I’ve promised to write about the surveillance drone that I’ve been building over the past couple of months. I have always wanted to have my own drone that could send back a live video feed. This is partly inspired by products like the AeroVironment RQ-11 Raven, which is currently in use by the US military, and which you can view in action here. The Raven is basically just a glorified RC airplane, with a sophisticated landing system that allows it to be recovered by a soldier without great pilot skills (which is one reason they cost around $35,000 each).To get to the bottom line, my drone has taken its first flights, the results of which you can see in a video of my office at Stanford and in a local park.When my kids were younger I looked into buying an RC helicopter for this purpose and actually tried to wire a camera on a car, but the consumer technology wasn’t up to snuff back then. Now it is.Instead of using an RC airplane I went with a helicopter for a couple of reasons. I could test the helicopter in my back yard, while an airplane would require a runway. Helicopters are better for precise, close-in surveillance because they can hover. The big drawback is that they are very hard to fly; indeed, learning to fly an RC helicopter is the single biggest impediment to the use of this kind of drone. (Among other reasons, they’re hard to fly because left and right switch meanings on the joystick when the helicopter is pointing toward you.)I slowly worked my way up the hierarchy of helicopters, from a Syma S107 to a Blade CX2 to a T-Rex 450 (pictured above) to a DJI Innovations F450 quadcopter (below), which is the platform I used for the videos. It is very difficult to learn to fly a helicopter without a simulator; I’ve logged quite a number of hours on RealFlight 6. While many people use the single main-rotor T-Rexs or their clones as platforms for cameras, they are not very stable; their main purpose is acrobatic flying (they can be flown upside down, among other things, because of the main rotor collective pitch). The practical implication of this is that you have to constantly repair your crashed helicopters, which costs lots of money and takes lots of time.The DJI F450 quadcopter on the other hand uses an extremely sophisticated Naza controller with a three-axis accelerometer that can sense where the machine is going, and automatically corrects for movement. As a result, they are stable and easy to fly. You still need basic piloting skills, and it is often hard, as with many quadcopters, to see where the nose is pointing, making it hard to maneuver properly when at the limit of visual range. But they hover beautifully and have the lifting capacity to loft a small digital recorder which I used for the videos above. I’m currently using an old Sony flip video camera.It is extremely easy to build a drone now that can do not just surveillance but can carry rather large payloads. If you want to see how large some of these planes get, check out this video of a model Airbus A380. I don’t have to spell out the implications of this. I want to have my drone before the government makes them illegal. The US has been fighting such low-tech enemies lately that we haven’t thought through the nature of a world in which lots of people have sophisticated drones, not just other countries but private individuals. One somewhat worrying thing is that virtually all of this equipment comes from China or Taiwan.The next stage in this project is to equip the drone with telemetry. I’ve bought the package that includes a real time video transmitter and receiver, camera, and telemetry system that will send back GPS data on the drone’s location, heading, airspeed, etc. This requires, among other things, a ham radio license. Stay tuned.
Published on: February 12, 2012Surveillance Drone, Maiden Flight