Unmanned Aircraft Systems (UAS) have seen unprecedented levels of growth during the last two decades. Although many challenges still exist, one of the main UAS focus research areas is in navigation and control. This paper provides a comprehensive overview of helicopter navigation and control, focusing specifically on small-scale traditional main/tail rotor configuration helicopters. Unique to this paper, is the emphasis placed on navigation/control methods, modeling techniques, loop architectures and structures, and implementations. A 'reference template' is presented and used to provide a basis for comparative studies and determine the capabilities and limitations of algorithms for unmanned/autonomous flight, as well as for navigation, and control. A detailed listing of related research is provided, which includes model structure, helicopter platform, control method and loop architecture, flight maneuvers and results for each. The results of this study was driven by and has led to the development of a 'one-fits-all' comprehensive and modular navigation controller and timing architecture applicable to any rotorcraft platform.
A modal approach is investigated for real-time deformation shape prediction of lightweight unmanned flying aerospace structures, for the purposes of Structural Health Monitoring (SHM) and condition assessment. The deformation prediction algorithm depends on the modal properties of the structure and uses high-resolution fiber-optic sensors to obtain strain data from a representative aerospace structure (e.g., flying wing) in order to predict the associated real-time deflection shape. The method is based on the use of fiber-optic sensors such as optical Fiber Bragg Gratings (FBGs) which are known for their accuracy and light weight. In this study, the modal method is examined through computational models involving Finite-Element Analysis (FEA). Furthermore, sensitivity analyses are performed to investigate the effects of several external factors such as sensor locations and noise pollution on the performance of the algorithm. This work analyzes the numerous complications and difficulties that might potentially arise from combining the state-of-the-art advancements in sensing technology, deformation shape prediction, and structural health monitoring, to achieve a robust way of monitoring ultra lightweight flying wings or next-generation commercial airplanes.
Recent improvements in technology has enabled the use of very sophisticated sensors such as embedded fiber bragg gratings (FBGs) to obtain strain measurements from a variety of structural types. Conventional strain gauges tend to be heavy and bulky. Because of their accuracy, light weight, small size and flexibility these fiber optic sensors have big potential to be used in space exploration and the aerospace industry especially for flying aircraft that have strict weight and size limitations. These strain measurements can be used to predict the deformation shape of aircraft during real-time flights. The development of such methods for monitoring and control can potentially reduce the risk of in-flight breakups, such as that of the Helios Wing. The Structures, Propulsion, And Control Engineering (SPACE) NASA sponsored University Research Center (URC) of excellence has concentrated in the development of small, lightweight Uninhabited Air Vehicles (UAVs) that have excelled in the area of endurance. Today, the UAV project is focused on the design of a multi-mission multipurpose air system that can operate autonomously. The configuration is a twin boom, pusher, and conventional wing design. In this paper, methods developed by the National Aeronautic and Space Administration (NASA)鈥檚 Dryden Flight Research Center for real-time deformation shape prediction of lightweight unmanned flying aerospace structures for the purposes of Structural Health Monitoring (SHM) and condition assessment are investigated. SHM may allow for useful monitoring that would prevent such an event by providing wing shape information and structural monitoring to either a pilot or the flight system, allowing for evasive maneuvers before the breakup would occur. These methods also have the potential for increasing safety, allowing monitoring of structural integrity, detecting damages, and providing real-time flight control feedback. These methods are applied to the SPACE Center UAV for the purpose of assessing the effectiveness of the method and the potential for both SHM and control applications. In this paper, a computational finite element model of the SPACE Center UAV is developed and used to examine the method.
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