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N. Chandrasekaran

Bio: N. Chandrasekaran is an academic researcher from Texas A&M University. The author has contributed to research in topics: Finite element method & Mixed finite element method. The author has an hindex of 1, co-authored 2 publications receiving 52 citations.

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TL;DR: In this article, a finite element solution method for the analysis of frictional contact problems is presented, which is solved by imposing geometric constraints on the pseudo equilibrium configuration, defined as a configuration at which the compatibility conditions are violated.
Abstract: A new finite element solution method for the analysis of frictional contact problems is presented. The contact problem is solved by imposing geometric constraints on the pseudo equilibrium configuration, defined as a configuration at which the compatibility conditions are violated. The algorithm does not require any a priori knowledge of the pairs of contactor nodes or segments. The contact condition of sticking, slipping, rolling or tension release is determined from the relative magnitudes of the normal and tangential global nodal forces. Contact iterations are in general found to converge within one or two iterations. The analysis method is applied to selected problems to illustrate the applicability of the solution procedure.

51 citations


Cited by
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TL;DR: In this article, a geometric nonlinear finite element method is used to analyze fabric deformation characterized by large displacements and rotations, but small strains, using shell/plate elements.
Abstract: Fabric deformation characterized by large displacements and rotations but small strains is analyzed using a geometric nonlinear finite element method. The fabrics are modeled by shell/plate elements. Special considerations for applying the finite element method to fabric analysis are discussed and several examples of fabric deformation presented. The results from the finite element model are compared with experimental data and are in good agreement.

84 citations

Journal ArticleDOI
TL;DR: A simulation-based comparison between deformable grasping and rigid body grasping reveals why soft objects are easier to pick up than hard ones, and demonstrates how a rigid body grasped strategy may fail on soft objects in certain situations.
Abstract: This paper describes a strategy for a robotic hand to pick up deformable 3D objects on a table. Inspired by human hand behavior, the robotic hand employs two rigid fingers to first squeeze such an object until it ?feels? the object to be liftable. Such ?feeling? is provided by a virtual liftability test that is repeatedly conducted during the squeeze. Passing of the test then triggers a lifting action. Throughout the manipulation the object's deformation and its state of contact with the fingers and the table are being tracked based on contact events. Deformable modeling uses the finite element method FEM while slip computation employs the homotopy continuation method to determine the contact displacements induced by finger movements. The experiment was conducted for everyday items ranging from vegetables to a toy. A simulation-based comparison between deformable grasping and rigid body grasping reveals why soft objects are easier to pick up than hard ones, and demonstrates how a rigid body grasping strategy may fail on soft objects in certain situations.

61 citations

Journal ArticleDOI
TL;DR: In this paper, a unified PQP (Parametric quadratic programming) model related to contact problems as well as to elasto-plastic structures is constructed.
Abstract: In this paper, the stiffness matrix of a contact element is introduced by means of a penalty function expression of the contact pressure and frictional force. The contact condition and the flow rule are expressed by the same form as in a non-associated plastic flow problem. A unified PQP (Parametric Quadratic Programming) model related to contact problems as well as to elasto-plastic structures is constructed. A series of PQP formulae for contact problems and elastic-plastic structures is derived in the text, and some numerical examples are illustrated as well.

57 citations

Journal ArticleDOI
TL;DR: In this paper, the application of the finite element method to dynamic contact buckling problems is discussed, where the penalty function method is applied to incorporate the contact conditions in the equation of motion and a trial-and-error method is employed to obtain the converged contact state.
Abstract: The present paper deals with the application of the finite element method to dynamic contact buckling problems. The penalty function method is applied to incorporate the contact conditions in the equation of motion and a trial-and-error method is employed to obtain the converged contact state. Numerical examples are analysed to show the effectiveness and the validity of the method, and it is applied to a dynamic buckling problem involving contact phenomena.

54 citations

Journal ArticleDOI
TL;DR: This paper presents a grasping strategy that squeezes the object with two fingers under specified displacements rather than forces, and states that a ‘stable’ squeeze minimizes the potential energy for the same amount of squeezing, while a 'pure' squeeze ensures that the object undergoes no rigid body motion as it deforms.
Abstract: Robotic grasping of deformable objects is difficult and under-researched, not simply due to the high computational cost of modeling. More fundamentally, several issues arise with the deformation of an object being grasped: a changing wrench space, growing finger contact areas, and pointwise varying contact modes inside these areas. Consequently, contact constraints needed for deformable modeling are hardly established at the beginning of the grasping operation. This paper presents a grasping strategy that squeezes the object with two fingers under specified displacements rather than forces. A 'stable' squeeze minimizes the potential energy for the same amount of squeezing, while a 'pure' squeeze ensures that the object undergoes no rigid body motion as it deforms. Assuming linear elasticity, a finite element analysis guarantees equilibrium and the uniqueness of deformation during a squeeze action. An event-driven algorithm tracks the contact regions as well as the modes of contact in their interiors under Coulomb friction, which in turn serve as the needed constraints for deformation update. Grasp quality is characterized as the amount of work performed by the grasping fingers in resisting a known push by some adversary finger. Simulation and multiple experiments have been conducted to validate the results over solid and ring-like 2D objects.

52 citations