Sharif Digital Repository

In this thesis a 2-3PRS hybrid mechanism is presented. This manipulator is consisted of two serially connected parallel 3PRS mechanisms, each mechanism has three degrees of freedom, so that the overall degrees of freedom of the manipulator are six. The relations for position, velocity and acceleration of the mechanism in both forward and inverese kinematics are derived and then singular points are determined. After that, the inverse dynamic equations for one of the 3PRS mechanisms are derived through the Newton-Euler and aslo Lagrange approach and the results are verified. Then the derived Newton-Euler equations are implemented for inverse and forward dynamics of the hybrid manipulator. The... 

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... 

In the present study, an adaptive sliding mode control method was employed to control a fish robotic system using the method of hardware in the loop. Following the introduction of the nonlinear model for the robot, elongated body theory, suggested by Lighthill, was used to analyze fish movements. Lighthill’s theory inspired from slender body theory in aerodynamics scope could be viable to exercise upon the carangiform mode of swimming. By simplifying Lighthill’s equations in planar motion of fish robot, the number of degrees of freedom exceeds the number of the control variables. In view of the fact that the presented model is an under-actuated model, there exist some parametric and... 

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... 

Non rigidity of the soil beneath the structure, alters elastic and inelastic response of it. This effect is caused by the soil-structure interaction. The effect of soil-structure interaction is studied in two parts, Kinematic interaction and inertial interaction. Among these, kinematic interaction effects are often assumed to be negligible so that even in existing regulations it has been ignored. While the kinematic part of soil-structure interaction effect could produce a rocking input motion that might be important. In recent years, according to expanding usage of performance based design philosophy, researches on inelastic behavior of the soil-structure systems has been done which is... 

One of the main causes of low back pain is mechanical loads acting on it. These loads can be measured by in vivo measurement using force and pressure sensors. Although this method leads to accurate results, it is invasive and costly. Currently the only noninvasive way to estimate these loads is to utilize biomechanical models. Using these models requires body posture as an input. Imaging techniques are suitable for determining the posture accurately, but these equipments are expensive and often impractical. So today posture prediction models are used as an alternative cost effective with acceptable accuracy. These mechanisms predict body posture using body mass, height, position and the... 

Recent studies show that spherical shape robots have been widely developed by many robotic researchers. A spherical shape can be also benefited in keeping mechanical components and electronic circuits inside a compact volume. The shell can also perform rolling motions for going fast and smooth on flat area. The reconfigurable spherical robot can be configured into a form of two interconnected hemispheres with three legs equipped with three Omni-directional wheels. The conceptual design of the robot will be initially packed and deployed in a spherical configuration. The spherical construction offers ease in transportation and deployment; for example, a number of these robots can be packed and... 

In recent years, industrial robots have been greatly used as orienting devices in industry, especially in the automotive, shipbuilding and aerospace manufacturing industries. Industrial robots are gradually finding their niche in manufacturing, replacing less universal and more expensive CNC-machines. Application area of robots is constantly growing; they begin to be used for the assembly, pick-and-place operations, machining operations and etc. The use of robots for machining operations is growing because of their flexibility to perform a broad spectrum of tasks at a lower cost when compared with machine tools. Recently, parallel robots have attracted more and more researchers’ attention in... 

In the resent years, social robots has been emerged to improve the interactions between humans and robots. These intractions are intended more in human environment. So the reasonable performance of such robots is achieved if robots’ motion; become similar to humans. Hence, despite the complexities of manufacturing and controlling the bipedal and humanoid robots, the researches on this class of robots are still in continuing more and more. In 2013, the humanoid robot, R-50, made by Robokind Company, was purchased by the Mechanical Engineering Department of Sharif University of Technology. This robot was named Mina and to be used in the researches on the treatment of autism patients. Although... 

Two robots with same number of degrees of freedom (DOF) may have different motion patterns. Planar, spherical and translational motions are typical 3 DOF motions. So far, many studies in the field of less than 6 DOF mechanisms have been focused on synthesis and development of parallel mechanisms (PM) with a specific motion pattern. Recent investigations show that there is possibly new type of PMs that could change their operation modes and satisfy more than one motion pattern. For applications in which the platform should undergo one motion pattern at part of workspace and a different motion pattern in some other poses, utilizing these PMs instead of a 6 DOF robot obviously reduces number of... 

Motorcycle has one of the most complicated geometries and mechanisms and its kinematic, according to the articles surveyed, has always been expressed with approximation and simplification in the degrees of freedom and especially in the magnitude of the angles. Analyzing the dynamic model of bodies, using methods like Kane, Lagrange, Boltzmann-Hamel, Gibbs-Apple, Newton, Hamilton and Ross, lead to mechanism’s equations of motion. While the equations of motions, obtained from alternative methods, lead to the same result, but the number of differential equations and sometimes their order, are different in different methods, and therefore their numerical solving time for the body’s motion, are... 

In this study, an elastic-plastic analysis of fiber reinforced metal matrix composite structures loaded by uniaxial uniform tension in the direction perpendicular to the fiber is carried out by assuming elastic-plastic matrix with kinematic hardening. Representative volume element (RVE) is used for this analysis. The element consists of a combined square field composed of a solid circular cylinder fiber and matrix in plane strain condition. Elastic analysis is carried out using Airy stress function and Michell solution. Unknown coefficients of the Airy stress function are determined by satisfying boundary conditions as well as continuity conditions. The governing equation of plastic zone is... 

Cerebral palsy (CP) is one of the most common motor disability among children that caused by damage to brain or defective development of brain before, during or just after birth. Due to this damage, children with CP have cognitive and motor problems. As an important activity of daily living, walking enhances independence, social activities and quality of life. Much of therapy for children is aimed to improve their gait. A usual technique to evaluate how a person walk and detect abnormal features in walking pattern is gait analysis. Lots of studies have been done on gait kinematics of CPs and classified them based on their kinematis. The purpose of this thesis is studying muscles activity of... 

The primary objective of this dissertation is to obtain a mechanism from the family of 5-dof parallel mechanisms of type 3T2R which gains the advantages of higher kinematic performance, low coupling of motion, and simple kinematics and control commands. Based on this aim, at first a method for structural synthesis of this type of mechanisms is introduced. The method is based on the theory of linear transformation and a geometrical analysis. By using this method, a set of novel 5-dof 3T2R parallel mechanism are introduced for the first time in the literature. In order to compare the designed mechanisms and to identify the promising ones, some important criteria which are a) low coupling... 

The goal of fracture reduction in orthopedic surgery is to reposition the bone fragments in their anatomical orientation (alignment), and the fracture ends closed to each other (apposition). Reduction of long bone fractures is became an interesting subject in the field of robotic aided surgery in pervious decade. Nowadays reduction of femur is carried out by surgeons and medical staff in surgery. Due to the large holding forces necessary, exact positioning is difficult and time consuming. What is needed is an automated system whereby the fractured ends of the bone may be precisely positioned without the need for multiple docking attempts. The fragments need to be held in place as long as... 

In this project the goal is to study where, when and how the cracks in the steel connection plate between beam and column initiate and how far would the crack grow before failure and how to detect crack initiation by utilizing piezoelectric sensors. In this analysis piezoelectric is placed in line of crack propagation for sensing strain and changing it to voltage. A thin plate with edge notch which is an ideal model of typical beam to column connection is assumed. The plate is subjected to a uniaxial uniform load. With the aid of ANSYS software, the plate is analyzed in both elastic and plastic stages. The strain-stress curve with kinematic hardening part is considered and modeled with... 

Impedance measurement is one of the most efficient electrochemical methods to investigate the mechanism and kinetics of electrode reactions. This method can detect the steps of successive or parallel electron and mass transfer chemical reactions based on measuring the response time constant. The method of showing results, commonly known as Nyquist diagram,which is based on drawing real and imaginary components of the impedance, with respect to each other in different measurement frequencies, is very useful for determining the mechanism of electrode reactions and the kinetic measurements. The main objective of this thesis is totheoretically determine the impedance response of six... 

A large number of structures subjected to the seismic loading have been damaged or have experienced failure in different parts such as the pile structure or even in the entire structure due to unanticipated effects of the soil-pile-structure interaction.The complexity of problems regarding the soil-pile-structure interaction is an influencing factor in prediction of the behavior of structure during the earthquakes. In this study, the effect of the interaction on the dynamic response of bridges was investigated using the finite element software ABAQUS. The primary purpose of this study, as previously described, is to study the effects of the soil-structure interaction on a bridge located on a... 

Direct in vivo measurements of spinal loads and muscle forces are invasive. Investigators have thus used musculoskeletal biomechanical models that require kinematic data including trunk and pelvis angular movements as their inputs. . Novel devices measure anglular movements using both inertial sensors (such as gyroscopes and accelerometers) and miniature magnetometers. Relative low cost, portability, and accuracy are among specific characteristics of inertial tracking devices. The main objective of the present study was set to measure spinal kinematics including the lumbopelvic rhythm as the ratio of total lumbar rotation over pelvic rotation during trunk sagittal movement which is essential... 

Manual material handling (MMH) activities are identified as risk factors for occupational low back pain (LBP). Task-related variables including load and posture characteristics are required as input into these models and tools for estimation of trunk external moment. Biomechanical modeling studies that aim to mathematically estimate low back loads currently need an inevitable parallel time-consuming in vivo study in an equipped laboratory to measure trunk posture under physical activities. Inertial sensors as a portable, accurate, almost inexpensive, and small device could be very helpful in order to capture the kinematic data of movement in human activities. My master thesis aims to...