Sharif Digital Repository

One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human gait was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. The foot-ground contact was simulated using a five-point penetration contact model. The elastic impact and friction effects are considered in the ground reaction force modeling. Optimization of the normal human walking model provided constant coefficients for simple PD controllers’ (driving torque) equations that could reasonably reproduce the normal kinematical pattern. Then, in the second... 

This research focuses on the dynamic analysis of an exoskeletal system to assist a paraplegic motion. Research in powered human exoskeletons began in the late 1960s, almost in parallel between the numbers of research groups for different applications. The main challenges for the recent work in exoskeletons were focused on the design and demonstration of an initial prototype. To this point, the reported advantages of the autonomous exoskeleton systems are largely anecdotal. Indeed, there is a marked lack of published quantitative performance results for exoskeleton devices that reportedly improve human locomotion. Considering this, there are many design challenges remained that may lead to... 

Patellofemoral joint has an important role in knee extension. Because of this joint importance and complicated mechanical behavior, a lot of mathematical models have been used, to obtain a better understand of this joint, considering this joint as a part of knee joint or as a separate joint. Although these works have comprehensively studied the patellofemoral joint but they don’t emphasis on dynamic aspects. Also there is no work to compare the experimental and theoretical results calculated from one specified subject knee.In this study, the kinematic and dynamic of patellofemoral joint has been studied, constructing a three dimensional dynamic model of patellofemoral joint and experimental... 

Researches in the field of human gait have a lot of applications in medicine, ergonomics, sport science and technology. Lower limb prostheses design is one of the fields in which human gait is important. One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. In this model the foot-ground contact was is estimated using Taylor series after running experiment and it’s analysis which is expendable to people with different ages and different weight and... 

In this work, we want to gain and analyze the dynamic equations of an open four bar mechanism with two flexible links and three flexible hinges. In continue, one of the applications of a 3-RRR mechanism has been mentioned and dynamic equations and angles behavior have been analyzed. The effect of hinge stiffnesses and their sequence has been investigated by using Hamilton principle. In addition, The behavior of the mechanism with flexible links has compared to the mechanism with non-flexible. At last, the results have been validated by ADAMS software.

 

In this work, A new hybrid approach is presented to optimize a trajectory of Micromechanical Flying Insect in an obstacle reach environment. Here, a singleobjective Evolutionary Algorithm is utilize for finding solutions corresponding to multiple conflicting goals, which include minimizing the length of the path while maximizing safety margin by avoiding hard and non-moving obstacles. On the other hand, dynamic constraints of Micromechanical Insect such as maximum and minimum attitude angles and speed should be taken into account. In order to reduce the computational cost, a novel hybrid two-layer procedure is suggested for trajectory optimization. In the first layer, the algorithm generates... 

In this project Sharif Gas Turbine laboratory turbojet engine, and the turboshaft engine which is designed based on the turbojet gas generator are statically and dynamically modeled and required functions for turboshaft control are extracted. In static modeling a repetitive process is applied to reach static operation points. Static operation line and static characteristics of turbojet engine are extracted and compared to relevant sources. In dynamic modeling of turbojet engine a lumped volume is allocated to each component of engine and gas dynamic equations are solved in this volume along with individual performance map of engine components to acquire output characteristics in each time... 

Ducted fan vertical take-off and landing (VTOL) aerial vehicles have drawn many attentions in the world because of their capability to offer high power to weight ratio for a certain vehicle diameter relative to open rotors or helicopters. However, due to inherent uncertainties in dynamics and inefficient and poor quality responses, significant control challenges are still unsolved and exciting fields for research. In the current study, a nonlinear dynamic model is proposed for the controller design purpose. This model is validated against simulation by performing several standard scenarios. An adaptive control method, named model reference (MRAC), is utilized to design a perfect controller... 

Compression systems are widely used in industry. Dynamic Modeling is a necessary step in design procedure of a safe compression system. A dynamic model should be adequate and simulate dominant elements of system. One important element of industrial compression systems is downstream pipelines. In this work, a dynamic model including pipeline acoustics is developed. It is accepted that changes of working gas molecular weight can cause inception of instabilities in compression systems. The dynamic model used to study mechanisms of these instabilities. A conventional control system is modeled and tuned for the compression system. The ability of this control system to prevent such instabilities... 

In recent years, the area of research on micro flying robots has been developed, because of the development in micro manufacturing technologies. These flying robots can be used in military and Civilian missions such as identifying, espionage, aerial relays, traffic surveillance rescue, help and…because of their advantages. Ability to fly in finite areas, no human injuries, low manufacturing and power cost, easy and fast Application, Easy Maintenance and … are some advantages of these robots. We can control these robots manually by RC remote controllers or by Auto guidance system. On the other hand, these robots are used in research laboratories for testing new control algorithms such as ... 

This work concerns with experimental and modeling investigation of the asphaltene damage removal using ultrasonic wave irradiation. A specific core holder apparatus was designed and utilized for in situ ultrasonic exposure to damaged core plug at different conditions of exposure time, ultrasound power and distances between sound source and plug. Injection of many pore volumes of an asphaltenic crude oil was used for creating asphaltene induced damaged in porous media through permeability measurements. The deposited asphaltene during oil injection as well as asphaltene removal due to ultrasonic exposure was evaluated using IP-143 analysis. The results revealed that ultrasound application... 

In recent decades, micro-electromechanical systems – MEMS – havefound extensive applications in applied science and engineering. One of the most popular MEMS actuatorsis micro Scratch Drive Actuator (SDA), which can be used in various applications, for instance: precision positioning, micro-chip displacement and rotating micromotors. Their outstanding capabilities such as: high controllability, precise step displacement, vast transportation domain and large force relative to their small size, have made them popular among researchers. Recently, a new generation of SDA is introduced, known as Bounce-back Scratch Drive Actuator or BSDA, which is fundamentally different in motion generation from... 

In recent years, the area of research on micro flying robots has been developed due to the development in micro manufacturing technologies. Due to extra advantages of these flying robots, they are implemented in military and civilian missions such as identifying, espionage, aerial relays, traffic surveillance, rescue, aid, etc. Ability to fly in specified areas, without human injuries, low manufacturing and energy costs, easy and fast implementation, Easy Maintenance, etc, which are some advantages of these robots. We can control these robots manually by remote controllers (RC) or by Auto guidance systems. On the other hand, these robots are used in research laboratories for testing new... 

Due to high cost and ineffectiveness of molecular models a new method for coupling continuum models with molecular models is used. In this method, the continuum and molecular domains are overlapped. Comparing the results obtained from the concurrent simulations and molecular dynamic simulations proves the accuracy of the method used. The method is used for modeling single layered graphene sheets, stress contours are presented for multiscale and both static and dynamic simulations of concurrent. For multiscale simulations two different carbon nano tubes are investigated and strees-bond angle and strees-bond length are also presented  

Natural gas power plant installed in power system as rapid start unit. In the recent decades, with increasing in the number of gas generating units in the world, consideration of natural gas transmission network in optimal solution of security-constrained unit commitment (SCUC) become a non-negligible problem. The gas transmission grid constraints integrated into the scheduling of thermal units in the proposed model for minimizes power system operating cost. In a power plant transmission of natural gas to power plant is very important because congestion in natural gas pipeline increases. This model could consider natural gas storage tank in gas transmission network as decision variable.... 

The present research has dealt with developing theoretic basis for technology of a modern and beneficial robot. There has been an old aspiration to attain some machine which can enclose body and move exactly in concert with it so as to maximize human might and endurance via powerful actuators. Exoskeleton robot is a recent successful invention regarding this aspiration, the lower-limbs type of which being sufficient for enhancing gait and load carrying capabilities.
Modeling the dynamics of this robot is very fundamental and was done thoroughly for the first time in this research. In the available articles, at most, simplified models are investigated. Mechanical structure was selected... 

Fish robot has attracted many attentions in the last decade due to several types of its applications. Many researches have been done recently on this type of robot. Dynamic modeling and control of a fish robot are important and challenging problems. This issue has a great influence on design, manufacturing, efficiency and control of the fish robot. According to the literature review, it seems that no exact analytical model exists for predicting the propulsive forces which are used in controlling and simulating dynamic behavior of the robot. Fortunately, Lighthill has proposed an analytical relation to predict propulsive forces of carangiform fishes in his research. Large amplitude elongated... 

The present research has dealt with the modeling and control of a robotic prosthetic foot for transfemoral amputees. In the beginning of this research, we have modeled the normal gait. In order to accomplish this modeling, we have chosen a 7-body segment skeletal model of the human body and derived the motion equations using Lagrangian equations. Then, we have developed a smooth contact model for the ground. After controlling normal gait, we have attempted to model and control the ankle and knee prosthesis. We assumed a rigid model for the ankle prosthesis and derived its dynamic equations. Then, we developed a robust model reference adaptive impedance control (RMRAIC) scheme based on the... 

3D reconstruction and tracking of deformable surfaces has received lots of attention in the past decade. This field has been studied from two major aspects: 1) machine vision and 2) computer graphic, and has been used in many applications ranging from industrial design, animation and medical surgeries. One of the most challenging problems in this area is monocular 3D reconstruction, which is an ill-posed problem and involves many ambiguities. Generally, methods which are proposed for monocular 3D reconstruction can be divided into two categories: 1) Template-based methods and 2) Structure from motion methods. Methods of the first category utilize a template model which consists of an image... 

Dealing with different supply chain risks and how firms should prepare against them has become an important issue in real world application. In this paper, we propose a periodic model to fortify supply chain structure against disruption by remanufacturing different types of returned products at first priority and manufacturing raw materials at second priority only if it is necessary. Additionally, our approach to model disruption is that there are two kinds of facilities for manufacturing/ remanufacturing centers. The first one is reliable and the second one is unreliable. Therefore, in this paper, we formulate and solve a reliable discrete dynamic linear programming with different types of...