushes, possibly from different sides of the object, to move the object to a desired grasp. The controller generates local corrective pushes to keep the object close to the planned pushing strategy. With a variety of regrasp examples, we demonstrate that our planner-controller framework allows the robot to handle uncertainty in physical parameters and external disturbances during manipulation to successfully move the object to a desired grasp.by Nikhil Chavan-Dafle.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineerin
Experimental Validation of Contact Dynamics for In-Hand Manipulation
No full textThis paper evaluates state-of-the-art contact models at predicting the motions and forces involved in simple in-hand robotic manipulations. In particular it focuses on three primitive actions—linear sliding, pivoting, and rolling—that involve contacts between a gripper, a rigid object, and their environment. The evaluation is done through thousands of controlled experiments designed to capture the motion of object and gripper, and all contact forces and torques at 250 Hz. We demonstrate that a contact modeling approach based on Coulomb’s friction law and maximum energy principle is effective at reasoning about interaction to first order, but limited for making accurate predictions. We attribute the major limitations to (1) the non-uniqueness of force resolution inherent to grasps with multiple hard contacts of complex geometries, (2) unmodeled dynamics due to contact compliance, and (3) unmodeled geometries due to manufacturing defects.
Keywords: Contact Force, Contact Model, Grasp Object, Contact Compliance, Grip Force Increas
A two-phase gripper to reorient and grasp
No full textThis paper introduces the design of novel two-phase fingers to passively reorient objects while picking them up. Two-phase refers to a change in the finger-object contact geometry, from a free spinning point contact to a firm multipoint contact, as the gripping force increases. We exploit the two phases to passively reorient prismatic objects from a horizontal resting pose to an upright secure grasp. This problem is particularly relevant to industrial assembly applications where parts often are presented lying on trays or conveyor belts and need to be assembled vertically. Each two-phase finger is composed of a small hard contact point attached to an elastic strip mounted over a V-groove cavity. When grasped between two parallel fingers with low gripping force, the object pivots about the axis between the contact points on the strips, and aligns upright with gravity. A subsequent increase in the gripping force makes the elastic strips recede into the cavities letting the part seat in the V-grooves to secure the grasp. The design is compatible with any type of parallel-jaw gripper, and can be reconfigured to specific objects by changing the geometry of the cavity. The two-phase gripper provides robots with the capability to accurately position and manipulate parts, reducing the need for dedicated part feeders or time-demanding regrasp procedures.National Science Foundation (U.S.). National Robotics Initiative (NSF-IIS-1427050
Heat transfer through a condensate droplet on hydrophobic and nanostructured superhydrophobic surfaces
No full textUnderstanding the fundamental mechanisms governing vapor condensation on non-wetting surfaces is crucial to a wide range of energy and water applications. In this thesis, we reconcile classical droplet growth modeling barriers by utilizing two-dimensional axisymmetric numerical simulations to study individual droplet heat transfer on non-wetting surfaces (90° < θ_a < 170°). Incorporation of an appropriate convective boundary condition at the liquid vapor interface reveals that the majority of heat transfer occurs at the three phase contact line, where the local heat flux can be up to 4 orders of magnitude higher than at the droplet top. Droplet distribution theory is incorporated to show that previous modeling approaches under predict the overall heat transfer by as much as 300% for dropwise and jumping-droplet condensation. To verify our simulation results, we study condensed water droplet growth using optical and ESEM microscopy on bi-philic samples consisting of hydrophobic and nanostructured superhydrophobic regions, showing excellent agreement with the simulations for both constant base area and constant contact angle growth regimes. Our results demonstrate the importance of resolving local heat transfer effects for the fundamental understanding and high fidelity modeling of phase change heat transfer on non-wetting surfaces.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-05-01The student, Shreyas Chavan, accepted the attached license on 2016-04-25 at 17:05.The student, Shreyas Chavan, submitted this Thesis for approval on 2016-04-25 at 17:16.This Thesis was approved for publication on 2016-04-27 at 09:11.DSpace SAF Submission Ingestion Package generated from Vireo submission #9489 on 2016-07-07 at 13:50:52Made available in DSpace on 2016-07-07T20:35:15Z (GMT). No. of bitstreams: 2
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Phase change phenomena on water repelling and biphilic surfaces
No full textThis Dissertation was approved for publication on 2019-04-10 at 09:54.Water-repelling surfaces have been studied for many decades. Hydrophobic and superhydrophobic surfaces are beneficial in phase change heat transfer applications, specifically during condensation because of the enhanced heat transfer and during freezing because of the anti-freezing properties. The current study is focused on enhanced phase change phenomena on superhydrophobic and biphilic surfaces. Hydrophobic surfaces that enable dropwise condensation exhibit 5-10X higher heat transfer. Coalescence induced droplet jumping on superhydrophobic surfaces further increases the heat transfer by 30%. Here, biphilic surfaces consisting of hydrophilic spots on a superhydrophobic background are studied for enhanced condensation. Water droplets nucleating at the hydrophilic spots grow to sizes defined by the biphilic geometry, followed by coalescence and departure. A high fidelity model that captures departure dynamics during droplet jumping on biphilic surfaces and predict the overall condensation heat transfer has been developed. By controlling the spatial geometry and length scale of the hydrophilic spots, enhanced (10X) jumping-droplet condensation heat transfer is obtained.
In terms of freezing and frost formation, understanding the mechanisms of frost formation is essential to a variety of Heating, Ventilating, Air Conditioning and Refrigeration (HVAC&R) applications. When water vapor in the ambient condenses on a chilled substrate in the form of liquid water and then freezes, it is known as condensation frosting. The dominant mechanism governing the spread of condensation frosting is inter-droplet ice bridge frost wave propagation. When a subcooled condensate water droplet freezes on a hydrophobic or superhydrophobic surface, neighboring droplets still in the liquid phase begin to evaporate. The evaporated water molecules deposit on the frozen droplet and initiate the growth of ice bridges directed toward the water droplets being depleted. Neighboring liquid droplets freeze as soon as the ice bridge connects. In this study, the significance of individual droplet freezing on frost wave propagation is studied. 10X slower frost wave propagation speeds on superhydrophobic surfaces are observed. Furthermore, at larger length scales, during bulk freezing of water, it has been shown that superhydrophobic surfaces offer no delay in freezing.
Although frosting delay has been shown with superhydrophobic surfaces, complete elimination of frosting has not been achieved. Given enough time, frosting will initiate and spread to cover the entire surface. In the HVAC&R sectors, the most common approach to remove frost from a surface (defrost) is to reverse the system cycle direction and heat the working fluid. However, water retention on the heat exchanger surface during defrosting decreases the long term heat transfer performance. In this study, the defrosting behavior of superhydrophobic and biphilic surfaces comprising of spatially distinct superhydrophobic and hydrophilic domains is used to accelerate defrosting. During defrosting, biphilic surfaces are shown to exhibit enhanced surface cleaning with no water retention. Furthermore, an ultra-efficient method to defrost a surface covered with ice/frost by focusing energy at the substrate-ice interface is studied. To remove ice/frost efficiently, only the interfacial layer adhering the ice/frost to the solid surface is melted by using a localized ‘pulse’ of heat, allowing gravity or gas shear in conjunction with the ultra-thin lubricating melt water layer to remove the ice/frost. A high fidelity numerical model is developed to simulate pulse defrosting. This work not only provides a fundamental understanding of phase change processes on superhydrophobic and biphilic surfaces, but also elucidates its applications for a plethora of energy industries.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Shreyas Chavan, accepted the attached license on 2019-04-09 at 16:13.The student, Shreyas Chavan, submitted this Dissertation for approval on 2019-04-09 at 16:16.DSpace SAF Submission Ingestion Package generated from Vireo submission #13540 on 2019-08-22 at 16:20:55Made available in DSpace on 2019-08-23T20:44:41Z (GMT). No. of bitstreams: 2
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Extrinsic Dexterity: In-Hand Manipulation with External Forces
No full textAbstract — “In-hand manipulation ” is the ability to reposition an object in the hand, for example when adjusting the grasp of a hammer before hammering a nail. The common approach to in-hand manipulation with robotic hands, known as dexterous manipulation [1], is to hold an object within the fingertips of the hand and wiggle the fingers, or walk them along the object’s surface. Dexterous manipulation, however, is just one of the many techniques available to the robot. The robot can also roll the object in the hand by using gravity, or adjust the object’s pose by pressing it against a surface, or if fast enough, it can even toss the object in the air and catch it in a different pose. All these techniques have one thing in common: they rely on resources extrinsic to the hand, either gravity, external contacts or dynamic arm motions. We refer to them as “extrinsic dexterity”. In this paper we study extrinsic dexterity in the context of regrasp operations, for example when switching from a power to a precision grasp, and we demonstrate that even simple grippers are capable of ample in-hand manipulation. We develop twelve regrasp actions, all open-loop and handscripted, and evaluate their effectiveness with over 1200 trials of regrasps and sequences of regrasps, for three different objects (see video [2]). The long-term goal of this work is to develop a general repertoire of these behaviors, and to understand how such a repertoire might eventually constitute a general-purpose in-hand manipulation capability. I
ANALYSIS OF PUBLICATION PROFILE OF ACADEMIC LIBRARIANS IN MAHARASHTRA
No full textResearch has always been regarded as the most important intellectual activity in the higher education system; therefore this research article aims to provide a comprehensive picture of research productivity in symposia, seminars, conferences, journals, book chapters, research projects and patents carried out by various academic librarians during 2004 to 2013. A questionnaire was designed for data collection and the same was sent to the academic librarians by e-mail/in print. The results indicate that there were total 1325 research productivity in symposia, seminars, conferences, journals, book chapters, research projects and patents during the year 2004 to 2013. Highest 405 (30.57%) research papers published in conferences. Maximum 28.98% research publications appeared during the year 2013. Dr. S.P. Chavan was the most prolific author he has published 85 (6.41%) research papers. Librarian preferred English language to write research papers. Researchers communicated their research through variety of communication channels. The librarian mostly preferred to journals for communication channel. Highest 57 (74.03%) librarians have used single authorship pattern for their publications. Mostly 68 (88.31%) librarians have attending the workshops/symposia/seminars/conferences to acquire new skills, latest technology, update knowledge
Subdued Voices: Women Characters and Their Author in Inside the Haveli
No full textRama Mehta is an eminent novelist who contributed significantly to Indian English fiction by bringing female issues to the fore through her exemplary novel, Inside the Haveli. The novel shows a predominant concern with the subjugating condition of women characters shackled in the Indian patriarchal structure and brings, particularly, into light the repressed state of female characters and the elements that determine their submission. Simultaneously, based on the incident, the novel reveals silence and submission on the part of the novelist as well. Nevertheless, the work seems stifled when dealing with women's issues; its movements are confusing, contradicting and oscillating. The characters and their author appear tense under pressure showing a disinclination to adopt a bold stance. This cramped and oscillating situation speaks of their helplessness and repressed situation
Green synthesis of silver Nanoparticle using Carica Papaya and study there Biochemical Application
No full textAbstract: The nanopartical offer several advantages over other conventional drug delivery systems. Nanoparticles have gained importance in technological advancements due to their modifiable physical, chemical and biological properties with improved performance over their bulk foils. Nanoparticles can simply move in the body due to their small size and reach very complex organs through divers routes. The high stability, controlled drug release makes nanoparticles the most suitable drug delivery system. The study of different methods of synthesis of nanoparticles is essential to obtain desired nanoparticle with specific sizes and shapes. They are suitable candidates for various marketable and local application, which include imaging, catalysis medical application and environmental application.
Keywords: Nanopartical, bulk foil, divers routes.
Title: Green synthesis of silver Nanoparticle using Carica Papaya and study there Biochemical Application
Author: Ms.Pallavi R.Bhagat, Ms. Shubhangi Sahebsingh Rajput, Ms. Shruti Prashant Chavan
International Journal of Interdisciplinary Research and Innovations
ISSN 2348-1218 (print), ISSN 2348-1226 (online)
Vol. 10, Issue 4, October 2022 - December 2022
Page No: 35-39
Research Publish Journals
Website: www.researchpublish.com
Published Date: 06-November-2022
DOI: https://doi.org/10.5281/zenodo.7296295
Paper Download Link (Source)
https://www.researchpublish.com/papers/green-synthesis-of-silver-nanoparticle-using-carica-papaya-and-study-there-biochemical-applicationInternational Journal of Interdisciplinary Research and Innovations, ISSN 2348-1218 (print), ISSN 2348-1226 (online), Research Publish Journals, Website: www.researchpublish.co
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