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Unmanned Aerial Vehicle - Demonstration of Autonomous Flight, 09-9822

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Principal Investigators
Richard D. Somers
Ronald D. Knuppel
Steven T. Spence
David A. Ogden

Inclusive Dates: 01/17/94 - 03/31/97

Background - In April 1993, a proposal team consisting of Alliant Techsystems, MI-TEX, and SwRI was formed to pursue the tactical unmanned aerial vehicle (TUAV) program. The corporate team supported its proposal with a demonstrator air vehicle that included flight sensors, autopilot, autonomous flight capability, uplink/downlink telemetry, and a ground control station with digital map-based mission-planning equipment. SwRI was tasked with producing all vehicle avionics, autonomous flight control development, flight software using the Ada language, antenna characterization, telemetry, ground controls and displays, and a full-fidelity personal computer-based flight simulator. The Aerospace Electronics and Training Systems Division and the Instrumentation and Space Research Division collaborated with the other proposal team members on these TUAV tasks. In May 1996, the corporate team was awarded the TUAV contract. The Aerospace Electronics and Training Systems Division was also awarded, as a separate development effort, the U.S. Marine Corps (USMC) autonomous resupply demonstration program, which culminated in a successful series of flights at the Marine Corps training center in Twenty-Nine Palms, California, and was filmed for an appearance on the Cable Network News. Proposal activity during April to November 1999 includes competition in a fly-off at Ft. Huachuca, Arizona, for the Limited Rate Initial Production contract for the U.S. Army TUAV program. SwRI supported all phases of this proposal including the operational tempo flights scheduled for November 2-8, 1999 at Ft. Huachuca.

Team development efforts began in mid-1993 when Alliant Techsystems conducted activities associated with the airframe, propulsion system, and flight test. During September 1993 to January 1994, the Institute sponsored a quick-look internal research program to characterize the air vehicle flight dynamics concurrently with three Alliant Techsystems-sponsored flight tests. Later, the Institute sponsored internal research activities to support a demonstration of autonomous flight, with Alliant Techsystems again funding airframe, propulsion, and flight test activities. The concurrent autonomous flight tasks occurred during 25 flights at Hondo, Texas, and Fort Sumner, New Mexico. Since the formal internal research program ended, two other programs have provided significant data for autonomous flight performance evaluation. From October 1994 to May 1995, 21 flights were completed using both the original airframe and the newly designed high-lift airframe. Division resources were used to support the autonomous control, data collection, and data analysis activities of these flights. From May 1995 to December 1996, SwRI provided flight test support for 17 flights sponsored and funded by Alliant Techsystems, including support for government-witnessed performance flights in March 1996 during the TUAV proposal evaluation. The USMC resupply vehicles were equipped with similar hardware and software, and 23 flights were completed between January 1997 to March 1997 for the USMC demonstration.

Approach - SwRI developed an unmanned aerial vehicle (UAV) control system concept based on global positioning system (GPS) guidance and radio control (R/C). SwRI analyzed the R/C transmitter messages that drive position information for the flaps, ailerons, rudder, throttle, nose wheel, and stabilator. The characterization provided real-time access to flight control commands that were used later in data acquisition and correlation. Existing Aerospace Electronics and Training Systems Division capital equipment was configured in the UAV to instrument altitude, altitude rate, airspeed, pitch, roll, yaw, GPS position, three-axes angular rates, and three-axes accelerations, as well as to provide a separate battery system and power bus for the instrumentation. Distributed processing systems were developed to share the load of data acquisition, computation, data storage, and downlink telemetry communications. Software preparation to support this program was divided into three parts: R/C command log, telemetry data receive and display, and the UAV operational flight program (OFP). Feasibility was demonstrated by simulation and test flights. The USMC program used an advanced version of the autonomous control with simplified lower cost commercial off-the-shelf (COTS) sensors and a spread-spectrum uplink/downlink radio modem.

Accomplishments - SwRI staff analyzed flight test data using hardware-in-the-loop simulators for takeoff, straight and level flight, controlled banks and turns, and landings. The data were used to refine SwRI computer models and simulation tools to assist in the development of future flight control systems development. Sensor data integrity, system noise characteristics, and antenna propagation patterns were also evaluated. SwRI developed a six-degree-of-freedom flight simulator for the UAV, based on standard flight rules and tailored using wind tunnel data. The hardware was low-cost, COTS equipment items. Flight computer command and control was provided by an SwRI-developed OFP developed in the Ada programming language. A mission planning and ground control station was also configured using COTS equipment and SwRI-developed display management software. The TUAV flight demonstration and proposal were successful. The autonomous flight capabilities of the TUAV demonstrated in this program were developed further under a government subcontract. From April to August 1997, a total of 206 flights were staged for the government at Hondo, Texas, and Ft. Hood, Texas.

In addition, the equipment and technology developed for the TUAV program are being applied to various other air vehicle platforms. The first successful demonstration of this technology transfer was the U.S. Marine Corps (USMC) resupply vehicle demonstration for the HUNTER WARRIOR military exercises. The TUAV used a powered ram-air parachute vehicle capable of fully autonomous takeoff, landing, and GPS waypoint guided flight. The demonstration vehicle achieved a flight altitude exceeding 10,000 feet and was designed for a flight duration greater than eight hours. SwRI participated in USMC exercises named URBAN WARRIOR in 1998 for nonlethal weapons demonstration using the powered parafoil air vehicle. SwRI also provided a subscale parafoil test vehicle for the NASA X-38 program. 

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Tactical Unmanned Aerial Vehicle (TUAV) (top) controlled in flight by SwRI autonomous autopilot and modular mission payload (bottom).

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