A simplified model of a multi-jointed mechanical finger calibrated with experimental data by vision system

2021 ◽  
Vol 235 (1) ◽  
pp. 164-175
Author(s):  
C Cosenza ◽  
V Niola ◽  
S Savino
Keyword(s):  
Experimental Data ◽  
Vision System ◽  
Control Strategies ◽  
Image Correlation ◽  
Robotic Hand ◽  
Prosthetic Device ◽  
Prosthetic Hands ◽  
Mechanical Hand ◽  
Free Mode ◽  
Mechanical Finger

The development of suitable models for mechanical fingers, whether they are part of prosthetic device or of a robotic hand, is a powerful tool to predict the behaviour of their components since the early stages of design, especially for underactuated mechanisms. Experimental data can improve the reliability of such models and promote their application to build proper control strategies especially for prosthetic hands. Here, we have developed a multi-jointed model of a mechanical finger. The finger is part of the Federica hand: an underactuated mechanical hand that was conceived for prosthetic purpose. The model accounts for friction phenomena in the finger and it is tuned with experimental data acquired through a digital image correlation device. The model allowed us to write kinematics relations of the phalanges and evaluate finger configurations in relation to the closure velocity. Moreover, it was possible to estimate the tendon force and the work analysis occurring during the closure tasks, both in free mode and in presence of objects.

scholarly journals Material parameter identification using finite elements with time-adaptive higher-order time integration and experimental full-field strain information

2021 ◽  
Author(s):  
Stefan Hartmann ◽  
Rose Rogin Gilbert
Keyword(s):  
Experimental Data ◽  
Finite Elements ◽  
Parameter Identification ◽  
Material Parameter ◽  
Measurement Data ◽  
Least Square ◽  
Image Correlation ◽  
Field Strain ◽  
Material Parameter Identification ◽  
Full Field

AbstractIn this article, we follow a thorough matrix presentation of material parameter identification using a least-square approach, where the model is given by non-linear finite elements, and the experimental data is provided by both force data as well as full-field strain measurement data based on digital image correlation. First, the rigorous concept of semi-discretization for the direct problem is chosen, where—in the first step—the spatial discretization yields a large system of differential-algebraic equation (DAE-system). This is solved using a time-adaptive, high-order, singly diagonally-implicit Runge–Kutta method. Second, to study the fully analytical versus fully numerical determination of the sensitivities, required in a gradient-based optimization scheme, the force determination using the Lagrange-multiplier method and the strain computation must be provided explicitly. The consideration of the strains is necessary to circumvent the influence of rigid body motions occurring in the experimental data. This is done by applying an external strain determination tool which is based on the nodal displacements of the finite element program. Third, we apply the concept of local identifiability on the entire parameter identification procedure and show its influence on the choice of the parameters of the rate-type constitutive model. As a test example, a finite strain viscoelasticity model and biaxial tensile tests applied to a rubber-like material are chosen.

SIF determination with digital image correlation

2015 ◽  
Vol 6 (6) ◽  
pp. 668-676 ◽  
Author(s):  
Paulo J Tavares ◽  
Tiago Ramos ◽  
Daniel Braga ◽  
Mario A P Vaz ◽  
Pedro Miguel Guimarães Pires Moreira
Keyword(s):  
Experimental Data ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Fatigue Testing ◽  
Image Correlation ◽  
Image Method ◽  
Mode Ii ◽  
Pure Mode ◽  
Great Success ◽  
Content Type

Purpose – Hybrid methods, wherefore numerical and experimental data are used to calculate a critical parameter, have been used for several years with great success in Experimental Mechanics and, in particular, in fracture mechanics. The purpose of this paper is to report on the comparison of the strain field from numerical modelling forecasts against the experimental data obtained with the digital image correlation method under Mode II loading in fatigue testing. The numerical dual boundary element method has been established in the past as a very reliable method near singular regions where stresses tend to grow abruptly. The results obtained from the strain data near the crack tip were used in Williams expansion and agree fairly well with both the numerical results and the analytical solution proposed for pure Mode II testing. Design/methodology/approach – The work presented in this note is experimental. The proposed methodology is of an hybrid experimental/numerical nature in that a numerical stress intensity factor calculation hinges upon a stress field obtained with an image method. Findings – The obtained results are an important step towards the development of a practical tool for crack behaviour prediction in fatigue dominated events. Research limitations/implications – The results also stress the necessity of improving the experimental techniques to a point where the methods can be applied in real-life solicitations outside of laboratory premises. Originality/value – Although several research teams around the globe are presently working in this field, the present research topic is original and the proposed methodology has been presented initially by the research team years ago.

scholarly journals The Development of Body-Powered Prosthetic Hand Controlled by EMG Signals Using DSP Processor with Virtual Prosthesis Implementation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Fathia H. A. Salem ◽  
Khaled S. Mohamed ◽  
Sundes B. K. Mohamed ◽  
Amal A. El Gehani
Keyword(s):  
High Performance ◽  
State Of The Art ◽  
The Body ◽  
Prosthetic Hand ◽  
Prosthetic Hands ◽  
Emg Signal ◽  
Mechanical Hand ◽  
Fast Processing ◽  
Opening And Closing ◽  
Two Stages

The state of the art in the technology of prosthetic hands is moving rapidly forward. However, there are only two types of prosthetic hands available in Libya: the Passive Hand and the Mechanical Hand. It is very important, therefore, to develop the prosthesis existing in Libya so that the use of the prosthesis is as practical as possible. Considering the case of amputation below the elbow, with two movements: opening and closing the hand, this work discusses two stages: developing the operation of the body-powered prosthetic hand by controlling it via the surface electromyography signal (sEMG) through dsPIC30f4013 processor and a servo motor and a software based on fuzzy logic concept to detect and process the EMG signal of the patient as well as using it to train the patient how to control the movements without having to fit the prosthetic arm. The proposed system has been practically implemented, tested, and gave satisfied results, especially that the used processor provides fast processing with high performance compared to other types of microcontrollers.

scholarly journals Robust Feedback Control Design of Underactuated Robotic Hands with Selectively Lockable Switches for Amputees

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Bilal M. Yousuf ◽  
Asim Mehdi ◽  
Abdul Saboor Khan ◽  
Aqib Noor ◽  
Arslan Ali
Keyword(s):  
Low Cost ◽  
Cost Effective ◽  
Second Step ◽  
Robotic Hand ◽  
Effective Solution ◽  
Robotic Hands ◽  
Daily Lives ◽  
Mechanical Hand ◽  
Controlling System ◽  
The Coefficient Of Friction

In recent years, reproduction of human mechanical hand with upgraded abilities is one of the major concerns. This paper addresses the problems of underactuated robotic hand with low cost design as it avoids electromyogram (EMG) sensors. The main goal is to balance the hand in the way, like grabbing, speed, and power, and provide a more robust and cost effective solution. All fingers have some mechanical consistency for picking up objects in a better way. A Flex sensor is attached to all fingers and it is interfaced with a computer using Arduino UNO microcontroller. The sensor aids the arm in three different directions: at first it senses whether an object is grasped or not. In the second step, it determines the coefficient of friction between the objects. Finally it grasps the object and stops. One of the primary issues of prosthetic hand is to have the capacity to satisfy every detail of torque, speed, and latency. In this research, we have developed a model of robotic hand with some modifications. The adaptability of grasping is compared with the degree of freedom (DOF) along with the quantity of fingers. We are controlling our hands via sensors based signal controlling system. The idea is to design a robotic hand, which has low cost, is easy to use, and is light in weight, which helps the amputees to use it with ease in their daily lives. The efficacy of the proposed control is verified and validated using simulations.

scholarly journals Experimental and numerical study of the interaction between dynamically loaded cracks and pre-existing flaws in edge loaded PMMA specimens

2020 ◽  
Author(s):  
Chuzhali Nilath Irfan Habeeb ◽  
shmuel osovski
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Numerical Study ◽  
Damage Model ◽  
Image Correlation ◽  
High Speed Photography ◽  
Dynamic Fracture Tests ◽  
Micromechanical Damage ◽  
Fracture Tests ◽  
Micromechanical Damage Model

Dynamic fracture tests are carried out for four groups of hole-containing edge loaded specimens. The crack growth velocity, crack path, and dynamic toughness are extracted from the experiments using high-speed photography and digital image correlation. The importance of the interaction between the in-coming stress wave and the pre-existing hole is revealed and analyzed. A micromechanical damage model is calibrated to the experimental data from two of the specimens' designs and evaluated for its predictive capabilities using the other experimental configurations. The studied model is shown to be in reasonable agreement with the experimental data, and its limits are discussed

Real-Time Simulation of an Experimental Rig With Pressurized SOFC

2011 ◽  
Author(s):  
Paolo Pezzini ◽  
Francesco Caratozzolo ◽  
Alberto Traverso
Keyword(s):  
Experimental Data ◽  
Real Time ◽  
Control Strategies ◽  
Simulation Models ◽  
Electrical Current ◽  
Cell System ◽  
Time Model ◽  
Transient Behaviour ◽  
Set Up ◽  
Time Required

The availability of reliable simulation models can reduce the time required for commissioning test rigs as well as preventing components from suffering serious damage during testing. The aim of this study is to set up and validate, against experimental data, a real-time model referring to the Rolls-Royce Fuel Cell System Limited (RRFCS) hybrid system concept, based on SOFCs. The dynamic model of the SOFC “block” has been developed, run in real-time, and successfully validated against experiments. Initially, the dynamic evolution of the model is considered under constant inputs at steady-state and is compared against experimental data; secondly, transient behaviour is also considered. Step variations of the main air flow, main fuel flow, syngas flow and electrical current were performed. The model can now be employed to carry out the following: performance analysis, design verification, development of control strategies, on-line analysis and integration with Human Machine Interface.

scholarly journals Bayesian Parameter Determination of a CT-Test Described by a Viscoplastic-Damage Model Considering the Model Error

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1141 ◽  
Author(s):  
Ehsan Adeli ◽  
Bojana Rosić ◽  
Hermann G. Matthies ◽  
Sven Reinstädler ◽  
Dieter Dinkler
Keyword(s):  
Experimental Data ◽  
Health Monitoring ◽  
Measurement Errors ◽  
Model Updating ◽  
Surface Displacement ◽  
Life Time ◽  
Model Error ◽  
Image Correlation ◽  
Parameter Determination ◽  
Model Parameters

The state of materials and accordingly the properties of structures are changing over the period of use, which may influence the reliability and quality of the structure during its life-time. Therefore identification of the model parameters of the system is a topic which has attracted attention in the content of structural health monitoring. The parameters of a constitutive model are usually identified by minimization of the difference between model response and experimental data. However, the measurement errors and differences in the specimens lead to deviations in the determined parameters. In this article, the Choboche model with a damage is used and a stochastic simulation technique is applied to generate artificial data which exhibit the same stochastic behavior as experimental data. Then the model and damage parameters are identified by applying the sequential Gauss-Markov-Kalman filter (SGMKF) approach as this method is determined as the most efficient method for time consuming finite element model updating problems among filtering and random walk approaches. The parameters identified using this Bayesian approach are compared with the true parameters in the simulation, and further, the efficiency of the identification method is discussed. The aim of this study is to observe whether the mentioned method is suitable and efficient to identify the model and damage parameters of a material model, as a highly non-linear model, for a real structural specimen using a limited surface displacement measurement vector gained by Digital Image Correlation (DIC) and to see how much information is indeed needed to estimate the parameters accurately even by considering the model error and whether this approach can also practically be used for health monitoring purposes before the occurrence of severe damage and collapse.

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