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Lifting Body Reentry Vehicle Guidance in Landing using Fuzzy Algorithms
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
In this thesis, active guidance of a reentry vehicle using fuzzy logic is investigated. The guidance commands of the reentry vehicle (pitch and bank angles) are computed based on estimation of the final conditions, including range and cross-range errors and time-to-go. The final conditions are predicted utilizing a neural network. Inputs of this neural network are the current states of the vehicle and flight time. The first advantage of this approach is that no reference trajectory is required, which is mostly generated optimally for ideal conditions. Moreover, the methods based on keeping the nominal trajectory produce severe guidance commands for sudden disturbances (e.g. wind gusts),...
Satellite-based forward scatter passive radar
, Article Proceedings International Radar Symposium, 10 May 2016 through 12 May 2016 ; Volume 2016-June , 2016 ; 21555753 (ISSN) ; 9781509025183 (ISBN) ; Bayat, S ; Farina, A ; Hajsadeghian, S ; Nayebi, M. M ; Sharif University of Technology
IEEE Computer Society
2016
Abstract
In this paper we present a feasibility study on using satellite signal for passive radar application. Our focus is on utilizing GEO (geostationary Earth orbit) satellite signal with suitable properties. The feasibility of using such satellite signal for passive radar application is evaluated. In particular, a space shuttle as the target of interest is considered. In addition to being covert, it will be shown that using such passive radar system, we can benefit the forward scatter enhancement, which enables us to detect such high-altitude target that is totally undetectable to conventional radar systems
Vision-based navigation in autonomous close proximity operations using neural networks
, Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 47, Issue 2 , April , 2011 , Pages 864-883 ; 00189251 (ISSN) ; Saghafi, F ; Sharif University of Technology
Abstract
Tight unmanned aerial vehicle (UAV) autonomous missions such as formation flight (FF) and aerial refueling (AR) require an active controller that works in conjunction with a precise sensor that is able to identify an in-front aircraft and to estimate its relative position and orientation. Among possible choices vision sensors are of interest because they are passive in nature and do not require the cooperation of the in-front aircraft in any way. In this paper new vision-based estimation and navigation algorithms based on neural networks is developed. The accuracy and robustness of the proposed algorithm have been validated via a detailed modeling and a complete virtual environment based on...
An accurate guidance algorithm for implementation onboard satellite launch vehicles
, Article Scientia Iranica ; Volume 17, Issue 2 D , JULY-DECEMBE , 2010 , Pages 175-188 ; 10263098 (ISSN) ; Mobed, M ; Sharif University of Technology
2010
Abstract
An algorithm for guiding a launch vehicle carrying a small satellite to a sun synchronous LEO is presented. Before the launch, a nominal path and the corresponding nominal control law for the entire journey are computed. For each sampling instant during the guided flight, a linear equation approximately relating the differences between the actual and nominal values is considered, and a LeastSquares formula using data from on-line state measurements is applied to compute the actual control. The coefficient matrices of the Least-Squares formula can be determined by off-line computations. The method enjoys simplicity of implementation by onboard computers, as well as robust accuracy against...
Catching the high altitude invisible by satellite-based forward scatter PCL
, Article Signal, Image and Video Processing ; Volume 11, Issue 3 , 2017 , Pages 565-572 ; 18631703 (ISSN) ; Bayat, S ; Farina, A ; Hajsadeghian, S ; Nayebi, M. M ; Sharif University of Technology
Springer London
2017
Abstract
This paper presents a feasibility study on using satellite signal for passive radar application. Our focus is on utilizing geostationary Earth orbit satellite signal with suitable properties, like Inmarsat. Then, a new method of detection for passive coherent location using adaptive filter weights variation model is presented. To evaluate the performance, three different scenarios including a low Earth orbit satellite, a space shuttle, and a high-altitude aircraft as the targets of interest are considered. In addition to being covert, it will be shown that using such passive radar system, we can benefit the forward scatter enhancement, which enables us to detect such high-altitude targets...