I Have Variable Pitch but What Flight Controller?

[691175002]

I've built a set of these guys:

Each one weighs 122g with blades and can produce 600g of thrust in either direction off of a 2s lipo so including battery the weight is comparable to a standard quad motor.

I have no idea how I am going to make it fly. It looked like the coptorcontrol board was my best option because it was easy to adjust the min/max throttle and update rate (so I could seamlessly use servos instead of ESCs) but I don't forsee getting my hands on one anytime soon.

 

[Macsgrafs]

A few days ago on an FPV forum I was talking about using heli tail rotor units, but with 1 large motor & torque tibe drive the tail units. To answer your question, how many units are you going to use & it what formation?

Ross

 

[691175002]

It will be a standard quad. I've got two clockwise and two counter-clockwise units.

If this works out I'm hoping to do a belt/torque tube version with a single motor.

 

[Stacky]

I love seeing people try stuff out. Hope you are successful.

 

[MombasaFlash]

I love seeing people try stuff out. Hope you are successful.

Me too. That is quite an adventure you have started there. And really neat job too!

 

[Macsgrafs]

It will be a standard quad. I've got two clockwise and two counter-clockwise units.

If this works out I'm hoping to do a belt/torque tube version with a single motor.

So let me get this right, a quad with a total of 2.4Kg of lift. Looks like you will have to watch the weight of any flight controller very carefully!!! I would personally go for one of the well known brands, MK, Wookong? or the like, especially since in the very near future you will be upgrading to something more powerful & bigger.

 

[DennyR]

Neat idea, autorotations possible! As a proof of concept I think your best bet would be coptercontrol to keep it as light as possible. The thing to remember is that you need very fast response so don't get too large on the rotor dia. The nice thing about the pitch control is that it should be faster than the motors torque change.

 

[RTRyder]

Very nice! I'd like to have something like that to work with myself, been giving it a lot of thought and what you have seems to make the most sense on how to do it. Regardless of the flight controller you use I think it's probably going to take custom code to make it work, servos vs ESC is just too different for anything off the shelf to work perfectly with both. In any case you might try this as a starting point for a flight controller, Minsoo has the code written to work with 4 servos, how well it works or if it's suited to you application I have no idea... http://www.kkmulticopter.kr/index.h...=KKMulticopter&sn=multicopter_v02_si&id_no=55

Ken

 

[DennyR]

I have flown a minsoo servo copter and it was good.

 

[Macsgrafs]

I have flown a minsoo servo copter and it was good.

Is that a tricopter?

I was thinking if its a quad then 4 x cheap gyros & 4 servos + standard RC receiver might also work? You can use a PMIX on your transmitter to mix each servo to operate in time with its 180 degree partner but opposite as well, bit like ailerons on a plane wing.

Ross

 

[Droider]

It looked like the coptorcontrol board was my best option because it was easy to adjust the min/max throttle and update rate (so I could seamlessly use servos instead of ESCs) but I don't forsee getting my hands on one anytime soon.

I have one sitting in my drsk draw if you really want one

DAve

 

[Bartman]

are you going to have constant RPM with variable pitch for lift and control? I'd think you could use the standard MK mixer table but it would be interesting to see if the control algorithms can keep up.
a suggestion for future development would be two motors per rotor offset laterally from the centerline of the arm. if you run constant rpm you could swing a pretty big rotor like that. eraly on I was considering it but with fixed pitch and variable RPM. what you're doing would be so much more elegant.

 

[Bartman]

Very nice! I'd like to have something like that to work with myself, been giving it a lot of thought and what you have seems to make the most sense on how to do it. Regardless of the flight controller you use I think it's probably going to take custom code to make it work, servos vs ESC is just too different for anything off the shelf to work perfectly with both. In any case you might try this as a starting point for a flight controller, Minsoo has the code written to work with 4 servos, how well it works or if it's suited to you application I have no idea... http://www.kkmulticopter.kr/index.h...=KKMulticopter&sn=multicopter_v02_si&id_no=55

Ken

isn't the command range for control the same for an ESC as it is for a servo?

 

[691175002]

I'm hoping for an all up weight of 1-1.2Kg and total thrust of ~2.4Kg which should fly very well. I suspect that variable pitch can get away with less thrust:weight because it is capable of delivering maximum thrust in an instant instead of using the power to spin up the prop. The four motor/prop assemblies weigh 500g together so that leaves 700g for the battery (4000mAh 2s), frame and electronics.


I've been going through the docummentation for the various flight controllers.
While servos and escs are controlled fairly similarly there are a few differences - Many of the flight controllers output the pulses at 400-490Hz whereas most digital servos can only handle 333Hz. As well, I need to slightly limit the travels on my servos because at maximum pitch the blades might stall. Some sub-trim would also save me a lot of fiddling with the linkages. So far the CopterControl board is the only one that offers all those features (And even better, they are all configurable from a GUI) so it looks like the best choice.

My initial plan was to run the motors in governor mode (constant RPM) and vary only the pitch. Governor mode looks like a real pain to set up though so I might configure it more like a traditional CP heli with normal and idle up throttle curves.
I noticed the custom mix settings for the CC board will allow ten outputs which means that in the future I can also take advantage of the ESCs and mix yaw into RPM or other tricks.


I believe I've picked up one of the CC boards which will help things out greatly. The alternative would require a lot of code and pain.

 

[Bartman]

what is governor mode? I'd think a switch on the transmitter with a set motor speed would deliver what you'd need, no? wouldn't the motor work to return to the set value if a sudden pitch change loaded up the motors? maybe a mix in the transmitter to help the motor a little with big pitch changes?