Algorithmic Fingertip Repositioning for Enhanced In-Hand Manipulation of the Objects

2021 ◽  
pp. 1-17
Author(s):  
Rajesh Kumar ◽  
Sudipto Mukherjee
Keyword(s):  
Contact Point ◽  
Object Motion ◽  
The Other ◽  
Object Surface ◽  
Force Closure ◽  
Finger Gaiting

Abstract This paper focuses on a method to relocate the robotic fingertips on the surface of the object when the fingertips instantaneously hold the object under precision grasp. Precision grasp involves holding the object using fingertips. Finger gaiting involves repositioning the fingertips on the surface of the object and then manipulation of the object. During repositioning, one contact point leaves the object surface and recontacts at the other point. A metric is defined on the set of feasible grasp configurations to limit deviation from force closure during repositioning of the fingertips. Then, a manipulability based metric is described to search for the optimal goal grasp states on the object's surface. The manipulability based metric is used to search the grasp state to relocate the contacts, such that the range of object motion is increased.

scholarly journals Prediction of the Resonant Response of Frictionally Constrained Blade Systems Using Constrained Mode Shapes

1998 ◽  
Author(s):  
J. J. Chen ◽  
C. H. Menq
Keyword(s):  
Contact Point ◽  
Element Model ◽  
The Other ◽  
Mode Shapes ◽  
Vibration Modes ◽  
Cyclic Symmetry ◽  
Resonant Response ◽  
Friction Contact ◽  
Blade System ◽  
Free Mode

In this paper, the concept of constrained mode shapes is employed to predict the resonant response of a frictionally constrained blade system. For a tuned blade system, the constrained mode shapes can be calculated using a finite element model of a single blade along with the cyclic symmetry constraint that simulates a fully stuck friction contact. The resulting constrained mode shapes are often complex and can be used to obtain the constrained receptance of the frictionally constrained blade. It is shown that by examining each mode’s contribution to the receptance at the friction contact point, the importance of each individual modes to the prediction of the resonant response of a frictionally constrained blade can be determined. Furthermore, by comparing the receptances calculated from free mode shapes and those from constrained mode shapes, it is found that in the neighborhood of the fully slipping region, the prediction of resonant response requires fewer number of modes when using free mode shapes compared to using constrained mode shapes. On the other hand, in the neighborhood of the fully stuck region, it requires fewer number of modes if constrained mode shapes are used. Therefore, when high preload at the friction contact is desirable, such as for shrouded blade systems, using the constrained mode shapes for the prediction of resonant response is preferred. Moreover, the concept of hybrid receptance is introduced so as to yield very accurate prediction of the resonant response based on only very few vibration modes.

Neighboring Degree-of-Approximation Equating Method for Computing Contact Points between Robot and Convex Object

1993 ◽  
Vol 5 (1) ◽  
pp. 19-25
Author(s):  
Makoto Kaneko ◽  
◽  
Kazuo Tanie ◽  
Keyword(s):  
Contact Point ◽  
Degree Of Approximation ◽  
Mathematical Framework ◽  
Object Surface ◽  
Convex Object ◽  
Contact Points ◽  
Nearest Point ◽  
Before And After ◽  
Compliant Joint ◽  
Computation Scheme

With a proper combination of compliant joint and position- controlled joint, a link system changes its posture with keeping contact between link system and environment. This is so-called Self-Posture Changing Motion (SPCM) and conveniently used to detect a contact point between robot and unknown object. In conventional approach, a contact point has been computed as an intersecting point between two different link postures before and after SPCM. In general, this computation scheme gives us a contact point with unsatisfactory approximation, while it furnishes us with an exact contact point for a sharp-edged object. In this paper, we first introduces a concept of degree-of-approximation, which is defined as the distance between a computed point and the nearest point over the object surface, and then propers the Neighboring Degree-Of Approximation Equating Method which improves the degree-of-approximation drastically and provides exact contact points not only for a sharp· edged object but also for a constant curved object. Mathematical framework is provided for the proposed computation scheme. Finally, the effectiveness of the proposed scheme is verified by simulations.

Snap-Through Phenomenon and Self-Contact of Spatial Elastica Subjected to Mid-Torque

2015 ◽  
Vol 07 (04) ◽  
pp. 1550057
Author(s):  
Boonchai Phungpaingam ◽  
Lawrence N. Virgin ◽  
Somchai Chucheepsakul
Keyword(s):  
Differential Equations ◽  
Shooting Method ◽  
Contact Point ◽  
Point Load ◽  
The Other ◽  
Arc Length ◽  
System Of Differential Equations ◽  
Kinematic Singularity ◽  
Euler Parameters ◽  
Equilibrium Configurations

This paper presents the snap-through phenomenon and effect of self-contact of the spatial elastica subjected to mid-length torque. One end of the elastica is clamped while the other end is placed in a sleeve joint. The total arc-length of the elastica can be varied by sliding the end through the sleeve joint. At a certain value of total arc-length, the sleeve joint is clamped and an external torque is applied at the mid-length of the elastica. The system of governing differential equations is derived from the equilibrium of an elastica segment and geometric relations of the inextensible elastica. The transformation matrix formulated in terms of Euler parameters is utilized to avoid the kinematic singularity. To display the behavior of the elastica, the system of differential equations needs to be integrated numerically from one end to the other end. The integration is performed so that the boundary conditions and some constraint conditions of the problem are satisfied, i.e., a shooting method is used. The effect of self-contact is taken into account by considering the contact force as a point load applying at contact point. From the results, the snap-through phenomenon, effect of self-contact and equilibrium configurations are highlighted herein.

Figure and texture presentation capabilities of a tactile mouse equipped with a display pad of stimulus pins

Robotica ◽  
2007 ◽  
Vol 25 (4) ◽  
pp. 451-460 ◽  
Author(s):  
Masahiro Ohka ◽  
Hiroshi Koga ◽  
Yukihiro Mouri ◽  
Tokuhiro Sugiura ◽  
Tetsu Miyaoka ◽  
...  
Keyword(s):  
Virtual Reality ◽  
Design Method ◽  
Tactile Display ◽  
The Other ◽  
Shearing Force ◽  
Object Surface ◽  
Matrix Type ◽  
The Real ◽  
Tactile Displays

SUMMARYTo obtain specifications for a tactile display that would be effective in virtual reality and tele-existence systems, we have developed two types of matrix-type experimental tactile displays. One is for virtual figures (display A) and the other is for virtual textures (display B). Display A's pad has a 4 × 6 array of stimulus pins, each 0.8 mm in diameter. Three pad configurations, in which distances between any two adjacent pins (pin pitch) are 1.2, 1.9, or 2.5 mm, were developed to examine the influence of distance on a human operator's determination of virtual figures. Display B has an 8 × 8 array of stimulus pins, each 0.3 mm in diameter and with 1-or 1.8-mm pin pitch, because presentation of virtual textures was presumed to require a higher pin density. To establish a design method for these matrix-type tactile displays, we performed a series of psychophysical experiments using displays A and B. By evaluating variations in the correct answer percentage and threshold caused by different pin arrays and different pin strokes, we determined under what conditions the operator could best feel the virtual figures and textures. The results revealed that the two-point threshold should be adopted as the pitch between pins in the design of the tactile display, that a pin stroke should exceed 0.25 mm, and that the adjustment method is the most appropriate to evaluate the capabilities of tactile displays. Finally, when we compared the virtual texture with the real texture, we found that the threshold for the real texture is almost 1/3rd that of the virtual texture. This result implies that it is effective to present variations in patterns caused by rotation and variation in shearing force, itself produced by relative motion between the finger surface and object surface.

scholarly journals Effect of Viscosity and Speed on Oil Cavitation Development in a Single Piston-Ring Lubricant Assembly

Lubricants ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 88
Author(s):  
Jamshid Nouri ◽  
Ioannis Vasilakos ◽  
Youyou Yan ◽  
Constantino-Carlos Reyes-Aldasoro
Keyword(s):  
High Speed ◽  
Piston Ring ◽  
Contact Point ◽  
Great Influence ◽  
The Other ◽  
Cavity Formation ◽  
Sliding Velocity ◽  
High Quality ◽  
Time Resolved ◽  
Lubricant Flow

A high-speed camera has been used to produce unique time-resolved images of high quality to describe the dynamics of the lubricant flow and cavitation characteristics in a sliding optical liner over a fixed single piston-ring lubricant assembly for three lubricants with different viscosities to establish their impact on cavitation formation and development. The images were obtained at two cranking speeds (or liner sliding velocity) of 300 rpm (0–0.36 m/s) and 600 rpm (0–0.72 m/s), at a lubricant temperature of 70 °C and a supply lubricant rate of 0.05 L/min. A special MATLAB programme has been developed to analyse the cavitation characteristics quantitatively. The dynamic process of cavities initiation was demonstrated by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at a liner sliding velocity of around 0.17 m/s. The results for both up- and down-stroke motions showed that the cavities reach their fully developed state downstream of the contact point when the liner velocity reaches its highest velocity and that they start to collapse around TDC and BDC when the liner comes to rest. Within the measured range, viscosity had a great influence on length of cavities so that a decrease in viscosity (from Lubricant A to C) caused a reduction in length of cavities of up to 35% for Lubricant C. On the other hand, an increase in speed, from 300 rpm to 600 rpm, have increased the number of string cavities and also increased the length of cavities due to thicker oil film thickness with the higher speed. Overall, the agreement between the processed data by MATLAB and visualisation measurements were good, but further thresholds refinement is required to improve the accuracy.

Studies of Conditions Affecting the Vulcanization of Rubber. IV. Heat Reaction during Vulcanization

1930 ◽  
Vol 3 (3) ◽  
pp. 384-385
Author(s):  
Yutaka Toyabe
Keyword(s):  
Electric Furnace ◽  
Present Author ◽  
Contact Point ◽  
Glass Tube ◽  
The Other ◽  
Thermal Resistivity ◽  
Horizontal Line ◽  
Differential Thermocouple ◽  
The Absolute ◽  
Heating Medium

Abstract The heat reaction during vulcanization was traced by means of a differential thermocouple, of which one contact point was placed in a sealed glass tube enclosed in the sample and the other in the heating medium of a small electric furnace, e. g., asbestos yarn windings. Specially prepared rubber precipitated from latex by acetone was milled with varying quantities of sulfur and was vulcanized at 155° C. The heat change was observed during the vulcanization. The curves are shown in Fig. 1. Although the absolute or relative amount of heat evolved seems to be shown by the ordinate of the curves, it is not the case because of the uneven thermal resistivity of the samples. From these curves, therefore, it may only be seen that the profiles of them are similar to each other, showing maximum points at 60 to 70 minutes and decreasing asymptotically to a horizontal line, i. e., the temperature of the heating medium of the furnace. It is observed that the maximum points lie at about the same period, though the sulfur contents of the samples were varied. Similar results are shown by Perks (J. Soc. Chem. Ind., 1926, 142T). The present author analyzed the vulcanizates corresponding to the maximum points of the curves, the results of which are shown in the following table.

scholarly journals A Comparative Study on Evaluation Methods of Fluid Forces on Cartesian Grids

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Taku Nonomura ◽  
Junya Onishi
Keyword(s):  
Reliable Method ◽  
Cartesian Grid ◽  
Object Motion ◽  
Shear Stresses ◽  
Ghost Cell ◽  
Object Surface ◽  
Ghost Fluid Method ◽  
Grid Systems ◽  
Fluid Forces ◽  
Different Types

We investigate the accuracy and the computational efficiency of the numerical schemes for evaluating fluid forces in Cartesian grid systems. A comparison is made between two different types of schemes, namely, polygon-based methods and mesh-based methods, which differ in the discretization of the surface of the object. The present assessment is intended to investigate the effects of the Reynolds number, the object motion, and the complexity of the object surface. The results show that the mesh-based methods work as well as the polygon-based methods, even if the object surface is discretized in a staircase manner. In addition, the results also show that the accuracy of the mesh-based methods is strongly dependent on the evaluation of shear stresses, and thus they must be evaluated by using a reliable method, such as the ghost-cell or ghost-fluid method.

Two-Degree-of-Freedom Decoupled Nonredundant Cable-Loop-Driven Parallel Mechanism

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Hanwei Liu ◽  
Clément Gosselin ◽  
Thierry Laliberté
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
The Other ◽  
End Effector ◽  
Two Degrees Of Freedom ◽  
Actuation Redundancy ◽  
Rigid Link ◽  
Force Closure ◽  
Two Degree Of Freedom

A novel two-degree-of-freedom (DOF) cable-loop slider-driven parallel mechanism is introduced in this paper. The novelty of the mechanism lies in the fact that no passive rigid-link mechanism or springs are needed to support the end-effector (only cables are connected to the end-effector) while at the same time there is no actuation redundancy in the mechanism. Sliders located on the edges of the workspace are used and actuation redundancy is eliminated while providing force closure everywhere in the workspace. It is shown that the two degrees of freedom of the mechanism are decoupled and only two actuators are needed to control the motion. There are two cable loops for each direction of motion: one acts as the actuating loop while the other is the constraint loop. Due to the simple geometric design, the kinematic and static equations of the mechanism are very compact. The stiffness of the mechanism is also analyzed in the paper. It can be observed that the mechanism's stiffness is much higher than the stiffness of the cables. The proposed mechanism's workspace is essentially equal to its footprint and there are no singularities.

scholarly journals Still standing. On the use of dioramas and mannequins in Sámi exhibitions

1970 ◽  
pp. 58-72 ◽  
Author(s):  
Silje Opdahl Mathisen
Keyword(s):  
Contact Point ◽  
The Other ◽  
Exhibition History ◽  
Other Hand ◽  
Museum Exhibitions

This article is about the use of dioramas in Sámi exhibitions. The author discusses the use of a specific exhibition technique where a mannequin and a taxidermied reindeer are grouped together, and often placed in an illusionary winter landscape. She has named this the Lappish Equipage. This form of representation has a long history both inside and outside museums, and it can be found in both Sámi and ethnic Norwegian and Swedish museums. The author discusses how this diorama works, and how its chequered past through appearances in various types of exhibitions makes it problematic to use in contemporary museum exhibitions about the Sámi. On the other hand, the author also points out that if the Lappish Equipage is re-framed and re-contextualized, and its exhibition history is consciously activated, the Lappish Equipage has a potential to work as a contact point between Sámi history and visitors in the museums today.

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