Numerical Analysis of Contact Area under Slippage Conditions

في هذا البحث، تم دراسة منطقة التماس التي تتولد بين جسمين (أحدهما سطح مستو والاخر سطح نصف أسطواني) تحت تأثير الانزلاق، حيث أنها تمثل واحدة من المشاكل الهامة في الهندسة الميكانيكية وخاصة في تصميم الروبوتات. تم دراسة العديد من المعاملات مثل قوى الاحتكاك، الاجهادات المكافئة، معامل الاحتكاك، وتشوه منطقة التماس. حيث تم رصد سلوك هذه العوامل خلال الانزلاق الذي يتم إنشاؤه بين سطح مستو مصنوع من سبائك الحديد الصلب والجزء الآخر المصنوع من المطاط. أظهرت نتائج المحاكاة سلوكا هاماً، وخاصة في بداية الانزلاق وظاهرة (الالتصاق-الانزلاق) بمعنى آخر، مخرجات المحاكاة تشير إلى أن تأثير الانزلاق له سلوك هام، خاصة عندما تبدأ كل من ظاهرة الانزلاق والالتصاق بالحدوث. وتهدف هذه التحليلات إلى فهم كيفية تأثر منطقة التماس لتصميم ما يمنع حدوث الانزلاق والضرر في الاجزاء الهندسية المتماسة. In the present paper, the contact of area, which is produced between a pair of bodies (flat surface and hemi-cylindrical shape), has been studied under the effect of slippage occurrence, where it represents one of the important problems in the mechanical engineering, especially in robotic design. Many parameters have been studied, like frictional forces, equivalent stresses, friction coefficient, and contact area of deformation. The behavior of these parameters has been monitored during the slippage that is generated between the flat surface made from cast alloy steel and the other part made from rubber. The finite element method (FEM) with SOLIDWORKS software was used to simulate this contact area under the slippage effect. The results of the simulation showed a significant behavior, particularly at the beginning of slippage and the stage of (stick-slip) phenomena, in other words, the simulation outputs indicated that the slippage influence has an important behavior, especially when the phenomena of both slippage and stick-slip stage start to occur. These analyses are intended to understand how the contact area affected to design measures to prevent the slippage occurrence and the damage in contacted bodies

Grasping Force Prediction for Underactuated Multi-Fingered Hand by Using Artificial Neural Network

In this paper, the feedforward neural network with Levenberg-Marquardt backpropagation training algorithm is used to predict the grasping forces according to the multisensory signals as training samples for specific design of underactuated multifingered hand to avoid the complexity of calculating the inverse kinematics which is appeared through the dynamic modeling of the robotic hand and preparing this network to be used as part of a control system.Keywords: Grasping force, underactuated, prediction, Neural networ

Static and Dynamic Calibration for FlexiForce Sensor Using a Special Purpose Apparatus

This paper introduces an experimental apparatus to be implemented for calibrating the FlexiForce sensor both statically and dynamically. This sensor uses a resistive – based technology and it has force range of (0-111N). The static calibration is done with static weights under static conditions, also these sensors are calibrated dynamically with the use of an inertial force of a mass as the known dynamic force; the acceleration of the mass is measured by an accelerometer board attached to the oscillating mass. These sensors are calibrated with the same conditions under which force sensors are supposed to be used, as to measure the force on the fingertip of a robotic manipulator. Results of both calibration methods are presented and discussed herewith. Keywords: Force sensors, dynamic calibration, special apparatu