Finite Time Guidance Law to Intercept Desired LOS Angle Using NTSM Control
Vahid
Behnamgol
Malek Ashtar University of Technology
author
Ahmadreza
Vali
MalekAshtar University of Technology
author
ali
mohammadi
MalekAshtar University of Technology
author
text
article
2018
per
Nonsingular terminal sliding mode (NTSM) guidance for intercepting the desired line of sight (LOS) angle in terminal phase is proposed in this paper. In order to satisfy the predefined LOS angle and to intercep into target, a nonsingular terminal sliding variable is introduced. In reaching phase, in the presence of uncertainties such as target maneuvers, robust NTSM guidance law is designed in order forzeroing the sliding variable in finite reaching time. Then, in sliding phase, due to introducing nonsingular terminal sliding variable, finite time stability of line of sight angle and line of sight angular rate is granteed without singularity in commanded acceleration as control signal Numerical simulations are presented to illustrate the potential of the proposed guidance law.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
1
10
http://jsst.ias.ir/article_75178_8bb6e1396a9da17e868579f2822a59c3.pdf
Numerical Simulation and Optimization of Forced Convection Heat Transfer of Magnetic Nanofluid in a Channel in the Presence of a Non-Uniform Magnetic Field
Mohmmad
Goharkhah
Sahand university
author
Mostafa
Esmaeili
Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, Tehran, Iran.
author
Mehdi
Ashjaee
Department of Mechanical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran
author
text
article
2018
per
In this paper, the effect of an external non-uniform magnetic field on forced convective heat transfer of magnetite nanofluid (ferrofluid) in a heated channel is studied numerically. The main goal is to emphasize the importance of magnetic field location and investigate the possibility of heat transfer enhancement by finding the optimum location of magnetic field source.It is observed that the magnetic field results in creation of recirculation zones which affect the thermal boundary layer thickness and Nusselt number. Results show that the effect of magnetic field location on the heat transfer is completely dependent on the thermal boundary condition. It is also shown that the flow and temperature fields can be manipulated by application of multiple magnetic field sources. Using genetic algorithm (GA), an optimum arrangement for locations of eight magnetic field sources is obtainedresulting in a27% heat transfer enhancement compared to the case of no magnetic field.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
11
19
http://jsst.ias.ir/article_75179_1e47d57b1cbbbfdbaccbdf06e4d69162.pdf
Robust Switching Surfaces Sliding Mode Guidance for Terminal Rendezvous in Near Circular Orbit
seyed aliakbar
kasaeian
mechanical engineering department, tarbiat modares university,tehran, iran
author
Masoud
Ebrahimi
Tarbiat Modares university,Tehran, Iran
author
text
article
2018
per
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.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
21
31
http://jsst.ias.ir/article_75180_3737e3a2607c774d27f5edb3cc8c04d0.pdf
Lyapunov-basedAdaptive SmoothSecond-order Sliding Mode Guidance Law with Proving Finite Time Stability
Vahid
Behnamgol
Malek Ashtar University of Technology
author
Ahmadreza
Vali
malek ashtar university of technology
author
ali
mohammadi
malek ashtar university of technology
author
َAshknaz
Oraee
Cambridge University
author
text
article
2018
per
A new adaptive smooth second-order sliding mode control is proposed for uncertain nonlinear systems in this paper. The finite time stability is proved using a Lyapunov technic. The proposed controller consists of an adaptive term equal to the uncertainty in ﬁnite time. This algorithm is used to design terminal guidance law for homing interceptors to intercept maneuvering targets. The guidance law generates smooth acceleration commands and the control signal is able to stabilize relative lateral velocity in a desired time. Finally, the proposed guidance law is compared with the second-order sliding mode guidance law from carried out simulations.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
33
39
http://jsst.ias.ir/article_75252_cb6a6aea09b50b52e2c9bdefda74e82c.pdf
Velocity and Body Rate Control of a Spacecraft Using Robust Passivity-Based Control
Hamed
Chenarani
- School of Electrical and Electronic Engineering. Shiraz university of Technology
author
Tahereh
Binazadeh
دانشگاه صنعتی شیراز
author
Mohammad Hosein
Shafiei
Shiraz University
author
text
article
2018
per
This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides a useful tool for analysis of nonlinear systems has been also used for asymptotic stabilizing of nonlinear dynamical systems especially mechanical systems. The passivity-based control law is a static output feedback and has valuable features. Because of existence of uncertainties and external disturbances in the state-space of equations of physical systems; first the robust version of passivity-based control method, which is recently developed in literature, is given and the control law for nonlinear uncertain systems with affine structure is presented. Then, this approach is used in controller design for a spacecraft. Since, this paper considers only the stabilization of velocity and body rates, therefore the reduced-order model is extracted from the state-space equation of a spacecraft with six degree of freedom and then the robust control law is designed. Computer simulations show the efficiency of the proposed controller in robust asymptotic stabilizing of the velocity and body rate vectors of the spacecraft in the presence of uncertainties and external disturbances.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
41
46
http://jsst.ias.ir/article_75253_12f5ade3c9a99b09938e7415e35cc86d.pdf
Optimal Mission Design for Moon Exploration Expedition
Hassan
Naseh
ARI
author
Mehran
Mirshams
K. N. Toosi University of Technology
author
Elyas
Fadakar
K. N. Toosi University of Technology
author
Mehdi
Jafari Nadoushan
K. N. Toosi University of Technology
author
text
article
2018
per
The main goal of this paper is to introduce the Moon exploration mission design based on existing technology.The Moon exploration mission design entailsoptimal maneuvering orbit, payload and launch vehicle design. Optimal maneuvering orbit is designed with respect to Circular Restricted Three Body Problem (CRTBP) to model the motion of a spacecraft in the Earth/Moon system. To this end, optimal maneuvering orbitadopted CRTBP as dynamical model and obtained three-dimensional Earth to Moon transfers with low cost. This method is more preferable and flexible than Hohmann transfer because of its lower cost and its access to various inclinations in departure and arrival.The optimal Launch Vehicle Conceptual Design (LVCD) algorithm is based on optimization of major design parameters. LVCD algorithm is coded in a software to let the design engineer explore the design space and to reduce the cost and time of the conceptual design phase that is developed by the authors.The optimization process is performed subject to the restrictions and the performance index is optimized in a mutual iteration mechanism. Consequently, the designed launch vehicle ability to satisfy the mission objectives and its requirements is evaluated.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
47
53
http://jsst.ias.ir/article_75256_677d651fc48ea0338ac1eefdc274a3ee.pdf
Low-Profile Helical Antenna for Space Application
Fatemeh
Sadeghikia
ARI
author
Ali
Karami Horestani
ARI
author
text
article
2018
per
The aim of this study is to examine the effects of diameter of ground conductor in an axial mode helical antenna on some of the characteristics of the antenna. It is shown that a proper ratio of diameter of ground plane to diameter of helix can be chosen to make a trade-off between the performance of helical antenna and its mass budget. It is shown through computational analysis that this optimum ratio is about 1.5. The results show that an increase in this ratio increases the mass budget, but it does not improve the antenna performance significantly. The simulation results also indicatethat this ratio is independent of the number of helix turns. After measurement, it was found that the simulation results of the antenna well agreed with its measured results acquired at the anechoic chamber.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
11
v.
2
no.
2018
55
59
http://jsst.ias.ir/article_75257_8d9923370dda659dabc50a7427f9ef59.pdf