scholarly journals Crack Lip Contact Modeling Based on Lagrangian Multipliers with X-FEM

2016 ◽  
pp. 123-142 ◽  
Author(s):  
Yuan Jin ◽  
Olivier Pierard ◽  
Eric Wyart ◽  
Eric Béchet
Keyword(s):  
Contact Modeling ◽  
Lagrangian Multipliers

scholarly journals Internal contact modeling for finite strain topology optimization

2021 ◽  
Author(s):  
Gore Lukas Bluhm ◽  
Ole Sigmund ◽  
Konstantinos Poulios
Keyword(s):  
Topology Optimization ◽  
Finite Strain ◽  
Contact Modeling ◽  
Internal Contact

The boundary element method with Lagrangian multipliers

2008 ◽  
Vol 25 (6) ◽  
pp. 1303-1319 ◽  
Author(s):  
Gabriel N. Gatica ◽  
Martin Healey ◽  
Norbert Heuer
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Lagrangian Multipliers ◽  
Element Method

Contact modeling in forging simulation

2002 ◽  
Vol 125-126 ◽  
pp. 583-587 ◽  
Author(s):  
B Boroomand ◽  
J Parvizian ◽  
A.R Pishevar
Keyword(s):  
Contact Modeling

Correspondence. Dynamic Programming and Lagrangian Multipliers

1965 ◽  
Vol 4 (4) ◽  
pp. 488-490 ◽  
Author(s):  
N. V. Junnarkar ◽  
S. M. Roberts
Keyword(s):  
Dynamic Programming ◽  
Lagrangian Multipliers

Contact Modeling Technique of a Flexible Piston and Cylinder Using Modal Synthesis Method

2005 ◽  
Author(s):  
W. K. Kim ◽  
S. H. Sohn ◽  
H. J. Cho ◽  
D. S. Bae ◽  
J. H. Choi
Keyword(s):  
Contact Force ◽  
Synthesis Method ◽  
Normal Modes ◽  
Modeling Technique ◽  
Mode Shapes ◽  
Dynamics Analysis ◽  
Contact Modeling ◽  
Static Correction ◽  
Modal Synthesis ◽  
Contact Surfaces

In this paper, contact modeling technique and dynamics analysis of piston and cylinder system are presented by using modal synthesis method. It is very important to select mode shapes representing a global or local behavior of a flexible body due to a specified loading condition. This paper proposes a technique to generate the static correction modes which are nicely representing a motion by a contact force between a piston and cylinder. First normal modes of piston and cylinder under a boundary condition are computed, and then static correction modes due to a contact force applied at contacted nodes are added to the normal modes. Also, this paper proposes an efficient dynamics analysis process while changing the shape of the piston and cylinder. In optimization process or design study, their geometric data can be changed a bit. The slight changes of their contact surfaces make a high variation of the magnitude of a contact force, and it can yield the different dynamic behavior of an engine system. But, since the variations of the normal and correction modes are very small, the re-computation of their normal and correction modes due to the change of contact surfaces can be useless. Until now, whenever their contact surfaces are changed at a design cycle, the modes have been recomputed. Thus, most engineers in industries have been spent many times in very tedious and inefficient design process. In this paper, the normal and correction modes from the basic geometry of the piston and cylinder are computed. If the geometry shape is changed, nodal positions of the original modal model are newly calculated from an interpolation method and changed geometry data. And then the updated nodes are used to compute a precise contact force. The proposed methods illustrated in this investigation have good agreement with results of a nodal synthesis technique and proved that it is very efficient design method.

scholarly journals Joint 3-D Positioning and Power Allocation for UAV Relay Aided by Geographic Information

2021 ◽  
Author(s):  
Pengfei Yi ◽  
Liang Zhu ◽  
Lipeng Zhu ◽  
Zhenyu Xiao
Keyword(s):  
Power Allocation ◽  
Upper Bound ◽  
Three Dimensional ◽  
Geographic Information ◽  
Base Station ◽  
Lagrangian Multipliers ◽  
Loop Optimization ◽  
Convex Problem ◽  
Communication Links ◽  
Minimum Capacity

<div>In this paper, we study to employ geographic information to address the blockage problem of air-to-ground links between UAV and terrestrial nodes. In particular, a UAV relay is deployed to establish communication links from a ground base station to multiple ground users. To improve communication capacity, we fifirst model the blockage effect caused by buildings according to the three-dimensional (3-D) geographic information. Then, an optimization problem is formulated to maximize the minimum capacity among users by jointly optimizing the 3-D position and power allocation of the UAV relay, under the constraints of link capacity, maximum transmit power, and blockage. To solve this complex non-convex problem, a two-loop optimization framework is developed based on Lagrangian relaxation. The outer-loop aims to obtain proper Lagrangian multipliers to ensure the solution of the Lagrangian problem converge to the tightest upper bound on the original problem. The inner-loop solves the Lagrangian problem by applying the block coordinate descent (BCD) and successive convex approximation (SCA) techniques, where UAV 3-D positioning and power allocation are alternately optimized in each iteration. Simulation results confifirm that the proposed solution signifificantly outperforms two benchmark schemes and achieves a performance close to the upper bound on the UAV relay system.</div>

Spherical Hands: Toward Underactuated, In-Hand Manipulation Invariant to Object Size and Grasp Location

2016 ◽  
Vol 8 (6) ◽  
Author(s):  
Raymond R. Ma ◽  
Nicolas Rojas ◽  
Aaron M. Dollar
Keyword(s):  
Common Point ◽  
Object Size ◽  
Parallel Mechanisms ◽  
Dexterous Manipulation ◽  
Contact Modeling ◽  
Contact Conditions ◽  
Unstructured Environments ◽  
Instantaneous Screw ◽  
Insight Into

Minimalist, underactuated hand designs can be modified to produce useful, dexterous, in-hand capabilities without sacrificing their passive adaptability in power grasping. Incorporating insight from studies in parallel mechanisms, we implement and investigate the “spherical hand” morphologies: novel, hand topologies with two fingers configured such that the instantaneous screw axes, describing the displacement of the grasped object, always intersect at the same point relative to the palm. This produces the same instantaneous motion about a common point for any object geometry in a stable grasp. Various rotary fingertip designs are also implemented to help maintain stable contact conditions and minimize slip, in order to prove the feasibility of this design in physical hand implementations. The achievable precision manipulation workspaces of the proposed morphologies are evaluated and compared to prior human manipulation data as well as manipulation results with traditional three-finger hand topologies. Experiments suggest that the spherical hands' design modifications can make the system's passive reconfiguration more easily predictable, providing insight into the expected object workspace while minimizing the dependence on accurate object and contact modeling. We believe that this design can significantly reduce the complexity of planning and executing dexterous manipulation movements in unstructured environments with underactuated hands.

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