Sharif Digital Repository

In this paper, we consider a control strategy of multi-robot systems, or simply, swarms, based on emotional control technique. First, we briefly discuss a "kinematic" swarm model in n-dimensional space introduced in an earlier paper. In that model, motion of every swarm member is governed by predefined inter-individual interactions. Limitations of every member's field of view are also considered in that model. After that, we consider a general model for vehicle dynamics of each swarm member, and use emotional control theory to force their motion to obey the dynamics of the kinematic model. Based on the kinematic model, stability (cohesion) analysis is performed and coordination controller.is... 

The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

Because of errors in the geometric parameters of parallel robots, it is necessary to calibrate them to improve the positioning accuracy for accurate task performance. Traditionally, to perform system calibration, one needs to measure a number of robot poses using an external measuring device. However, this process is often time-consuming, expensive and difficult for robot on-line calibration. In this paper, a methodical way of calibration of parallel robots is introduced. This method is performable only by measuring joint variable vector and positioning differences relative to a constant position in some sets of configurations that the desired positions in each set are fixed, but the moving... 

In this paper, modeling and control of a new cable-driven robot is presented. In this mechanism, the cable arrangement eliminates the rotational motions leaving the moving platform with three translational motion. The mechanism has potentials for large scale manipulation and robotics in harsh environments. In this article kinematics and dynamics models for the proposed cable-driven architecture are derived. Additionally, Feedback linearization under input constraints is used for the control of the robot. The control algorithm ensures the cable tensions are positive while minimizing the sum of all the torques exerted by the actuators. Finally, the implementation of the proposed method is... 

The robots that can move on rough terrains are very important especially in Rescue operation, exploration, etc. In this research, a mechanism is introduced for a ring-like robot with a flexible body. This robot is moved by arms which are placed radially and have Reciprocating motion in this direction. By controlling the contraction and the extension of the arms which contact lhe ground, the robot will be forced to move which is called rolling-creeping motion. The robot is stable in stationary state.; also the maximum angle which it can be stable is determined. Considering the speed of contracted arm is the input parameter, the speed of the extended arm for locomotion of the robot has been... 

Purpose - This paper aims to present the design and implementation of VirSense, a novel six-DOF haptic interface system, with an emphasis on its gravity compensation and fixed-base motors. Design/methodology/approach - In this paper, the design and manufacture of the VirSense robot and its comparison with the existing haptic devices are presented. The kinematic analysis of the robot, design of the components, and manufacturing of the robot are explained as well. Findings - The proposed system is employed to generate a Virtual Sense (VirSense) with fixed-base motors and a spring compensation system for counterbalancing the torques generated by the weight of the links. The fixed bases of the... 

We apply the weak field approximation limit of the covariant scalar-tensor-vector gravity theory, so-called MOdified gravity (MOG), to the dynamics of clusters of galaxies by using only baryonic matter. The MOG effective gravitational potential in the weak field approximation is composed of an attractive Newtonian term and a repulsive Yukawa term with two parameters α and μ. The numerical values of these parameters have been obtained by fitting the predicted rotation curves of galaxies to observational data, yielding the best-fitting result: α =8.89±0.34 and μ = 0.042 ± 0.004 kpc-1. We extend the observational test of this theory to clusters of galaxies, using data for the ionized gas and... 

Background: An effective master robot for haptic tele-surgery applications needs to provide a solution for the inversed movements of the surgical tool, in addition to sufficient workspace and manipulability, with minimal moving inertia. Method: A novel 4+1-DOF mechanism was proposed, based on a triple parallelogram linkage, which provided a Remote Center of Motion (RCM) at the back of the user's hand. The kinematics of the robot was analyzed and a prototype was fabricated and evaluated by experimental tests. Results: With a RCM at the back of the user's hand the actuators far from the end effector, the robot could produce the sensation of hand-inside surgery with minimal moving inertia. The... 

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... 

A wide range of loading conditions involving external forces with varying magnitudes, orientations and locations are encountered in daily activities. Here we computed the effect on trunk biomechanics of changes in force location (two levels) and orientation (5 values) in 4 subjects in upright standing while maintaining identical external moment of 15. Nm, 30. N. m or 45. Nm at the L5-S1. Driven by measured kinematics and gravity/external loads, the finite element models yielded substantially different trunk neuromuscular response with moderate alterations (up to 24% under 45 Nm moment) in spinal loads as the load orientation varied. Under identical moments, compression and shear forces at... 

An anatomically detailed eighteen-rotational-degrees-of-freedom model of the human spine using optimization constrained to equilibrium and stability requirements is developed and used to simulate several symmetric tasks in upright and flexed standing postures. Predictions of this stability and kinematics-driven (S. +. KD) model for trunk muscle forces and spine compressive/shear loads are compared to those of our existing kinematics-driven (KD) model where both translational and rotational degrees-of-freedom are included but redundancy is resolved using equilibrium conditions alone. Unlike the KD model, the S. +. KD model predicted abdominal co-contractions that, in agreement with... 

Kinematic boundary condition is usually used when dealing with transient free-surface flow problems in isotropic media. When dealing with anisotropic problems, a transformation can transform the anisotropic media to an equivalent isotropic media for seepage analysis, but the kinematic boundary condition cannot be used directly in the transformed media. A generalization of the kinematic boundary condition along any arbitrary direction is derived for use in the transformed domain for general three-dimensional anisotropic problems. A boundary element method for solving transient free-surface seepage problems is developed and the treatment of the proposed kinematic boundary condition in the... 

Recent research indicates that accurate material behavior modeling plays an important role in the estimation of residual stresses in the bore of autofrettaged tubes. In this paper, the material behavior under plastic deformation is considered to be a function of the first stress invariant in addition to the second and the third invariants of the deviatoric stress tensor. The yield surface is assumed to depend on the first stress invariant and the Lode angle parameter which is defined as a function of the second and the third invariants of the deviatoric stress tensor. Furthermore for estimating the unloading behavior, the Chaboche's hardening evolution equation is modified. These... 

The aim of this study was to determine the workspace of surgeon's body for designing more efficient surgical robots in the operation rooms. Five wearable inertial sensors were placed near the wrist and elbow joints and also on the thorax of surgeons to track the orientation of upper limb. Assuming that the lengths of five segments of an upper limb were known, measurements of the inertial sensors were used to determine the position of the wrist and elbow joints via an established kinematic model. subsequently, to assess the workspace of surgeon upper body, raw data were collected in the arthroscopy and laparoscopy operations. Experimental results demonstrated that the workspaces of surgeon's... 

As an alternative to dark matter models, Modified Gravity (MOG) theory is a covariant modification of Einstein gravity. The theory introduces two additional scalar fields and one vector field. The aim is to explain the dynamics of astronomical systems based only on their baryonic matter. The effect of the vector field in the theory resembles a Lorentz force where each particle has a charge proportional to its inertial mass. The weak field approximation of MOG is derived by perturbing the metric and the fields around Minkowski space-time. We obtain an effective gravitational potential which yields the Newtonian attractive force plus a repulsive Yukawa force. This potential, in addition to the... 

Discrete kinematic synthesis of discretely actuated hyper-redundant manipulators is a new practical problem in robotics. The problem concerns with determining the type of each manipulator module from among several specific types, so that the manipulator could reach several specified target frames with the lowest error. This paper suggests using a breadth-first search method and a workspace mean frame to solve this problem. To reduce errors, two heuristic ideas are proposed: two-by-two searching method and iteration. The effectiveness of the proposed method is verified through several numerical problems  

The objective of this research is geometrical and kinematical optimization of full-toroidal continuously variable transmission (CVT) in order to achieve high power transmission efficiency and low mass. At first, a dynamic analysis is performed for the system. A computer model is developed to simulate elastohydrodynamic (EHL) contact between disks and roller and consequently, calculate CVT efficiency. The validity of EHL model is investigated by comparing output of this model and experimental data. Geometrical parameters are obtained by means of Particle Swarm Optimization algorithm, while the optimization objective is to maximize CVT efficiency and minimize its mass. The algorithm is run for... 

A safe rehabilitation exercise for anterior cruciate ligament (ACL) injuries needs to be compatible with the normal knee arthrokinematics to avoid abnormal loading on the joint structures. The objective of this study was to measure the amount of the anterior tibial translation (ATT) of the ACL-deficient knees during selective open and closed kinetic chain exercises. The intact and injured knees of fourteen male subjects with unilateral ACL injury were imaged using uniplanar fluoroscopy, while the subjects performed forward lunge and unloaded/loaded open kinetic knee extension exercises. The ATTs were measured from fluoroscopic images, as the distance between the tibial and femoral reference... 

Hexapod robots gives us the ability to study walking robots without facing problems such as stability in many aspects. It has a great deal of flexibility in movement even if a leg becomes malfunctioned. Radially symmetric (hexagonal) hexapods have more flexibility in movement than rectangular leg alignments. Because of symmetry they can move in any direction and time efficiently. Inverse kinematic problem of this kind of hexapods is solved through a modular mobile view considering six degrees of freedom for the trunk. Then typical tripod and wave gaits are analyzed and simulated through the presented formulation. In Reinforcement Learning algorithm for walking it is important how to make... 

A two-dimensional, seven link, nine degrees of freedom biped model was developed to investigate the dynamic characteristics of normal and transfemoral amputee locomotion during the entire gait cycle. The equations of motion were derived using the Lagrange method and the stance foot-ground contact was simulated using a five-point penetration model. The joint driving torques were obtained using forward dynamic optimization of the normal human gait and applied to the intact joints of the amputee. Three types of motion controllers; frictional, elastic and hydraulic were considered for the prosthetic joints of the amputee and their design parameters were optimized to achieve the closest...