This paper is concerned with the problem of the two-dimensional optimal online trajectory generation for a flying robot for terrain following/terrain avoidance purposes using neural network. To this end, the terrain is modeled as a terrain following constraint. In the next step, the inverse dynamics method is utilized for offline trajectory generation. Since the main objective of this research is online trajectory generation, the neural network method is employed for this purpose. To train the neural network, various approaches such as steepest descent, conjugate gradient, resilient back propagation, and Levenberg-Marquardt are explored in detail, and finally, the Levenberg-Marquardt method is selected on account of some merits. The efficacy of the neural network method is demonstrated by extensive simulations, and in particular, it is verified that this method is able to produce a solution satisfying all hard constraints of the underlying problem.
In this paper, a new path planning method is proposed to resolve the problem of two-dimensional terrain following flight of flying robots in mountainous regions. The performance criteria considered for this mission design could include either the minimum vertical acceleration or the minimum flying time. To impose the terrain following/terrain avoidance constraints, various approaches such as least square method, Fourier series method, Gaussian estimation method, and Chebyshev orthogonal polynomial are explored. The resulting optimal control problem is discretized by employing a numerical technique namely direct collocation and then transformed into a nonlinear programming problem. The efficacy of the proposed method is demonstrated by extensive simulations, and particularly, it has been verified that this method is able to produce a solution that satisfies all hard constraints of the underlying problem.
In this paper, the problem of two dimensional Terrain Following / Terrain Avoidance trajectory optimization has been considered for an Unmanned Aerial Vehicle (UAV) in vertical flight plane. This problem is formulated as an optimal control problem, and then Direct Collocation method is employed as a solver tool for generating flyable path. Chebyshev polynomial has been used to model the geographical data of the terrain in a given route. The results indicate that the method is suitable for the terrain following problem especially in the case of producing more reliable flyable path based on the system dynamics, physical limitations and also the mission requirements.
This paper is concerned with the three-dimensional constrained optimal path planning. To this end, an objective function is defined as the shortest trajectory length in such a way that some constraints including rough terrain avoidance, forbidden zone avoidance, initial and terminal constraints, allowable altitude constraint and maximum allowable curvature of trajectory are satisfied. These leads to a challenging problem for aircraft guidance and control that solution requires great experience, skill, accuracy, and a powerful strategy. For this purpose, pseudospectral technique, which is one of the direct methods, is applied in this paper based on the Chebyshev nodes through which the complexity of the problem is reduced by transforming the optimal control problem into the parametric optimization one. The efficacy of the proposed method is demonstrated by extensive simulations, and it is particularly verified that this method is able to produce a solution satisfying all hard constraints of the underlying problem.
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