I've been working on a new helicopter platform the last few months. Based on an MSH Protos heli which I chose because it's an extremely light weight platform, weighing in at only ~1200g without battery. It has a full belt drive which I much prefer to gears as it's quieter, lower vibration and more reliable. I've had a few problems with it because the belt drive makes a really awesome Van deGraaf generator... not a good thing on a UAV. But I solved that, and am conducting test flights now.
The flight controller is a modified PX4v1. I replaced the switching regulator with a MIC29300, so that I can run it on 2S direct with the servos. Main motor power is 4S 5000, typically this heli would run on 6S 3300. Using the MSH stretch kit and 465mm Spinblade Asymmetric blades. In otherwise standard form, this heli flew for 17 minutes on an old crusty battery, in -10C temperatures.
I have now added a subframe to hold an extra battery, FPV gear with a camera in the nose, and a vibration damped NADIR camera mount to be used for aerial mapping. The idea is to develop a mapping UAV that is superior to a multirotor, offering a valid alternative to a fixed wing for short to medium range missions. The VTOL capabilities would eliminate all the nastiness of catapults, and controlled-crash landings with onboard cameras in rugged areas. Even the price is attractive at about $400 for the basic kit with motor and ESC (no servos).
Specifications show the advantage of a heli platform. This machine has an AUW including the batteries and camera of only ~3kg. It is 80m long, and about 15cm wide not including the extended legs, and 30cm high. The blades fold for easy transport, without requiring any lose wires or vibration-prone electrical connectors as a folding multirotor does. It actually looks much bigger on the table than it really is. This seems to be very good compared to multirotors I've seen with the same performance. (payload and duration)
Vibrations are always a problem with helis, but manageable with the right design and construction techniques.
Arducopter really makes helis worthwhile. You could buy two entire heli systems including a Tx for the price of a single DJI Ace One non-waypoint controller. Or 7 for the cost of a single Ace One waypoint enabled controller. I strongly prefer the PX4 controller over the APM and Pixhawk, because it offers 32-bit performance in a small package that is easier to mount in a heli frame.
So does it work? I took it up for it's first photo tests yesterday, and it worked beautifully. Better than 80% photos are usable. It flies for 20 minutes in a hover with old, cold batteries (-5C). I'm hoping for closer to 30 minutes while actually moving (helis are more efficient moving than hovering), in warmer weather with new batteries. It should have an easy cruising speed of 15 m/s with little or no reduction in flight time. At 20 minutes, this would offer an 18km range, and 27 if it can do 30 minutes. If you wanted to do FPV and not mapping, you could configure it with a 3rd battery in place of the SX260 and fly for... 30-45 minutes, and a range of up to 36km. Top airspeed is still TBD, but probably 20-25 m/s.
Wind penetration and stability is excellent compared to both multirotors and fixed-wing. You could do a mapping mission in winds up to 40 km/h with little effect on stability or duration.
If the success continues, I'm going to consider building a large gasser heli. This would allow flight times up to 2 hours, or payloads on the order of 10 lbs for 30 minutes. So you could map large areas, or even perform light duty spraying operations. I'm thinking about local application of a herbicide for things like Giant Hogweed elimination, that sort of thing. Such a large heli does pose significant danger and should only be used in industrial, agricultural or remote areas.
Comments
It would be easy to mount a hall effect sensor on the main rotor. They come in biased and unbiased versions. They can be very small and light. Another option would be to do it optically, but I think even two LEDs (TX/RX) would be heavier than a hall effect sensor, and more prone to interference.
Rob, Would you be so kind to post a picture of your gimbal and mount. I am thinking about adding a gimbal but not sure where I want to mount it to start with. Thinking about under the heli directly below the main shaft.
Regards
David Boulanger
Oh, and I finally got my big heli up in the air with the Nex5 on the 3-axis brushless gimbal. No jello! I still have some work to do as it wasn't the most stable, but it's not too bad. The wind was actually very high, about 30-40 km/h with gusts 50-70. So, not the best flying conditions. ;) Actually had a couple sketchy ground events, was glad I had stabilize mode on APM.
I am sorry but i dont understand how do you know the rpm of the rotor at any moment.
I actually have motor speed code running on an Arduino Pro MIni. I just need to interface it back to the APM over I2C.
Which helicopter exactly are you referring to?
This midsize heli, AUW is 3200g. Typically one of these helis is 1700g with battery. So I've almost doubled the AUW. So about 1500g extra payload on it, including the subframe, FPV gear, camera and mount and extra battery.
I wouldn't try flying with more weight than this, unless I increased the rotor speed. But increasing the rotor speed would mean it will start to use much more power. I think at this point, this thing is on the down-slope of the efficiency curve.
R_Lefebvre i have been looking for rotor speed sensors but i have not found much. Can you tell me what you had in mind?
Have you got an idea on how much payload including batteries this heli could lift?
@David and @Robert. thank you for your interest. I'll open a thread with full detail on support forum.
Cliff, there's little doubt in my mind that, size for size, multirotors are safer. There's just more mass in the blades. But I really like this 500 size. I find it's "safe enough". I still wouldn't want to get hit with it, but, you really shouldn't be operating near people with a quad of similar capability anyway.
I was just about to start building a quad capable of flying 30 minutes for a few different purposes. Spec would have been a Tarot 650 folding quad frame. iPower MT4108-580kV motors and 17" CF props. 17" props will still be fairly dangerous. And the machine still weighs 3kg so you don't want it falling on your head either.
There's a good thread here:
http://www.rcgroups.com/forums/showthread.php?t=2025307
What I realized by playing with the numbers in eCalc, is that my 500 heli already outperforms one of these anyway. I haven't broken 30 minutes, but I could easily if I tried. Just take the subframe off and attach 2 batteries. Done. I already had it flying for 17 minutes in -10C weather and a crap battery, with only a single 5000 mAH battery. That quad uses 2 8400 mAH batteries to hit 30 minutes.
had that problem too , I ditch my 450 cp heli for a 450 multiriotor cause I cant get all the mechanics balance.
and the funny fact I ask some of my buddies at the field is most would be comfortable having a multirotor flying nearby than a similar size CP heli .....False sense of safety??
Gokay, I believe the problems is that when you switch modes, you have not <armed> the system.
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