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obstacle-avoidance
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Comparative Study Collision Avoidance Algorithm for Cooperative Systems
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
Cooperative system is a system in which agents jointly try to reach a common goal. In order to achieve the desirable goal, a cooperative system needs some conditions such as agents moving as a flock and avoiding to conflict with each other and obstacles. Collision avoidance is one of the most important and notable factor in cooperative systems. This issue has been addressed by many researchers and different solutions have been proposed so far. In this thesis, existing methods and algorithms are studied. Among these algorithms two well-known ones have been investigated having considered their advantages and disadvantages in more detail. Some improvements on these two algorithms are proposed...
Optical Flow Based Flight of a Small Fixed-Wing Aircraft in Ideal Urban Environments
, Ph.D. Dissertation Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
This thesis represents the obstacle avoidance of a fixed-wing small aircraft using optical flow information of cameras mounted on the aircraft. The thesis consists of two main sections. In section one, the ideal optical flow has been simulated based on the camera model, complete six DOF of flight equations, and the geometry of the environment. An analytical formula has been derived to relate the obstacle detection distance to the maneuverability of the aircraft. Having the obstacle detection distance, the control and navigation algorithms have been developed to achieve a collision-free flight for the aircraft in urban canyons and junctions. The effect of some parameters such as approach...
Trajectory Planning of a Spider Robot Considering Obstacle Avoidance
, M.Sc. Thesis Sharif University of Technology ; Ghaemi Osgouie, Kambiz (Supervisor) ; Khayyat, Amir Ali Akbar (Supervisor)
Abstract
Legged walking and climbing robots have recently achieved important results and developments, but they still need further improvements and study. The spider modeled as an eight-legged system. Legged robots have a body and a number of articulated legs which originate from the body and are put on the ground to hold robot’s weight or are swinging in the air to their new position. Each leg as a kinematic chain can be viewed as a manipulator that acts like a limb and contributes to the overall position and equilibrium of the structure. In order to evaluate and create an effective legged robot, the idea is to draw inspiration from nature. Spider robots present very good performances in terms of...
Design of Distributed Control System for AUV Swarms to Circle Around a Body
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this thesis, a new procedure is presented for control and analysis of a group of autonomous underwater vehicle achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. Desired path for AUV’s has been developed using Virtual agents with mass point dynamics. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based...
A Fuzzy-Behavior Based Approach to “Dynamic and Static Obstacles” Avoidance in an Unknown Space
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
In this article, research has been carried out on the control technique of autonomous mobile robots to navigate in unknown environments, avoiding static and moving obstacles using eight ultrasonic sensors for obstacle recognition.
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s...
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s...
Design, Fabrication and Control of Swarm Robots
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor)
Abstract
Swarm robotics is a new approach to the coordination of large numbers of relatively simple robots. The approach takes its inspiration from the system level functioning of social insects which demonstrate three desired characteristics for multi-robot systems: robustness, flexibility and scalability. This research describes development of an autonomous miniature mobile robot for swarm robotics research and education. Several common platforms were studied and this prototype was designed. Wireless communication was selected to transmit robot’s messages. The design of this testbed aims for enhancing the sensing capability of the robotic agents, overcoming the constraints led by lack of...
Time-varying formation tracking for noisy multi-agent systems with unknown leader trajectory
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 236, Issue 7 , 2022 , Pages 1386-1399 ; 09596518 (ISSN) ; Bigdeli, N ; Haeri, M ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
In this article, time-varying formation tracking problem for multi-agent systems is investigated. It is assumed the number of agents is changing and obstacles should be avoided along the trajectory. In addition, the tracking formation should be reached while the leader trajectory is unknown and communication data are noisy. To reach the desired formation tracking, first, a virtual leader is constructed using the local neighbouring data. Second, the reference signal is created based on the virtual leader and the leader data (which is available for some agents). The data fusion at this stage is done based on Kalman filtering to reduce the effect of communication noise. Third, an integral state...
Dynamic Motion Planning and Obstacle Avoidance Simulation for Autonomous Robot-car in Webots
, M.Sc. Thesis Sharif University of Technology ; Jamzad, Mansour (Supervisor)
Abstract
Motion planning in an autonomous vehicle is responsible for providing smooth, safe and efficient actions. Besides reducing the risk of collision with static and moving obstacles, the ability to make suitable decisionsencountering sudden changes in environment is very important. Many solutions for dealing this problem have been offered, one of which is, Artificial Potential Fields (APF). APF is a simple and computationally low cost method which keeps the robot away from the obstacles in the environment. However, this approach suffers from trapping in local minima’s of potential function and then fails to produce a plan. Furthermore,Oscillation in presence of obstacles or in narrow passages...
Variable Formation & Decentralized Control of Multi-Quadrotor Having Same Dynamic System Using Consensus Algorithm
, M.Sc. Thesis Sharif University of Technology ; Sayyadi, Hassan (Supervisor)
Abstract
Since Formation control have potentail applications in civil and military industries, decenterlized control of formation control is studied in this work using consensus algorithm. A specific robot quadrotor with 3D motion is used in this work. Quadrotor is an underactuated vehicle. First, we derivate twice from dynamical equations of linear positions. Hence, we can obtain appropriate form using linearization of output equations for design a consensus control algorithm. It is needed to design fourth order control algorithm for control of multiagent systems, beacause of twice derivation. Two methods that have been used for formation control in many works are potential function method and...
Dynamic Trajectory Generation and Obstacle Avoidance for a Reconfigurable Spherical Robot
, M.Sc. Thesis Sharif University of Technology ; Ghaemi Osgouie, Kambiz (Supervisor) ; Salarieh, Hassan (Supervisor)
Abstract
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...
Obstacle Avoidance Control Algorithm for Multi Agent Autonomous Underwater Vehicle
, M.Sc. Thesis Sharif University of Technology ; Sayyaadi, Hassan (Supervisor)
Abstract
According to the importance of obstacle and collision avoidance for multiple Autonomous underwater vehicle (AUV) that are synchronized for starting the path following, in this study the coordination path following controller for a group of underactuated underwater vehicle with considering of obstacle and collision avoidance presented. The proposed control method is based on graph theory and back stepping with modeling of obstacle using limit cycle. At first, for controller design the back stepping method for path following of one AUV is used. Then the designed controller using of principles of graph theory, has been extended for multiple AUV and as the result multiple AUV is synchronized and...
Stable and Connected Coordination of Robotic Swarms Through Local Information
, Ph.D. Dissertation Sharif University of Technology ; Alasty, Aria (Supervisor) ; Vossoughi, Gholamreza (Supervisor)
Abstract
In this thesis, coordination of a group of autonomous agents, through a scalable control structure and with very limited communications, is addressed. Inter-agent action functions are designed to guarantee the network connectivity. Two coordinator agents with different natures are designed. One is attractive and is named leader-agent (LA). The other is repulsive and is named shepherd-agent (SA). Under the assumption that both coordinators locally affect the group, we have proved that the governing equation of the whole group may have variable order.
By using nonlinear control techniques, coordination algorithms are designed to move the group on a predefined path or to a destination. It...
By using nonlinear control techniques, coordination algorithms are designed to move the group on a predefined path or to a destination. It...
Mobile Robot Navigation and Localization in the Presence of Hurdles in Cluttered Environment Using Fuzzy Control and Kalman Filter
, M.Sc. Thesis Sharif University of Technology ; Khayyat, Ali Akbar (Supervisor)
Abstract
In this thesis, in order to improve the performance of the mobile robot navigation, a Fuzzy approach is used for making a safe path in the cluttered environment with hurdles in the work space of the robot. To this end, based on data collected from instantaneous location of the robot and location of the robot, heuristic rules are extracted. Also, in order to obtain optimal data fusion of the sensors, Kalman filter is used to localize the robot. In this regards, by using the kinematics of the robot and supposing the white noise in the process and measurements, the position and orientation of the mobile robot are estimated in a real-time and adaptive manner
Position and Attitude Control for a Quadrotor Using Nonsmooth Feedback
,
M.Sc. Thesis
Sharif University of Technology
;
Namvar, Mehrzad
(Supervisor)
Abstract
In recent years, autonomous unmanned aerial vehicles (UAVs) have attracted considerable amount of interest because of a wide area of applications and a lot of advantages. UAVs have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Quadrotor, which is a kind of rotary wing UAVs, has many advantages such as the vertical take-off and...
Flight Formation Control & Obstacle Avoidance of a UAV Team Using Fuzzy Predictive Artificial Potential Field Method
, M.Sc. Thesis Sharif University of Technology ; Nobahari, Hadi (Supervisor)
Abstract
This thesis focuses on the development of a flight formation control algorithm and obstacle avoidance of a UAV team using fuzzy predictive artificial potential field (FPAPF) method. One of the common methods for path generation and obstacle avoidance is the artificial potential field (APF) method. The basis of the APF method is that the UAV is attracted to the target point and repelled from the obstacles by using the potential fields of attraction and repulsion. The popularity of this method is due to its computational simplicity and efficiency. The APF method has limitations due to constant attraction and repulsion coefficients. The proposed real-time FPAPF method uses fuzzy logic to...
3D offline path planning for a surveillance aerial vehicle using B-splines
, Article International Conference on Advanced Mechatronic Systems, ICAMechS, Luoyang ; 2013 , Pages 306-311 ; 23250682 (ISSN) ; 9781479925193 (ISBN) ; Banazadeh, A ; Sharif University of Technology
Abstract
This paper presents an offline path planning method in 3D space for a surveillance aerial vehicle. In this method, the aerial vehicle is supposed to visit particular points on the path, and the collision between the vehicle and the fixed obstacles in the environment must be avoided. In order to accomplish the mission, first, the path is generated using B-splines. Then, the feasibility of tracking the designed path for the vehicle is considered by analyzing the vehicle's dynamic constraints, such as limitations on deflections of control surfaces. The analysis is supported by a simulation. Potential extension of the proposed analysis to multiple aerial vehicles has been also discussed at the...
A new obstacle avoidance method for discretely actuated hyper-redundant manipulators
, Article Scientia Iranica ; Volume 19, Issue 4 , August , 2012 , Pages 1081-1091 ; 10263098 (ISSN) ; Zohoor, H ; Habibnejad Korayem, M ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper, a new method is proposed for solving the obstacle avoidance problem of discretely actuated hyper-redundant manipulators. In each step of the solution, the closest collision to the base is removed and then the configuration of the next part of the manipulator is modified without considering the obstacles. This process is performed repeatedly until no collision is found. The Suthakorn method is applied to solve the inverse kinematics problem. Two new ideas are proposed to reduce the errors of this method: the two-by-two searching method, and iterations. To verify the proposed method, some problems are solved numerically for 2D and 3D manipulators, each in two different obstacle...
Development of an Optimal Path Planning Algorithm for Aerial Robots Based on GPOPS Program
, M.Sc. Thesis Sharif University of Technology ; Banazadeh, Afshin (Supervisor)
Abstract
In this thesis the problem of path planning for aerial robots,specifically the UAVs, is studied. Some software packs aiming to perform optimal path planning are already published worldwide. In this thesis, these software are investigated and UAV path planning is done by them. In UAV path planning using these software, due to the high number of equations, number of constraints in solution increases and even in a simple problem, the process of solving becomes difficult for software. Among introduced software packs, “GPOPS”, which uses pseudospectral methods, is chosen as the best. Avoiding obstacles in different problems is checked. Obstacle avoidance and waypoint tracking at the same time,...
Cooperative Slung-Load Transportation by Quadrotors in Urban Environment, Path Planning and Tracking
, Ph.D. Dissertation Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this research, the aerial load transportation in the urban environment by cooperative quadrotors is investigated. This system requires two sub-systems: path planning and control. The path planning subsystem designs the payload's path and at the same time determines the shape of the flight formation of agents in order to be able to carry the payload. The design of the path-formation is done in the presence of constraints such as the collision avoidance with obstacles, inter-collision avoidance to each other, the collision avoidance of the slung load with the obstacles and the minimum and maximum allowable cables' forces. Therefore, the shape of the formation flight is determined...
Collision-free path planning of a novel reconfigurable mobile parallel mechanism
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 389-394 ; 9781467372343 (ISBN) ; Kazemi, H ; Masouleh, M. T ; Novin, R. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This paper initially deals with the design of a new customized reconfigurable mobile parallel mechanism. This mechanism is called "Taar Reconfigurable ParaMobile (TRPM)", consisting of three mobile robots as the main actuators. Then, the kinematics and path planning for this mechanism are represented. The newly proposed mechanism is expected to circumvent some shortcomings of inspection operation in unknown environments with unexpected changes in their workspace, e.g., in a water pipe with non-uniform section area. In this paper, "Artificial Potential Field (APF)" has been assumed to be the path planning algorithm and its resulting attractive and repulsive forces are only applied to the...