The problem of air-to-surface trajectory optimization for a low-altitude skid-to-turn vehicle is considered. The objective is for the vehicle to move level at a low altitude for as long as possible and perform a rapid bunt (negative sensed-acceleration load) maneuver near the final time in order to attain terminal target conditions. The vehicle is modeled as a point mass in motion over a flat Earth, and the vehicle is controlled using thrust magnitude, angle of attack, and sideslip angle. The trajectory
optimization problem is posed as a two-phase optimal control problem using a weighted objective function. The work described in this paper is the first part of a two-part sequence on trajectory optimization and guidance of a skid-to-turn vehicle. In both cases, the objective is to minimize the time taken by the vehicle to complete a bunt maneuver subject to the following constraints: dynamic, boundary, state, path, and interior-point event constraints. In the first part of this two-part study, the performance of thevehicle is assessed. In particular, the key features of the optimal reference trajectories and controls are provided. The results of this study identify that as greater weight is placed on minimizing the height of the bunt maneuver or as the maximum altitude constraint is raised, the time of the bunt maneuver decreases and the time of the problem solution increases. Also, the results of this study identify that as the allowable crossrange of the vehicle is reduced, the time and height of the bunt maneuver increases and the time of the problem solution decrease
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Performance Optimization and Guidance of a Low-Altitude Skid-to-Turn Vehicle. Part II: Optimal Guidance
The problem of guidance and control of an air-to-surface low-altitude skid-to-turn vehicle is considered. The objective is to steer the vehicle to a ground target from an initial state such that the vehicle remains at a constant low altitude for as long as possible and performs a bunt maneuver (negative sensed-acceleration load) rapidly at the end of the trajectory in order to attain terminal target conditions. The vehicle is modeled as a point mass in motion over a flat Earth, and the vehicle is controlled using thrust magnitude, angle of attack, and sideslip angle. The guidance and control problem is posed as a decreasing-horizon optimal control problem and is re-solved numerically at constant guidance cycles. The work described in this paper is the second part of a two-part sequence on trajectory optimization and guidance of a skid-to-turn vehicle. In both cases, the objective is to minimize the time taken by the vehicle to complete a bunt maneuver subject to the following constraints: dynamic, boundary, state, path, and interior-point event constraints. In the second part of this two-part study, a numerical guidance law is employed to re-solve the optimal control problem on a shrinking horizon. An assessment is made as to the time required to re-solve the optimal control problem both in the absence and presence of a time delay, where the time delay is the amount of time required to solve the numerical approximation of the optimal control problem at the start of each guidance cycle. The results of this study identify that in the absence and presence of a time delay, the size of the mesh on subsequent guidance cycles decreases, the time required to solve the reduced-horizon optimal control problem is small compared to the guidance cycle duration time, and the terminal conditions are met with sufficient accuracy. Thus, the results show that the guidance law presented in this paper has the potential to solve optimal control problems in real-time.
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- NSF-PAR ID:
- 10094024
- Date Published:
- Journal Name:
- 2019 AIAA Guidance, Navigation, and Control Conference, San Diego
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2019-0355
