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
I thought having less blades (and longer blades) are more efficient no? Can you better explain the tradeoff of going with 3 or 5 blades setups over 2 longer blades if the size of the blades isn't an issue?
It's like working with Full Size helis. 5 or 3 blades are always smoother than 2.
We also have a large Gasser from Vario. great endurance. but feels very heavy. The TDR is much better and more responsive and uses modified spin assy. blades in a fixed 5 blade head.
I'm in your camp Rob! I can wait to get my 800 flying as well as my 450. Then onto heavy lifting and maybe a gas conversion if I need more flight time.
Nice work Denny!
One of the major problems with a SR heli is the blade strobing into the sun. I have a few custom made hoods that help, but the problem is difficult to be rid off in certain conditions. If the sun passes though the blade arc and can strike the front element at any angle you have a problem. Later versions had a hood fixed to the main frame that also reduced the wind disturbance on the camera. The high zoom ratio was done with a Sony HDR CX730E.with a Boss lens.
https://vimeo.com/59133955
Heres one I made last year, It is apart again having the gimbal converted to voice coil. The GoPro was hard mounted to check the frame vibration. The performance of the Zenmuse needs no further discussion.
weight and stiffness are old standbys in the vibration world, but it is also worthwhile to consider soft rubber. Rubber works by displacement and since the shore hardness determines natural frequency it is wise to select different amounts of "squish" for multiple mounts if you want a flat response. I have seen so many installations that use the same rubber mount on every corner only to have murphy intervene and cause the mounted item to resonate at the rotor frequency (if it is out of track or balance) or other designed in frequency. Also, symmetrically organized mounts are more prone to vibration than asymmetric ones. Full size helos are in the 3-5 Hz range for the main - real headaches sometimes.
@Thomas: The sensor is 41MP, the images are stored at a much lower resolution as otherwise you would need large amounts of storage. What you get by using a 41MP sensor is that it reduces noise in the downscaled image. The results are essentially ie 5MP images with much less noise in them, so they look better.
Oh yeah, and a really fast wifi external antenna output so 41.5 MPs get to the ground in real time. Is that even doable yet?
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