A Variable Stiffness Joint by Granular Jamming

2012 ◽  
Author(s):  
Allen Jiang ◽  
Asghar Ataollahi ◽  
Kaspar Althoefer ◽  
Prokar Dasgupta ◽  
Thrishantha Nanayakkara
Keyword(s):  
Granular Matter ◽  
Variable Stiffness ◽  
Fold Increase ◽  
Medical Robotics ◽  
Matte Surface ◽  
Stiffness Control ◽  
Articulated Robot ◽  
The Cost ◽  
High Degree ◽  
The Continuum

We propose a novel, high degree of freedom variable stiffness joint for use in a miniature snake-like robot for minimally invasive surgeries via granular jamming. By pulling granule filled membrane-columns under vacuum, the columns and joint stiffen as the granular matter begin to jam. In our experiments, we achieved a four-fold increase in stiffness, and the stiffness can be achieved while the columns are straight or bent. Current flexible manipulators in industrial and medical robotics have followed two dominating methods of actuation and stiffness control. The first method is the continuum manipulator, which utilizes tendons or rods to bend the manipulator in a continuous fashion. The second method is classified as the highly articulated robot, where the manipulator is comprised of multiple segments linked by motor-driven universal joints. Like the latter, our manipulator is highly articulated, however stiffness of each joint can be independently controlled by the granular jamming principle. This paper studies the effect of grain type and vacuum pressure for stiffness tuning. We found that granules with a matte surface were able to achieve higher stiffnesses, with a cube shape exhibiting the highest stiffness, but at the cost of high levels of hysteresis.

Pharmacoeconomical approaches for assessing the rational use of ophthalmic drugs in polyclinic settings

2021 ◽  
pp. 143-145
Author(s):  
N.A. Nefedov ◽  
◽  
D.S. Ramonas ◽  
B.G. Khasanov ◽  
A.S. Alexandrov ◽  
...  
Keyword(s):  
Fold Increase ◽  
Eye Drops ◽  
Ophthalmic Drugs ◽  
Rational Use ◽  
Rational Drug ◽  
Acquisition Costs ◽  
The Cost ◽  
Drug Provision ◽  
Combined Drugs

Purpose. To evaluate the results of the rational use of ophthalmic medicines with the use of pharmacoeconomical analysis. Material and methods. With the help of ABC-VEN analysis, a comparative study of the quality of pharmacotherapy and drug provision of patients who were monitored and treated by an ophthalmologist of the polyclinic in 2015 and 2019 was conducted. Results. As a result, it was found that the share of costs for vital drugs increased by 10.1% and amounted to 71.1% in 2019, which corresponds to the standardized criterion (70-80%). There was a reduction in the cost of purchasing secondary drugs by 7.6%, which indicates a rational drug supply of ophthalmic drugs. The most commonly used drugs for the treatment of glaucoma were 27.8% in 2015 and 35.1% in 2019. The share of their acquisition costs was 54.9% and 67.9%, respectively. There was a significant increase in the range and number of drugs for the treatment of patients with glaucoma: a 2.8-fold increase in the number of purchased eye drops for monotherapy and a 12% increase in the number of combined drugs. Conclusion. Pharmacoeconomical analysis showed an optimization of spending money on the purchase of drugs used in ophthalmology: an increase of 10.1% in the share of vital drugs and a decrease of 7.6% in the cost of purchasing secondary drugs. There was an increase in the range and quantity of drugs for the treatment of patients with glaucoma. Key words: ABC-VEN-analysis, drugs, ophthalmology, pharmacoeconomics.

scholarly journals Simultaneous position and stiffness control of a revolute joint using a biphasic media variable stiffness actuator

2019 ◽  
Vol 1 (2) ◽  
pp. 80-97
Author(s):  
Jesus H Lugo
Keyword(s):  
Control Method ◽  
Variable Stiffness ◽  
Industrial Processes ◽  
Revolute Joint ◽  
Additional Information ◽  
Physical Prototype ◽  
Stiffness Control ◽  
Variable Stiffness Actuator ◽  
Control Fluid ◽  
And Control

Safe interactions between humans and robots are needed in several industrial processes and service tasks. Compliance design and control of mechanisms is a way to increase safety. This article presents a compliant revolute joint mechanism using a biphasic media variable stiffness actuator. The actuator has a member configured to transmit motion that is connected to a fluidic circuit, into which a biphasic control fluid circulates. Stiffness is controlled by changing pressure of control fluid into distribution lines. A mathematical model of the actuator is presented, a model-based control method is implemented to track the desired position and stiffness, and equations relating to the dynamics of the mechanism are provided. Results from force loaded and unloaded simulations and experiments with a physical prototype are discussed. The additional information covers a detailed description of the system and its physical implementation.

Variable stiffness control of series elastic actuated biped locomotion

2018 ◽  
Vol 11 (3) ◽  
pp. 225-235 ◽  
Author(s):  
Jianwen Luo ◽  
Shuguo Wang ◽  
Ye Zhao ◽  
Yili Fu
Keyword(s):  
Variable Stiffness ◽  
Biped Locomotion ◽  
Stiffness Control ◽  
Series Elastic

A micromechanically calibrated numerical model reproducing earthquake cycle in the lab

2021 ◽  
Author(s):  
Guilhem Mollon ◽  
Jérôme Aubry ◽  
Alexandre Schubnel
Keyword(s):  
Acoustic Waves ◽  
Granular Matter ◽  
Fluid Pressure ◽  
Triaxial Tests ◽  
Zone Model ◽  
Geophysical Research ◽  
Stick Slip ◽  
Space And Time ◽  
Discrete Part ◽  
The Continuum

<p>In this communication, we present a novel numerical framework which consists in a direct coupling between a discrete micromechanical modelling of rock damaging processes and a continuous modelling of elastic deformation and acoustic waves. It includes a polygon-based conforming Discrete Element Method (DEM) with a cohesive zone model (CZM, [1]) for the discrete part and a meshfree formulation for the continuum part. This framework is applied to the numerical reproduction of sawcut triaxial tests performed in the lab on marble samples under seismogenic conditions [2]. Realistic boundary conditions (in terms of the elasticity of the loading system, of the absorption of the elastic waves and of the fluid pressure applied on the lateral boundaries) are introduced. Constitutive laws (in the continuum part) and micromechanical parameters (in the discrete part) are calibrated by performing independant simulations based on experimental results found in the literature [3].</p><p>Upon loading, this model provides information on the system behavior that nicely complement the experimental data, such as (i) the progressive damaging of the contacting surfaces, leading to the emission of granular matter in the interface, to the formation of a gouge layer, and to a modification of the interface rheology, (ii) the space and time distribution and statistics and the detailed kinematics of the slip events related to the interface evolution, and (iii) the acoustic wave emission and propagation in the medium associated with such events.</p><p>The model shows that, depending on the experimental conditions (confining pressure, loading rate, surface roughness, etc.), and without relying to any prior choice of slip- or rate-dependent friction laws, a large number of sliding regimes can emerge from this system. This includes large stress drops, regular stick-slip, or stable sliding. This model thus provides an unprecedented view of both local and global phenomena at stake during lab earthquakes, at sampling rates in both space and time which remain out of reach for experimental instrumentation.</p><p>[1]. Mollon, G. (2015). “A numerical framework for discrete modelling of friction and wear using Voronoi polyhedrons”, Tribology International, 90, 343-355<br>[2]. Aubry, J. (2019). “Séismes au laboratoire: friction, plasticité et bilan énergétique”, PhD Thesis, Ecole Normale Supérieure.<br>[3]. Fredrich, J. T.; Evans, B. & Wong, T.-F., (1989). “Micromechanics of the brittle to plastic transition in Carrara marble”, Journal of Geophysical Research: Solid Earth, <span></span></p>

The Benefits of a Modified-Chemistry, High-Strength, Low-Alloy Steel

1987 ◽  
Vol 3 (02) ◽  
pp. 111-118
Author(s):  
John C. West
Keyword(s):  
Heat Input ◽  
Arc Welding ◽  
High Strength ◽  
Submerged Arc Welding ◽  
Low Alloy Steel ◽  
Labor Costs ◽  
Lower Strength ◽  
The Cost ◽  
High Degree ◽  
Submerged Arc

Steels with 50 ksi and up yield points usually acquire their strength from some form of heat treatment. Most of these steels, 11/2 in. thick and up, must be welded using sustained preheat and controlled interpass temperatures, plus controlled welding heat input of approximately 50 to 60 kJ/in. These two items can add as much as 50 percent to the cost of submerged-arc welding, and increases of up to 30 percent are common for manual welding when compared with lower-strength steels previously used. To reduce costs, a quenched and precipitation-hardened steel, ASTM A710 Grade A Class 3, with a high degree of weldability, was tested. This steel, which can be welded without sustained preheat and almost unlimited heat input, has been extensively tested in thicknesses from 21/4 through 6 in. Although this steel costs more than the usual quenched-and-tempered plates at these strength levels, reductions of 40 to 75 percent in welding labor costs are probable. In addition, sizeable material savings should be realized when these items are used in place of HY-80 and HY-100.

scholarly journals Critical Review of the Parameters Affecting the Effectiveness of Moisture Absorption Treatments Used for Natural Composites

2019 ◽  
Vol 3 (1) ◽  
pp. 27 ◽  
Author(s):  
Ahmad Al-Maharma ◽  
Naser Al-Huniti
Keyword(s):  
Moisture Absorption ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Complete Discussion ◽  
Natural Composites ◽  
Review Study ◽  
Fiber Matrix ◽  
Physical Treatments ◽  
The Cost ◽  
High Degree

Natural composites can be fabricated through reinforcing either synthetic or bio-based polymers with hydrophilic natural fibers. Ultimate moisture absorption resistance at the fiber–matrix interface can be achieved when hydrophilic natural fibers are used to reinforce biopolymers due to the high degree of compatibility between them. However, the cost of biopolymers is several times higher than that of their synthetic counterparts, which hinders their dissemination in various industries. In order to produce economically feasible natural composites, synthetic resins are frequently reinforced with hydrophilic fibers, which increases the incompatibility issues such as the creation of voids and delamination at fiber–matrix interfaces. Therefore, applying chemical and/or physical treatments to eliminate the aforementioned drawbacks is of primary importance. However, it is demonstrated through this review study that these treatments do not guarantee a sufficient improvement of the moisture absorption properties of natural composites, and the moisture treatments should be applied under the consideration of the following parameters: (i) type of hosting matrix; (ii) type of natural fiber; (iii) loading of natural fiber; (iv) the hybridization of natural fibers with mineral/synthetic counterparts; (v) implantation of nanofillers. Complete discussion about each of these parameters is developed through this study.

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