Attitude Constrained Robust Explicit Guidance for Terminal Phase of Autonomous Lunar Soft-Landing

Padhi, R and Banerjee, A and Sai Kumar, PSVS and Parvathi, SP (2024) Attitude Constrained Robust Explicit Guidance for Terminal Phase of Autonomous Lunar Soft-Landing. In: Journal of the Astronautical Sciences, 71 (2).

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Abstract

An attitude-constrained jerk-minimizing optimal explicit terminal guidance is presented in this paper for the terminal phase of a multi-phase lunar soft-landing. An analytic expression for the acceleration vector serves as the guidance command that can be computed by low-speed onboard processors in real-time. High terminal accuracy in each phase is achieved by enforcing �hard terminal constraints� on the position, velocity, and acceleration (hence attitude) of the spacecraft. The initial conditions on position, velocity and acceleration are also enforced as hard constraints to ensure a smooth handover between consecutive phases. The required time-to-go is computed to minimize the deviation of the acceleration from the average of initial and final values. This results in a very smooth variation of the acceleration vector (hence attitude as well, owing to the strap-down nature of the thruster), starting from the applicable initial value to the desired final value in the segment. Along the trajectory, compatibility of the recomputed time-to-go in the absence of additional perturbation is maintained by auto-adjusting a tuning parameter. Moreover, if necessary, the time-to-go is adjusted once again to prevent altitude excursion beyond a pre-selected safety margin. This process of careful online auto-adjustment of the time-to-go, followed by using it to recompute the guidance command, makes the guidance operate in closed-loop with significant robustness. Consequently, it enables a larger capture region and introduces the capability to recover from partial failures, which are critical requirements for such challenging missions. © The Author(s), under exclusive licence to American Astronautical Society 2024.

Item Type:	Journal Article
Publication:	Journal of the Astronautical Sciences
Publisher:	Springer
Additional Information:	The copyright for this article belongs to Springer.
Keywords:	Landing; Lunar landing; Moon, Attitude constrained guidance; Landing guidance; Lunar soft landing; Minimum jerk guidance; Minimum jerks; Optimal guidance; Optimal guidance for soft-landing; Soft landing; Soft-landing guidance, Acceleration
Department/Centre:	Division of Interdisciplinary Sciences > Robert Bosch Centre for Cyber Physical Systems Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	28 Aug 2024 10:59
Last Modified:	28 Aug 2024 10:59
URI:	http://eprints.iisc.ac.in/id/eprint/84809

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