Search for: guidance-laws
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    Development and stability analysis of a cooperative search algorithm by multiple flying vehicles

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Vol. 228, issue. 7 , May , 2014 , p. 1058-1075 Esmailifar, S. M ; Saghafi, F ; Sharif University of Technology
    The problem of finding a lost target in a noisy environment by a group of flying vehicles is studied in this article. The developed cooperative search algorithm that is decentrally applied on the flying vehicles is a combination of searching guidance and neighborhood laws. The searching guidance law generates an acceleration command to direct each flying vehicle to the position of the lost target. The command is generated based on the information gathered by those flying vehicles that are categorized as neighbors by the neighborhood law. The neighborhood law specifies the sharing network between the flying vehicles for intelligent cooperation. Various neighborhood laws are introduced for... 

    Explicit minimum fuel intercept strategy for high-order dynamics

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 34, Issue 2 , 2010 , Pages 197-213 ; 10286284 (ISSN) Jalali Naini, S. H ; Pourtakdoust, S. H ; Sharif University of Technology
    An optimal fuel guidance strategy with acceleration limit is derived for interception of maneuvering targets. The guidance/control system is assumed as a linear time-varying arbitraryorder and is identical in each channel. An approximate model for drag acceleration is also considered in the solution. The optimal fuel strategy has some detrimental effects in most practical situations, if it is used entirely to the end. This strategy can be used at the beginning of the guidance phase for large initial heading errors in order to quickly reduce it with minimum effort. An explicit guidance law is then developed for minimum and nonminimum phase autopilots in order to modify the undesirable effects... 

    Multi-Objective Optimization of An Explicit Guidance Law for Space Reentry Vehicle Using Bezier Curves

    , M.Sc. Thesis Sharif University of Technology Goldasteh, Ali (Author) ; Fathi Jegarkandi, Mohsen (Supervisor)
    The goal of this thesis is to devise a guidance law that has the required ability and flexibility to construct a variety of return trajectories for a reentry capsule to the atmosphere. One of the commonly used methods for guiding flying vehicles with a fixed initial position and a fixed target is to load the trajectory data into the vehicle's computer memory. But the devised guidance law in this thesis does not require the trajectory data. Based on the relations governing the Bezier curve, it constructs the desired trajectory online. It also has the ability to provide the desired angle of landing and the desired magnitude of final speed. Further studies indicate that this ability is also... 

    Optimal fuzzy CLOS guidance law design using ant colony optimization

    , Article 3rd International Symposium on Stochastic Algorithms: Foundations and Applications, SAGA 2005, Moscow, 20 October 2005 through 22 October 2005 ; Volume 3777 LNCS , 2005 , Pages 95-106 ; 03029743 (ISSN); 3540294988 (ISBN); 9783540294986 (ISBN) Nobahari, H ; Pourtakdoust, S. H ; Russian Foundation for Basic Research ; Sharif University of Technology
    The well-known ant colony optimization meta-heuristic is applied to design a new command to line-of-sight guidance law. In this regard, the lately developed continuous ant colony system is used to optimize the parameters of a pre-constructed fuzzy sliding mode controller. The performance of the resulting guidance law is evaluated at different engagement scenarios. © Springer-Verlag Berlin Heidelberg 2005  

    A Model Predictive Differential Game Guidance Algorithm for Precise Trajectory Tracking of a Fixed Wing UAV

    , M.Sc. Thesis Sharif University of Technology Asghari, Javad (Author) ; Nobahari, Hadi (Supervisor)
    This research presents three new guidance laws for trajectory tracking of an unmanned aerial vehicle in the presence of wind disturbances. The first method is a linear combination of line-of-sight and velocity-pursuit guidance laws, the parameters of which are tuned using a fuzzy system in an online manner. The second method is an adaptive optimal guidance law based on the differential game theory. The third method (main method) is a model predictive guidance law based on the differential game theory. In the main method, linear point mass equations of motion are used to predict the future path of the vehicle. Also, the linear model predictive control is used to achieve an optimal analytical... 

    Closed-form optimal cooperative guidance law against random step maneuver

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 52, Issue 1 , 2016 , Pages 319-336 ; 00189251 (ISSN) Nikusokhan, M ; Nobahari, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Based on the optimal control theory, the present study proposes a novel approach to derive a cooperative guidance law for two pursuers with an arbitrary-order linear dynamics against one zero-lag evader with random step maneuver. This approach is intended to minimize the mean value of the resultant control effort taken over a set of possible evader maneuvers which is modeled as a step function, the parameters of which are unknown. Since the resultant control effort is the minimum effort among the pursuers, we encounter the nonlinear "min" function in the performance index. By introducing binary parameters, it is changed to a linear function including binary parameters and continuous... 

    Design of a supervisory controller for CLOS guidance with lead angle

    , Article AIAA Guidance, Navigation, and Control Conference 2005, San Francisco, CA, 15 August 2005 through 18 August 2005 ; Volume 4 , 2005 , Pages 3083-3095 ; 1563477378 (ISBN); 9781563477379 (ISBN) Nobahari, H ; Alasty, A ; Pourtakdoust, S. H ; Sharif University of Technology
    This paper proposes a supervisory Command to Line-of-Sight (CLOS) guidance law with lead angle. The proposed scheme guarantees the missile to fly within the beam, when there is a beam angle constraint. In this regard a supervisory controller is coupled with a main Sliding Mode Controller (SMC). The supervisory control signal is activated when the beam constraint goes to be violated. First the supervisory controller is designed based on a recent idea on how the states of a nonlinear system with local stable controller can be controlled to stay within the domain of attraction. Then a sliding mode controller is designed, as the main tracking controller, to force the missile to fly along the... 

    Modern midcourse guidance laws in the endoatmosphere

    , Article AIAA Guidance, Navigation, and Control Conference 2005, San Francisco, CA, 15 August 2005 through 18 August 2005 ; Volume 6 , 2005 , Pages 4560-4576 ; 1563477378 (ISBN); 9781563477379 (ISBN) Jalali Naini, S. H ; Pourtakdoust, S. H ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2005
    In this paper, midcourse guidance strategies are derived considering approximate models for drag and thrust in the presence of gravity and autopilot dynamics. The guidance/control system is assumed as a linear time-varying and of arbitrary-order. The zero-effort miss differential equation is obtained in a way that three classes of guidance laws, namely optimal fuel, optimal energy, and closed-loop explicit strategy, can be derived by available methods for minimum and nonminimum phase autopilots. The resulting guidance laws have the structure of a guidance gain multiplied by the zero-effort miss. Several thrust/drag models arc also considered and discussed to obtain the effective navigation... 

    Performance Improvement of a Cooperative Aerial search Algorithm by Analyzing its Important Parameters

    , M.Sc. Thesis Sharif University of Technology Ramzgooyan, Amir Arya (Author) ; Saghafi, Fariborz (Supervisor)
    In the past few decades, regarding the advancement of science and technology, the application of Unmanned Aerial Vehicles (UAVs) are increasingly on the rise. One of these applications is to search and localize ground targets. Among the advantages of drones, removing the manpower to carry out exploration and positioning is one of the most important benefits. This feature can reduce the risk of mission, reduce the burden of the plane and increase the height and range of operations. On the other hand, using a group of intelligent robots to increase speed and accuracy in the mission, is one of the topics that have been discussed in recent years. By merging these two topics and utilizing a... 

    Cooperative Search and Localization Using Multiple Fixed Wing Unmanned Aircraft

    , Ph.D. Dissertation Sharif University of Technology Esmailifar, Majid (Author) ; Saghafi, Fariborz (Supervisor)
    Nowadays, regarding the advancement of unmanned aerial vehicles and low cost sensors, the idea of utilizing a group of aerial vehicles to perform risky and complicated missions has attracted the attentions of researchers. One of the main subjects in aerial missions is target search and localization. Cooperative target search by the use of multiple aerial vehicles equipped with sensors, could construct a sensor network that makes the system more robust against failures and reduce noises and uncertainties. In addition, the observability and quality of sensor signals could increase if the motion and positions of the vehicles are intelligently optimized.In this research, establishing an... 

    Causal description of the interaction of a two-level atom with a classical field

    , Article Physica Scripta ; Volume 78, Issue 3 , 28 August , 2008 ; 00318949 (ISSN) Mousavi, S. V ; Golshani, M ; Sharif University of Technology
    We discuss the Bohmian paths of two-level atoms moving in a waveguide through an external resonance-producing field, perpendicular to the waveguide and localized in a region of finite diameter. The time spent by a particle in a potential region is not well-defined in standard quantum mechanics, but it is well defined in Bohmian mechanics. Bohm's theory is used for calculating the average time spent by a transmitted particle inside the field region and the arrival-time distributions at the edges of the field region. Using the Runge-Kutta method for the integration of the guidance law, some Bohmian trajectories were also calculated. Numerical results are presented for the special case of a... 

    Non-linear feedback optimal control law for minimum-time injection problem using fuzzy system

    , Article Aircraft Engineering and Aerospace Technology ; Volume 77, Issue 5 , 2005 , Pages 376-383 ; 00022667 (ISSN) Pourtakdoust, S. H ; Rahbar, N ; Novinzadeh, A. B ; Sharif University of Technology
    Purpose - To devise a new technique to synthesise optimal feedback control law for non-linear dynamic systems through fuzzy logic. Design/methodology/approach - The proposed methodology utilizes the open-loop optimal control solutions (OCSs) of the non-linear systems for the training of the fuzzy system in the process of developing closed-loop fuzzy logic guidance (FLG). This is achieved through defining a set of non-dimensionalised variables related to the system states. Findings - FLG is capable of generating closed-loop control law for the non-linear problem investigated. Since the proposed fuzzy structure is independent of the system equations, the approach is potentially applicable to... 

    A neuro-optimal approach for thrust-insensitive trajectory planning

    , Article Aircraft Engineering and Aerospace Technology ; Volume 81, Issue 3 , 2009 , Pages 212-220 ; 00022667 (ISSN) Pourtakdoust, S. H ; Pazooki, F ; Noushabadi, F ; Sharif University of Technology
    Purpose - The purpose of this paper is to devise a new approach to synthesize closed-loop feedback guidance law for online thrust- insensitive optimal trajectory generation utilizing neural networks. Design/methodology/approach - The proposed methodology utilizes an open- loop variational formulation that initially determines optimal launch/ ascent trajectories for various scenarios of known uncertainties in the thrust profile of typical solid propellant engines. These open-loop optimized trajectories will then provide the knowledge base needed for the subsequent training of a neural network. The trained network could eventually produce thrust-insensitive closed-loop optimal guidance laws... 

    Fuzzy trajectory tracking control of an autonomous air vehicle

    , Article ICMEE 2010 - 2010 2nd International Conference on Mechanical and Electronics Engineering, Proceedings, 1 August 2010 through 3 August 2010 ; Volume 2 , August , 2010 , Pages V2347-V2352 ; 9781424474806 (ISBN) Soleymani, T ; Saghafi, F ; Sharif University of Technology
    The development and the implementation of a new guidance law are addressed for a six dimensional trajectory tracking problem, three dimensions for position tracking and three dimensions for velocity tracking, of a micro air vehicle. To generate the desired trajectory a virtual leader is defined which is moved in space. In the guidance law, position and velocity feedbacks are used by fuzzy controllers to generate two acceleration commands. Then, a fuzzy coordinator is applied to coordinate the acceleration commands. Nonlinear six-degree-of-freedom equations of motion are used to model the vehicle dynamics. Also, a bank-to-turn acceleration autopilot for vehicle is considered to follow the... 

    Finite-Time guidance laws for landing process of a spacecraft subjected to disturbances

    , Article 2016 4th International Conference on Control, Instrumentation, and Automation, ICCIA 2016, 27 January 2016 through 28 January 2016 ; 2016 , Pages 296-300 ; 9781467387040 (ISBN) Abooee, A ; Moravej Khorasani, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    This paper investigates the finite-Time landing of a spacecraft on a celestial target subjected to disturbances and air drag forces. Based on nonsingular fast terminal sliding mode control, a novel guidance law is designed to accomplish the landing goal within a specified finite time while the upper bound of disturbances is assumed to be known. Finally, a numerical example of the spacecraft landing problem is simulated by applying the proposed scheme. The obtained results illustrate that the designed guidance law can achieve the landing goal in the specified finite time