scholarly journals Fast, Accurate Models for Predicting the Compliance of Elastic Flexure-Jointed Robots

2010 ◽  
Author(s):  
Lael Odhner ◽  
Aaron Dollar
Keyword(s):  
Parametric Models ◽  
Loop Control ◽  
Proposed Model ◽  
Collision Safety ◽  
Beam Bending ◽  
Flexible Mechanism ◽  
Flexure Joints ◽  
Rigorous Model ◽  
Euler Bernoulli Beam ◽  
Flexible Member

Robot manipulators having elastic links or flexure joints have a number of advantages, especially in simplifying the control of contact with other objects. However, current simplified parametric models of flexure motion do not accurately predict the behavior of these mechanisms under large deflections. This paper presents a “smooth curvature model” of flexure behavior that describes the curvature of a highly flexible member such as a flexure joint using a basis of three orthogonal polynomials. Using this model, we show that it is possible to predict the planar stiffness these mechanisms, even in cases where the deformation of the hinge is too large for the linear Euler-Bernoulli beam bending model. Using both finite element methods and the much less computationally expensive proposed model, numerical results will demonstrate that it is possible to accurately predict the in-plane compliance of a highly flexible mechanism in the presence of an external load. The results of this work are significant because they demonstrate that the behavior of flexure-based robotic mechanisms can be modeled quickly and with few parameters, enabling their use in closed-loop control for situations where collision safety is a concern, and rigorous model-based path planning for obstacle avoidance, among other applications.

An Analytical Tension Model for Continuum Robots with n Generally Positioned Tendons

2019 ◽  
Vol 04 (03n04) ◽  
pp. 1942003
Author(s):  
Mohsen Moradi Dalvand ◽  
Saeid Nahavandi ◽  
Robert D. Howe
Keyword(s):  
Stereo Vision ◽  
Control Algorithm ◽  
Open Loop ◽  
Open Loop Control ◽  
Continuum Robots ◽  
Loop Control ◽  
Proposed Model ◽  
Continuum Robot ◽  
Tension Loading ◽  
Tendon Compliance

The estimation of tension loads in multi-tendon continuum robots or catheters plays an important role not only in the design process but also in the control algorithm to avoid slack. An analytical tension loading model is developed that, for any given beam configuration within the workspace, calculates tendon tensions in [Formula: see text]-tendon continuum robots with general tendon positioning. The model accounts for the bending and axial compliance of the manipulator as well as tendon compliance. A 6-tendon continuum robot integrated with a stereo vision-based 3D reconstruction system is utilized to experimentally validate the proposed analytical model in open-loop control architecture. The proposed model demonstrates around 95% accuracy in estimating tendon tensions in a continuum robot with general tendon positioning and axial stretch in its tendons for all of the trials and experiments.

Modeling of a Dynamic Mirror With Antagonistic Piezoelectric Stack Actuation

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
James A. Mynderse ◽  
George T. C. Chiu
Keyword(s):  
Constitutive Models ◽  
Open Loop ◽  
Step Response ◽  
Experimental Frequency ◽  
Loop Control ◽  
Response Data ◽  
Input Control ◽  
Proposed Model ◽  
Single Input ◽  
Charging Dynamics

A dynamic mirror actuator utilizing antagonistic piezoelectric stack actuators is presented for use in laser printers. Exhibiting hysteresis and other nonlinearities in open-loop operation, the dynamic mirror actuator (DMA) requires a control structure to achieve accurate mirror positioning. A linear DMA model is developed for extending operational bandwidth under closed-loop control, employing explicit piezoelectric stack actuator (PESA) charging dynamics and incorporating two modes for single input control of opposing PESA drives. Compared to constitutive models from literature, the proposed model displays a comparable fit with experimental frequency response data while retaining a lower model order. As further validation, simulated step response data are shown to agree with experimental data.

Research on a Composite Polynomial Model for Magnetorheological Damper

2012 ◽  
Vol 482-484 ◽  
pp. 843-847
Author(s):  
Jia Ling Yao ◽  
Wen Ku Shi ◽  
Jin Feng Lu
Keyword(s):  
Experimental Data ◽  
Nonlinear Behavior ◽  
Mr Damper ◽  
Open Loop ◽  
Polynomial Model ◽  
Magnetorheological Damper ◽  
Damping Force ◽  
Loop Control ◽  
Proposed Model ◽  
Loop Control System

The reported mathematical models of magnetorheological (MR) damper cannot make a good tradeoff among reflecting the damper’s nonlinear behavior and controllability. Damping characteristic experiments have been conducted on a MR damper. A composite polynomial model has been proposed integrating the experimental investigation and the polynomial model, in which the plot of polynomial coefficient vs. current is divided into two sections to reflect the property of the current saturation, meanwhile, the affections of exciting amplitude and frequency are considered in this model. The reverse model of the proposed model is easy to be obtained, so it is convenient to realize an open-loop control system to achieve a desirable damping force. The parameters of this model are identified using experimental data in a certain frequency and amplitude, as well as diverse currents. Compared numerical simulation with experimental data, it is verified that the proposed model can accurately predict the damping force without modifying the parameters of the model when frequency, amplitude and current changed.

scholarly journals Static form-finding of normal and defective catenaries based on the analytical exact solution of the tensile Euler–Bernoulli beam

2018 ◽  
Vol 233 (7) ◽  
pp. 691-700 ◽  
Author(s):  
Farzad Vesali ◽  
Mohammad Ali Rezvani ◽  
Habibolah Molatefi ◽  
Markus Hecht
Keyword(s):  
Exact Solution ◽  
Equilibrium Configuration ◽  
Field Measurements ◽  
Steady State Solution ◽  
Contact Wire ◽  
Proposed Model ◽  
Before And After ◽  
Novel Method ◽  
Static Form ◽  
Euler Bernoulli Beam

The aim of this research is to propose and develop an analytical exact solution for finding the static equilibrium configuration of a catenary before and after incurring defects such as tension loss or a broken dropper. The procedure includes considering the steady-state solution of the dynamic motion equation of the contact wire and the messenger cable. The wire and the cable are considered as tensile Euler–Bernoulli beams. The stiffness matrix of the beam is configured and is used to calculate the dropper's dead load. Progressively, a novel method is proposed to find the equilibrium configuration of the same catenary after the defect. The results prove that the tension loss in the messenger cable is more precarious than the tension loss in the contact wire. The broken dropper causes a significant sag in the sub-span and increases the static forces of the adjacent droppers. A comparison with field measurements justifies the accuracy of the results of the proposed model.

Linear model to describe the working of a three layers CLT strip slab: Experimental and numerical validation

2021 ◽  
pp. 136943322110204
Author(s):  
Martina Sciomenta ◽  
Angelo Di Egidio ◽  
Chiara Bedon ◽  
Massimo Fragiacomo
Keyword(s):  
Tangential Direction ◽  
Elastic Model ◽  
Bernoulli Beam ◽  
Rolling Shear ◽  
Bending Tests ◽  
Linear Elastic ◽  
Numerical Predictions ◽  
Proposed Model ◽  
Out Of Plane ◽  
Euler Bernoulli Beam

Experimental out-of-plane, four-points bending tests were performed on two series of three-layered Cross Laminated Timber (CLT) panels made of Calabrian Beech and Calabrian Beech and Corsican Pine respectively. The predominant failure mechanism was rolling shear alongthe innerlayer and the glue line. A linear elastic model of a three-layered, CLT panel was developed to describe the stress distribution in CLT slabs in bending, with a focus on their load-bearing performance before the propagation of cracks. In the analytical model, each timber layer was defined as an Euler-Bernoulli beam. The two glue lines were modeled using extensional springs, infinitely rigid in the direction perpendicular to the beam’s axis, and with a defined stiffness in the tangential direction. The outer layers are assumed axially flexible whilethe innerone is regarded as axially rigid. The results of the proposed model were thus compared and validated with the experimental evidence and with additional FE numerical predictions given by 3D numerical simulations carried out in Abaqus.

scholarly journals Comprehensive Study on Shape Shifting Behaviors of Thermally Activated Hinges in FDM-based 4D Printing

2021 ◽  
Author(s):  
Iman Salimi Nezhad ◽  
Mohammad Golzar ◽  
Amirhossein Behravesh ◽  
Shahabaddin Zare
Keyword(s):  
Layer Structure ◽  
Single Layer ◽  
4D Printing ◽  
Thermally Activated ◽  
Proposed Model ◽  
3D Printed ◽  
Beam Bending ◽  
Nozzle Temperature ◽  
Fractional Zener Model ◽  
Semi Empirical

Abstract 4D printing of shape shifting structures, aka “hinges”, has raised a new standard in many fields. By using these hinges in certain parts of a 3D printed structures, a pre designed complex 3D shape with potential multifunctional application can be achieved from flat structure. This paper proposes a comprehensive semi-empirical model to predict the final shape shifting behavior and magnitude of the hinges printed by FDM process. First, all FDM main parameters are selected and reduced by design of experiment to printing speed, lamina thickness, nozzle temperature as well as printing pattern. In order to develop the model, a time-dependent constitutive model with these four process parameters were extracted for strain of an SMP homogeneous single layer structure using a fractional Zener model accompanied with Multiple Linear Regression (MLR) technique. Thereafter, the mathematical relations for shape shifting behavior of bilayer 4D printed structures were developed for beam bending and twisting by modifying Timoshenko’s constitutive equations. A comprehensive shape-shifting model was established including 3D printing parameters, angles, thickness ratios, activation time and temperature which was compared to the experimental data and results predicted both shape shifting behavior and magnitude of the hinges with good agreement. In addition, a novel flowchart was suggested to design and achieve the desired shape shifting behaviors. The proposed model and flowchart are novel tools to design 4D structures through desired shape-shifting of the hinges.

scholarly journals Euler-Bernoulli cantilever beam bending considering the inner diffusion flows finite propagation speed

2020 ◽  
pp. 107-114
Author(s):  
Андрей Владимирович Земсков ◽  
Георгий Михайлович Файкин
Keyword(s):  
Mass Transfer ◽  
Propagation Speed ◽  
Bernoulli Beam ◽  
Elastic Diffusion ◽  
Multicomponent Media ◽  
Equivalent Boundary ◽  
Beam Bending ◽  
Finite Propagation Speed ◽  
Euler Bernoulli Beam ◽  
Diffusion Flows

Исследуются нестационарные колебания балки Эйлера-Бернулли с учетом массопереноса. Используется модель упругой диффузии для многокомпонентных сред. Для получения решения задачи используются вариационный принцип Даламбера и метод эквивалентный граничных условий. Unsteady vibrations of the Euler-Bernoulli beam are studied taking into account mass transfer. The model of elastic diffusion for multicomponent media is used. To obtain a solution to the problem, the d’Alembert variational principle and the equivalent boundary conditions method are used.

scholarly journals Analysis and Implementation of Noncontact Level Sensing for a Pressurized Cylinder

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Hsien-Huang P. Wu ◽  
Chung-Wen Hung ◽  
Shih-Hsin Chang ◽  
Zong-Hao Yang
Keyword(s):  
Beam Theory ◽  
Bernoulli Beam ◽  
Fluid Level ◽  
Detailed Model ◽  
Gas Cylinder ◽  
Proposed Model ◽  
Empty Condition ◽  
Euler Bernoulli Beam ◽  
Gas Cylinders ◽  
Pressurized Cylinder

Fluid level detection for a sealed and pressurized mobile container is very useful for the provider to schedule the delivery of a new one before it runs out of the liquid. This study suggested using the frequencies of tone generated by knocking on the outside surface of the container to detect the liquid level inside. A detailed model based on Euler-Bernoulli beam theory has been proposed to study the feasibility of this method for a cylinder with complicated but practical structure. Household gas cylinders were used to validate the proposed model and the results show that experimental data agree well with the theoretical analysis. The results indicate that the proposed model can accurately explain the behavior of the vibratory frequencies under different liquid levels. An apparatus has been successfully implemented to automatically sense the near empty condition of the gas cylinder.

scholarly journals Facial Landmarks Detection on Faulty Datasets with Regression Trees and Principal Component Analysis Parametrization

2018 ◽  
Author(s):  
Abner S. Nascimento ◽  
Danilo A. Oliveira ◽  
Maria Raquel L. De Couto ◽  
Iális C. De Paula Júnior
Keyword(s):  
Principal Component Analysis ◽  
Principal Component ◽  
Regression Trees ◽  
Component Analysis ◽  
Parametric Models ◽  
Essential Step ◽  
Proposed Model ◽  
Combined Use ◽  
Regression Algorithms ◽  
Missing Labels

Tracking landmarks points of the human face is an essential step for the construction of interfaces capable of taking advantage of the communicative potential of facial expressions. Many strategies based on parametric models and regression algorithms with boosting can be applied to this problem. This paper proposes a solution based on the combined use of principal component analysis and regression trees. The main purpose of the presented method is to reduce the sensibility of the system to the presence of missing labels when trained with faulty datasets, by the adoption of corrective heuristics. On such cases, the proposed model achieves performance similar to the reference results, obtained by training on fault free datasets.

Sign in / Sign up

Export Citation Format

Share Document