Adaptive glide slope control for autonomous airdrop systems

Abstract

Airdrop systems provide a unique capability of delivering large payloads to undeveloped and inaccessible locations. Guided airdrop systems based on steerable, ram-air parafoils have been developed with the goal of improving the precision and accuracy of air-dropped payload delivery. In practice, the gliding ability of the ram-air canopies can actually create major problems for airdrop systems by making them more susceptible to winds and allowing them to achieve far greater miss distances than were previously possible. Research and development work on guided airdrop systems has focused primarily on improving the guidance algorithm. By comparison, the navigation and control algorithms have changed little since the initial guided systems were developed. Furthermore, the control mechanisms have not changed since the invention of the ram-air canopy in the 1960's. This work seeks an improvement in landing accuracy over current state of the art airdrop systems through the incorporation of advanced control algorithms and novel control mechanisms. The key concepts utilized are system identification in real-time during each flight and glide slope control through in-flight incidence angle variation coupled with symmetric trailing edge brake deflection. Simulation and flight test results demonstrate a factor of two improvement in landing accuracy with the use of glide slope control. Simulation results also demonstrate that the adaptation of internal models with in-flight system identification can dramatically improve landing accuracy in situations where there is significant uncertainty in the system flight characteristics.