Reza Esmaelzadeh; Abolghasem Naghash; mahdi mortazavi
Volume 10, Issue 3 , December 2017, , Pages 15-24
Abstract
An optimal explicit guidance law that maximizes terminal velocity is developed for the reentry of a vehicle to a fixed target. The equations of motion are reduced with differential flatness approach and acceleration commands are related to the parameters of trajectory. An optimal trajectory is determined ...
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An optimal explicit guidance law that maximizes terminal velocity is developed for the reentry of a vehicle to a fixed target. The equations of motion are reduced with differential flatness approach and acceleration commands are related to the parameters of trajectory. An optimal trajectory is determined by solving a real-coded genetic algorithm. For online trajectory generation, optimal trajectory is approximated. The approximated trajectory is compared with the pure proportional navigation and genetic algorithm solutions. The near optimal terminal velocity solution compares very well with these solutions. The approach robustness is examined by Monte Carlo simulation. Other advantages such as trajectory representation with minimum parameters, applicability to any reentry vehicle configuration and any control scheme, and Time-to-Go independency make this guidance approach more favorable.
farshad shamlu; Abolghasem Naghash
Volume 10, Issue 2 , September 2017, , Pages 1-8
Abstract
In this study, a different approach to the prediction of satellite position is introduced.All methods are based on the Kepler’s laws of planetary motion and the orbitalperturbations such as the Earth’s oblateness, atmospheric drag, third-body perturbationand the solar-radiation pressure. ...
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In this study, a different approach to the prediction of satellite position is introduced.All methods are based on the Kepler’s laws of planetary motion and the orbitalperturbations such as the Earth’s oblateness, atmospheric drag, third-body perturbationand the solar-radiation pressure. All these perturbations are modeled and are includedseparately in the equation. However, this paper offers a new view of the prediction whichsuggests the use of artificial neural networks and observation data. The advantage of thismethod is based on the usage of observation data, so that all disturbances are taken intoaccount and there is no need to use perturbation models. For this reason, the use of theTLE as the most reachable actual data is considered. Comparison of the output of thismethod with actual data shows the accuracy of the proposed method which is very high.
Payman Torabi; Abolghasem Naghash
Volume 9, Issue 2 , September 2016, , Pages 77-83
Abstract
This paper presents a new methodology for a quick and efficient numerical determination of the condition for repeat ground tracks to be employed in an orbital optimization design methodology. This methodology employs the simplicity and reliability of the epicyclical motion condition for a repeat ground ...
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This paper presents a new methodology for a quick and efficient numerical determination of the condition for repeat ground tracks to be employed in an orbital optimization design methodology. This methodology employs the simplicity and reliability of the epicyclical motion condition for a repeat ground track to find a semimajor axis for a given repetition cycle and inclination. Then the semimajor axis is re fined for application to any elliptical motion. This methodology was discovered by comparing two recent methods in addition to a new proposed method offered in this paper investigating both nonlinear algebraic and polynomial formulations of the governing repeat-ground-track condition relationship. A lesser known simplified method is used for preliminary solution refinement. The advantages and disadvantages of each approach are weighed with each method ’s reliability, performance, and computational ease based on a case study. From these criteria, one method is recommended for use in repeat-ground-track orbit design optimization methodology.
R. Jamilnia; A. Naghash
Volume 1, Issue 2 , December 2008, , Pages 35-42
Abstract
In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is ...
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In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is an efficient numerical method for solving optimal control problems, is used. By using this method, the problem of trajectory optimization is fully discretized and converted to a nonlinear programming problem. This discrete problem with large numbers of variables and constraints is solved by a powerful nonlinear programming solver (IPOPT). Finally, optimal state and control variables are achieved for optimal orbit transfer with minimum fuel consumption.
