Object stable grasping control by dual robotic fingers with soft rolling contacts

This paper presents a novel robotic hand with a metamorphic palm which changes the traditional structure of a robotic hand. Based on this new hand structure, the paper investigates motion of the robotic fingers with respect to the palm by presenting finger operation planes and by revealing the relationship between finger motion and palm motion. The study presents the normals of the finger operation planes as a function of the input angles of the palm and uses these normals to relate finger motion to palm motion. This leads to the coaxial condition of the finger-palm relationship that is then converted to the coplanar condition of normals of all finger operation planes. The condition is then used to generate a coupler trajectory, and the iterative trajectory fitting and curve approximation are used for synthesis of palm links, leading to differential geometry based synthesis of angular lengths of the metamorphic palm.

Download Full-text

Object Manipulation Using Unlimited Rolling Contacts: 2-D Kinematic Modeling and Motion Planning

IEEE Transactions on Robotics ◽

10.1109/tro.2015.2411351 ◽

2015 ◽

Vol 31 (3) ◽

pp. 790-797

Author(s):

Ehsan Noohi ◽

Hadi Moradi ◽

Sina Parastegari ◽

Majid Nili Ahmadabadi

Keyword(s):

Motion Planning ◽

Object Manipulation ◽

Kinematic Modeling ◽

Rolling Contacts

Download Full-text

Algorithmic Selection of Preferred Grasp Poses using Manipulability Ellipsoid Forms

Journal of Mechanisms and Robotics ◽

10.1115/1.4053374 ◽

2021 ◽

pp. 1-24

Author(s):

Rajesh Kumar ◽

Sudipto Mukherjee

Keyword(s):

Geodesic Distance ◽

Object Surface ◽

Kinematic Constraints ◽

Rolling Contacts ◽

Manipulability Measure ◽

Robotic Grasp ◽

Selection Of

Abstract An algorithm to search for a kinematically desired robotic grasp pose with rolling contacts is presented. A manipulability measure is defined to characterise the grasp for multi-fingered robotic handling. The methodology can be used to search for the goal grasp pose with a manipulability ellipsoid close to the desired one. The proposed algorithm is modified to perform rolling based relocation under kinematic constraints of the robotic fingertips. The search for the optimal grasp pose and the improvement of the grasp pose by relocation is based on the reduction of the geodesic distance between the current and the target manipulability matrices. The algorithm also derives paths of the fingertip on the object surface in order to achieve the goal pose. An algorithmic option for the process of searching for a suitable grasp configuration is hence achieved.

Download Full-text

Validation of the Stress Predictions in Rolling EHL Contacts Having In-Line Roughness Using the Inverse Method

Journal of Tribology ◽

10.1115/1.2345396 ◽

2006 ◽

Vol 128 (4) ◽

pp. 745-752 ◽

Cited By ~ 1

Author(s):

C. J. Hooke ◽

K. Y. Li

Keyword(s):

Fluid Flow ◽

Inverse Method ◽

Rough Surfaces ◽

Three Dimensional ◽

Plane Flow ◽

Preliminary Results ◽

Rolling Contacts ◽

Out Of Plane ◽

Transverse Roughness

Using modern EHL programs it is relatively simple to determine the pressures and clearances in rough EHL contacts. The pressures may then be used to calculate the subsurface stresses in the two contacting components. However, the results depend on the assumptions made about the fluid’s rheology. While it is possible to measure the clearances using interferometric techniques, measurement of either the pressures or stresses is extremely difficult. However it is these, rather than the clearances, that determine the life of the contact. In previous papers the authors have described how the inverse method may be used to validate the stress predictions for contacts with transverse roughness. This type of contact has fluid flow in only one plane and it remained necessary to check the results for more general rough surfaces where the flow is three-dimensional. Accordingly, the inverse method is extended, in this paper, to a situation where out-of-plane flow is significant. The paper describes the approach and presents some preliminary results for rolling contacts.

Download Full-text

Traction of Lubricated Rolling Contacts Between Thin Film Coatings and Steel

ASME/STLE 2007 International Joint Tribology Conference, Parts A and B ◽

10.1115/ijtc2007-44261 ◽

2007 ◽

Author(s):

Ryan D. Evans ◽

J. David Cogdell ◽

Gary L. Doll

Keyword(s):

Thin Film ◽

Rolling Contact ◽

Carbon Coatings ◽

Test Configuration ◽

Film Coatings ◽

Thin Film Coatings ◽

Rolling Contacts ◽

Traction Coefficient ◽

Coated Surfaces ◽

Stribeck Curves

Tribological thin film coatings can enhance performance in mechanical components such as bearings and gears. Although lubricant is present in most applications, the interactions of the lubricant with coated surfaces are not always well understood. In the present study, Stribeck curves (i.e., traction coefficient vs. dimensionless film thickness Λ) were generated for lubricated rolling contact between coated and uncoated surfaces. Chromium nitride, tungsten carbide reinforced amorphous hydrocarbon, and silicon-incorporated diamond-like carbon coatings are evaluated. A ball-on-flat test configuration is used in a 100% slide-to-roll condition. The test lubricant was a polyalphaolefin containing rust and oxidation inhibitor additives only. Differences in traction performance are observed for different coating types. The traction coefficient decreases at high Λ with increasing hydrocarbon content in the coating. The combination of coating micro-texture and composition are believed to influence traction as A becomes small.

Download Full-text

A New Approach for Fatigue Damage Modeling of Subsurface-Initiated Spalling in Large Rolling Contacts

Journal of Tribology ◽

10.1115/1.4033054 ◽

2016 ◽

Vol 139 (1) ◽

Cited By ~ 11

Author(s):

Aditya A. Walvekar ◽

Neil Paulson ◽

Farshid Sadeghi ◽

Nick Weinzapfel ◽

Martin Correns ◽

...

Keyword(s):

Fatigue Damage ◽

Damage Mechanics ◽

Numerical Models ◽

Rolling Contact ◽

Fe Model ◽

Triangle Mesh ◽

Computationally Efficient ◽

New Approach ◽

Rolling Contacts ◽

Delaunay Triangle

Large bearings employed in wind turbine applications have half-contact widths that are usually greater than 1 mm. Previous numerical models developed to investigate rolling contact fatigue (RCF) require significant computational effort to study large rolling contacts. This work presents a new computationally efficient approach to investigate RCF life scatter and spall formation in large bearings. The modeling approach incorporates damage mechanics constitutive relations in the finite element (FE) model to capture fatigue damage. It utilizes Voronoi tessellation to account for variability occurring due to the randomness in the material microstructure. However, to make the model computationally efficient, a Delaunay triangle mesh was used in the FE model to compute stresses during a rolling contact pass. The stresses were then mapped onto the Voronoi domain to evaluate the fatigue damage that leads to the formation of surface spall. The Delaunay triangle mesh was dynamically refined around the damaged elements to capture the stress concentration accurately. The new approach was validated against previous numerical model for small rolling contacts. The scatter in the RCF lives and the progression of fatigue spalling for large bearings obtained from the model show good agreement with experimental results available in the open literature. The ratio of L10 lives for different sized bearings computed from the model correlates well with the formula derived from the basic life rating for radial roller bearing as per ISO 281. The model was then extended to study the effect of initial internal voids on RCF life. It was found that for the same initial void density, the L10 life decreases with the increase in the bearing size.

Download Full-text