Integrated Adaptive Guidance and Control for Re-Entry Vehicles with Flight Test Results

TLDR

The trajectory‑reshaping algorithm is known as the optimum‑path‑to‑go methodology. The study aimed to demonstrate that integrating trajectory reshaping with control reconfiguration and guidance adaptation enables autonomous recovery of reusable launch vehicles after major anomalies. The system, tested on Boeing’s X‑40A, uses a model‑following/dynamic‑inversion inner loop with optimal control allocation, a backstepping guidance law with adaptive gains, and an offline‑precomputed trajectory database queried in flight to select the best reshaped path according to current control authority. Flight tests showed that when multiple control failures occur, only the combination of control reconfiguration, guidance adaptation, and trajectory reshaping can recover the mission.

Abstract

To enable autonomous operation of future reusable launch vehicles, reconfiguration technologies will be needed to facilitate mission recovery following a major anomalous event. The Air Force’s Integrated Adaptive Guidance and Control program developed such a system for Boeing’s X-40A, and the total in-flight simulator research aircraft was employed to flight test the algorithms during approach and landing. The inner loop employs a modelfollowing/dynamic-inversion approach with optimal control allocation to account for control-surface failures. Further, the reference-model bandwidth is reduced if the control authority in any one axis is depleted as a result of control effector saturation. A backstepping approach is utilized for the guidance law, with proportional feedback gains that adapt to changes in the reference model bandwidth. The trajectory-reshaping algorithm is known as the optimum-path-to-go methodology. Here, a trajectory database is precomputed off line to cover all variations under consideration. An efficient representation of this database is then interrogated in flight to rapidly find the “best” reshaped trajectory, based on the current state of the vehicle’s control capabilities. The main goal of the flight-test program was to demonstrate the benefits of integrating trajectory reshaping with the essential elements of control reconfiguration and guidance adaptation. The results indicate that for more severe, multiple control failures, control reconfiguration, guidance adaptation, and trajectory reshaping are all needed to recover the mission.