254 research outputs found
Orbit Transfer Manoeuvres as a Test Benchmark for Comparison Metrics of Evolutionary Algorithms
No full textIn the present paper some metrics for evaluating the performance of evolutionary algorithms are considered. The capabilities of two different optimisation approaches are compared on three test cases, represented by the optimisation of orbital transfer trajectories. The complexity of the problem of ranking stochastic algorithms by means of quantitative indices is analyzed by means of a large sample of runs, so as to derive statistical properties of the indices in order to evaluate their usefulness in understanding the actual algorithm capabilities and their possible intrinsic limitations in providing reliable information
Frenet-Based Algorithm for Trajectory Prediction
No full textAn algorithm for aircraft trajectory prediction is presented that is based on two algebraic representations of
the aircraft c.g. trajectory in the Frenet frame: (1) a cylindrical helix, during steady flight segments, and (2)
a third-order accurate expansion, during transient maneuvering phases. This technique allows for an efficient
evaluation of future c.g. positions in a time interval the extension of which depends on the aircraft maneuver state,
without requiring the implementation of the aircraft dynamic model. A Kalman filtering technique with a fixed-lag
smoother is used for simultaneously filtering the sensor noise and estimating accelerometer and rate-gyro signal
derivatives. The effect of a step variation of commanded load factor and/or roll angle on the aircraft position at
following times is displayed to the pilot as a visual aid for representing achievable future positions during the
maneuver. The algorithm is demonstrated by computer simulation of reverse turn maneuvers of an F-16 fighter
aircraft model
Model predictive control architecture for rotorcraft inverse simulation
No full textA novel inverse simulation scheme is proposed for applications to rotorcraft dynamic models. The algorithm adopts an architecture that closely resembles that of a model predictive control scheme, where the controlled plant is represented by a high-order helicopter model. A fast solution of the inverse simulation step is obtained on the basis of a lower-order, simplified model. The resulting control action is then propagated forward in time using the more complex one. The algorithm compensates for discrepancies between the models by updating initial conditions for the inverse simulation step and introducing a simple guidance scheme in the definition of the tracked output variables. The proposed approach allows for the assessment of handling quality potential on the basis of the most sophisticated model, while keeping model complexity to a minimum for the computationally more demanding inverse simulation algorithm. The reported results, for an articulated blade, single main rotor helicopter model, demonstrate the validity of the approach
A Simple Lambert Algorithm
No full textA classic result for the two-point boundary value problem in the framework of Keplerian motion allows the
derivation of a novel parametrization of orbits passing through two arbitrary points in space. In particular, it is
shown that these orbits can be unambiguously identified in terms of their eccentricity vector component in the
direction perpendicular to the chord connecting the two points. The parametrization, in terms of transverse
eccentricity component, lends itself to an efficient and intuitive solution algorithm for the classical Lambert problem,
that is, the determination of the orbit that connects two points in space in a prescribed time. Although, from the
computational point of view, the resulting numerical procedure does not provide advantages over the elegant
Battin’s method, its derivation is considerably less demanding from the mathematical standpoint and physically
more intuitive
Shape-Based Design of Low-Thrust Trajectories to Cislunar Lagrangian Point
No full textThe shape function is defined on the basis of a few parameters that can be modified by means of an optimization algorithm to improve transfer performance in some sense and guarantee its feasibility. The final solution does not need to be the optimal one, but it should provide a reasonable first guess for more sophisticated optimization procedures. Most of the applications of the shape-based approach are proposed in the framework of the two-body problem, where the spacecraft moves under the action of low thrust and a single primary body. This approach is reasonable for most mission scenarios, during preliminary steps of mission design, when approximate solutions are sufficient and a single primary mass is considered during each mission segment. However sometimes it is necessary to account for gravity pull from more than a single primary mass
- …
