Attempt to build and fly a bi-copter VTOL

[L Edge]

A number of years ago I wanted to explore the area of bi-copter VTOL's and was unsuccessful due to vibrations problems I could not solve which caused wild gyrations and frustrations with the FC. Fortunate that I put aside the beast and going to attack it for the third time.

In the meantime, used the FC and learned how to use it for differential thrust on a set of 64 EDF's.
Later on, I decided to fly (UFO), a flat piece of foam having no rudder or vertical stab using the FC.

So now I am ready to tackle it again, but decided to take on a simpler model and then my old boneyard project.. I know "Unique" does fly and if it is' totaled, not much of a lost..
Background:
https://forum.flitetest.com/index.php?threads/designing-and-flying-a-unique-plane.71513/#post-737816

It will have problems when it descends (prop wash and winds if any) but will glad to work on it if I get that far. The transition from vertical to forward and reverse will be important to get right.

So, I am going to sort of write a diary of what I encounter along the way.

 

[L Edge]

In working with VTOL's, the first thing to look at is the available FC software. The three components to look at are 1) hover, 2) transition, 3) forward flight. Forward flight is the easiest where in many cases, very little is used with the Flight Controller (FC).

Hover requires you to define and program what is needed to stabilize your launch and hover. External factors like a poorly structured vehicle, vibrations, poor programming, and airflow are factors that can destroy or damage your progress (yes, spinning prop(s)) .

Outbound Transition (IMHO) requires a time period and proof of enough thrust/lift (stability needed) to insure not dropping out of the sky.
Inbound transition(flight to hover) is usually a lot less of a program transitioning from flight to hover. Make sure there is some way to allow for programming (time and buildup of speed/slowdown and hover) in the FC.

Years ago, the FC I reviewed and picked the OpenAero-VTOL Firmware for KK2.1x Boards (V1.5)

Support:
Nothing like not knowing a thing in which you, if you forget something, end up crashing and burning. So make sure you have written instructions, support groups that cover the product(like RC Groups) and individuals that you can exchange your frustrations!!!!!!!!!!!!!!!! and continue on. Mine started the day I got the FC and try downloading the software onto the FC.

My third attempt to approaching VTOL's.
When I began, I dove into it immediately, purchased the equipment to duplicate TS VTOL project. HA!!! It beat me twice over the years and a number of close calls with the props. Before VTOL's, I tried drones(P,I,D's) adjustment and they flew like wet dishrags.

So resolved the issue by taking a plane that doesn't exist (all controls in front) and go for the third time. Hoping to simplify the experience. As I explore and play with setup of PID's etc., already know a new problem I will face. Since all controls are ahead of plane, tail buffets from prop wash is a problem as it clears ground.

What to do!!!!!

 

[Inq]

In recent years I've gotten into microelectronic hardware and programming (Arduino type stuff) and haunt a robotics forum... did a couple of robots including a self balancing 2-wheel job. At some point I'd like to look into a VTOL as @L Edge suggests with a full FC system.

However, I was raised a gear-head and like the mechanical engineering challenges also. You might consider designs that are inherently stable in the hover mode and flight modes. They did make VTOL aircraft before electronics FC. The main thing is to just get the majority of the weight below the lifting props. But that tends to set up some kind of mechanical engineering challenge.

• Convair Pogo, Martin 262A - challenge - counter rotating props so torque balances out.
• V-22 Osprey - challenge - synchronizing the props. The real plane uses a drive shaft between the two engines to ensure synchronization even if one engine goes out.

 

[LitterBug]

I have several KK2s which I have played with on the bench but never flown. ArduPilot supports quite a few cheaper F4 flight controllers these days and has great support including VTOL/transition. Been wanting to do a tailsitter VTOL myself.....

 

[Piotrsko]

Back in the day, people used a hiller style hub that was mechanically compensating for minor disturbances with paddles 90 degrees offset to account for blade precession

 

[L Edge]

I have several KK2s which I have played with on the bench but never flown. ArduPilot supports quite a few cheaper F4 flight controllers these days and has great support including VTOL/transition. Been wanting to do a tailsitter VTOL myself.....

I caught the bug when kk2 board had problems where they couldn't upload the software onto the boards. Ended up prices were slashed and discontinued by the seller. Got 6 of them.
The best thing I like about the program is in the transition you can move up by 10% increments. Where that really helps you is when you have wind, you can start it up by 10% in the transition so that it is leaning into the wind as it leaves the ground. Does the ArduPilot have that feature?

 

[LitterBug]

I will have to look through the documentation...

https://ardupilot.org/plane/docs/guide-tilt-rotor.html
https://ardupilot.org/plane/docs/quadplane-transitions.html

Maybe this is similar:. Weathervaning

https://ardupilot.org/plane/docs/quadplane-weathervaning.html

 

[L Edge]

I will have to look through the documentation...

https://ardupilot.org/plane/docs/guide-tilt-rotor.html
https://ardupilot.org/plane/docs/quadplane-transitions.html

Maybe this is similar:. Weathervaning

https://ardupilot.org/plane/docs/quadplane-weathervaning.html

Took a quick look at your refs, bookmarked it. Very similar to Open Aero, so I found the site for Open Aero version 6, so if you want to download, it has a section of how to approach tuning and good definitions for understanding, etc. I even got to understand ardupilot.
It appears in RCGroups in the first thread under files to be downloaded labeled Docs.

https://www.rcgroups.com/forums/sho...-with-transitional-mixers-(perfect-for-VTOLs)

 

[CampRobber]

In recent years I've gotten into microelectronic hardware and programming (Arduino type stuff) and haunt a robotics forum... did a couple of robots including a self balancing 2-wheel job.

Bicopters and two-wheel balancers have something in common: they both rock back and forth instead of hovering if you have any backlash in the drive system.

If I build another bicopter something I'm going to try is using spring-pull vectoring.

 

[L Edge]

After setting up the FC to the rx, decided to do safety first, so added the throttle cut to the radio to prevent prop accidents.
I decided to bypass liftoff(if programmed wrong, crash is it and damage) and start with it in the hover.
.

Will do video show how I got it to hover in bedroom.

Bicopters and two-wheel balancers have something in common: they both rock back and forth instead of hovering if you have any backlash in the drive system.

If I build another bicopter something I'm going to try is using spring-pull vectoring.

That's why I joined the servo movements to the motor/prop. The servos are metal gear driven and high torque.

 

[LitterBug]

Need to bust out my RCExplorer BiCopter. Been a while since I've played with it. Might make a good starting point for a VTOL of some sort.

 

[L Edge]

Here is first attempt to get PID right. Got some roll and pitch to adjust.

 

[L Edge]

Need to bust out my RCExplorer BiCopter. Been a while since I've played with it. Might make a good starting point for a VTOL of some sort.

go for it!!!

 

[L Edge]

LitterBug

Now is to explore PID settings so you are covering all possibilities in hovering. I intend on just cycling over and over just hovering so the end result is there are no surprises. More than once in the past attempts, the system starts vibrating, oscillating (no apparent reason) and doing damage. That's why I took a breather.

My next concerns will require me to takeoff and hover. Not having any surface controls on the bottom, prop wash and ground winds is an issue. Will liftoff and landings be an issue? Yes, so I am going to use training wheels to save the day. Much like flying a heli with fixed blades with no gyro, the skids saved the day.


See you have a variety of interest. Got yourself a 3d printer. Are you exploring 64 EDF's still?(Viggen) Is there a program for the 3D printer for a 64 mm thrust vectoring nozzle?

 

[LitterBug]

I have waaaayyyy to many projects going and the 64mm EDF BiCopter went by the wayside. Dual motor tail sitting elevon wing is what I want to do. Fairly "simple".... LOL

 

[L Edge]

I have waaaayyyy to many projects going and the 64mm EDF BiCopter went by the wayside. Dual motor tail sitting elevon wing is what I want to do. Fairly "simple".... LOL

So basically a HH X-Vert.

 

[LitterBug]

So basically a HH X-Vert.

Sorta ish

 

[L Edge]

Today, I finished up playing with the PID settings when it began to hover by itself(with drifting due to up and downdrafts created by the props.
Again, did not do lift off by itself or land. It was released after hover about 4 ft above ground in bedroom.

Made a pair of homemade skids(rounded off at ends) so it would slid. That way, I would keep the damage of props, servos, motors to a minimum.

Used ties to hold wood dowels to rudder.

Now I would be able to bypass the prop turbulence and eliminate the tipping over doing t/o and landings and losing it trying to fly it.

Sure enough, the bird was out of trim and I had many saves by the skids.

It is weird to add throttle and jockey it to hold the height,(always fighting gravity for up and adding gravity for down motion)
elevator pushed forward to move away from you,
right aileron has the left wing coming at you to roll it,
and when you hit right rudder(you better not mover the throttle up or down), left wing rises up and it slides to the right.

Got about 10 min of play with 2 batteries. No damage.

What is needed:
1) retrim hover settings.
2) redo P,I,D setting
3) got to really do a lot of hovering(project good for winter months) and adapt so hovering is just as comfortable as regular flying.

My goal is to hover, make transition to forward flight(easy since it has a large wing) and do forward flight.

The transition time back to hover is going to be short and into the new way flying mode. Think about backing down say 20 ft. Remember, I don't have elevons in the rear, all control is in the top area. I hope to come across the field about 2-3 ft and pull up into vertical and stop about 5 ft high. Then descend and land. Did I cover any wind? Will address weapon I have for that.

So, you want to try a tail sitting bi-copter VTOL?

 

[LitterBug]

So, you want to try a tail sitting bi-copter VTOL?

Yes! Yes I do! There are times and places where being able to climb out of a hole, transition to flight, transition back to hover, and land back in that hole would be most benefitial. Like leaving from and returning to the Bat Cave!

LB

 

[L Edge]

It is a very interesting project. I am finally up and running.

It reached the point it is cellar time. With the control of action of roll, pitch and yaw all taking place before the leading edge with the assist of the flight controller, it reacts different then flying my 3D plane. Yaw moves "eyespy" sideways so quickly due to prop thrust and rotation is slow, and pitching forward/aft is right on. Lifting off produces swirls and really moves the plane around erratic. Hope I can solve all my problems. at.

So now I will to start re-tuning PID, auto level and fast changing altitude. Meantime, I went back to the sim, need to find a 3d plane that acts like mine and do some practice hovering. Can't wait for a calm day outside to get away from prop wash generated in the cellar. Basically, I am flying a vertical flat plate.

Will do video in cellar when I get a "good handle on it".