Winner of the SAE Aero Design competition in 2006, 2007 and 2008 for Micro class #1 in the east region, Wright State University has staked its claim as a key university in Micro Air Vehicle (MAV) research and design. Led by George Huang, Wright State University's newly formed Micro Air Vehicle Research Center of Excellence has partnered with Wright Patterson Air Field Base to tackle the tough problems associated with MAVs that mimic the flight of insects and weigh only several grams. With their existing dragonfly-based MAV, Huang has an excellent starting point.
What is the main difference between the MAV you are pursuing and a fixed-wing airplane?
For a fixed-wing aircraft, the eddy (the airflow moving counter to the main airflow) is small compared to the airplane itself. There is significant interaction in the dragonfly MAV, (so) you have to look at the whole body in designing the aerodynamics. You cannot look at one section of it because they all interact with each other. Because of the eddy, the flow is disturbed by the body itself. That's probably the most significant difference. With a MAV, you cannot only look at the wing or a simplified form because any part is going to be important. That makes the design significantly more difficult.
What is the biggest challenge you are investigating?
We can fly this airplane about 15 minutes, continuously. Remember that 15 minutes means this Micro Air Vehicle just continues flapping. In reality, insects don't really flap all the time. If you look at butterflies, they fly from Canada to Mexico. If they keep flapping, they will run out of energy in just one or two miles. The way they do it is, they have sensors on the body. This is what we want to have on our airplane — sensors that can detect the wind.
If the MAVs are used inside buildings, how does the wind come into consideration?
Even in a room, you will find that the air is circulating; it is not going to be steady. This airplane will sense the air blast, the wind coming up, and it will ride the upstroke of the gust wind. If the airplane can rise up, then it has more distance to travel. It can also detect a temperature gradient and it will rise by taking the temperature gradient.
Does any aircraft do that now?
No. Not yet. The reason is right now, this kind of situation can only apply to small airplanes. The gust wind can only help smaller aircraft. For big aircraft, if you have gust wind, it really doesn't do very much because it is so heavy.
How does a university help solve this problem?
Control theory can be used. I am writing an SBIR (Small Business Innovation Research) proposal with one of the local companies to come up with the control theory to do this. If you look at the airplane moving, first you need to have a sensor. The sensor will be able to sense the flow direction and will be able to sense the temperature gradient. Then you will try to adjust the cell to take this ride. The feedback control will look at the air coming in and make adjustments. It is an optimization problem where I want to keep my height constant and convert minimum energy.