Designing/making a VTOL (aka V-280 Valor, Bell XV-15, or the V-22 Osprey)

[JasonK]

Some random related bits of math for if this flies good and I want to rebuild it 'better'.

based on WCL, I can increase the wing by about 160% and double the AUW. Making the craft bigger definitely improves the ability to make it 'work' ->

	Wing Area (in^2)	weight (oz)	WCL
approx current	144	15	15
'doubled'	229	30	15

given a bunch of the weights of stuff won't double with increasing the wing span by 26% (26% upscale in width/length of wing, length of tail boom, width/length of tail feathers), some stuff won't change weight at all (flight controller, some of the servos, motor pods other then a bigger motor)... I will actually end up better off on weight and even be able to reinforce some parts that would be good being stronger, but I can't afford more mass to do so right now.

 

[quorneng]

jason
Remember the strength of a structure made of the same material does not increase at the same rate as its weight. In principle bigger is weaker unless you get clever with the stress analysis and use appropriate materials and sections.

 

[JasonK]

jason
Remember the strength of a structure made of the same material does not increase at the same rate as its weight. In principle bigger is weaker unless you get clever with the stress analysis and use appropriate materials and sections.

I know that, but my wing spar is stronger then I need it as is... and other parts will be fine as is. there is also the whole span related stuff... IIRC 2x the span 4x the flex for the same material (or something like that).

 

[JasonK]

today:

• got power pods mechanically built & installed on craft
• got serial receiver to bind to TX, got it talking to the flight controller board.

waiting for a longer servo extension to make wiring up the pods easier.

hoping to be at a point were I could test hover by the end of the week.

 

[JasonK]

well.... my goal of testing this weekend might have been set back a bit... it looks like iNav, Clean flight, & betaflight all appear to share motor mixing code and it assumes a fixed(ish) motor position... or at least one were the impact on pitch/yaw/roll is constant, which doesn't work for tilt motor vtol as motor differential is roll in bi-copter config and yaw in fixed wing config.

means I need to find a firmware that does support what i need, figure out how to update the code to add my needed feature, messy hack in what I need... or write custom firmware ;(

a quick look at ardupilot's code, I see something that looks like a bi-copter vtol option. will have to look at this further.

 

[CampRobber]

a quick look at ardupilot's code, I see something that looks like a bi-copter vtol option. will have to look at this further.

It wasn't hard to set up the appropriate mixes to make bicopter mode work in inav. I haven't attempted forward flight yet, though.

I am going to attempt the messy hack.

 

[JasonK]

It wasn't hard to set up the appropriate mixes to make bicopter mode work in inav. I haven't attempted forward flight yet, though.

I am going to attempt the messy hack.

right... the issue isn't bicopter, it the transition between bicopter and forward flight which requires changing the mix for the motors, which isn't supported in any of the listed FC firmwares (they all share quite a bit of their code base, that part in particular).

I would have no issues with bi-copter or forward flight with iNav, it is the abilility to do _both_ with one config, that is the problem.

 

[F106DeltaDart]

1 - that craft looks intresting, how big/heavy is it? is there any more details on it?

I already have a F411 wing FC sitting on my bench.. but haven't seen openaerovtol yet, will look it up.

It was known as the Bell BAT (Bell Advanced Tiltrotor). Was designed as a single person scout aircraft.

 

[JasonK]

ardupilot:
https://ardupilot.org/plane/docs/guide-tilt-rotor.html#bicopter-tilt-rotor

looks like this is what I am looking for...

 

[Zephyr1]

It was known as the Bell BAT (Bell Advanced Tiltrotor). Was designed as a single person scout aircraft.

Yup, and i've gotten a few flights out of it. This is my really garbage first build. I purposefully put not extra work into this so when it crashed (and it has many times) I wouldn't be too upset.

 

[tamuct01]

ardupilot:
https://ardupilot.org/plane/docs/guide-tilt-rotor.html#bicopter-tilt-rotor

looks like this is what I am looking for...

Ardupilot does have many VTOL options built into the QuadPlane line of code. I've been doing some research on it myself for my V-22 build, but they currently don't have support for my frame class. I'd have to write my own. That's fine by me, but I don't have a good handle on the code structure yet to be able to do that.

My V-22 is made up of two 450-sized heli rotors with 3 cyclic servers per rotor. I had a prototype built using a S8R receiver and Arduino doing the mixing, but it was not very stable. I've just purchased a pair of Castle ESCs that support heli governor mode, so that should help some. The previous ESCs were cheap without governors.

 

[JasonK]

Ardupilot does have many VTOL options built into the QuadPlane line of code. I've been doing some research on it myself for my V-22 build, but they currently don't have support for my frame class. I'd have to write my own. That's fine by me, but I don't have a good handle on the code structure yet to be able to do that.

My V-22 is made up of two 450-sized heli rotors with 3 cyclic servers per rotor. I had a prototype built using a S8R receiver and Arduino doing the mixing, but it was not very stable. I've just purchased a pair of Castle ESCs that support heli governor mode, so that should help some. The previous ESCs were cheap without governors.

ahh yes, I don't think anything has something for that setup... which actually sounds like it could work better after all the tuning/etc gets worked out.

 

[JasonK]

got the wires all fished through the plane:

456g without the ESCs... so about 465g AUW... about 15% more then my goal.. should still leave me with 1.72:1 thrust to weight, I think this will still hover ok, but will have to see, might be to close.

 

[JasonK]

It looks like I will be delayed in finishing the electronics, ran into an issue with the power issue for the servos on the FC.

See this thread: https://forum.flitetest.com/index.p...-troubleshooting-servo-bec-power-issue.66287/

If not for that, I would be hover testing right now.

 

[JasonK]

motor pod servos are working... just gluing down the wing, so I can do the final setup and prep testing to setup the hover test.

 

[JasonK]

well... it "hovers" after fixing an issue with my TX -> FC config which was causing an issue with yaw, were the gyro was amplifying any issues instead of reducing them... Still has a whole mess of tuning it needs before it is stable however.

Initial 3 'flights' I had the yaw and roll backwards on my TX compared to what the FC expected, so I had both yaw and roll failures on the first attempts of flight. Flights 4 & 5 are after I fixed the TX config and then fixed the FC config that was wrong because of the TX config issue.

Looks like I will have to play with the PIDs and Rates a bit to get this more functional.

 

[JasonK]

• Setup angle mode (get the FC to help with balance, maybe didn't work as well as I would have liked)
• lowered the rates, removed the I term on pitch (so it doesn't I to the moon)

ended up with really bad pitch oscillation. I think I need to turn down the Feed Foward and the P gain on pitch. For some reason the D term is disabled in the iNav configuration... I suspect this setup could use some D term here, but will wait and see with lowering the P and FF to see what happens.

cracked a motor pod on the landing and will need to reprint it and give the craft a check over from that landing. if not for level issues, moving to something softer to test over would be a good idea to ease up the landing.

 

[JasonK]

More tests in angle mode after making part of the motor pod thicker (it kept snapping at the same point). Yaw seems just fine, roll has some minor oscillations, but the pitch oscillations are basically out of control . for some reason iNav has the D term disabled on me and won't let me set a D term and I suspect that it is probably needed given the response speed of the servos/etc.

 

[CampRobber]

for some reason iNav has the D term disabled on me and won't let me set a D term and I suspect that it is probably needed given the response speed of the servos/etc.

Inav disables the D term in fixed wing mode.

 

[JasonK]

Inav disables the D term in fixed wing mode.

ugg that sucks... because "other" errors, and the quad/tri stuff reserves most of my ports for motors.

I am starting to think that I need to re-write the system...