Search

The minimum-fuel, multi-pulse and time-fixed rendezvous problem is investigated, and a population entropy based particle swarm optimization (EPSO) algorithm is proposed to optimize the rendezvous trajectory. The relative motion of two spacecrafts between two near circular orbits is described by the linearized C-W equations, and taking the minimum energy as a control object, the optimal transfer trajectory based on continuous impulse is got to determine the pulse point location. For the engineering practicability, a multi-pulse control method is used. The location parameters of the pulse point are used to establish the optimization object function of taking the time interval between two pulse-points as the decision variable, and it is solved using the EPSO algorithm. In EPSO, the population entropy is used to describe the particles' location confusion degree, and the search space is determined by using the previous population entropy, thus reducing the waste of search space, and improving the searching speed and accuracy of convergence. Simulation results demonstrate the algorithm has better optimization performance, and it is suitable for the spacecraft trajectory optimization. [ABSTRACT FROM AUTHOR]

Aiming at planning the vehicle's entry trajectory for Mars Pin-Point Landing, a new method based on hp-Radau pseudospectral algorithm is proposed. The vehicle's dynamics, state constraints during Mars Entry phase and vehicle' s mobility and safety constraints are taken into consideration synthetically. By combining the properties of collocation points of hp-Radau pseudospectral algorithm, the problem of trajectory optimization can be converted into a large-scale parameters optimization problem with multi-constraints, thus a solving framework of trajectory optimization is obtained. Also, the analytical form of Jacbian matrix of performance index and constraint equations is derived in order to improve the method's efficiency. The simulation result indicates that; (1) the hp-Radau pseudospectral algorithm can be used to solve the trajectory optimization problem during Mars Entry ,and has more efficient performance compared with the radau pseudospectral algorithm; (2) Compared with the numeric difference method, the analytical form of Jacbian matrix could substantially increase the method's efficiency and time-consuming stability by 58.75% and 85.58% respectively. [ABSTRACT FROM AUTHOR]

Trajectory optimization for spacecraft proximity maneuver with vision guidance path constraints is studied in this paper. At the beginning, the model of spacecraft proximity orbit maneuver for elliptic orbit optimization problem with path constraints is built. After that, the optimal problem is transformed into a Nonlinear Programming problem (NLP) by using gauss pseudospectral method. The state variables and control variables are selected as optimization parameters at all collocation nodes. Then, the resulting NLP is solved by using MATLAB software package SNOPT. Finally, simulation results verify that the proposed method is valid and robust. [ABSTRACT FROM AUTHOR]

The global optimal 4-D trajectory (t, x, y, z) for a spacecraft controlled by low thrust and launched from the Earth to fly around the Sun is proposed in this paper. To optimize the 4-D trajectory of the spacecraft, a set of numerical algorithm, including a searching algorithm and a 4-D trajectory optimization algorithm is presented. The searching algorithm is used for finding as many as possible asteroids near the 4-D trajectory of the Earth chosen from all the 248997 asteroids in the whole Sun system. The performance index of optimal trajectory is to maximize the number of asteroids met with the spacecraft and the rendezvous times with them, and also maximize the final mass. The 4-D trajectory optimization algorithm is composed of improved dynamic programming algorithm, conjugate gradient algorithms based on optimal control theory and static parameter optimization algorithm. Based on a great deal of numerical flight simulation by using this combined algorithm, the 4-D optimal trajectory of the spacecraft is obtained, the spacecraft passes by 12 asteroids among the 248997 asteroids in the whole Sun system within one year. [ABSTRACT FROM AUTHOR]

A high efficient hybrid algorithm based on support vector machine (SVM) and genetic algorithm (GA) is proposed for near space vehicle trajectory optimization with multiple constraints. The mathematical model for trajectory optimization is derived and the trajectory optimization problem is converted into a parameter optimization problem through parameterization and penalty function approach. The parameter optimization problem is solved by a hybrid trajectory optimization algorithm, in which SVM is used to classify chromosomes generated during GA operation in order to eliminate unfitted chromosomes and accelerate optimization speed An example used for downrange optimization in the proposed algorithm is presented, and simulation results show that the proposed approach is more efficient than the approach based on basic GA. [ABSTRACT FROM AUTHOR]