Mohammadvali Arbabmir; Masoud Ebrahimi Kachoei
Volume 12, Issue 3 , September 2019, , Pages 43-54
Abstract
In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. ...
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In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. In this approach, in order to estimate the feature points in the current image, the INS states, the feature points of the previous image and dynamic equations are used. Also, in this approach, for improving the estimation of terrain points, the outlier estimated feature points delete. Furthermore, in this article, for improving the altitude error, a barometer is used by the mentioned vision navigation system. The simulation results illustrate the desirable accuracy of the vision system and barometer observations in the update step of Extended Kalman Filter (EKF) and remarkable performance of integrated navigation system for calculating the UAV navigation parameters.
seyed aliakbar kasaeian; Masoud Ebrahimi
Volume 11, Issue 2 , September 2018, , Pages 21-31
Abstract
The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe ...
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The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe rendezvous for reaching the target. Switching is conducted in the guidance scheme by utilizing a self-defined sign function. Moreover, a new modified saturation function is employed instead of the discontinuous part of the sliding mode. The Lyapunov function approach guarantees the asymptotic stability. Numerical simulations are conducted by both linear and nonlinear models of relative dynamics. Mean anomaly, angular velocity, and eccentricity of target orbit are considered as the uncertainties. Finally, the results indicate the performance and robustness of the proposed guidance in the presence of non-linearity, uncertainties, and disturbances, compared to the conventional sliding mode.
arman samadi; Masoud Ebrahimik; Hossein Jahanbakhsh
Volume 10, Issue 3 , December 2017, , Pages 25-39
Abstract
The main objective of this research is to improve the distribution of electrical potential on spacecraft surfaces by changing the surface coatings to reduce the risk of electrostatic discharge in the spacecraft. For this purpose, SPIS software, the EU standard software for modeling and simulating the ...
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The main objective of this research is to improve the distribution of electrical potential on spacecraft surfaces by changing the surface coatings to reduce the risk of electrostatic discharge in the spacecraft. For this purpose, SPIS software, the EU standard software for modeling and simulating the interaction of space plasma with the spacecraft is used. The spacecraft has 8 nodes, and each node is related to a particular substance. The simulations were compared with the variation in the materials of these nodes in terms of differential electric and floating potential. Investigating materials that differed in the differential electric potential of zero showed that they are conductive materials. In order to choose among several conductive materials, these materials were compared in terms of electric floating potential. Simulations on satellite surfaces showed an average of 11% improvement in the electrical potential on surfaces
Masoud Ebrahimi Kachoie; Mohammadvali Arbabmir; Mohammad Norouz
Volume 10, Issue 2 , September 2017, , Pages 33-52
Abstract
Inertial navigation system error increases due to sensor errors with the increase intime. Usually, to prevent the growth of navigation system error, inertial navigationsystems are integrated with sensors or auxiliary systems. The importantly aided system isGNSS. Because of GNSS outage or its invalidity, ...
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Inertial navigation system error increases due to sensor errors with the increase intime. Usually, to prevent the growth of navigation system error, inertial navigationsystems are integrated with sensors or auxiliary systems. The importantly aided system isGNSS. Because of GNSS outage or its invalidity, the other auxiliary sensors are used toincrease the accuracy of the inertial navigation system. In this article, the types ofmethods which are used by imaging camera for navigation or for the accuracyimprovement of an inertial navigation system for UAVs are discussed. After reviewing theliterature in the field of vision navigation in UAVs, the proper classification for visionnavigation methods and the development of these methods are presented. In UAVs, thevision navigation techniques are based more on Map metric, optical flow, featuretracking, odometers and simultaneous localization and mapping.
Jafar Roshanian; Mehdi Hassani; Shabnam Yazdan; Masoud Ebrahimi
Volume 5, Issue 4 , January 2013, , Pages 1-8
Abstract
Star tracker is an attitude determination device which determines the satellite or spacecraft’s attitude using the star position information in inertial and body references. Star information is collected and stored onboard as a “Star or mission catalog”. There are several star catalogs ...
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Star tracker is an attitude determination device which determines the satellite or spacecraft’s attitude using the star position information in inertial and body references. Star information is collected and stored onboard as a “Star or mission catalog”. There are several star catalogs that contain different kinds of information with different accuracy. In this paper the most used star catalogs are introduced and a few star catalog selection features are recommended. These features are weighted according to the star tracker mission type. For the selected star tracker mission, results demonstrate that Hipparcos star catalog is the best choice. Eventually using Hipparcos star catalog, a mission catalog is developed to be used onboard a typical star tracker.
Jafar Roshanian; Shabnam Yazdani; S. Mehdi Hasani; Masoud Ebrahimi Kachouie
Volume 5, Issue 2 , July 2012, , Pages 15-23
Abstract
Star trackers are one of the most accurate attitude determination devices of a spacecraft. Star trackers are able to determine the spacecraft attitude with the use of recognizing the stars within their field of view. One of the major subsystems of star tracker software is the star pattern recognition ...
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Star trackers are one of the most accurate attitude determination devices of a spacecraft. Star trackers are able to determine the spacecraft attitude with the use of recognizing the stars within their field of view. One of the major subsystems of star tracker software is the star pattern recognition algorithm. In this research a novel star pattern recognition algorithm called Non-Dimensional is considered. This algorithm can recognize the stars within its field of view without using the information of camera calibration. In order to fulfill this goal, the algorithm requires a database which contains the star inertial information. Afterwards a fast search method is used to compare the combinations on the image with database. Eventually there has been a tradeoff between database volume and the update frequency for a better performance.
J. Roshanian; M. Ebrahimi; A. Bataleblu
Volume 4, Issue 2 , January 2012, , Pages 23-34
Abstract
The purpose of this paper is introducing the concept of nondeterministic optimal design or optimal design in the presence of uncertainty based on researches done in the past two decades. Therefore, after an introduction about uncertainty, the uncertainty and uncertainty modeling techniques are described. ...
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The purpose of this paper is introducing the concept of nondeterministic optimal design or optimal design in the presence of uncertainty based on researches done in the past two decades. Therefore, after an introduction about uncertainty, the uncertainty and uncertainty modeling techniques are described. After that, thetraditionalmethodof dealingwith uncertaintyin thedesignis described. The importance of paying attention to the uncertainty and its benefits for different projects and companies is described. The third section is dedicated to introducing the methods of interval analysis, fuzzy logic and probability analysis, which are used in the analysis of uncertainty.The two general categories of nondeterministic design problems, the robust optimal design and reliability-based optimal design are reviewed. The next section introduces the application of nondeterministic design methods in the different disciplines and recent researches in the world on this topic. Finally, future aspects and challenges of the nondeterministic design are addressed.
