Helcopter Flybarless controllers

[Pchristy]

I now have a couple of helicopters with flybarless control systems, both using obsolete components provided by my son (his cast-offs)! New ones are very expensive, so I've been looking at alternatives.

A couple of years back, I came across a thing called Rotorflight. This was a modification of the Betaflight software popular with drone flyers. Both are community led, open-source projects. In other words, like OpenTx and EdgeTx, these were created by model flyers, for model flyers.

Of course, having the software is one thing, but you need hardware to use it. Fortunately, as Tobe and Mike_K have shown elsewhere on this forum, it is not difficult for those with the necessary expertise to have small, but very profssionally manufactured production runs of quite sophisticated electronic systems. So it is with the drone controllers.

By the time I started getting involved, one of the common modules was the Foxeer722 series. I got two of the version 3 boards (since superseded - development is that fast!) with which to experiment. These boards can be programmed to accept a wide variety of inputs, but the simplest and easiest involve SBUS (for the control channels) and SPort (for telemetry). Most FrSky receivers offer both these as standard, making connection between a standard receiver and the controller a simple matter of two 3-wire servo leads. There is now a later protocol called FPort which combines SBUS and SPort into a single, bi-directional connection, meaning that it should now be possible to connect using a single 3-wire cable.

My first attempt at this worked, and was fitted into an Align 450 size helicopter belonging to my son, and successfully test hovered.

However, is has to be said that it was not the easiest thing in the world to set up!

Spurred on by this, I made a second prototype, this time incorporating a built in receiver, making an all-in one unit:

I made a 3D printed case for it, and the FrSky R-XSR receiver is tiny enough (11x16mm) to fit snugly inside the case. SBUS and SPort connections directly to the stabiliser board mean that only 4 wires (2 power, 2 data) connections are required for the receiver to talk to the controller. A five connector servo board is added for four servos (3 cyclic control, 1 tail-rotor) plus a power/esc connection.

Several manufacturers are now producing very nice ready made units, to save the trouble of making your own. Most still require an external receiver, though it is possible to use satellite (Lemon/Spektrum) or micro-receivers (like the aforementioned FrSky) connected externally.

I have just bought a Radiomaster unit to play with, which is beautifully made, and one of Stuart's Lemon satellites is curently winging its way to me to experiment with.

Here's a comparison with my home-made, all-in-one unit with the Radiomaster Nexus:

Of course, all these still need programming, but Rotorflight released Version 2.0.0 earlier this year. This is a major upgrade (and sadly, not backwards compatible) which promises to make things easier to set up. Programming is carried out from Rotorflight's own configurator program (available for Windows, Mac and Linux) via USB - with no dongles required. Just plug straight in to the computer.

Fine tuning can be done from the transmitter via LUA scripts - if you have OpenTx or EdgeTx.

Still lots of playing around to do before I get any of this in the air, but it should be interesting! And even the ready built units are around half the price of the cheapest fully commercial flybarless controllers! Win-Win!

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Pete

[Phil_G]

The all-in-one is really neat Pete, I wonder if there any possibility for Lemon to integrate Rotorflight into their stabilised receivers?

[Pchristy]

The hardware is common to the drone stabilisers, as used by Betaflight. Rotorflight is a firmware adaption to make it work with conventional helis. There are manufacturers already making "all-in-one" units, but the receivers they have chosen are not ones I currently have in my arsenal!

The Nexus unit has a dedicated DSM port, so I got a Lemon satellite receiver off Stuart to experiment with. Sadly it doesn't appear to support telemetry, unless connected to a "normal" receiver, and my efforts to get it to talk properly to the Nexus have so far failed! (Almost certainly a misconfiguration on my part!)

I have got it to talk to a FrSky X4R receiver over F.Port. F.Port is FrSky's own protocol, which combines S.Port and SBUS into one connection, meaning you only need a single 3-wire connection to join them. That tiny R-XSR receiver I used in my "all-in-one" unit also supports F.Port, but I made that before F.Port was available as an upgrade. Also, as its hard wired internally, it only needs one extra wire to have both SBUS and S.Port connections to the flight controller anyway.

Unfortunately, FrSky seem to be phasing out their ACCST receivers in favour of ACCESS, and the available range is growing ever narrower. I bought an X10S transmitter thinking it would see me through to the end of my flying days, and I'm certainly not going to splash out on another expensive Tx anytime soon! That's why I was looking at the Lemon satellite as a possible alternative, but it doesn't quite tick the boxes. Close, but no cigar!

I would have thought an outfit with their manufacturing skills would have found it easy to produce an all-in-one unit, but perhaps they don't have many drone or heli pilots on their staff. The guys on the Rotoflight forums are raving over the Nexus and similar ready-to-use controllers. They are certainly a LOT cheaper than the established controllers, if not quite as easy to set up.

Can't help feeling I should have posted this project under electronics rather than 3D printing! I just wanted to show how compact it was possible to make these things. My all-in-one unit is about the same size as the MacGregor Minimac I cur my teeth on, back in the 60's.....

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Pete

[Phil_G]

Can't help feeling I should have posted this project under electronics rather than 3D printing!

Done!

Might be worth having a chat with Frederick, he's very approachable and open to ideas...