There are several experimental projects that I have been involved in, but currently only the Micro Air Vehicle (MAV) project is included here. As time permits, several other projects will be added.

Our contribution to Micro Air Vehicle technology involves the development of flapping-wing propulsion, unconventional by human standards, but clearly the norm in the animal kingdom. There are several arguments in support of flapping-wing propulsion, the most common being that since evolution has selected flapping-wings, they must be optimal. However, this is not necessarily a valid argument. While one cannot easily argue against the principle of optimization inherent in an evolutionary process, one must consider the initial conditions and constraints imposed on the process. For example, we do not see many creatures in nature with rotating parts, therefore I would suggest that evolution did not choose flapping-wings over propellers; but rather propellers were eliminated due to organic constraints. Nevertheless, there are flight regimes where flapping-wings do appear to be superior, in particular, for small, slow-flying vehicles.

While flapping-wing model aircraft have been around for more than a century, almost all previous designs have been bio-mimetic, basically trying to imitate bird or insect mechanics, but with far fewer degrees of freedom. Our approach has been a little different. We look at typical bird-like flapping and see several flaws; things that cannot be easily changed by evolution. Keep in mind that birds and insects have been optimized for a wide variety of tasks, whereas we may design our vehicle for a small subset, perhaps efficient cruising flight and maybe some maneuvering criteria. Some of the perceived flaws are that the plunge amplitude of a bird's wings varies along the span, such that the root portion contributes little to the thrust. Additionally, when a bird flaps its wings up and down, the inertial and aerodynamic loads cause the body to oscillate in opposition, and the work done to accelerate the body is essentially wasted energy. With regard to this last note, it is likely that evolution has given birds the ability to benefit from body oscillations, but I think it is fair to say that no manmade ornithopters are this evolved, and any oscillations of their fuselage should be thought of as wasted energy.

Our philosophy has been to not limit ourselves to the same constraints as biological systems, but rather to observe how animals which were subject to these constraints have adapted their behavior to compensate for limitations. The most obvious adaptation we could see was the propensity of birds to fly in ground effect, as seen in the photos below of the Brown Pelican, flying over Monterey Bay, and the Great Egret flying over Elkhorn Slough. By flying low over the water the birds experience favorable wake interference, getting increased thrust at an increased efficiency.

While the birds can only benefit from ground effect when they are close to the ground, we have devised a scheme that gives us the benefit of ground effect without having to be near the ground. Additionally, the configuration is aerodynamically and mechanically balanced, so we minimize energy spent accelerating non lifting surfaces, and the main body is a more stable platform for controls and instrumentation.

When we first started our research program we were primarily concerned with thrust production, so we designed models like the one shown to the right. The 15cm span model has a flapping-wing pair which flap in counterphase to capitalize on the benefits of ground effect and to form a balanced system. The models were powered by tiny stepping motors with a 25:1 planetary gear drive. To test the models they were suspended on very thin copper wires, as shown in the figure, with the power for the model fed in through these wires. Some of these models could flap at up to 40 Hz, and they were used to demonstrate vertical flight.

Work is being done now to integrate the flapping wing propulsion systems into complete radio controlled flying models. The models use 3-channel radio gear that weighs about 3-4 grams for a receiver, electronic speed control, and two magnetic-coil servos. We power the systems with rechargeable Li-Po batteries which weigh 2-3 grams, and we build tiny 1/3gram DC-DC step-up circuits that bump the battery voltage up to a regulated 5 volts. The complete models weigh in as low as 10 grams. For info about the flying model shown in the figure below, check out the last paper cited below, or look at the videos of the first few flights.

Throttle-only model: (A note on the movies: I recently replaced the movies with higher quality versions. The filesize is unfortunately considerably larger, but the picture quality is much better. I apologize to those that surf via a modem, but those with faster connections will appreciate it. I have provided three video qualities for each movie, so download the largest file that your bandwidth/patience can handle. All files are Windows Media Audio/Video format - WMV.)

• First flight: about 27 seconds of flight ending in a near miss with a building and guard rail.
  low (2MB), medium (6MB), high (13MB)
• Second flight: about a 2 minute flight with an uncommanded landing in a nearby tree. Fortunately, the model survived.
  low (7MB), medium (19MB), high (41MB)

Throttle/rudder model: Finally, a model that can avoid buildings and trees. Model 2 is smaller, with a 27cm span and 18 cm length. It uses a magnetic actuator for rudder control, and has a flying weight of about 13.4 grams. With a 135 mAh Li-poly battery it has enough power for about a 20 minute flight. The model is shown in the carrying case above.

• First flight of Model 2: A full 3 minute flight. Warning, it was a windy day, and along with the higher flight speed and the ability to turn without notice, the cameraman had a tough time keeping up.
  low (7MB), medium (16MB), high (41MB)
• Flight in the World's largest wind-tunnel: We gave an AIAA Technical Seminar at NASA Ames on February 12th, 2003, and due to rain or planned outdoor flight was out. Fortunately some NASA experimentalists in the audiance gained access to the NFAC 80x120 tunnel and we flew the model in the test section. Due to the anechoic walls of the tunnel, the gear and flapping noise of the model, which are usually drowned out by background noise, can actually be heard. The flight was about 3:30 in length.
  low (10MB), medium (12MB), high (30MB)
• Four minute flight in the Monterey County Herald Parking lot on March 11th, 2003.
  low (10MB), medium (21MB), high (56MB)

• CNN Science & Technology Week, report on micro air vehicle research at NPS and SRI, aired September 1999.
• KSBW TV, report on local homeland security research since 9/11, aired September 11, 2002.
• Robotic Bird Takes Flight, by Kevin Howe, The Monterey County Herald, Wednesday, March 12th, 2003. (PDF)
• KICU Silicon Valley Business, report on the flapping-wing micro air vehicle, aired on March 29, 2003.
• Tiny Flying Robots, Current News, Backyard Flyer, Volume 2, Number 4, May, 2003, page 20. (PDF)
• Flapping-Wing MAV, Cloud 9, Radio Control MicroFlight, Volume 5, Number 7, July, 2003.

Jones, K.D., Dohring, C.M. and Platzer, M.F., "An Experimental and Computational Investigation Of the Knoller-Betz Effect," AIAA Journal Vol. 36, No. 7, 1998, pp. 1240-1246.

Jones, K.D., Dohring, C.M. and Platzer, M.F., "Wake Structures Behind Plunging Airfoils: A Comparison of Numerical and Experimental Results," AIAA Paper No. 96-0078, 34th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan., 1996.

Jones, K.D. and Center, K.B., "Numerical Wake Visualization for Airfoils Undergoing Forced and Aeroelastic Motions," AIAA Paper No. 96-0055, 34th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan., 1996.

Jones, K.D. and Platzer, M.F., "Numerical Computation of Flapping-Wing Propulsion and Power Extraction," AIAA Paper No. 97-0826, 35th AIAA Aerospace Sciences Meeting, Reno Nevada, Jan., 1997.

Jones, K.D. and Platzer, M.F., "An Experimental and Numerical Investigation of Flapping-Wing Propulsion," AIAA Paper No. 99-0995, 37th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan., 1999.

Jones, K.D., Davids, S. and Platzer, M.F., "Oscillating-Wing Power Generator," ASME/JSME Joint Fluids Engineering Conference, San Francisco, CA, July 18-23, 1999.

Jones, K.D. and Platzer, M.F., "Flapping-Wing Propulsion for a Micro Air Vehicle," AIAA Paper No. 2000-0897, 38th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan., 2000.

Jones, K.D., Lund, T.C. and Platzer, M.F., "Experimental and Computational Investigation of Flapping-Wing Propulsion for Micro Air Vehicles," Conference on Fixed, Flapping and Rotary Wing Vehicles at Very Low Reynolds Numbers, Notre Dame, Indiana, June 5-7, 2000.

Jones, K.D., Castro, B.M., Mahmoud, O., Pollard, S.J., Platzer, M.F., Neef, M., Gonet, K. and Hummel, D., "A Collaborative Numerical and Experimental Investigation of Flapping-Wing Propulsion," AIAA Paper No. 2002-0706, Reno, Nevada, Jan. 2002.

Jones, K.D., Castro, B.M., Mahmoud, O. and Platzer, M.F., "A Numerical and Experimental Investigation of Flapping-Wing Propulsion in Ground Effect," AIAA Paper No. 2002-0866, Reno, Nevada, Jan. 2002.

Jones, K.D. and Platzer, M.F., "Experimental Invesitigation of the Aerodynamic Characteristics of Flapping-Wing Micro Air Vehicles" AIAA Paper No. 2003-0418, Reno, Nevada, Jan. 2003.

Jones, K.D., Bradshaw, C.J., Papadopoulos, J. and Platzer, M.F., "Development and Flight Testing of Flapping-Wing Propelled Micro Air Vehicles" AIAA Paper No. 2003-6549, San Diego, California, Sept. 2003.

Jones, K.D., Bradshaw, C.J., Papadopoulos, J. and Platzer, M.F., "Improved Performance and Control of Flapping-Wing Propelled Micro Air Vehicles" AIAA Paper No. 2004-0399, Reno, Nevada, Jan. 2004.