Browsing by Author "Kim, Youngil"

Now showing 1 - 3 of 3
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    Design framework for optimizing waypoints of vehicle trajectory considering terminal velocity and impact angle constraints
    (Taylor and Francis, 2021-05-17) Kim, Youngil; Cho, Namhoon; Park, Jongho; Kim, Youdan
    Ballistic missiles often require the terminal velocity and impact angle to be confined to a certain region around a desired value considering a wide variety of uncertain initial conditions and operational ranges. This study presents a design framework to determine optimum waypoints that satisfy constraints for given launch conditions and mission profiles. As a systematic approach to this kinodynamic motion planning problem, the proposed framework deterministically samples the waypoints. The trajectory generated by the determined waypoints in consideration of various conditions satisfies the terminal constraint. Numerical simulations are performed to demonstrate the effectiveness of the proposed method.
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    Guidance of gliding vehicles with energy management based on approximate prediction of speed
    (2022-05-05) Cho, Namhoon; Kim, Youngil; Shin, Hyosang; Kim, Youdan
    This study presents a guidance method for flight vehicles gliding in the vertical plane to achieve desired position and velocity at the final time. The proposed guidance algorithm combines two decoupled elements to plan future flight trajectories satisfying the given constraints at each guidance update cycle: i) parametric path generator, and ii) approximate speed predictor. The parametric path generator is capable of producing an altitude profile as a parametric function of downrange by solving a convex optimisation problem considering only the shape properties of a flight path. An approximate method for predicting the future speed history endows the proposed guidance algorithm with the capability to address energy management objectives in trajectory planning. Provided that an altitude profile is specified by the parametric path generator and the lift-to-drag ratio model is known, the approximation neglecting gravitational acceleration turns the speed dynamics along the given path into a scalar linear first order ordinary differential equation, the form which admits a closed-form solution that can be represented by definite integrals. In this way, the proposed method opens a possibility to update the trajectory in flight to achieve the desired final speed by reducing the computational load due to speed prediction task, although the predicted speed contains approximation errors of certain degrees.
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    ItemOpen Access
    Online trajectory replan for gliding vehicle considering terminal velocity constraint
    (IEEE, 2022-08-08) Kim, Youngil; Cho, Namhoon; Park, Jongho; Kim, Youdan
    Controlling the terminal velocity can improve the effectiveness of guided missiles. In particular, a ballistic missile propelled by solid rocket motors can successfully accomplish its mission when it hits the target at an appropriate speed. In this study, a method for modifying the trajectory of gliding vehicle, i.e., gliding ballistic missiles is proposed to meet the terminal velocity constraint by reflecting the effects of the environment during a flight. The proposed framework consisting of trajectory generation and dynamic propagation compensates for errors due to uncertainties in real time. The trajectory generation step provides various trajectories that satisfy the given constraints based on information about the current state. The dynamic propagation step efficiently predicts the terminal velocity for each of the generated trajectories and finds the trajectory with the lowest terminal speed error. A numerical simulation is performed considering various conditions to demonstrate the performance of the proposed method.