I see multiple comments saying that the blades are harmless, but a quick search through google photos seems to imply otherwise to me. Not to mention the force of this thing dropping on your head after it clips a nearby branch, or has a system failure.
I suppose the answer is that the owner needs to be responsible with its usage. The example footage seemed fairly reasonable use-cases (no bystanders).
Yeah, those blades are NOT harmless. They will cut you up on the thinner skin bit and do some serious bruising on the thicker skin. Also, anything around the head is asking for losing any eye or something else.
I've been building and flying quads for years now and Anything over the tiny indoor ones commands a LOT of respect from me due to experience.
The idea of these things autonomously following you is cool but a HUGE liability.
Unless they have some major obstacle avoidance on board they you basically could never safely use this around other people and honestly you shouldn't even use it around yourself.
'harmless' drone blades are the exception, if they even exist. Note that drones designed to operate indoors have some form of protection for the blades (Parrot drone, for instance).
In addition, 'cheap' blades have sharp edges due to the manufacturing process. Some drone owners recommend sanding them to get rid of those, to minimize injuries.
I could think of a pretty much harmless blade design that MIGHT work (soft blades), but they'd be woefully inefficient AND they would only work for those super-ultra-light micro/nano drones.
Anything else is not harmless. Even a tiny quadcopter can easily cut your skin, because the plastic is hard and sharp. Think of it as one of those plastic picnic knives, except not that sharp --- BUT rotating very, very fast.
I can't speak for the Lily blades, but I have a couple of drones a little larger and the blades are harmless - they stop as soon as they detect obstruction and they are flexible/not sharp. It won't cut anyone.
I just got the DJI Phantom 3 and got hit by the blades after a collision. Sliced up my arms -- didn't require stitches, but 10 days later i still have evidence that the blades aren't totally harmless.
I have NEVER seen a controller that would "stop as soon as they detect obstruction" like you say. In reality the flight controller is likely to do the opposite. Once it detects that the current speed of the blade is not enough to provide the desired lift, it will INCREASE the speed.
Telling people the blades are harmless is very irresponsible.
The electronic speed controllers we use in RC have a loop time of a few milliseconds and are fully programmable. Some of them are capable of sensing the current going into the motor. You can also monitor the voltage instead of/in addition to the current. It's easy to cut the throttle when there is an unexpected power surge.
I personally haven't seen this technology in DIY multirotor parts, but I know that the AR.Drone has what they call "cut-out detection". They use it to prevent damage to the craft rather than humans, but the technology could be tuned for this as well.
The most popular low end quadcopter, the Syma X5C, has this. The blades are flexible and stop almost instantly when obstructed. This is great for preventing breakage when you hit a tree. I've stuck my finger in there intentionally without even mild pain.
If a $60 device has it I bet the multi-hundred and thousand dollar devices will not have trouble.
