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Temperature dependence study of nonocontact AFM images using molecular dynamics simulations [electronic resource]
, Article Int. Journal of Modern Physics ; 2012, Vol. 5, pp. 418-432 ; Meghdar, Ali ; Sharif University of Technology
Abstract
The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have...
Design and performance analysis of a transparent force control strategy for an exoskeleton
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 563-568 ; 9781467372343 (ISBN) ; Zibafar, A ; Khezrian, R ; Vossoughi, G ; Sharif University of Technology
Abstract
Exoskeleton robots are developed for human rehabilitation and power augmentation. Human and robot interaction is an important issue involved with these robots. In this paper, the interaction force reduction is considered leading to the transparency of a lower limb exoskeleton during swing phase of walking. Achieving this goal, a robust Lyapunov based motion control method has been developed. The desired reference signals for motion control are generated using a direct force control approach. Robot accelerations are estimated by an observer to be employed in the control loop. An adaptation procedure has been proposed for the bound estimation of uncertainties. As part of assumptions, the...
A new strut model for solid masonry infills in steel frames
, Article Engineering Structures ; Volume 135 , 2017 , Pages 222-235 ; 01410296 (ISSN) ; Mohammadi, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
This paper presents in-depth results of a proposed strut model for masonry infill walls in moment-resisting steel frames. The proposed model is based on the results of calibrated finite element analyses and hence gives realistic representation of infilled frames behavior. Comparisons are made between the results of the proposed model and other existing strut models; ASCE beam-to-beam, ASCE column-to-column and El-Dakhakhni. The results prove that considerable improvement has been made in capturing the internal forces of the frame members and force-displacement diagram of infilled frames by the new model compared to the existing models. Robustness of the proposed model is also confirmed in...
Design and Implementations of an Intelligent Control System for a Lower Limb Extremity Robot Based on Human-Robot Interaction and Muscular Activity to Reduce Human Energy Consumption
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Gholamreza (Supervisor) ; Jahed, Mehran (Co-Supervisor)
Abstract
With advancements in control and robotics technology, wearable robots have gained multiple applications in rehabilitation and power augmentation. In robots developed for power augmentation purposes, human decisions are combined with robot power to enhance the human ability to perform various activities, such as carrying heavy loads and walking for a long time. In cases where robots are designed to help humans to carry heavy loads, the robot control strategy should minimize the human-robot interaction forces. In this case, heavy loads influence the robot and the user no longer need to use more energy than normal walking, and the robot works following human intentions. Where the robot works to...
A fast kinematic-based control method for lower-limb power augmentation exoskeleton
, Article 2014 2nd RSI/ISM International Conference on Robotics and Mechatronics, ICRoM 2014 ; 2014 , pp. 678-683 ; ISBN: 9781479967438 ; Vossoughi, G. R ; Ghafari, A. S ; Jokar, M ; Sharif University of Technology
Abstract
Exoskeletons are robotic devices which are used in power augmentation and rehabilitation robotics. The exoskeleton control system is one of the most challenging issues in humanrobot interaction systems. Although the rehabilitation robotic control methods are well studied, little research has been conducted on power augmenting control methods. This paper presents a novel idea in control system of exoskeletons for load carrying and power augmentation. Here, the desired linear velocity of the exoskeleton in interaction points are taken to be proportional to interaction force at the corresponding location. The introduced control method is merely based on kinematic model and thus easy to...
Passive dynamic object manipulation: A framework for passive walking systems
, Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 227, Issue 2 , 2013 , Pages 185-198 ; 14644193 (ISSN) ; Meghdari, A ; Sohrabpour, S ; Sharif University of Technology
2013
Abstract
In this study, we deal with passive dynamic object manipulation. During passive dynamic object manipulation, a passive object is manipulated using passive manipulators. Like other passive robotic systems, there are no actuators in these systems. The object follows a path and travels along it under the effect of its own weight, as well as, the interaction force applied by each manipulator on it. The objects are not necessarily rigid, but we manipulate passive multibody objects as well as rigid ones. Thus, for a passive walking system, we assume that the passive walker is a multibody object and is manipulated by the ground (zero degree-of-freedom manipulator). As an example, we show that a...
Passive dynamic object manipulation: preliminary definition and examples
, Article Zidonghua Xuebao/Acta Automatica Sinica ; Volume 36, Issue 12 , 2010 , Pages 1711-1719 ; 02544156 (ISSN) ; Meghdari, A ; Sohrabpour, S ; Sharif University of Technology
2010
Abstract
In this work, we introduce a category of dynamic manipulation processes, namely passive dynamic object manipulation, according to which an object is manipulated passively. Specifically, we study passive dynamic manipulation here. We define the main concept, discuss the challenges, and talk about the future directions. Like other passive robotic systems, there are no actuators in these systems. The object follows a path and travels along it under the effect of its own weight, as well as the interaction force applied by each manipulator on it. We select some simple examples to show the concept. For each example, dynamic equations of motion are derived and the stability of the process is taken...
Interaction of two oscillating sonoluminescence bubbles in sulfuric acid
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 82, Issue 1 , 2010 ; 15393755 (ISSN) ; Rezaee, N ; Ebrahimi, H ; Mirheydari, M ; Sharif University of Technology
2010
Abstract
The mutual interaction of two oscillating gas bubbles in different concentrations of sulfuric acid is numerically investigated. A nonlinear oscillation for spherical symmetric bubbles with equilibrium radii smaller than 10 μm at a frequency of 37 kHz in a strong driving acoustical field Pa =1.8 bar is assumed. The calculations are based on the investigation of the secondary Bjerknes force with regard to adiabatic model for the bubble interior which appears as repulsion or attraction interaction force. In this work the influence of the various concentrations of sulfuric acid in uncoupled and coupled distances between bubbles has been investigated. It is found that the sign and value of the...
Transformation of sliding motion to rolling during spheres collision
, Article Granular Matter ; Volume 19, Issue 4 , 2017 ; 14345021 (ISSN) ; Kaviani Rad, H ; Jafari Shad, H ; Sharif University of Technology
Abstract
In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and...
A novel stable robust adaptive impedance control scheme for ankle prostheses
, Article 5th RSI International Conference on Robotics and Mechatronics, IcRoM 2017, 25 October 2017 through 27 October 2017 ; 2018 , Pages 63-68 ; 9781538657034 (ISBN) ; Sharifi, M ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Abstract
A stable robust adaptive impedance control strategy is introduced here as a model-based low-level control scheme for active ankle prostheses. The effects of amputee-prosthesis and prosthesis-environment interactions are included in the controller design. An interesting feature of the proposed controller is that only shank and ankle angles and angular velocities, and ground reaction forces are required to implement the control law. In other words, no feedback from amputee-prosthesis interaction forces and moment, global or local positions, and accelerations of amputated place is required. Using a Lyapunov analysis, exponential convergence characteristics of the proposed controller are proven....
Design and implementation of an intelligent control system for a lower-limb exoskeleton to reduce human energy consumption
, Article 10th International Conference on Modern Circuits and Systems Technologies, MOCAST 2021, 5 July 2021 through 7 July 2021 ; 2021 ; 9781665418478 (ISBN) ; Karami, M ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Power augmentation is known to be one of the important applications of Exoskeletons. This paper designs a control strategy to reduce the energy consumed by users in power augmentation mode. The strategy aims to calculate and apply the interaction force between humans and robots according to human intentions. To realize human intentions, the movement's kinematic characteristics and the user's muscular activity were used. The movement patterns were learned by the robot using a set of adaptive oscillators. The human movement pattern in each movement cycle was considered the basis for predicting human intention in the next cycle. Thereby, the robot's optimal path and interaction torque were...
Development and Implementation of a Control System for Minimum Interaction Force between Human and Lower Limb Exoskeleton
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor)
Abstract
Nowadays exoskeltons are developed because of improvements carried out in mechatronic technologies, to use in applications such as human rehabilitation and power augmentation. By reason of interaction between exoskeleton robot and human, an appropriate control strategy should be considered to implement regulated interaction force between them. As an example there are situations that a person wants to carry heavy load with this robot without suffering from weight of the load, so control of robot movements is of great importance. The aim of this thesis is dedicated to develop and implement a control strategy achieving minimum ineraction force in a 2 degree of freedom lower limb exoskeleton....
Development and Implementation of a Wearable Robot Interaction Force Control Method Based on Switch Between the Swing and Stance Phases using Hybrid Systems Theory
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Gholamreza (Supervisor)
Abstract
Exoskeleton robot is so useful because of the interaction with them and human and are used in rehabilitation and augmentation applications. These robots can be either passively or actively actuated. Human and robot interaction is an important issue involved with these robots. In this thesis, the interaction force reduction is considered leading to the transparency of a lower limb exoskeleton during switch between swing and stance phasees of walking. Achieving this goal, a robust Lyapunov based motion control method has been developed. The desired reference signals for motion control are generated using a direct force control approach. Robot accelerations are estimated by an observer to be...
Variable Impedance Control of the Lower Limb Exoskeleton
, Ph.D. Dissertation Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Selk Ghafari, Ali (Co-Advisor)
Abstract
Todays, the exoskeleton is known as a practical device for use in robotic rehabilitation and elderly assistance and has attracted the attention of many researchers. Impedance control is the most widely recognized control strategy in research on exoskeletons. Impedance control can properly handle soft interaction of robots with the environment. Optimal target impedance selection can increase the performance of the overall system and guarantee the stability. The main objective of this research was to introduce a variable impedance control system and verifying the presented control system on an exoskeleton. In this research, an exoskeleton with 4 active DoF and 8 semi-passive DoF is designed...
Design a Model Predictive Control System for Empowerment and Rehabilitation of a Lower Limb Exoskeleton
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Gholamreza (Supervisor)
Abstract
With the development of technology in the field of control, biomechanics and robotics, wearable robots have found many applications in the field of rehabilitation and empowerment. In the empowerment phase, due to the interaction of these robots with humans, it is necessary to manage the interaction forces between the robot and humans with the help of appropriate control methods. One of the applications of these robots is when a person wants to carry a heavy load attached to the structure of the robot and the robot should be able to transfer the force caused by this load to the ground. At this time, humans should not be exposed to this load and the relationship between the robot and humans...
Investigation of a mutual interaction force at different pressure amplitudes in sulfuric acid
, Article Chinese Physics B ; Volume 20, Issue 8 , 2011 ; 16741056 (ISSN) ; Sadighi Bonabi, R ; Mirheydari, M ; Ebrahimi, H ; Sharif University of Technology
2011
Abstract
This paper investigates the secondary Bjerknes force for two oscillating bubbles in various pressure amplitudes in a concentration of 95% sulfuric acid. The equilibrium radii of the bubbles are assumed to be smaller than 10 μm at a frequency of 37 kHz in various strong driving acoustical fields around 2.0 bars (1 bar=10 5 Pa). The secondary Bjerknes force is investigated in uncoupled and coupled states between the bubbles, with regard to the quasi-adiabatic model for the bubble interior. It finds that the value of the secondary Bjerknes force depends on the driven pressure of sulfuric acid and its amount would be increased by liquid pressure amplitude enhancement. The results show that the...
Atomic interactions between metallic tips and surfaces in NC-AFM
, Article Journal of Physics D: Applied Physics ; Volume 48, Issue 12 , February , 2015 ; 00223727 (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
In this paper, the atomic-scale interactions between metallic tips and samples in noncontact atomic force microscopy (NC-AFM) are studied using molecular dynamics simulations. The effects of the tip and sample materials, the surface plane direction and the lateral position of the tip with respect to the sample, on the interaction force and the dissipated energy, are investigated. The simulations conducted demonstrate that, generally, we can classify the possible outcomes for the dynamics due to the tip-surface interactions into four major categories. The first category includes all cases in which there are no considerable instabilities in tip-surface interactions, leading to negligible...
Steered molecular dynamic simulation approaches for computing the blood brain barrier (BBB) diffusion coefficient
, Article IFMBE Proceedings ; Volume 51 , 2015 , Pages 1699-1703 ; 16800737 (ISSN) ; 9783319193878 (ISBN) ; Shamloo, A ; Alasti, A ; Zadeh, E. G ; Jaffray D. A ; Sharif University of Technology
Springer Verlag
2015
Abstract
In the recent years a great attention of research deals with different physical and biological aspects of the BBB structure, a robust shield that separates the blood and brain, a recent research held by the authors of this paper has focused on figuring out computing the diffusion coefficient of endothelial cell membrane. In this study, the major efforts have been concentrated on calculating a standardized measure for the amount of permeability and diffusion of this barrier. As a result, this work is dedicated to molecular dynamics (MD) simulation of calculating the interaction force between nano-particle and BBB membrane. data is recorded by using steered molecular dynamics simulation and...
Analytical and experimental frequency response analysis of microcantilevers subject to tip-sample interaction
, Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009 ; Volume 6 , September , 2010 , Pages 575-581 ; 9780791849033 (ISBN) ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
Abstract
Improvement of microcantilever-based sensors and actuators chiefly depends on how comprehensively they are modeled and precisely formulated. Atomic Force Microscopy (AFM) is the most widespread application of microcantilever beam as a sensor, which is usually influenced by the tip-sample interaction force. For this, vibration of AFM microcantilever probe is analyzed in this paper, along with analytical, numerical and experimental investigation of the influence of the sample interaction force on the microcantilever vibration. Nonlinear integro-partial equation of microcantilever vibration subject to the tip-sample interaction is then derived and numerically simulated. Moreover, multiple time...
Optimal target impedance selection of the robot interacting with human
, Article Advanced Robotics ; Volume 31, Issue 8 , 2017 , Pages 428-440 ; 01691864 (ISSN) ; Vossoughi, G ; Selk Ghafari, A ; Sharif University of Technology
Robotics Society of Japan
2017
Abstract
Human–robot interaction is an important issue in robotic researches which is the key in many rehabilitation and robot-assisted therapy applications. Impedance control can properly handle soft interaction of robots with the environment. Optimal target impedance selection can increase the performance of the overall system and guarantee the stability. The target impedance cannot be selected without proper knowledge about the stiffness and inertia parameters of the human. In this paper, a systematic analysis is done to introduce a method to estimate the human stiffness and consequently adjust the robot target stiffness. Then, particle swarm optimization is used to find the damping and inertia...