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Li X, Qian Y, Li R, Niu X, Qiao H. Robust form-closure grasp planning for 4-pin gripper using learning-based Attractive Region in Environment. Neurocomputing 2020. [DOI: 10.1016/j.neucom.2019.12.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
Friction uncertainty and contact position uncertainty may have a disastrous effect on the closure properties of grasps. This paper reflects our approach to handling these uncertainties in force-closure analysis. The former uncertainty is measured by the possible reduction rate κ of friction coefficients, while the radius ρ of contact regions is used to quantify the latter uncertainty. The actual contact point may deviate from the desired position but not farther than ρ ρS, the supremum of ρ without loss of force-closure, indicates the grasp tolerance to contact position uncertainty. For investigating the above uncertainties systematically, we propose three new problems in force-closure: whether a grasp with given κ and ρ achieves force-closure, what value ρS equals if κ is given, and how ρS varies versus κ. To facilitate their solutions, we extend the scope of the infinitesimal motion approach from form-closure analysis to force-closure. A necessary and sufficient condition for force-closure is deduced by means of the duality between some convex cones, which play the key role in solving the problems. Finally, efficient algorithms are developed and applied to two illustrative examples.
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Affiliation(s)
- Yu Zheng
- Robotics Institute, Shanghai Jiao Tong University, Shanghai, China 200030,
| | - Wen-Han Qian
- Robotics Institute, Shanghai Jiao Tong University, Shanghai, China 200030,
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Abstract
SUMMARYParallel-jaw gripper finds wide applications in various industrial sectors. In this paper, we mainly focus on the problem of form closure caging grasps of polygons with a parallel-jaw gripper equipped with four fingers. The form closure caging grasp is helpful for the fingers placements and contact region selections of a pneumatic gripper, as it is less sensitive to fingers misplacements.We firstly prove that there is always a path from a cage to a form closure grasp of the object that never breaks the cage, as long as the attractive region constructed in the configuration space has a local minimum. If such a minimum cannot be found, we further adjust the fingers arrangements to produce the form closure grasp. Meanwhile, we also develop an algorithm to compute the initial cage of the form closure grasp. Simulations of the grasping process witness the effectiveness of the above analysis results.
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