It's raining robots-
That will be the headline all of us will cringe at, when the Media goes manic over the first commercial drone crashes of any significance. The same way they do anytime something new takes a stumble (or two).
The thought of my craft hitting somebody really haunts my mind. I'm sorry to be a downer, this topic is definitely a buzz-kill from the heady intoxication of being in the midst of the next great economic boom, but I can't let it go.
So the topic is failure. Despite what your high school sports coach told you, failure is not just an option, it's a guarantee. Yes- our thrust makers, power systems, flight controls, and firmware will get better quickly. However, even if we could magically achieve 100% reliability with all of our flight critical components, failure will still be there. The most random shit is always going to happen.
The project-
I'm focusing on multicopters in particular with this project, but I feel that a similar strategy would be effective with fixed wing craft as well, in fact it's used all the time.
The specific type of failure scenario I want to tackle here is a total loss of thrust and/or control. Deployable parachutes are being developed, and seem to be working well. I would like to pursue a more passive system, an aerodynamic design built into the airframe itself. Inspired by watching Marcy fly around and wingsuit pilots, I hope to achieve a passive "auto-rotation" or glide of the entire airframe. If the the craft looses thrust, the actual act of falling makes the conversion into an alternate flight mode. A slow spiraling glide to the ground, with a gear down orientation maintained. Energy absorbing landing gear, maybe even a supplemental air bag would compliment the design. The key in my opinion is making the recovery mode completely non-dependent on any system other than gravity and wind resistance. Time is so critical in a recovery scheme for these types of failures at the altitude multis usually work. No sensors, servos, or firmware required, just a thoughtful arm and frame design. The challenge will be to prevent undesired flight characteristics while in normal powered flight, in fast controlled descents we don't want to be induced into a flat spin! Can the free fall decent rate be slowed enough to usefully lower the risk of damage on the ground and airframe itself?
Step one- Get to the sewing machine and build a Bat suit for one of my quads
To be continued.
Comments
I agree with R_Lefebvre, Forget Autorotation- it will never happen as you have no energy stored in the rotors, everything esle is too complex.
the KISS aproach is always better and more relaible (Keep It Simple or you'r Stupid). every additional part that you put into a system doubles the probability of failure. A multi-copter is a collection of parts that you fly until something fails, then its an expensive brick. Thats why I fly planes. nothing wrong with Multi-copters but for me the combined risk is too great. If you accept the risk than use a parachute BUT how do you determine the minimum deployment height that it needs to operate and slow the brick down to a speed that it will not injure someone. On top of that the legs and frames on some multicopters look dangerous in themselves. sharp edges and points everywhere. Safety is not just about reacting to a failure in the air. sometimes the failure is the human variety but for the unsuspecting vctim the result is the same.
JAB, I agree. Combine that with the fact that with so many newbies, and their first model is highly complex, they are very likely to build a machine which is quite likely to fail. We see that over and over.
My opinion, it is will be hard to improve upon the parachute approach. Seems everything else being suggested is a massive compromise of weight, complexity, and aerodynamics. You can't have anything on the multi-rotor that will catch the wind until you WANT it to catch the wind (ie: when falling). Otherwise any gust of wind will flip your copter over.
I think an Octocopter which can survive a motor failure, along with a parachute is about as safe as you're going to get.
Interesting point. Currently, the FAA won't license any aircraft that isn't capable of landing without power. I would assume this is because they carry people, but I could see them taking up a similar concern for the people on the ground with commercial drones.
Multi-rotors are neat because they're easy to tune, but they're not very efficient, and they just don't do well when a single power source fails. I don't think we're going to see many large commercial multi-rotors for that reason.
Does anybody know of somebody who has developed a parachute like system for multicopters, that can be deployed in case of failure?
John, I see exactly where you're coming from, and tend to agree for the most part, as far as a hobby is concerned it's as safe as the person flying. From a technology standpoint, I'd love to see it go more commercial, it's got incredible benefits for society, but before it's practical to release these into the commercial world where where the dollar rules and moron's rein supreme, we'd really need some sort of safety device, I for one feel while the motives may be different, at the core of it, sooner or later we may come up with one.
So you could potentially set it up as two separate systems, with complete redundancy. You would have to be sure that both setups was powerful enough to fly by it self.
Of course there would be things that would be hard to implement and I'm far from sure that the two systems would not just work against each other.
There could be different ways of setting it up.
Dual TX where you'd add trust from one TX and the other one would be in control.
The single TX but with two RX on the same frequency.
Just a thought
I think much of this is about what mindset you have, and where you are coming from.
People with experience from R/C flying airplanes and helicopters won't even blink if there is a crash. To put it bluntly, crashing is just another part of the hobby.
But on the other hand, for people new to the hobby jumping straight into the drone aspect. Crashing the new expensive drone that is supposed to fly all by itself, can be a traumatic experience. But the fact is that regardless of how much money or autopilot electronics you put into your drone, it is going to crash. It is just a matter of time. At the hobby level, we are all flying motors and electronics made as cheap as possible in some Chinese factory, with little or no maintenance done between flights.
And for the average R/C pilot this is just fine. Flying in a regulated R/C field, a crash has no consequence. Other then burning a hole in you wallet and entertaining your friends that is. But at the same time a R/C pilot would not even dream of flying over a populated area, like you see in many, many drone videos.
Auto-rotation only works when the accumulated rotational energy is converted back into lift at the final phase by using collective to slow decent and forward motion to create an air cushion under the rotors... if you where trying to achieve this with a hex I'd suggest perhaps an independent 'flaps' (for lack of a better word) that at rest sit vertically in line with the arms, upon a sudden decent or any other 'emergency situation' they would move horizontally to induce the auto-rotation with the decent and in the last phase say, 2-3ft of the decent they would give 10-15 degrees to induce some lift and slow rotation...
Matthew, I just wonder if that would make it difficult to descend under normal conditions. In my mind the rotation is key because it can happen very quickly and it gives us effective relative airspeed even if ground speed is zero.
Edit: Sorry, I see where you address adjusting the required closing pressure to avoid closure in normal speed descents. I can picture what you're saying, like punched louvers on a hot rod(but flexible), could be a nice way to direct air flowing through the frame in specific directions also.
This Idea is way out there and slightly crazy but here it goes.
Build a frame that has lots of small flaps that when air is applied to the top (or with very low pressure on the bottom) they stay open. But when air pressure is applied to the bottom they close, thus causing resistance. Like an air diode. If it worked it would not affect flight to much, and would help slow it down in free fall. You would just have to keep as much of the weight as possible below it.
Sounds good at least.
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