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Sheep herding quad build. Mavic 2 as benchmark

evranch

Active member
#1
I've never been a quad man. But a friend sent me this video yesterday:

This made me think that quads might finally be practical on the farm as these guys are actually making use of a quad in conditions like mine. And I love the idea of playing loud sounds from a quad to chase the sheep. Buying, training, and maintaining a good border collie is expensive, making a herding drone seem cheap in comparison. The Mavic 2 Enterprise they quoted around $3500, and I'm sure I can build one at a fraction of the cost, especially using my existing TX, goggles etc.

Sheep do not care much about airplanes by the way, they are too fast. They consider them much like a bird, flip their heads up, maybe spooked for a second or two.

Their specs seem pretty reasonable for my use, can anyone more experienced point me in the right direction on a frame and motors for implementing something of this scale? Almost everyone is building miniquads and racers, it seems.

Mavic 2 Enterprise specs:

- 322x242 (12" x 10")
~1kg takeoff weight
- 30 minute flight time at 25kph
- resists wind up to 38kph
- can carry a small loudspeaker to yell at sheep
- fpv cam on gimbal, enough excess lift to carry a HD system like fpv.blue someday (if it's ever released...) and GoPro
- stabilization and basic RTH capability is all I really need out of the FC in case of a flyaway, this would be flown short LOS for the most part to sweep around behind sheep and push them through gates.
 

evranch

Active member
#2
Renamed thread to get more interest hopefully. Note that I'm not asking anyone to engineer my quad! I just know NOTHING about quads, so I need some guidance to get started. Like:

- what frame size would be reasonable
- what sort of power package am I looking at
- would a standard build suit my needs, i.e. versacopter or 250 race quad
 

PsyBorg

Wake up! Time to fly!
Mentor
#3
Realistcally the dog would be cheaper and more effective.

Herding takes time as I am sure you know. Battery limitations of 20 mins at best will not move a herd far as it would not be a straight line push.

Herding 5 - 10 head from pen to pen may be doable but much past that the amount of battery you would have to carry would be crazy expensive.

Repair and replacement costs over time vs a dog would be crazy.
Then add in the fact to legally do this as I am sure you are making money off the cows would require a part 107 certification.

That all said if you absolutly are set on this a platform made more for aerial photography would be better then race quad platforms to carry the massive battery weight needed to get any real flight times.

Get away from dji style gear and research more into aggricultural drones and modify to suit your needs.
 
#4
My main comment is that if you want to push forward with this, I think you'll be way better off in the long run just buying something (probably from dji) compared to DIY'ing your own. Every engineering choice is linked together ... if you don't have live video (and decent quality live video) you won't be able to see what's going on and you'll probably scatter the sheep more than herd them. You need a good gimbal to stabilize the camera. You need good video transmission so you can see your nice video. You'll need a good gps-based flight controller so you can focus on what's happening in your video and not have to be actively flying the drone. That means you'll need a ground station to monitor the drone health and some means to watch your video. And then even under the best circumstances you'll probably only have 20-25 minutes of air time per flight. DJI already does this at about the best quality possible. You'll be up flying the same day you get your drone.

I'm not a dji fan boy by any means, I would doing it myself if I owned a sheep.

I'm not saying you couldn't build something from parts that does all these things moderately well. But I think it will take anyone a long time and many iterations ($) to spin up to speed on all the things you'd need to know and all the equipment you'd need to buy to do this task effectively.

That said, if you want to build an inexpensive autonomous quad, then by all means build an inexpensive quad and put a capable flight controller in it, but do it because you want to learn how to DIY a quad, not because you want to heard sheeps with a drone. That's my 2c. :)
 

evranch

Active member
#5
Good points from both of you! I think I'm thinking simpler, though. Not true autonomy from the drone, but direct control with stabilization and FPV. I want rough position hold when I take my fingers off the sticks so I can look away. The video feed honestly would be more for orientation and flight of the quad than watching the sheep. HD was a "want" rather than a "need", and the gimbal was for looking to the side while circling... that's airplane thinking. I can strafe the quad.

I thought 20 minutes would be adequate, because for the most part, when I'm moving sheep, I'm following and pushing the herd myself. What I really need is something that can get around the other side of the herd faster than I can on foot or with my wheeler, over a ditch or fence. Also, sheep move like a fluid, and only really need persuasion for direction changes. So the primary usage cases would be:

- initial gather. One big loop around the pasture to bring sheep together and head them towards the gate. I can do this on the wheeler, really, but aerial would be a lot quicker than bouncing over rocks and brush. Sheep instinctively gather with a little chasing and horn beeping. Target time: 10-15 minutes.
- direction change. We are quietly driving along the road and come to an intersection. I need something ahead of the sheep to stop them and initiate the turn. Pull quad from saddlebag, slide goggles down from forehead, hand launch. Open sided Viper goggles or TX-mounted monitor let me see the sheep LOS at the same time as my video feed. Target time: 5 minutes.
- push from road through gate. Dogs excel at this, humans are too slow and vehicles too unmaneuverable. Sweeping big arcs behind the herd to build the pressure, once they start to flow they will all go on their own. Again, my eyes are primarily on the sheep with the video feed letting me know where my quad is. Target time: 10 minutes.

So for the majority of herding time the quad will not be in flight.


Changes in Canadian regs that were posted here awhile ago will now allow commercial use without any special permits, in exchange for having to do a silly license test and register the airframe. That's one of the reasons I can consider this now.
 

PsyBorg

Wake up! Time to fly!
Mentor
#6
If your not planning on being in air full time then yes most any platform would do as stated about your method of use.

Specially if you are mixed with a vehicle to carry gear and batteries
 

evranch

Active member
#7
Yeah, that's why I even considered a race quad as I can bring a bunch of smaller batteries on my wheeler and swap before or after each operation. No need to go massive, as long as I can complete the operation at hand without having to go retrieve my downed quad, that would kind of mess up everything.

With that in mind, what frame sizes should I consider to get performance like stated in the original post? Something fairly common is my goal, so I can readily change parts or even frames if things get damaged. I'm thinking the noisemaker can be just one of those tiny, earsplitting piezo sirens, not too much extra weight.
 

ElectriSean

Eternal Student
Mentor
#8
I think you'd be looking for a frame in the 8-10" prop range. I've never looked into builds in this size, so I'm not sure what's out there for frames but motors and ESC's should be easy to figure out. For something basic like this you want about a 2:1 thrust:weight ratio, and probably 600-800kV depending on the props you want to run. I'd go with an Omnibus F4 FC running iNav, this will get you all the stability and GPS assisted flight modes you need.

If you don't want HD recording, you don't need a gimbal. Trying to use one for FPV would be kind of a nightmare I think...

You probably could get away with a 6-7" race quad depending on your payload weight, but bigger stuff is definitely more efficient if that's the ultimate goal.
 

evranch

Active member
#9
Thanks, after looking at some of the larger frames I'm thinking 450 is around the size I'm looking for. They are about 12" square and will take up to a 10" prop. Sounds like 2212 is a common motor size for these. There is a lot of talk of 6s batteries out there, but seem to be a racer's battery right now... thinking 4s for this.

Portability-wise, I might look into some smaller frames, thinner shapes, or folding arms if they can deploy quickly. I'm also thinking folding props like DJI uses. 1' square plus props is pretty big to stick on a rack or saddlebag, it would probably have to be strapped to my back. There are also some awesome hexa/octo designs out there that would pack a lot of power into a small space... but I should probably stick to the basics for my first quad build.

I'm looking at 4-in-1 ESCs right now to save weight and wiring. Am I correct that these are rated in current per channel? They seem too cheap, but maybe that's what they are, cheap ESCs.

I've been planning to buy a headtracker to use on my planes, in fact if they were in stock I would have ordered one with my last HK order. So that was how I planned to drive the gimbal. But after watching some race footage... the quad can definitely put the camera anywhere I want it without having to add weight and complexity with a gimbal mount.
 

ElectriSean

Eternal Student
Mentor
#10
Thanks, after looking at some of the larger frames I'm thinking 450 is around the size I'm looking for. They are about 12" square and will take up to a 10" prop. Sounds like 2212 is a common motor size for these. There is a lot of talk of 6s batteries out there, but seem to be a racer's battery right now... thinking 4s for this.
Just make sure that the motor is rated for the prop and battery you plan to use. Too low of kV with 4S and you're lacking thrust. Too high a kV with 6S and you're smoking stuff :) Race quads running 6S are usually using lower kV (~1700) compared to the 2400+ they run on 4S.

I'm looking at 4-in-1 ESCs right now to save weight and wiring. Am I correct that these are rated in current per channel? They seem too cheap, but maybe that's what they are, cheap ESCs.
Correct, they are rated per ESC not total. Which ones are you looking at? I haven't been shopping lately, but the 2 I have definitely weren't cheap ;)

I've been planning to buy a headtracker to use on my planes, in fact if they were in stock I would have ordered one with my last HK order. So that was how I planned to drive the gimbal. But after watching some race footage... the quad can definitely put the camera anywhere I want it without having to add weight and complexity with a gimbal mount.
I've always thought of head trackers as being for planes, but the multirotors I fly are all mini or micro and I'm moving too fast to look around lol.
 

evranch

Active member
#11
Just getting a feel for the market, looking at sites like https://www.getfpv.com/electronics/electronic-speed-controllers-esc/4-in-1-esc-s.html
You can spend as much or as little as you want, I guess, and it's hard to tell where the breakpoint is of quality vs. markup as the price goes up. As low as $30 for 4x30A, that's cheaper than buying 4 low-end HK ESCs.

The stacks are pretty neat too, this stack would be almost everything I need for this build for $80USD - F4 controller, 4x38A ESC, 350mW VTX - neat idea, shame the reviews are poor for these, probably because everything starts to get hot in that tiny package.

Looking at the iNav modes I would likely add a GPS and fly in NAV_POSHOLD with ALTHOLD+HEADING_HOLD enabled (interesting compared to Ardupilot, you can stack multiple modes). Not very exciting flying, but if I had to look away at the sheep I could simply take my hands off the sticks and the quad should just hang in the air. I probably will buy a separate small TX for this with a springloaded left stick. It's tempting to skip the GPS and just let it drift about in ANGLE+ALTHOLD+HEADING_HOLD, but the way the wind blows here it could vanish on me pretty fast!
 

ElectriSean

Eternal Student
Mentor
#12
I have a slightly older version of that HGLRC stack in my 3" Sparrow, it's really nice. Would look pretty funny on a 10" copter, but if the ESC's are capable I think it would probably work well. All it's missing is a barometer, but you can get them separately for cheap.

Definitely get a GPS unit with a magnetometer, they are cheap as chips and great insurance.
 

evranch

Active member
#13
Your 3"... heh, I figured they were small, but didn't really look at the size that closely. 20x20mm. They are REALLY tiny.

You must have got a good one, the reviews are highly variable on them. Of course, there are a lot of opportunities to mess up such a small device, and lots of hobbyists who probably shouldn't have a soldering iron in their hands.

That tiny stack should be able to put out more than enough amperage, I could even use the 28A version. And it has options to trigger the buzzer and toggle the lighting from the transmitter - perfect! I can use the lighting output to blow the horn, to avoid deafening myself with the arming tones.

It looks like the 450 was a common size before mini/race quads really took off, so after digging through some older RCGroups threads I've found some popular setups. 2212-980 were a popular motor as that was the DJI E300 setup with a 9.5x4.5 prop. This draws about 20A/motor at full throttle. Lots of guys propping up to 10x5 for a calculated 1486g of static thrust per motor. Enough to make a rocket out of it. However, if I run 10x5 and drop to a 3s, I'm down to 941g per motor and only 17 amps. I read a couple claims of 20 minute flight times with this power system and ~4000mAh 3s.

Assuming I can make that 1kg takeoff weight, eCalc says I would need a throttle setting of 45% to hover at about 2.5A/motor. 10 amps = 1/4 hour 0.4 hours, never trust midnight math - sounds like a reasonable match for the claimed flight time. And if 2:1 is a reasonable TWR, I can just pile on more battery until it gets too lazy to chase sheep anymore.

Looks like the power package is pretty much worked out, just need to pick out a nice frame, work out the weight and plan to get this into the air!
 
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evranch

Active member
#14
So... there is not much selection in 450 frames, since everyone is flying smaller quads. Looking at smaller frames I found this.

https://www.flitetest.com/articles/fly-long-40min-on-mini-quadcopter

He used a 250 frame and shimmed the motors up so the 7" props would clear vertically. You would think this would result in efficiency loss where the rotors cross but... apparently not enough to make a difference. An interesting option to get bigger props onto smaller frames.

I don't think I would build his particular build since it looks a little flimsy and underpowered for the job, but the idea of overlapping props is one I didn't consider. Someone studied and charted noise and vibration in a simulated quad: https://diydrones.com/forum/topics/overlapping-props-on-multi-copters-1?page=3#comments and the only significant effect was more noise - better for chasing animals, anyways!

I found a video where someone put 10" props on a 250 frame. I don't think I'll go that small, but it looks like an option to cut down weight and carried size while retaining power and large props.

Edit: Hmm, 9.3" between the front and rear mount wouldn't make for too much overlap, has folding arms, clean frame for cam, landing skids for 172 grams and $40. A lot lighter than a 450 size frame at 400+ grams. And I just realized the motor mounts are already staggered, only thing is, would the props hit that top frame, is that why they claim it's a 6" prop max.

More edit: Actually, it looks like ditching the top frame, shimming two motors, and mounting all four arms to the baseplate would be the way to go. More weight reduction and nothing to hit with the props.
 
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evranch

Active member
#16
Really nice looking simple frame and it looks sturdy for the cost. Pretty light too, and loaded up with my power package the 7" frame/stack/motors only come to 476g. Not counting a GPS puck, the RX and camera at the moment as those are in the noise. I have over 500g left to my 1kg takeoff weight! That's enough to carry a 6000mAh 3s and get that 30 minute time.

Don't see any reason it couldn't be turned over to land on the "top", giving room to swing those 10x5 props with spacers under two motors on a diagonal. At 8.3" square (12" diagonal) that would give about 20% prop overlap, which seems to be an acceptable number. Or... I could just downsize the power package for 7" props, choose a smaller battery, and build it regular style :unsure:

As a plus for the overlapping props, it looks like quads with overlapping props sound like a whole hive of angry bees:
I like it
 

PsyBorg

Wake up! Time to fly!
Mentor
#17
I was searching x class frames and found one on ebay but wont let me link it for you. Looks to be in the 10 - 14 prop range.

Try googling x class frames then slide the row of pics one or two places. You will notice it as it has hook like landing skids on the ends of the arms.
 

evranch

Active member
#18
Wow, those X class are awesome! I think they might actually be a little... too big for this job. They do look like tons of fun to race and I can see where they are coming from to develop the sport. Much more fun for spectators when you can see the action, 250 class are a thrill ride from the cockpit and a real snooze to watch someone fly.

I threw some questions out on a multirotor group and got these two papers regarding overlap. Basically small amounts of rotor overlap actually will boost efficiency. So it looks like I will be building off the TBS Source One (going to have to backorder it from TBS) and trying to find a folding prop between 8" and 10" to build around.

I may end up not going so overboard and falling back on the 8330F prop since it is readily available from DJI at a fair price as well as aftermarket. I don't want to end up locked in to weird props from HK... I didn't realize, but nobody makes a 1038/1050 folding prop... only smaller and larger sizes! And folding props would make a huge portability difference.

Crash course in quad design going on here, lol

Edit: Ugh, the 8330F is such a nice prop, but it's got aftermarket quick-attach mounting tabs. Currently doing some research to see if there are bases available, or if the tabs can be removed and the props can be mounted on a regular shaft.
 
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evranch

Active member
#19
Update: my desire for folding props has been an issue.

I called my LHS today and had a chat with them. I asked them to measure up some Mavic 8330 props for me, and we blew about half an hour talking about them, the mounting style and modifying them. Shoutout to Express Hobbies @ Saskatoon, by the way, always helpful and friendly. Going to buy my Mavic props from them just to support them.

In short - not going to happen on a regular motor. The tabs could be removed readily, but the bore is only 3mm. There is not much meat to overbore it as it's more of a centering pin, the drive comes via the tabs. But there is one more option to swing these props... I visited the last place on the Internet I ever go to, the home of sketchy and fake everything and shipping that makes HK look fast.

https://www.ebay.com/itm/Original-Motor-For-DJI-Mavic-Pro/254038009431

Going for used rather than "NEW! Original" makes it less likely I'll get a fake. And at $17USD for a set of 4 motors that were engineered for the props, this looks like my power system. Mavic uses a 3s so these should work just fine. Luckily I'm not in a huge hurry to build, so I ordered a set.

Just waiting for the TBS Source One to be in stock at GetFPV so I can order it as well as the stack and a camera.