The drone was taking off and starting running the flight routine according to my program. "It works!!!" I almost screamed. However, it drifted a lot!?! Pretty soon I noticed that the reason may come from the drone's own shadow!
During the taking-off and hovering process, the drone uses its vertical camera to maintain its location. In the night time, the street light makes a vivid shadow of the drone, and the shadow becomes the most visible feature on the ground. When drone rises, the shadow moves away from the street light, and thus from the drone itself. The drone's control software will try to hover above its own shadow by moving toward it, and the shadow will further move away,......
So, the drone becomes a shadow chaser!
It sounds like an interesting combination of a feedback control problem and a related rates problem in calculus. The drone's own shadow might become a threat to its autonomous flight during night time. Any solutions? Sounds like a mini topic for MAV research. What do you think?
If it is indeed chasing its own shadow, it would happen in the daytime as well around noon.
ReplyDeleteApparently this is a problem some others have experienced: http://forum.parrot.com/ardrone/en/viewtopic.php?id=4864
http://www.ardrone-flyers.com/forum/viewtopic.php?t=991&p=6632
Try bringing a flashlight to illuminate the area where the Drone's shadow is to see if it is indeed the shadow. On second thought, try moving the flashlight around to see if you can control the drone that way.
This gives me an idea. Perhaps you could have 2 laser pointers of different color, say red and blue, and point them at the ground under the drone. Have the Drone recognize the 2 colored dots using its downward camera. Then make the Drone try to orient these dots a certain way, say horizontal with a certain distance between like 100 pixels with red on the left and blue on the right. This might allow you to control the Drone with laser pointers similar to a multi-touch interface. Altitude would be controlled by changing the distance between the laser points, and orientation would be controlled by moving the points around each other.
It would probably be difficult to control, though.
Your idea sounds very interesting. It's similar to the laser/infrared-guided weapon, but instead of locating a target, you use it for navigating/controlling the drone itself. As long as the ground is level, it can probably work to certain level. Worth trying!
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