scholarly journals Finite-strain three-dimensional solids with rotational degrees of freedom: non-linear statics and dynamics

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Abir Boujelben ◽  
Adnan Ibrahimbegovic
Keyword(s):  
Degrees Of Freedom ◽  
Finite Strain ◽  
Three Dimensional ◽  
Non Linear ◽  
Statics And Dynamics ◽  
Rotational Degrees Of Freedom

The analysis of inter-laminar stress and electric potential for a laminated piezoelectric plate with interfacial damage

2011 ◽  
Vol 16 (8) ◽  
pp. 793-811 ◽  
Author(s):  
Fu Yiming ◽  
Li Sheng
Keyword(s):  
Electric Potential ◽  
Degrees Of Freedom ◽  
Piezoelectric Plate ◽  
Plate Theory ◽  
Three Dimensional ◽  
Variation Principle ◽  
Interfacial Damage ◽  
Load Models ◽  
Non Linear ◽  
Piezoelectric Plates

This paper presents a non-linear model for laminated piezoelectric plates with inter-laminar mechanical and electrical damage. The model is based on the general six-degrees-of-freedom plate theory, and the discontinuity of displacement and electric potential on the interfaces are depicted by three shape functions. By using the variation principle, the three-dimensional non-linear equilibrium differential equations of simply supported laminated piezoelectric plates with interfacial damage are derived. Then, an analytical solution is presented by using the finite difference method. In numerical examples, the effects of different damage values, load models, and electric boundary conditions on the inter-laminar stress and electric potential profile of a laminated piezoelectric plate with interfacial imperfections are investigated.

scholarly journals A comparison of three-dimensional rotation formalisms for least-squares and Bayesian inverse kinematics

2021 ◽  
Author(s):  
Ben Serrien ◽  
Klevis Aliaj ◽  
Todd Pataky
Keyword(s):  
Least Squares ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Estimation Error ◽  
Computational Cost ◽  
Three Dimensional ◽  
Linear Least Squares ◽  
Computationally Efficient ◽  
Rotational Degrees Of Freedom ◽  
Value Decomposition

Marker-based inverse kinematics (IK) is prone to errors arising from measurementnoise and soft-tissue artefacts. Various least-squares and Bayesian methods canbe applied to limit the estimation error to a minimum. Recently proposed meth-ods like Bayesian IK come at an increased computational cost however. In thistechnical paper, we present an overview of eight different least squares or BayesianIK methods, including their accuracy and computational load for IK problemsinvolving a single rigid body and three rotational degrees-of-freedom, whose at-titude is estimated from four noisy marker positions. The results indicate thatNon-Linear Least Squares, Variational Bayesian and full Bayesian IK are supe-rior to Singular Value Decomposition in terms of accuracy, with approximatelya two-fold error reduction. However, only Non-Linear Least Squares and Varia-tional Bayesian IK are computationally efficient enough to scale towards practicaluse in biomechanical applications, with computational durations of 1-10 ms; fullyBayesian procedures required approximately 30 s for single rotation calculations.All Python code and supplementary material can be found in this paper’s GitHubrepository: https://github.com/benserrien/pybik.

A Non-Linear Numerical Method for the Simulation of Parametric Roll Resonance in Regular Waves

2008 ◽  
Author(s):  
T. M. Ahmed ◽  
E. J. Ballard ◽  
D. A. Hudson ◽  
P. Temarel
Keyword(s):  
Numerical Method ◽  
Potential Flow ◽  
Degrees Of Freedom ◽  
Linear Time ◽  
Three Dimensional ◽  
Regular Waves ◽  
Time Step ◽  
Parametric Roll ◽  
Non Linear ◽  
Parametric Roll Resonance

In this paper, a non-linear time-domain method is used for the prediction of parametric roll resonance in regular waves, assuming the ship to be a system with three degrees of freedom in heave, pitch and roll. Coupled heave and pitch motions are obtained using a three-dimensional frequency-domain potential flow method which also provides the requisite hydrodynamic data of the ship in roll i.e. the potential flow based added inertia and damping. Periodic changes in the underwater hull geometry due to heave, pitch and the wave profile are calculated as a function of the instantaneous breadth. This is carried out using a two-dimensional approach i.e. for sections along the ship and at each time step. This formulation leads to a mathematical model that represents the roll equation of motion with third order non-linearities in the parametric excitation terms. Non-linearities in the roll damping and restoring terms are also accounted for. This method has been applied to two different hull forms, a post-Panamax C11 class containership and a transom stern Trawler, both travelling in regular waves. Special attention is focused on the influence of different operational aspects on parametric roll. Obtained results demonstrate that this numerical method succeeds in producing results similar to those available in the literature, both numerical and experimental.

A Four-Node Tetrahedral Finite Element Based on Space Fiber Rotation Concept

2019 ◽  
Vol 11 (1) ◽  
pp. 67-78
Author(s):  
Kamel Meftah ◽  
Lakhdar Sedira
Keyword(s):  
Finite Element ◽  
Strain Field ◽  
Stiffness Matrix ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Field Tensor ◽  
Tetrahedral Element ◽  
Numerical Studies ◽  
Rotational Degrees Of Freedom ◽  
Tensor Approximation

Abstract The paper presents a four-node tetrahedral solid finite element SFR4 with rotational degrees of freedom (DOFs) based on the Space Fiber Rotation (SFR) concept for modeling three-dimensional solid structures. This SFR concept is based on the idea that a 3D virtual fiber, after a spatial rotation, introduces an enhancement of the strain field tensor approximation. Full numerical integration is used to evaluate the element stiffness matrix. To demonstrate the efficiency and accuracy of the developed four-node tetrahedron solid element and to compare its performance with the classical four-node tetrahedral element, extensive numerical studies are presented.

Novel Design and Three-Dimensional Printing of Variable Stiffness Robotic Grippers

2016 ◽  
Vol 8 (6) ◽  
Author(s):  
Yang Yang ◽  
Yonghua Chen ◽  
Ying Wei ◽  
Yingtian Li
Keyword(s):  
3D Printing ◽  
Degrees Of Freedom ◽  
Shape Memory Polymer ◽  
Three Dimensional ◽  
Acrylonitrile Butadiene Styrene ◽  
Variable Stiffness ◽  
Analytical Models ◽  
Printing Process ◽  
Finger Joints ◽  
Rotational Degrees Of Freedom

In this paper, a novel robotic gripper design with variable stiffness is proposed and fabricated using a modified additive manufacturing (hereafter called 3D printing) process. The gripper is composed of two identical robotic fingers and each finger has three rotational degrees-of-freedom as inspired by human fingers. The finger design is composed of two materials: acrylonitrile butadiene styrene (ABS) for the bone segments and shape-memory polymer (SMP) for the finger joints. When the SMP joints are exposed to thermal energy and heated to above their glass transition temperature (Tg), the finger joints exhibit very small stiffness, thus allow easy bending by an external force. When there is no bending force, the finger will restore to its original shape thanks to SMP's shape recovering stress. The finger design is actuated by a pneumatics soft actuator. Fabrication of the proposed robotic finger is made possible by a modified 3D printing process. An analytical model is developed to represent the relationship between the soft actuator's air pressure and the finger's deflection angle. Furthermore, analytical modeling of the finger stiffness modulation is presented. Several experiments are conducted to validate the analytical models.

scholarly journals A new meta-module design for efficient reconfiguration of modular robots

2021 ◽  
Author(s):  
Irene Parada ◽  
Vera Sacristán ◽  
Rodrigo I. Silveira
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Central Point ◽  
The Other ◽  
Three Dimensions ◽  
Modular Robots ◽  
The Novel ◽  
Modular Robot ◽  
Module Design ◽  
Rotational Degrees Of Freedom

AbstractWe propose a new meta-module design for two important classes of modular robots. The new meta-modules are three-dimensional, robust and compact, improving on the previously proposed ones. One of them applies to so-called edge-hinged modular robot units, such as M-TRAN, SuperBot, SMORES, UBot, PolyBot and CKBot, while the other one applies to so-called central-point-hinged modular robot units, which include Molecubes and Roombots. The new meta-modules use the rotational degrees of freedom of these two types of robot units in order to expand and contract, as to double or halve their length in each of the two directions of its three dimensions, therefore simulating the capabilities of Crystalline and Telecube robots. Furthermore, in the edge-hinged case we prove that the novel meta-module can also perform the scrunch, relax and transfer moves that are necessary in any tunneling-based reconfiguration algorithm for expanding/contracting modular robots such as Crystalline and Telecube. This implies that the use of meta-meta-modules is unnecessary, and that currently existing efficient reconfiguration algorithms can be applied to a much larger set of modular robots than initially intended. We also prove that the size of the new meta-modules is optimal and cannot be further reduced.

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