Entry guidance with smooth drag planning and non-linear tracking. (June 2017)

• Record Type: Journal Article
• Authors: Gifty, R.; Rajeev, U.P.; Lalithambika, V.R.; Dhekane, M.V.
• Is Part Of: Control engineering practice. Volume 63(2017)
• Page Start: 24
• Page End: 33
• Publication Date: 2017-06
• Subjects: Entry phase -- Energy dissipation -- Cubic splines -- Bank angle -- Continuous drag modulation -- Incremental dynamic inversion; Automatic control -- Periodicals; 629.89
• DOI: 10.1016/j.conengprac.2017.03.014
• Languages: English
• ISSNs: 0967-0661

Abstract

Abstract: A guidance strategy is developed for the entry phase, meeting range requirements while honouring the constraints on heat flux, dynamic pressure and structural load on the vehicle. Space shuttle guidance is taken as the baseline and an improved strategy to plan and track a reference drag acceleration profile is developed. Trajectory planning is done in drag-energy plane. Drag acceleration and its derivatives are stored as function of specific energy. An analytical, continuous drag modulation strategy is developed for generating the reference trajectory on-board honouring the constraints. The modulated reference trajectory is tracked by a non-linear controller using Incremental Non-linear Dynamic Inversion technique (INDI). The guidance scheme is demonstrated in a short-range re-entry technology demonstrator vehicle. Simulation studies are carried out to establish the robustness of the guidance algorithm for a wide range of performance dispersions. Abstract : Highlights: A guidance strategy is developed for the entry phase, meeting range requirements while honouring the constraints on heat flux, dynamic pressure and structural load on the vehicle. Trajectory planning is done in drag-energy plane. An analytical modulation strategy with a continuous modulation factor is used which avoids discontinuity in commands. If the modulated reference profiles violates the constraint boundary, trajectory re-shaping is done such that the constraints are honoured. Trajectory tracking is done by a non-linear controller using Incremental Non-linear Dynamic Inversion (INDI) which does not call for gain scheduling. The algorithm is versatile and the dependency of tracking controller design on trajectory is reduced.