Aerospace Science and Technology
Reza Jamilnia
Abstract
In this paper, in order to simultaneously optimize the staging and trajectory of launch vehicles, changes are made in the structure of the trajectory optimization problem. In this approach, the flight times of all stages are considered freely and as optimization variables. During the solution and in ...
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In this paper, in order to simultaneously optimize the staging and trajectory of launch vehicles, changes are made in the structure of the trajectory optimization problem. In this approach, the flight times of all stages are considered freely and as optimization variables. During the solution and in each iteration, by using the values of the flight times in that iteration and the fuel consumption rate of each stage, the masses of the fuel and structure of the stages and the initial and instantaneous masses of the vehicle are calculated. By minimizing the initial mass as the objective function of the integrated optimization problem, the optimal flight trajectory is obtained in the form of the optimal state and control values, and the optimal budget of the fuel and structure masses between different stages is calculated. In this paper, to implement the dynamic equations, the direct collocation method is used, and to approximate the variables, the B-spline curves are used. By using the B-spline curves, despite the discreteness of the relevant parameters as optimization variables, a continuous concept for the optimal solution can be created. The presented approach in this paper for integrated optimization of staging and trajectory and the use of B-spline curves in the approximation of the multiphase problem with free final times can lead to reduce the initial weight of the Europa 2 launch vehicle by 30% to perform a specific mission.
Aerospace Science and Technology
Shayan Dehkhoda; Mohammad-Ali Amiri Atashgah
Abstract
This paper is dedicated to the optimal path-planning of a quadrotor to deliver the goods in the form of a round-trip mission. At first, quadrotor modeling is performed by the Newton-Euler method and then the problem is formulated as an optimal control effort problem. Then, by discretization of the equations ...
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This paper is dedicated to the optimal path-planning of a quadrotor to deliver the goods in the form of a round-trip mission. At first, quadrotor modeling is performed by the Newton-Euler method and then the problem is formulated as an optimal control effort problem. Then, by discretization of the equations using the direct colocation method, the problem becomes a nonlinear programming system that can be solved by available optimization methods. This discretization helps to make the derivative values in the equations of motion as simple algebraic expressions and the path optimization problem becomes a standard form of nonlinear programming problem (NLP). In this method, instead of obtaining state and control functions, state and control values are obtained at the beginning and endpoints of smaller time intervals. This method is one of the most explicit methods for the numerical solution of differential equations. It should be noted that in this research, safe areas around urban obstacles are considered fixed cylinders. Extensive simulations are evidence of the usefulness of this method, while the vehicle realizes all geometric, dynamic, and kinematic constraints.
