Design, modeling and evaluation of a millimeter-scale SMA bending actuator with variable length

2021 ◽  
pp. 1045389X2110387
Author(s):  
Jianghua Chen ◽  
Qingpeng Ding ◽  
Yeongjin Kim ◽  
Shing Shin Cheng
Keyword(s):  
Longitudinal Axis ◽  
Beam Model ◽  
Cooling Conditions ◽  
Potential Development ◽  
Bending Actuator ◽  
Continuous Bending ◽  
End Effectors ◽  
Bending Length ◽  
Force Range ◽  
Assembly Tasks

Millimeter-scale continuum bending actuators are useful in minimally invasive surgery to allow distal visualization and manipulation outside the line of sight. This paper presents a new continuum bending actuator based on shape memory alloy (SMA) with variable bending length. It consists of two SMA wires antagonistically configured to produce bidirectional bending under Joule heating. A linearly actuated rigid tube along the longitudinal axis enables continuous bending length adjustment, thus enhancing its workspace and force range. The proposed fabrication method tackles the challenging assembly tasks of maintaining the antagonistic configuration of long SMA wires, and robust electrical and mechanical connection during actuation. A quasi-static model of the actuator based on beam model and SMA constitutive model is presented and verified. The bending actuator was evaluated comprehensively for its workspace, blocked force, and trajectory tracking capability at different bending lengths and under different cooling conditions. It is the first work that demonstrates real-time continuous bending length adjustment in SMA-based bending actuator, leading to the potential development of compact and compliant robotic end effectors with improved distal workspace and force.

Design of a Multi-Palm Robotic Hand for Assembly Tasks

2016 ◽  
Author(s):  
Reza Movassagh-Khaniki ◽  
Neda Hassanzadeh ◽  
Abhijit Makhal ◽  
Alba Perez-Gracia
Keyword(s):  
Collaborative Work ◽  
Synthesis Process ◽  
Robotic Hand ◽  
Robot Arm ◽  
Robotic Hands ◽  
Robotic Arms ◽  
Bimanual Task ◽  
Tree Topologies ◽  
End Effectors ◽  
Assembly Tasks

Some robotic tasks, especially those in which there are interactions between manipulated objects, require the collaborative work of two robotic arms equipped with end-effector grippers or robotic hands. Most of the current applications in which a bimanual task is attempted by a robot use two robot arm manipulators with simple grippers, in which the end-effectors are used for grasping and the remaining motion is performed by the robotic arms. In this work, we propose the design of a highly dexterous multi-fingered robotic hand, able to perform the bimanual task when attached to a simple arm manipulator. Dexterous robotic hands can be designed with more than one splitting stage; their design for a task can be done using kinematic synthesis for tree topologies. The synthesis process is applied in this case to the design of a robotic hand with three palms for a bimanual task consisting of assembling an emergency stop button.

scholarly journals Reference Value Selection in a Perturbation Theory Applied to Nonuniform Beams

2018 ◽  
Vol 2018 ◽  
pp. 1-25 ◽  
Author(s):  
Blake Martin ◽  
Armaghan Salehian
Keyword(s):  
Reference Values ◽  
Natural Frequencies ◽  
Unit Length ◽  
Reference Value ◽  
Bending Stiffness ◽  
Mode Shapes ◽  
Beam Model ◽  
Continuous Bending ◽  
Spatially Varying ◽  
Euler Bernoulli Beam

The Lindstedt-Poincaré method is applied to a nonuniform Euler-Bernoulli beam model for the free transverse vibrations of the system. The nonuniformities in the system include spatially varying and piecewise continuous bending stiffness and mass per unit length. The expression for the natural frequencies is obtained up to second-order and the expression for the mode shapes is obtained up to first-order. The explicit dependence of the natural frequencies and mode shapes on reference values for the bending stiffness and the mass per unit length of the system is determined. Multiple methods for choosing these reference values are presented and are compared using numerical examples.

Algorithm for the Extraction of Optimal Gripping Force Range with the Robot Gripper

2012 ◽  
Vol 251 ◽  
pp. 164-168 ◽  
Author(s):  
Dong Hwan Shin ◽  
Choong Pyo Jeong ◽  
Tae Sang Park ◽  
Yoon Gu Kim ◽  
Ji Nung An
Keyword(s):  
Permanent Deformation ◽  
Frictional Coefficient ◽  
Specific Work ◽  
Robot System ◽  
End Effector ◽  
Robot Gripper ◽  
Specific Object ◽  
End Effectors ◽  
Force Range ◽  
Gripping Force

The arm of robot consists of a manipulator and an end-effector. The end-effector is doing a specific work such as welding, picking and placing, sawing, deburring, suction, etc. with for the specific object of robot system. Here we are focused on the gripper among end-effectors. If the gripper generates the excessive gripping force, then the gripped material can have a permanent deformation. On the other hand, if the gripping force is too small, then the gripped material can be slip from the end-effector, drop to the floor and will get damaged. Therefore, it is important to use the adequate gripping force of the gripper. In this paper, we suggest the algorithm which is easy to automate, for the extraction of optimal gripping force range, with the estimation of frictional coefficient and young’s modulus.

scholarly journals Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

2021 ◽  
Author(s):  
Augusto Pedron ◽  
Nicola Tondini
Keyword(s):  
Failure Mode ◽  
Longitudinal Direction ◽  
Longitudinal Axis ◽  
Careful Analysis ◽  
Beam Model ◽  
Variable Cross ◽  
Fire Behaviour ◽  
Shell Elements ◽  
Cooling Phase ◽  
Thin Walled

AbstractThe present work investigates the fire behaviour of a prestressed thin-walled concrete V-beam with variable cross section along its longitudinal axis. In particular, the results obtained from different modelling strategies implemented through analytical computations and Finite Element (FE) thermo-mechanical analyses conducted both with Euler–Bernoulli beam elements and with shell elements were compared. The models were able to properly allow for the prestressing force and its variation with temperature. The mode of failure was analysed both at ambient temperature and at elevated temperature by employing the ISO 834 standard heating curve as well as parametric fire curves so as to investigate the behaviour in the cooling phase. The outcomes showed that the beam model was not capable of accurately predicting the failure mode by largely overestimating the time of collapse. Indeed, the FE analysis with shell elements highlighted that beam behaviour assumptions with sections that remain plane were not satisfied as fire progressed. Furthermore, it also showed that the failure mode was not flexural in the longitudinal direction but due to the failure of the webs in transverse bending that interacted with longitudinal stresses. Finally, the analyses conducted by applying parametric fire curves highlighted possible failure in the cooling phase, which emphasises the need of careful analysis for these types of structural members.

Design and Analysis of Pneumatic Bending Actuator Used in Soft Robotics

2021 ◽  
Vol 105 ◽  
pp. 194-201
Author(s):  
Xu Dong Wang ◽  
Heng Wei Chen ◽  
Liao Wang ◽  
Wen Zhou ◽  
Yi Qing Li
Keyword(s):  
Nonlinear Problems ◽  
Element Model ◽  
Air Pressure ◽  
Experimental Comparison ◽  
Pneumatic Actuators ◽  
Air Chamber ◽  
Bending Actuator ◽  
Continuous Bending ◽  
Soft Actuators ◽  
The Finite Element Model

Pneumatic soft actuators can change their shapes under pneumatic pressure actuation and are capable of continuous bending. However, the air chambers inside will expand during the actuation process and cause nonlinear problems. Therefore pneumatic actuators are difficulties to model. In this paper, three types of bending actuators with different air chamber shapes are designed and the finite element model (FEM) is developed to simulate the deformation under different air pressure actuation. A prototype of the bending actuator is fabricated and a method to limit the expansion of the air chamber is designed based on the FEM results, which can effectively improve the expansion and the response of the actuator under low air pressure conditions through experimental comparison.

Warm and freeze-fracture of cotton seed radicles

1987 ◽  
Vol 45 ◽  
pp. 984-985
Author(s):  
E. L. Vigil ◽  
E. F. Erbe
Keyword(s):  
Thin Film ◽  
Water Vapor ◽  
Fracture Surface ◽  
Membrane Structure ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Longitudinal Axis ◽  
Fracture Plane ◽  
Cotton Seeds ◽  
Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

Electronmicroscopic localization of ribonucleic acids in ciliate Bursaria truncatella during cell division

1990 ◽  
Vol 48 (3) ◽  
pp. 132-133
Author(s):  
Vladimir Popenko ◽  
Natalya Cherny ◽  
Maria Yakovleva
Keyword(s):  
Cell Division ◽  
High Specificity ◽  
Longitudinal Axis ◽  
Gold Complexes ◽  
Somatic Nucleus ◽  
Ribonucleic Acids ◽  
Biological Meaning ◽  
Bivalent Cations ◽  
Lowicryl K4m ◽  
Short Time

Highly polyploid somatic nucleus (macronucleus) of ciliate Bursaria truncatella under goes severe changes in morphology during cell division. At first, macronucleus (Ma) condences, diminishes in size and turns perpendicular to longitudinal axis of the cell. After short time, Ma turns again, elongates and only afterwards the process of division itself occurs. The biological meaning of these phenomena is not clear.Localization of RNA in the cells was performed on sections of ciliates B. truncatella, embedded in “Lowicryl K4M” at various stages: (1) before cell division (Figs. 2,3); (11) at the stage of macronucleus condensation; (111) during elongation of Ma (Fig.4); (1111) in young cells (0-5min. after division). For cytochemical labelling we used RNaseAcolloidal gold complexes (RNase-Au), which are known to bind to RNA containing cell ularstructures with high specificity. The influence of different parameters on the reliability and reproducibility of labelling was studied. In addition to the factors, discussed elsewhere, we found that the balance of mono- and bivalent cations is of great significance.

Strategies for using instructions in assembly tasks

2007 ◽  
Author(s):  
Elsa Eiriksdottir ◽  
Richard Catrambone
Keyword(s):  
Assembly Tasks

KOMPETENSI PEDAGOGIK GURU

2012 ◽  
Vol 10 (3) ◽  
Author(s):  
Achmad Habibullah
Keyword(s):  
Civil Servant ◽  
Lesson Plans ◽  
Islamic Education ◽  
Weak Point ◽  
Islamic School ◽  
Average Value ◽  
Central Java ◽  
Potential Development ◽  
Pedagogical Competence ◽  
Material Organization

AbstractPedagogical competence is one of important competencies to the teachers. Therefore, this study aims to determine how the pedagogical competence of teachers is, viewed from the aspects of learning know­ledge skills, preparation of lesson plans, and learning in the classroom. This study used the quantitative method with 631 respondents of civil servant teachers of Islamic Education at school and teachers of ge­neral subjects at madrasah (Islamic school) recruited from non-permanent teachers in 20 districts/cities in Central Java province, selected at random. The findings show that teachers’ pedagogical competence knowledge on the aspect of learning knowledge skills is in the “poor” category, the aspect of students’ potential development knowledge and reflective efforts to improve the learning quality becomes a very weak point at an average value with the “very poor” category. In addition, the aspect of ability to prepare lesson plans is in the “sufficient” category, the teaching material organization and the evaluation aspect are very weak competence aspects, which get “poor”. Meanwhile, the competence of learning implemen­tation aspect is in the “sufficient” category. AbstrakKompetensi pedagogik merupakan salah satu kompetensi yang penting bagi guru. Untuk itu, penelitian ini bertujuan untuk mengetahui bagaimana kompetensi pedagogik guru, dilihat dari aspek kemampuan pengetahuan pembelajaran, menyusun rancangan pembelajaran (RPP), dan pembelajaran di kelas. Penelitian ini menggunakan metode kuantitatif dengan responden 631 guru PNS Pendidikan Agama Islam pada sekolah dan guru mata pelajaran umum pada madrasah yang direkrut dari guru honorer di 20 Kabupaten/Kota di Provinsi Jawa Tengah yang dipilih secara random. Hasil penelitian menunjukkan bahwa kompetensi pedagogik guru pada aspek kemampuan pengetahuan pembelajaran dalam kategori “kurang”, aspek pengetahuan pengembangan potensi peserta didik dan upaya reflektif untuk meningkatkan mutu pembelajaran menjadi titik yang sangat lemah dengan mendapat nilai rata-rata dengan kategori “sangat kurang”. Selain itu, aspek kemampuan menyusun RPP dalam kategori “cukup”, aspek pengorganisasian materi ajar dan aspek evaluasi merupakan aspek kemampuan yang sangat lemah dengan mendapatkan nilai “kurang”. Sedangkan, aspek kemampuan dalam melaksanakan pembelajaran dalam kategori “cukup”.

Morphological, histological and molecular characterization of Myxidium cf. rhodei infecting the kidney of Rutilus rutilus

2020 ◽  
Vol 141 ◽  
pp. 39-46
Author(s):  
MD Dorjievna Batueva ◽  
X Pan ◽  
J Zhang ◽  
X Liu ◽  
W Wei ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Molecular Characterization ◽  
Rutilus Rutilus ◽  
Longitudinal Axis ◽  
Suture Line ◽  
Present Species ◽  
Supplementary Data

In the present study, we provide supplementary data for Myxidium cf. rhodei Léger, 1905 based on morphological, histological and molecular characterization. M. cf. rhodei was observed in the kidneys of 918 out of 942 (97%) roach Rutilus rutilus (Linnaeus, 1758). Myxospores of M. cf. rhodei were fusiform with pointed ends, measuring 12.7 ± 0.1 SD (11.8-13.4) µm in length and 4.6 ± 0.1 (3.8-5.4) µm in width. Two similar pear-shaped polar capsules were positioned at either ends of the longitudinal axis of the myxospore: each of these capsules measured 4.0 ± 0.1 (3.1-4.7) µm in length and 2.8 ± 0.1 (2.0-4.0) µm in width. Polar filaments were coiled into 4 to 5 turns. Approximately 18-20 longitudinal straight ridges were observed on the myxospore surface. The suture line was straight and distinctive, running near the middle of the valves. Histologically, the plasmodia of the present species were found in the Bowman’s capsules, and rarely in the interstitium of the host. Phylogenetic analysis revealed that M. cf. rhodei was sister to M. anatidum in the Myxidium clade including most Myxidium species from freshwater hosts.

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