This paper provides an alternative lambert solution based on the terminal velocity vector. The chordal terminal velocity component is selected as the independent variable since it is the final required parameter in La...
详细信息
This paper provides an alternative lambert solution based on the terminal velocity vector. The chordal terminal velocity component is selected as the independent variable since it is the final required parameter in lambert's problem and it can be directly solved in the minimum-fuel free-time impulsive targeting problem. The transfer time for arbitrary conic transfer is written as a function only of the terminal velocity component. The admissible ranges of the new independent variable are analytically derived for different trajectory types. The 180 deg case and the multiple-revolution case are also considered. The analytical derivative of transfer time is provided to improve computational efficiency in numerical iterations. Compared with the existing lambert methods, the proposed approach is direct from the viewpoint of problem and physically more intuitive, although it is not superior in numerical performance.
This paper presents a novel and fast solver for the J2-perturbed lambert problem. The solver consists of an intelligent initial guess generator combined with a differential correction procedure. The intelligent initia...
详细信息
This paper presents a novel and fast solver for the J2-perturbed lambert problem. The solver consists of an intelligent initial guess generator combined with a differential correction procedure. The intelligent initial guess generator is a deep neural network that is trained to correct the initial velocity vector coming from the solution of the unperturbed lambert problem. The differential correction module takes the initial guess and uses a forward shooting procedure to further update the initial velocity and exactly meet the terminal conditions. Eight sample forms are analyzed and compared to find the optimum form to train the neural network on the J2-perturbed lambert problem. The accuracy and performance of this novel approach will be demonstrated on a representative test case: the solution of a multirevolution J2-perturbed lambert problem in the Jupiter system. The performance of the proposed approach will be compared against a classical standard shooting method and a homotopy-based perturbed lambert algorithm. It will be shown that, for a comparable level of accuracy, the proposed method is significantly faster than the other two.
This paper presents a novel fuel-efficient continuous-thrust maneuver targeting (CTMT) algorithm that is capable of planning finite, continuous maneuvers in a larger autonomous spacecraft guidance architecture. This i...
详细信息
This paper presents a novel fuel-efficient continuous-thrust maneuver targeting (CTMT) algorithm that is capable of planning finite, continuous maneuvers in a larger autonomous spacecraft guidance architecture. This is accomplished using a constant-thrust bilinear tangent guidance law in conjunction with an optimal lambert algorithm and a Newton-Raphson predictor-corrector targeting scheme. This simple approach is capable of planning a plethora of different free-time and fixed-time single-burn, burn-coast intercept, or burn-coast-burn bilinear tangent maneuvers from an initial state/orbit to a desired state/orbit. For the study case of asteroid Bennu, when used with thrust levels that are greater than 5% of the surface acceleration of asteroid Bennu, the CTMT algorithm is able to converge on 99% of orbital transfers initiated from a circular, 1.5 km, terminator orbit. Furthermore, many of the continuous-thrust maneuvers calculated by the CTMT algorithm are the optimal constant-thrust trajectories between two states in the small-body dynamical environment, and they are able to be calculated hundreds of times faster with the CTMT algorithm than with state-of-the-art nonlinear optimization algorithms. Ultimately, the CTMT algorithm shows promise as a candidate for future autonomous guidance applications.
In multigravity-assist trajectory optimization, the size of the design space is a variable itself. The objective functions are usually replete with local minima. This paper presents a multi-objective hidden genes gene...
详细信息
In multigravity-assist trajectory optimization, the size of the design space is a variable itself. The objective functions are usually replete with local minima. This paper presents a multi-objective hidden genes genetic algorithm (MOHGGA) for trajectory optimization. The length of the chromosome is selected large enough to enable modeling a given maximum number of swing-bys and maximum number of deep space maneuvers (DSMs). Binary tags are appended to those genes that control the swing-bys and DSMs. These binary tags are used to remove/add swing-bys and DSMs to a trajectory solution, and hence enable optimization among solutions of different sizes (different topologies). The MOHGGA generates Pareto fronts that have solutions of, in general, different number of swing-bys, swing-by planets, launch and arrival dates, and number of DSMs. Two objectives are considered in this paper: the total mission cost and total time of flight. An elitist nondominated sorting genetic algorithm is used. Local optimization is conducted on one objective function, holding the other objective function constant, to further improve the resulting Pareto front. Numerical results of four benchmark test cases for missions to Mars, Jupiter, Saturn, and Mercury are presented. The results demonstrate the capability of MOHGGA in searching for optimal trajectory topologies while optimizing two objectives.
This paper proposes a new approach to solve lambert's problem using analytic gradient information. The initial flight-path angle has been selected as an iterator variable, and the gradient of the transfer time wit...
详细信息
This paper proposes a new approach to solve lambert's problem using analytic gradient information. The initial flight-path angle has been selected as an iterator variable, and the gradient of the transfer time with respect to the iterator variable has been derived using conditions for an orbital two-point boundary value problem for update of the flight-path angle at each iteration step. A comprehensive experimental study has been conducted to demonstrate the validity of the proposed algorithm. The study results indicate that the proposed algorithm converges in all problem instances generated in the experiments and its efficiency is comparable to that of one of the best published methodologies.
This paper proposes a dynamic algorithm selection procedure to accelerate the lambert's problem routine composed of two phases - the preparation phase and the execution phase. In the preparation phase, a performan...
详细信息
This paper proposes a dynamic algorithm selection procedure to accelerate the lambert's problem routine composed of two phases - the preparation phase and the execution phase. In the preparation phase, a performance comparison framework for different lambert algorithms using their characteristic parameters and cost formulae is used to generate a performance map containing the information on best algorithms for test problem instances. In the execution phase, the best algorithm for the given problem instance is selected based on the algorithm selection parameters and the performance map created in the preparation phase, and the instance is solved using the selected algorithm. The comparison results of experiments to solve a large number of test problem instances using the proposed procedure and the traditional static algorithm selection for three popular lambert algorithms demonstrate the effectiveness of the dynamics algorithm selection. (C) 2016 Elsevier Masson SAS. All rights reserved.
Practical uncertainties are not considered by optimal rendezvous trajectory designs proposed in many current studies. In this study, a robust optimization method for on-ground rendezvous trajectory design is proposed ...
详细信息
Practical uncertainties are not considered by optimal rendezvous trajectory designs proposed in many current studies. In this study, a robust optimization method for on-ground rendezvous trajectory design is proposed by considering the uncertainties and orbital replanning process. Two robust performance indices related to the final rendezvous errors and the total velocity increment v are first defined, then a multi-objective optimization model (including the minimum v and minimum rendezvous errors) is formulated. The unscented transformation method is used to efficiently compute the robust indices in optimization process, and a multi-objective, nondominated sorting genetic algorithm is employed to obtain a Pareto-optimal solution set. It is shown that the proposed approach can be used to design a rendezvous trajectory with the v and final rendezvous errors that are both robust against uncertainties. Furthermore, the proposed approach can identify the most preferable design space in which specific solutions for practical application of rendezvous control are selected.
Two methods for deriving first-order partial derivatives of the outputs with respect to the inputs of the lambert boundary value problem are presented. The first method assumes the lambert problem is solved via the un...
详细信息
Two methods for deriving first-order partial derivatives of the outputs with respect to the inputs of the lambert boundary value problem are presented. The first method assumes the lambert problem is solved via the universal vercosine formulation. Taking advantage of inherent symmetries and intermediate variables, the derivatives are expressed in a computationally efficient form. The typical added cost of computing these partials is found to be approximate to 15 to 35% of the lambert computed cost. A second set of the same partial derivatives is derived from the fundamental perturbation matrix, also known as the state transition matrix of the Keplerian initial value problem. The equations are formulated in terms of Battin's partitions of the state transition matrix and its adjoint. This alternative approach works with any lambert formulation, including one that solves a perturbed lambert problem, subject to the availability of the associated state transition matrix. The analytic partial derivatives enable fast trajectory optimization formulations that implicitly enforce continuity constraints via embedded lambert problems.
The Battin, Gooding, and Sun algorithms are able to converge for nearly 100% of all orbit combinations. Both the Gooding and Sun algorithms have approximately the same performance, whereas the Battin algorithm is cons...
详细信息
The Battin, Gooding, and Sun algorithms are able to converge for nearly 100% of all orbit combinations. Both the Gooding and Sun algorithms have approximately the same performance, whereas the Battin algorithm is consistently slower. The performance for each lambert algorithm, when run on the graphics processing unit (GPU), has been compared. Each lambert solution algorithm is able to compute tens of millions of solutions per second, with Sun's method having the best performance at nearly 32 million solutions per second. This represents an increase in performance of two orders of magnitude when using GPUs over standard CPU algorithms. Although even the grid search CPU run times are not high when compared with common high-performance computing algorithms, mission optimization algorithms often require run times ranging from hours to multiple days. By offloading computations for solutions to lambert's problem to GPU(s) and sufficiently parallelizing optimization algorithms, performance increases of up to two orders of magnitude can be realized when compared with standard CPU algorithms. This will allow mission designers to quickly compute complex trajectories when evaluating potential mission architectures.
A function has been developed that bypasses Battin's infinite continued fraction evaluations for the universal lambert problem. The ATANR(x) function requires three mathematical functions that are already intrinsi...
详细信息
A function has been developed that bypasses Battin's infinite continued fraction evaluations for the universal lambert problem. The ATANR(x) function requires three mathematical functions that are already intrinsic to most computer languages, and frees the user from having to evaluate the equivalent infinite continued fractions. As such, the universal lambert equation is refined somewhat to make the solution more readily implemented as a mathematical subroutine. The computational accuracy for the ATANR(x) is well within the expected square root of machine precision over the vast majority of the domain. One can expand the partition's width near the local discontinuity and evaluate the appropriate function using the first two partial convergents of the true representation to approximate their behavior.
暂无评论