Dextrous manipulation with rolling contacts

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.

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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.

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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.

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