Guided Airdrop System Research Articles

Adaptive Control of Precision Guided Airdrop Systems with Highly Uncertain Dynamics

The bulk of research in the field of precision guided airdrop systems has focused on improving landing accuracy in the presence of atmospheric winds that can exceed vehicle airspeed. One important challenge of parafoil systems is their highly uncertain flight dynamic behavior and control response, which can result from canopy degradation or an offnominal inflation event. This significantly impacts the ability to reach the target and can often lead to very large miss distances. This work addresses guided airdrop system model uncertainty with a novel combined direct and indirect adaptive control strategy to quickly characterize vehicle dynamics and lateral control sensitivity in flight. Extensive simulation and experimental flight testing indicate that the proposed adaptive algorithm is capable of high-accuracy landing in a large variety of degraded conditions, including unknown nonlinear changes in control sensitivity as well as control reversals. In comparison, current industry standard algorithms experience over an order of magnitude decrease in accuracy when tested under identical scenarios.

Autonomous Airdrop Systems Employing Ground Wind Measurements for Improved Landing Accuracy

Aerial cargo delivery, also known as airdrop, systems are heavily affected by atmospheric wind conditions. Guided airdrop systems typically employ onboard wind velocity estimation methods to predict the wind in real time as the systems descend, but these methods provide no foresight of the winds near the ground. Unexpected ground winds can result in large errors in landing location, and they can even lead to damage or complete loss of the cargo if the system impacts the ground while traveling downwind. This paper reports on a ground-based mechatronic system consisting of a cup and vane anemometer coupled to a guided airdrop system through a wireless transceiver. The guidance logic running on the airdrop system's onboard autopilot is modified to integrate the anemometer measurements at ground level near the intended landing zone with onboard wind estimates to provide an improved, real-time estimate of the wind profile. The concept was first developed in the framework of a rigorous simulation model and then validated in the flight test. Both simulation and subsequent flight tests with the prototype system demonstrate reductions in the landing position error by more than 30% as well as a complete elimination of potentially dangerous downwind landings.

Synthesis of Optimal Control and Flight Testing of an Autonomous Circular Parachute

Development of guidance and control algorithms for autonomous solid circular parachutes is addressed. This effort is a part of the Affordable Guided Airdrop System that integrates a low-cost guidance and control system into fielded cargo air delivery systems. First, the underlying Affordable Guided Airdrop System concept, architecture, and components are described. Then a synthesis of a classical optimal control based on Pontrjagin’s maximum principle is suggested. Then the development of a practical control algorithm is detailed. Simulation and flight-test results of the final Affordable Guided Airdrop System demonstration are also presented.

GUIDANCE AND CONTROL OF AFFORDABLE GUIDED AIRDROP SYSTEM

This paper addresses the development of an autonomous guidance, navigation and control system for a flat solid circular parachute. This effort is a part of the Affordable Guided Airdrop System (AGAS) that integrates a low-cost guidance and control system into fielded cargo air delivery systems. The paper describes the AGAS concept, its architecture and components. It further proceeds with the description of the control strategy based on Pontrjagin's principle of optimality. The paper ends with the results of the final AGAS demonstration performed at the U.S. Army Yuma Proving Ground in September, 2001.

Guidance and Control for Flat-Circular Parachutes

The Affordable Guided Airdrop System (AGAS) is being evaluated as a low-cost alternative for meeting the military’ s requirements for precision airdrop. Designed to bridge the gap between relatively expensive high-glide ratio parafoil systems and uncontrolled ballistic parachutes, the AGAS concept offers the benee ts of high-altitude parachute releases as well as the potential for highly accurate point-of-use delivery of material. The design goal of the AGAS development is to provide a guidance, navigation, and control system that can be placed in line with cargo parachute systems, for example the G-12 e at-circular parachute, and standard delivery containers (A-22) without modifying these e elded systems. The AGAS is required to provide an accuracy of 328 ft (100 m), circular error probable (CEP), with a desired goal of 164 ft (50 m) CEP. The feasibility of this concept was investigated through modeling and simulation. A three-degree-of-freedom (3DOF) point mass e ight dynamics model, sensor models of a commercial global positioning system (GPS) receiver and magnetic compass, and a model of the control and actuator system were incorporated into a Monte Carlo simulation tool. A bang-bang controller was implemented with trajectory tracking algorithms using position and heading information. Flight testing, using a radio-controlled scaled prototype, provided parachutedynamic and control response data to support themodeling efforts.Thestudy demonstrated thatthisconcepthas thepotential to providecontrolofpreviously unguided round parachutes to accuracies of approximately 210 ft (64 m) CEP. The program is now continuing into the next phase to include the development of a full-scale prototype system for payloads up to 2200 lb (1000 kg).