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Throttle Cut Mix on a Multirotor

FinalGlideAus

terrorizing squirrels
#1
One of the more annoying things I've had to put up with flying a multirotor coming from a fixed wing background is it's natural for me to chop the throttle during certain maneuvers. It's also a pain when you are trying to descend fast and you accidently drop the throttle just a little too much. The end result when you hit zero throttle is the motors stop and you loose all control and down it comes. Often throttling back up from a dead stop causes a spin which can be hard to recover in time. I have broken my fair share of props in similar circumstances and after getting my Warpquad airborne I heard some things the heli guys do so I decided to try a multirotor version out. One of the big reasons for trying this is because the Warpquad is soo over powered it hovers 20% throttle which gives little room for error when throttling back for descents.

Essentially what this mix does is allow a low enough throttle setting for the mulirotor to be armed and then after it is armed a throttle cut mix switch is used to change the minimum throttle stick position to just above zero throttle. This not only stops you from getting to the point where the motors stop but you also have full control at Zero throttle position. There are plenty of different ways to achieve this but I'll try to describe how I did it.

My quad's Flight Controller is a Naze 32 my TX is a DX18. When connect to the computer the Naze shows it is set up so minimum throttle is 1150 and max throttle is 1850. To get the quad to arm I must set the end point adjustment in my Transmitter to go lower than 1150 other wise the Naze will think I still have some throttle on an not allow me to arm. Normally you would set it to something like 1146 and it arms fine and you can fly but of course when you drop the throttle below 1150, the motors will stop.

What I did was adjust my throttle end point adjustment so low throttle was 1156 (just above the min value of 1150). This means the motors won't stop when I lower the throttle stick but I cannot now arm the quad to get them to spin in the first place. To fix this I then I set my throttle cut mix in my transmitter on a switch so that when it was active it lowered the throttle point to 1146 thus allowing it to be armed.

So now, after I plug the battery in I first make sure the throttle cut switch is on, then arm the quad and then turn off the throttle cut switch. This then starts the motors at idle speed and I have full control at Zero throttle. When I wish to stop the motors I simply flick the throttle cut switch again. It's really simple and works like a charm and I no longer need to worry about the motors stopping mid flight.

It is worth noting why I set the min throttle to 1156 and not to the Naze min level of 1150. I originally tried that but because the motors are so close to their min value some motors will cut out when you try to maneuver. Adding that little buffer fixes the problem and that value is less than .5% throttle you are loosing which was never really usable anyway.

Anyway, like I said, there are plenty of different ways to do this with your particular radio but if you spend a little time working out how to do it you'll never have to worry about that pesky in air motor stop while doing acro again.

I did a couple of zero throttle descents in the video I took of the maiden flight of my warpquad today:
https://vimeo.com/92301242
 

cranialrectosis

Faster than a speeding faceplant!
Mentor
#2
Couple of things here.
1. I see lots of video of copters. Small copters moving fast are notoriously out of the view or too far away to see in the videos. This is fantastic footage.
2. I love how you fly. Double flips. Yeah, someday soon....
3. Green grass. You bum! It was 50 degrees F and quiet wind yesterday and I had to work. By the time I got home the wind was doing 30mph. Today it will be 70 degrees F and quiet and calm all day until about 16:00 Mountain time. At which point the next snow storm moves in and the wind will be doing 40-50mph and snow all weekend long. I get home from work today about 16:30...Snow ends Sunday afternoon and the weather will be in the 60s Monday just in time for me to go back to work. Likely no flying all weekend for the sixth weekend in a row. Green is just now starting to show its face in Colorado and will be buried under white all weekend.
4. Man that is a BEAUTIFUL copter.
5. Are you doing flips in acro mode or in Horizon mode on the Naze?

Keep it coming FGA. Snow or no snow, the site of green grass and the sound of rotors is getting me all worked up to build and fly!
 

FinalGlideAus

terrorizing squirrels
#3
Happy to oblige Cranial. I feel very lucky to live in a beautiful part of the world. Mind you, the heat and humidity here during summer can stretch your tolerance levels at times. I'm glad you enjoyed watching the video. It was my first video uploaded to Vimeo which I think ill use from now on but I'll try to post the next movies in 1080p and try to fix the out of sync frame rate. Learning as I go.

All my flying is done in acro mode (or rate mode as Naze calls it). I tried self level mode early on in my flying and I despise it. To do proper acro flying you must be in acro mode. It is very important that the multicopter holds it's position when you centralize the sticks. Flying in a mode that fights your controls inputs all the time just makes things harder.

I'm really eager to hear how you progress with Warpquad.
 

ikem

Senior Member
#4
I dont use my throttle cut like you are talking about, but I programmed it to auto land where it is at. Just incase of an emergency situation.
 

Cyberdactyl

Misfit Multirotor Monkey
#5
Very nice flying! And man does it go. I don't fly anywhere near that radically so having my throttle shut off when the stick is all the way down isn't an issue. But thanks for the idea, I may need it someday once I get better.

Oh . . . and talk about FAST, check out a similar size quad Warthox is trying out with the developer. It's insane.

https://vimeo.com/92324878
 
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FinalGlideAus

terrorizing squirrels
#6
Very nice flying! And man does it go. I don't fly anywhere near that radically so having my throttle shut off when the stick is all the way down isn't an issue. But thanks for the idea, I may need it someday once I get better.

Oh . . . and talk about FAST, check out a similar size quad Warthox is trying out with the developer. It's insane.

https://vimeo.com/92324878
Thanks mate, Yes Soma and I are very keenly waiting for those KISS esc's to come out. 4s on those little motors is awesome!!! Soma has already done some testing on 4s but with the current esc's that we use now on the mini quads like the blue series 12a he gets really bad syncing issues which leads to dead motors. The KISS esc will fix this but then the weak link will be be the battery. We really need a 4s 1000 70c battery.

I think I'm getting addicted to speed and power. mwaaahhaaahaaahaaa.....:cool:
 

jhitesma

Some guy in the desert
Mentor
#7
So just to clarify, the Naze doesn't keep the motors spinning all the time when armed like MW does? I had just assumed it would since it's based off of MW and MW does that.

I do kind of wish I had a throttle cut setup on mine, but I'm out of appropriately placed switches at this point. I have a lot of fun with my X1 flying it with my 9x and using the throttle cut I have on there. It's the only way I've been able to do flips on that quad without the stock controller and it's auto flip button. (And even with the throttle cut it's tricky and takes a bit of wind and great timing to pull off - I've only done it successfully two or three times and failed quite a few more.)

I may try reclaiming my normal throttle cut switch to play with though since right now I'm just using it to trigger either headfree or headlock and I don't really use either of those....hmmm....
 

FinalGlideAus

terrorizing squirrels
#8
The Naze does spin up the motors when armed by default but you can remove that feature in the CLI. Besides, even with the motors spinning when armed you still don't have any control.

When buying a radio I have always put decent $$$ down when deciding which to buy. I never like to run out of mixes, switches and flight modes. This has always been important on my fixed wing aircraft but with multirotors the FC does most of the work until now when I've started to get tricky with my mixes.
 
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Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#9
as of at least 2.2, Multiwii will allow you to cut the armed motors off. You've got to uncomment the "MOTOR_STOP" define statement in config.h to do that.
 

jhitesma

Some guy in the desert
Mentor
#10
Good point about keeping them high enough to maintain control, and I knew MW could be configured to keep them from spinning...but personally I like it since there's no mistaking if it's armed or not.

I'm actually not out of switches on my 9x - just out of switches I'm used to reaching for while in flight ;) I could use one of my DR switches that I'm not using on my quad, but they're a bit tricky to reach for something like that. I am out of aux channels for switching things on the FC but that's a limit of the FC since with the openLRS I could run more than the 8 RF channels I'm currently using. But MW only supports the 4 aux channels without some code tweaks and I don't need the extra channels that much. I am starting to run out of memory in my 9x now but I've got a few models in there I don't use anymore and could zap if I really did run out.

I suppose I could try moving my headsfree/headlock aux channel to one of the DR switches and then I'd have my usual throttle cut switch available again. But I'm so used to what it is I'm worried I forget and hit the wrong switch ;) I may prep a mix and just not assign it to a switch yet in case I decide I want to try it out this weekend. Just not sure if I'll even get to fly. Tonight was supposed to be WTI where the marines do practice evacuations from a park in town just a few blocks away - it's like an airshow without leaving my house as their approach comes literally right over my house. Chinooks and Hueys about 200ft over my yard. But they had to cancel today because of the wind. Wouldn't you know, all week it was dead calm but I had no props - now I've got props and it's so windy the marines call of their exercise. Might be calm in the morning tomorrow and Sunday though...fingers crossed.