The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information AFRL/RQQA SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-RQ-WP-TR-2016-0001 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTESThis is a Small Business Innovation Research (SBIR) Phase III report. Barron Associates, Inc. has waived its SBIR data rights, and the report has been approved for public release (PA Case Number: 88ABW-2016-1452; Clearance Date: 11 March 2016). ABSTRACTThis report was developed under a SBIR contract. This report describes the technical progress made by Barron Associates, Inc. and its partners in runtime assurance (RTA) systems, which hold the promise of protecting advanced systems that cannot be fully certified at design time due to their inherent complexity. A number of technical hurdles remain in the implementation of RTA systems for highly complex safety-critical systems, and the main objective of this effort was to further address these issues. One main focus of this project was to investigate the necessary structure of RTA frameworks for multi-level interacting feedback systems. As such, a challenge problem was constructed for a fleet of unmanned aircraft systems (UASs) performing a surveillance mission. The demonstration platform consisted of RTA systems for the inner-loop control, outer-loop guidance, ownship flight management, and fleet mission planning elements. The framework design and certification requirements for such a system were explored in this program. For the inner-loop, the concept of employing multiple transition controllers in the reversionary control system was studied. For all feedback levels, the required RTA checks were developed and the critical reversionary switching conditions defined. The interactions between the RTA protected systems and certified collision avoidance systems were also investigated. A safety case argument for design-time certification of the RTA protected systems was constructed using subsystem requirements contracts that were developed from a compositional reasoning approach explored over the course of the project.

This paper summarizes development of a sense and avoid system (SAA) for a fleet of unmanned aircraft systems (UASs) in formation flight that are threatened by a noncooperative intruder. The intruder is not transponding its position and is assumed to be unaware of the impending collision. It is assumed the UASs are equipped with electrooptical, forward-looking infrared cameras, or other sensors such as radar to detect the intruder. Low-level sensor processing, detection, and tracking systems are not the focus of this work; however, we do explore the unique sensor fusion and estimation capabilities afforded by a formation of UASs. Using intra-fleet communication and a sensor fusion algorithm, the formation aircraft effectively form a stereo-optic solution by sharing their sensory information, which provides a rapidly-converging estimate of the intruder's position and velocity. At the core of the SAA system is a conflict resolution algorithm that continuously generates and updates a resolution path which satisfies a hierarchical set of safety constraints, including a pre-defined "well clear" volume. If the well clear criterion cannot be achieved, due to late detection of the intruder, for example, the conflict resolution algorithm maximizes the separation distance. The conflict resolution algorithm can generate a lateral avoidance maneuver, a vertical avoidance maneuver, or a combined maneuver, depending on the scenario and a user-defined resolution "strategy". The resolution strategy allows the overall system to adapt to evolving regulations and practices related to UAS incorporation in the NAS and other theaters. The airspeed of the formation can also be adjusted to aid in conflict resolution. The SAA algorithm has the ability to keep the fleet in formation during the conflict avoidance, or depending on the geometry of the scenario, allow the formation to split into sub-formations, each executing a separate avoidance path.

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A statistically based frequency-domain method for using flight data to update aerodynamic data tables used in flight simulators is developed and demonstrated. The capability to accurately and automatically update a simulation to incorporate nonlinear and unsteady aerodynamic effects embodied in the flight data is demonstrated. Useful features of this novel frequency-domain approach are highlighted, including computational efficiency, noise rejection, automated model structure determination in the frequency domain for nonlinear and unsteady aerodynamics, and the ability to generate simulation updates without air flow angle measurements in the flight data. An F-16 nonlinear simulation is used to demonstrate the technique.