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Aerospace Design Group

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End date: 2004 × Start date: 2004 × Has files: Yes × search.filters.applied.f.resourcesubtype: Proceedings ×

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Approaches to Vision-Based Formation Control

2004-12 , Johnson, Eric N. , Calise, Anthony J. , Sattigeri, Ramachandra J. , Watanabe, Yoko , Madyastha, Venkatesh

This paper implements several methods for performing vision-based formation flight control of multiple aircraft in the presence of obstacles. No information is communicated between aircraft, and only passive 2-D vision information is available to maintain formation. The methods for formation control rely either on estimating the range from 2-D vision information by using Extended Kalman Filters or directly regulating the size of the image subtended by a leader aircraft on the image plane. When the image size is not a reliable measurement, especially at large ranges, we consider the use of bearing-only information. In this case, observability with respect to the relative distance between vehicles is accomplished by the design of a time-dependent formation geometry. To improve the robustness of the estimation process with respect to unknown leader aircraft acceleration, we augment the EKF with an adaptive neural network. 2-D and 3-D simulation results are presented that illustrate the various approaches.

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Coordinated Decentralized Adaptive Output Feedback Control of Interconnected Systems

2004-06 , Hovakimyan, Naira , Lavretsky, Eugene , Yang, Bong-Jun , Calise, Anthony J.

A decentralized adaptive output feedback control design is proposed for large-scale interconnected systems. It is assumed that all the controllers share prior information about the system reference models. A linearly parameterized neural network is introduced for each subsystem to partially cancel the effect of the interconnections on tracking performance. Boundedness of error signals is shown through Lyapunov's direct method.

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Small Adaptive Flight Control Systems for UAVs Using FPGA/DSP Technology

2004-09 , Christophersen, Henrik B. , Pickell, Wayne J. , Koller, Adrian A. , Kannan, Suresh K. , Johnson, Eric N.

Future small UAVs will require enhanced capabilities like seeing and avoiding obstacles, tolerating unpredicted flight conditions, interfacing with payload sensors, tracking moving targets, and cooperating with other manned and unmanned systems. Cross-platform commonality to simplify system integration and training of personnel is also desired. A small guidance, navigation, and control system has been developed and tested. It employs Field Programmable Gate Array (FPGA) and Digital Signal Processor (DSP) technology to satisfy the requirements for more advanced vehicle behavior in a small package. Having these two processors in the system enables custom vehicle interfacing and fast sequential processing of high-level control algorithms. This paper focuses first on the design aspects of the hardware and the low-level software. Discussion of flight test experience with the system controlling both an unmanned helicopter and an 11-inch ducted fan follow.

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An Adaptive Vision-based Approach to Decentralized Formation Control

2004-08 , Sattigeri, Ramachandra J. , Calise, Anthony J. , Evers, Johnny H.

In considering the problem of formation control in the deployment of intelligent munitions, it would be highly desirable, both from a mission and a cost perspective, to limit the information that is transmitted between vehicles in formation. In a previous paper, we proposed an adaptive output feedback approach to address this problem. Adaptive formation controllers were designed that allow each vehicle in formation to maintain separation and relative orientation with respect to neighboring vehicles, while avoiding obstacles. In this paper, we consider a modification to the adaptive control law that enables each vehicle in a leader-follower formation to track line-of-sight (LOS) range with respect to two or more neighboring vehicles with zero steady-state error. We also propose a coordination scheme in which each vehicle tracks LOS range to up to two nearest vehicles while simultaneously navigating towards a common set of waypoints. This coordination scheme does not require a unique leader for the formation, increasing robustness of the formation. As our results show, such leaderless formations can perform maneuvers like splitting to go around obstacles, rejoining after negotiating the obstacles, and changing into line-shaped formation in order to move through narrow corridors.

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