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Shapiro A, Rimon E, Ohev-Zion A. On the mechanics of natural compliance in frictional contacts and its effect on grasp stiffness and stability. Int J Rob Res 2013. [DOI: 10.1177/0278364912471690] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This paper considers the effect of natural material compliance on the stiffness and stability of frictional multi-contact grasps and fixtures. The contact preload profile is a key parameter in the nonlinear compliance laws governing such contacts. The paper introduces the Hertz–Walton contact compliance model which is valid for linear contact loading profiles. The model is specified in a lumped parameter form suitable for on-line grasping applications, and is entirely determined by the contact friction and by the material and geometric properties of the contacting bodies. The model predicts an asymmetric stiffening of the tangential reaction force as the normal load at the contact increases. As a result, the composite stiffness matrix of multi-contact grasps governed by natural compliance effects is asymmetric, indicating that these contact arrangements are not governed by any potential energy function. Based on the compliant grasp dynamics, the paper derives rules indicating which contact point locations and what preload profiles guarantee grasp and fixture stability. The paper also describes preliminary experiments supporting the contact model predictions.
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Affiliation(s)
- Amir Shapiro
- Department of Mechanical Engineering, Ben Gurion University, Beer-Sheva, Israel
| | - Elon Rimon
- Department of Mechanical Engineering, Technion - Israel Institute of Technology
| | - Alon Ohev-Zion
- Department of Mechanical Engineering, Ben Gurion University, Beer-Sheva, Israel
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Hauser K, Bretl T, Latombe JC, Harada K, Wilcox B. Motion Planning for Legged Robots on Varied Terrain. Int J Rob Res 2008. [DOI: 10.1177/0278364908098447] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In this paper we study the quasi-static motion of large legged robots that have many degrees of freedom. While gaited walking may suffice on easy ground, rough and steep terrain requires unique sequences of footsteps and postural adjustments specifically adapted to the terrain's local geometric and physical properties. In this paper we present a planner that computes these motions by combining graph searching to generate a sequence of candidate footfalls with probabilistic sample-based planning to generate continuous motions that reach these footfalls. To improve motion quality, the probabilistic planner derives its sampling strategy from a small set of motion primitives that have been generated offline. The viability of this approach is demonstrated in simulation for the six-legged Lunar vehicle ATHLETE and the humanoid HRP-2 on several example terrains, including one that requires both hand and foot contacts and another that requires rappelling.
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Affiliation(s)
- Kris Hauser
- Department of Computer Science Stanford University Stanford,CA 94305-5447, USA,
| | - Timothy Bretl
- University of Illinois at Urbana-Champaign, Urbana,IL 61801-2935, USA,
| | - Jean-Claude Latombe
- Department of Computer Science Stanford University Stanford,CA 94305-5447, USA,
| | - Kensuke Harada
- Humanoid Research Group Intelligent Systems ResearchInstitute National Institute of Advanced Industrial Science and Technology(AIST) Tsukuba, Ibaraki 305-8568, Japan,
| | - Brian Wilcox
- Jet Propulsion Laboratory California Institute of TechnologyPasadena, CA 91109,
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