The wings should have their center of drag in line with the center of mass of the craft to avoid introducing the pitch moment that caused the oscillations. This is tough because the wings would have to be mounted even farther outboard to avoid colliding with the rotors. If the front/rear motor pairs were moved more frontward/rearward instead, clearance for the wing could be introduced without elongating it and the available pitch moment from the motors pair would be increased, allowing it to more effectively counteract any pitch-wise disturbance.
that plus these wings are dead they have no control surfaces to combat aerodynamic forces like you would have in any real or model rc aircraft, adding this would likely fix it. ditch the homemade wing and get one for a rc plane that has all the control surfaces built in and intergrate it into the drone so that its software begins operating them to keep it in line with its stabilization programing. Also there's another way to improve efficiency , by changing out the rotors for the torodial design they not only improve flight BUT are near whisper quiet making the drone hardly noticable
Yes. It should have neutral static stability so the rotors have authority. I.e. the aero body must be orientation agnostic with respect to the relative wind and generate no torques about the cg. I don't know how close one can come to this in reality. None of these designs ever come close though because they don't even try.
The other thing to consider is the fact that, not only is the wing causing a pitch moment due to induced forces, the center of mass is now shifted higher if not above the motors creating an unstable system. Even just adding a ballast below the quad could theoretically make the motor control play a little nicer.
I had a thought in a slightly different direction. How about 2 smaller wings, one in front of the front motors and staggered vertically but forward and out of the prop wash path, and the rear staggered slightly below the vertical rotation axis of the rear motors, behind the rear motors, again out of the wash path. So front and rear wings. This would of course require a landing gear to prevent awkward takeoff. But with the same pivoting wing with rotation stops would certainly have fair upward lift without the interference with prop flow paths. It should also equalize the load decrease across the motors..
The wing should be placed in the same way as it would be on an airplane, at the center of mass or further back. to me it looks like the quad is fighting against the instability of its back heavy nature. "A front heavy plane flies badly, a back heavy plane flies once" - Some kerbal space program enjoyer
Move the wings down to the center of mass of the drone, to avoid having it add a speed-pitch feedback making it unstable. Control the wing AoA with a servo so that it's always correctly oriented relative the direction of travel through the air. Perhaps add a few degrees of dihedral to the wings to get a bit more stability. Use an airfoil section optimized for the very low speeds seen here, something appropriate for maybe 1-3 million Re.
The "dihedral=stability" equation is not so clear cut. the way dihedral works is by rolling the plane in the direction opposite sideslip at positive AOA, but with this arrangement that just adds more complexity for the control system to fight against.
All the issues mentioned have been resolved and patented in US Patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones". We are scheduled for the release of our product line soon.
Maybe have the rod going through the wings be closer to the center of mass of the wing so it's easier to reach the edge case. This way, the drone uses less energy to keep the wing up
At Warwick university I saw a drone/fixed wing hybrid that had a stationary delta wing which was vertical when on the ground and then the drone completely turned horizontal during free flight thus turning into a fixed wing plane with a rotor above and below each side of the wing. I imagine this required custom software to calculate the best angle of attack for different speeds.
The RC aircraft X-Vert seems to be what you are describing, but with only a pair of motor. It uses pre-programmed maneuvers to transition to fixed wing and back again, while also changing the flight controls to be the standard for each.
Tailsitters are efficient for long range, although as a camera drone the body interferes with the downward field of view at low speeds or hovering, and cannot fly sideways at higher speeds. The concept in this video has been patented in US patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones" and we are scheduled for the release of our product line soon.
For years we have been privately testing this exact concept with over 300 test flights on DJI and other drones and we filed a patent in 2019. All the issues mentioned in the comments have been resolved and patented in US Patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones". We are scheduled for the release of our product line soon.
With a properly tuned flight controler taking the wing into account, I think your preliminary data shows the wing it might have a significant efficiency gain in forward flight. I think for certain mission profiles you're onto something. As always great video Thanks
I'd really like to see this experiment repeated with the anomalous motor issue fixed. Like you said having one motor completely idled is really going to mess up the quads ability to stabilize itself and it might be a lot better without that problem present.
The way you mounted the wing high above the quad puts the center of lift ahead of the CG when the quad pitches to translate forward. Thats almost certainly the main cause of your pitch instability in fast flight. The front motors are decreasing in speed to the point of idling because pitch moment from the forward positioned wing is so large it's taking all the load off them.
rctestflight your research is inspiring and see where you are going. Based on your RPM data showing distinct differences between 4 rotors perhaps prudent to try positioning 4 separate wings behind the thrustline (beneath) of each rotor. So as each rotor thrust will behave independently and observe any change in stall threads attached on low pressure surface of each wing in full throttle forward cruise. In turn cumulative lift may show where lift disparities exist. Good job of messing around so much with this, excellent!
A tail-sitter craft with four props in a quadcopter orientation, can easily make the transition to forward flight. The camera gimbal can be held on a swinging (pitch) axis. Keeping the entire camera assembly below the craft as it transitions back and forth between forward flight.
agreed. i have been watching his videos for years and its always fascinating yet informative along with his uniquely deep voice being chill to listen to lol
How about the sort of angle-of-attack control tail/elevator thing you used on your rigid wing sailboat? I think that would be a lot smoother than the hard stop on the wing angle.
Or an tuned progressive elastic resistance to the AOA? Like 3 different surgical tubing lengths in parallel, that way the AOA would be a function of the airspeed. You could still have a hard stop and the period of the oscillations may be longer as well. The tuning might be tricky, but maybe with force meter measurements on a hard stop for several AOA/airspeed combos you could tune the elastic dampening. Great video!
No way bud. The wing should be centered on the CG. Any aerodynamic stability, positive or negative, is going to fight the pid controllers. Aerodynamic stall is desirable in some cases and a normal part of the maneuvering flight regime. An AoA sensor should feed the FC to inform cruise efficiency. Get all these nasty aerodynamic flipperon things out of here. This is a quadcopter!
What if you put the wing fixed perpendicular to the rotors and in flight go full throttle and angle the quadcopter 90° forward and use it as a conventional aircraft. But then basically you've converted it into a VTOL
I love the idea and it apparently works a bit, extend the wings out beyond the rotors and mount it to the bottom of the frame of the unit. maybe make the size of the wings about 1/4 of the size that you have on there now. just a thought from my head.
For a future video, try mounting the wing below the rotors, this may seem more unstable but it's highlighted to be just as viable as above aerodynamically by the drone pendulum fallacy. Having the wings below will allow them to rotate without the consequence of hitting the rotors, potentially allowing you to bring the CoL closer to the CoG (although, I'm not sure whether the downwash from the rotors will impact this).
Great idea but I think it would need a rewrite to the controller. Combining what Zipline does with being able to take off and land anywhere would be great
Have you considered a "freewing" system? Essentially, build the wing as a flying plank with a reflexed airfoil, or with a trim tab to adjust the reflex for different speeds, and then set the pivot so that it matches the flying plank's CG. With this setup the wing should hunt for the ideal angle of attack in the relative wind without needing a stop.
The drone is missing some kind of more effective pitch control like in standard airplanes, i think this is causing the oscillations. Also fins below the rotors maybe would prevent the rotation of the airflow, which could boost efficieny as well
I agree. I think the flight controller program would need to be designed for this hybrid design and also include servo control for wing pitch, and then it should be able to effectively counter the instability.
I’ve been designing and flying RC planes for 40+ years. In order for this to have any chance of working, you need to do two things. First, get the center of mass (CG) of the drone about 35% back from the front of the wing. Second, use an accelerometer, servo, and small microcontroller that can adjust the wing’s angle of attack so regardless of the flight angle of the drone, you keep the wing’s angle of attack to the wind in the 0 to +3° range, depending on the airfoil. Otherwise, the wing just acts like a big sail.
Late to the party, but I think the performance would be better with the wing mounted just below the props instead of above them. It'll also be a more compact overall package.
the down wash of the props would keep pushing the wing down aswell as messing with the airflow over the wing so idk if it would be better, would like to see it tested still
Feedback: one way to avoid negative pitch moment at high speeds is mount a fixed-pitch wing forward of CG (1-3 degrees positive AoA); a slow climb is way better than a high speed crater Next experiment: Place the wing below the rotors & fix the pitch (to eliminate oscillations). Test your theory regarding rotor wash. You might also want to experiment on wing placement (test forward of CG & aft of CG).
I'd love to see you push this idea a bit further. an idea I had would be to have 2 wings across with 2 rotors set into each wing. That might give you more stability. in any case, love the vids and cant wait for the next one!
In the hover (or "drone") orientation, having the wing above the center of mass increases stability. (In terms of forwards/backwards speed: going forward increases drag on the wing, which is above the center of mass, so it pitches you back, which decreases drag, and so on.) If your drone pitches forwards into "plane-like" orientation and tries to go fast, it is putting the wing in front of its center of mass - A very famous thing that is making a craft unstable. There's 2 possible solutions: *Either* move the pivot rod to *below the rotors* to get it to the same height as the center of mass or below it. In this case you'll loose the stabilization in drone-mode. *Or* move the pivot rod further *towards the rear* of the drone. That will increase the stability in the airplane-like orientation. You can get away with keeping the wing above the propellers if your drone never pitches more than 35° or so down (which may _not_ be true, since I expect optimal efficiency gains close to 90° down pitch).
Here's my silly idea: Instead of large solid foam wings, use small spools of fabric and pairs of linear tracks to create the airfoil. Winches made with continuous servos will be used to extend the fabric, while the spool will be tensioned back by coil springs. This could provide more adjustments besides rotation, as there's total control over the airfoil's surface area. For example, to retract it partially or entirely when hovering or in turbulence. Wait a minute, did I just reinvent sails and repurpose it as a motorized kite...? 🤔
You essentially made a canard aircraft without the rest of the air frame and gave it some alternative form of P thrust. Thinking about how it all interacts is making my head spin, so keep going and make more iterations!
Very interesting, even to a non mechanical/non engineer amateur drone enthusiast like me. I subscribed after watching your first Dyson vacuum engine powered airplane flight . The more I watch, the more I'm hooked on watching your RUclips videos. You're a very smart young whipper snapper. And as I watch this video, it makes me proud to be from the Pacific Northwest. ( grew up in Bellevue) but live in downtown Seattle now. Keep up the good work!
Wow, this idea looks great, but I would suggest to mount the wing further rearwards and with a fixed pitch angle because when the center of lift of the wing is behind the CG the wing actually provides positive pitch stability so it wont get into those oscillations. Also would negative angle of attack not cause the drone to crash because it would limit the maximum forward pitch of the quad. I really would like another video of this concept with some design improvements.
I was thinking the same thing about wing location. When the drone tilts forward, the wings move forward causing lift in the front so the drone tilts back, shifting lift to the back etc etc. I have no expertise though so was looking for a comment that was similar.
Agreed with all the comments about the CG vs center of drag, but something else that might be worth trying is no stop on the AoA and then some kind of tail boom and stabilizer attached to the wing in the same way those drone sailboats get the perfect AoA on their sail
So, in my experience, drones often have to run their rear motors faster than their front motors when moving quickly because the faster they go the higher the righting moment in pitch due to aerodynamic forces. I don't know if that's universal, though. Maybe it depends on how your central body is shaped? But, as others have said, you are also getting a pitching moment from having the wings so high above the center of mass. Putting that all together, I'm impressed that it worked as well as it did.
Whenever I move to Washington in the future I hope I get to see your inventions getting tested around Seattle. How fun would that be to see some device and think "oh that's just rctestflight"
You are going to have to power the wings out of stall. Either by flying the drone fast to the point they pivot up out of stall or far, far more practical with active servo input, when forward velocity is achieved, raise the wing to +1-5* and revert the flight controller to attitude only. It will glide. If it glides, pivot forward slightly, add more power. Eventually, with the right config you should be able to get to nearly 90* with all 4 props providing 100% forward thrust!
Finally! I've been periodical searching online to see someone do this... I've been thinking of it as an attachment to dji drones that already have long flight times!
Drone programmer here, the wing seems way too complex system for the PID to handle, especially may be the following: at speed X, the wing is pushing you UP, and if this is more than the drone can compensate lowering motor speed, it goes crazy. Also sudden loss of lift (stalling) is something PID cannot handle. Also, where is your center of lift? PID are a more a final touch, the more the drone guidance know about its physic, the better result you have Edit: if you would ask me how to start programming this, i think that first think you need to control electronically the pitch, or you cannot handle dynamic speed, you have one speed that is your most efficient and you cant exceed without keeping altitude requirements. I would create a test in something like xplane, as it does actually simulate propeller physics and other aero property; and create a table to what best pitch give the best result. It is simply too many hour to properly create an optimizer , the lookup table is the best. Also while the wing are engaged, you probably want to use less motor and more wing control, as the wing itself will stabilize pitch roll and yaw.
Awesome idea to improve drone efficiency! I think the main cause of instability is the aerodynamic pitch instability induced by the airfoil. As soon as the wing starts flying. Every normal aircraft needs to adress this problem. Usualy its done by choosing diferent agles of incident between main wing and tail wing. The simplest way to fix this on your drone would be probably by using a stable airfoil like its used for flying planks. No need for a tail anymore.
Check out the British designed Fairey Rotodyne from the late 1950s. A single rotor was used for take off and landing and which was then then put into auto-rotation during level flight. Lift also came from 2 short span conventional wings where the propeller engines were mounted. The system worked well but the biggest con was the noise made by the rotor tip jets on take of and landing. Not a good point as the aircraft was intended to be operated from city centres. There was a hush kit in design when the project was cancelled but by then it was too late to get any more government funding :(
Nice work. Look at the scorpion/stargazer freewing UAV and design your wing the same way. Use a pitch neutral airfoil (flying wing airfoil) and you can remove the stops and have the wing self align regardless of airspeed. Aurora flight sciences also had a vtol with this idea many years ago
I like the approach as I've made similar concepts some time ago. I used servo-like stabilized AoA of the wing to maintain constant angle regardless copter pitch and current sensor to get real power consumption. I notified significant gain in efficiency, however I dealt a lot on control algorithms as copter's autopilots does not like a wing to be attached and provide lift. It is bit misleading to autopilot, you increase the forward speed and you generate lift so it needs to decrease the thrust having less authority to control pitch, roll and yaw.
A wing mounted on top, like Chocolate Rocket commented, added a pitch moment because the drag force is acting a distance away from the center of mass. On top of that, the center of mass has been shifted upwards, creating even more instability. To counteract both of these points, you could try sizing down the airfoils and adding equivalent airfoils to both the top and the bottom of the quad. You technically don't know exactly where your center of mass is unless you're able to model all of the parts in CAD and use an assembly to let the computer figure it out for you, but you can use intuition to approximate where it is. Even if the top and bottom airfoil aren't the same distance from the center of mass, the resultant forces and moments will bring the system much closer to stability.
The travel locks would seem to create an unavoidable positive feedback loop. The control software of the copter is expecting the forward angle to increase as speed increases without increasing altitude. The drag from the wing being on top will always try and rotate the copter rearwards. If the control software detects an increase in altitude because of the extra lift, it's going to reduce throttle thus increasing the influence of that drag, pulling the copter back further, increasing the angle of attack + lift + drag working to convert forward velocity into even more altitude until the wing stalls. Even so, I'm amazed you're able to see these efficiency numbers with the software being so confused. If the wing angle was controlled by the software and the software modeling was designed from the ground up to account for these effects, I think you'd certainly have something amazing here. Love this idea!
I don't want to give any suggestions but...The whole wing looks oversized. Try making it less wide (less wingspan) and possibly thinner with slightly reduced area and even 6 degrees dihedral. I believe it will help especially at 12+ m/s. I hope you can try again. Good Luck
Build one you can fly yourself around, everyone seems to place the pilot at or above the rotors, on a hard landing the pilot could be thrown down onto the rotors, and if the pilot is at rotor level a blade could snap and impale them, i'd like build my own with a fuel engine with two counter rotating props for the main lift, and four battery rotors for control. really enjoy your videos
okay this is super super cool. clearly needs some work but from these comments, it seems like there is A LOT of interest in this idea. I feel like this is going to be a huge innovation. super exciting. Initially, i thought it was going to be similar to a vtol and basically take it up like a normal drone, and then just rotate... i think if you put the wing under the rotors you could easily just convert to horizontal flight at a certain speed, but this is way cool too. either way, im excited to see this progress.
Cool idea. We went through this with the UAVforge spy drone project. Fixed wing VTOL planes do exist. Motors are mounted on the wings, but the whole wing can rotate so it effectively becomes a bi-copter.
As others have already pointed out, the problem is your center of lift is ahead of your CG. That is an inherently unstable configuration. This gets worse as it goes faster and pitches further forward. Will always be a problem with the wing mounted high above the center of the quad. Your idling front motor was probably due to the angle of attack of one half of the wing being a little higher than the other so it was always trying to roll a bit. FWIW, there is another way to get a fair bit of added efficiency with a multirotor like this, especially with large efficient props . Push it around horizontally. In other words, add a 5th motor mounted perpendicularly and push the aircraft around while it maintains a relatively level attitude with four main props just maintaining enough power for a hover (you'll find can actually reduce power below that a little). It's tricky to get prop clearance and it's generally loud as hell because that 5th prop is always cutting through the dirtiest air possible, but you can gain quite a lot of flight time. Foxtech FPV made the "Screamer" years ago, and even with five 5in props I could get almost double the flight time for a given forward velocity. The rear motor was larger and had > 1:1 power/weight ratio so I could pitch up to vertical and climb straight up at 50mph with the other 4 motors just idling.
Separate the wings by more so they are outside the area of the rotors . Also id lose the pitching of them. Not quite fixed but way less movent away from facing the way a wing should.... You know better than me AND know the quad but that still seems like what it wants..... Keep them coming dude! I love your videos. They're like mental chewimg gum.... 😎 Also.... It might be worth at least trying having the wing UNDER the rotors.... You never know it might add the low pressure needed above the wing if its at a helpful angle or something. In any case i think getting the wimgs outside of the rotor footprint would be a very good thing......
Two ideas that occurred to me watching this: 1.) Add four wings to a quadcopter where the propeller arms form the main spars. I think that with the right control algorithm you could directly control angle of attack (not just with ailerons/elevators), but could also purposely induce side slip/lateral motion without rolling or turning, which a conventional aircraft cannot really do. 2.) Create an aircraft with no control surfaces, that controls its orientation solely through rotating internal weights and conservation of angular momentum.
An idea I recently considered: Attaching helium filled balloons to a quadcopter to offset some of its weight and therefore reducing energy consumption for hovering. I have not gotten around to doing even some cursory math on how big these balloons would have to be to make any noticeable difference and so that the (volume of gas)/(weight of mount + balloon) works out to be at all productive, but I think it could be a fun thing to try. The attachment of the balloons would certainly have to be static, so that it is not a quadcopter swinging around helplessly on a cord below a balloon, and the large surface of a balloon could create some real problems with wind. Idk, maybe one could design a funky looking quadcopter airship.
I actually made something a lot like this a few years ago, but for a 4' quad style base, and rather than 1 wing in the middle, I had 2 wings front and back. They were automatically put level with 1 servo that was linked to both of them. It kinda worked for the lift aspect but the control algorithm had a ton of trouble with it. I never ended up getting a chance to fix that though.
That was entertaining! :-) I would build a smaller wing to get a happy medium between efficiency and stability. Also make the carbon rods a couple of feet longer to build the wings further out so there's no wing directly above the rotors. I think the rotors decrease the pressure from under the wing and disrupt airflow so you lose lift and efficiency. I'd love to see a brand new build and test flight. Thank you for making great videos!
Try a reflexive foil allowed to pivot freely without any servo control around pivot at ~30% chord - basically kicked up at the trailing edge to function like an integrated tail plane, it will set an angle of attack relative to the airstream all the time. Alternatively employ a small tailplane at lower AOA mounted off of a still freely pivoting main wing. This reflexive foil approach has been used a lot by traction kites to overcome tendency to luff, but was also an effort years ago to make microlights under name 'freewing'. A servo control on the tail plane AOA would allow you to set main foil AOA independent of drone pitch. Something similar is done on speed sailing craft and sail drone craft, to precisely and rapidly control the foil lift in rapidly changing incipient air directions.
You need to set the angle of attack of the main wing to just below the stall angle of attack. The pivoting wing is great. So, to set the angle of attack to a fixed number, put a trailing trim tab on the wing, like a horizontal stabilizer. The angle of attack of the trim tab sets the angle of attack of the rotating wing. Also, the Center of Lift should be at the CG of the drone. This is accomplished by putting the pivot point of the wing thru the CG. Without having Center of Lift aligned with the CG you are creating a pitching moment that will pitch the drone up or down. Lift is creating Pitching Moment, eliminate this by aligning lift thru the cg.
I think what's causing the drone to go unstable is the added speed is causing the wing to produce enough lift that causes the drone to start gaining altitude. This causes the drone to slow the motors down to maintain the proper altitude, thus causing an exponential drop in lift. Then the drone sees the altitude start to drop, so it speeds up the motors to regain altitude which then increases the airspeed over the wing causing it to produce more lift and quickly gaining more altitude than expected putting the drone in a positive feedback loop. I also think the changing of the angle attack might also be contributing this feedback loop.
Also, the wing will be doing some crazy stuff to the airflow into the top and bottom pairs of rotors during the different flight regimes, potentially creating a negative feedback loop and reducing control authority - ie accelerating the air into the bottom rotors reducing their net thrust and slowing the air into the top rotors increasing their net thrust
One key difference with the flight testing in this video is the all-up-weight of the drone was not the same with and without the wing. When flying without the wing an equivalent amount of weight should have been carried by the drone. Expect we'll see much better efficiency when the challengers have same AUW. (12:28) To avoid sketchy flight maneuvers, it would help to add a radius between waypoint legs. Those 180º turns are just asking for craziness. Not having a fixed wing (non-pivoting) would cause he centre of lift to vary as pitch angle varies. Location of centre of lift vs. centre of mass can effect stability. Overall a fascinating experiment Daniel. Like how you totally skipped any testing with a robust 5-inch, or 7-inch freestyle quadcopter and went straight to flight testing on a 13-inch monster-copter.
The propellers below are creating a huge suction on the wings and the wing essentially is seeing an even larger angle of attack than what has already been provided, hence with an already higher aerodynamic centre of the wing from centre of gravity, its mostly in stall throughout the flight creating drag and instability. My suggestion would be lower the wings closer to centre of gravity (in case you have symmetrical airfoil on the wings), have a very low, almost zero angle of attack as the suction from propellers below manages to increase the angle of attack easily on the wings and also some roll instability I can see: Aerodynamics!
Seems to me this is a really good way to smoke really expensive esc's If you want more efficiency for long range then you should probably go with the standard H frame and go tilt rotor. Avoiding all the added weight and drag but not sacrificing any stability. I would think you could set it up where the front rotors go flat to act as the wing or slightly tilted like a Gyro copter and tilt the rear rotors more forward like an Osprey for higher air speed at the same or less power. Heck that may even be able to back feed current from the front rotors to do a little regenerative charging in flight.
I really appreciate the stall visualizations you showed, even if it was predictable that this wouldn't work too well as implemented. It was more of a science project than an engineering solution, and that's totally okay with me.
The best example to take inspiration from for fixed wing efficiency & Quadcopter type VTOL (vertical take-off & landing ) performance will be a US made military aircraft called V-22 osprey . Hope some makes a RC drone based on it
the flight controller is probably doing weird things because it can't account for what it is happening because of the wing. The software will probably need adjustment in order to account for the sudden lift when the wing starts taking effect. Nice project!
if your quadcopter controller/software will support it, make it a BWB (Blended Wing Body) to house the camera and batteries, streamlined, tailsitter. VTOL , with the props horizontal as designed, but attached to a fixed wing airframe. at altitude, it tilts further and further in the direction of travel until it's flying with the props vertical and the wings make 100% of the lift.
Thanks for the interesting test. As already mentioned in other comments, the wing position was not close enough to the center of gravity for that flight phase. My assumption is that you could save the 24% much easier by using a more efficient propulsion concept: Larger propellers and adapted motors (lower KV, more torque). This also increases the area exposed to the wind and decreases stability in rough conditions - but much less than with wings added as in your example.
If the wings were located outboard the props, then they could provide lift more like a fixed wing aircraft. They could also be mounted lower to reduce drag related pitching moment. Interesting video.
Try Attaching a tail to the wing assembly that will hold the wing at the optimum angle of attack. Then allow the wing and tail assembly to rotate freely. A control surface on the horizontal stab could act as a trimming surface.
I think you should have a single divided wing. The wing should start outside the rotors. In the center part (within the rotors of the quadrocopter you might need an other stall. By that even turbulence up/downwinds can be better addressed. Smart idea- an other approach is the gyrocopter principle in quadrocoptersas foam or carbon is not really so heavy. Thank you for sharing
Aeroespace engineering student here, those oscilations are caused by positive arch wings by definition having a positive pitch moment alpha derivative, thats why flying wings need to be delta shaped or atleast have some negative tip angle of atack so that the total pitching moment derivative is negative, crating a self stabilized flight
Oh, also, just a fun note, but the actual oscilations are caused by the angle of attack becoming so steep that the wing stalls and the nose falls back down and the cycle repeats again
Add the automatic angle of attack control vane from your wing-sailboat. This way, the angle of attack will be controlled to some reasonable angle automatically, won't go negative, and you can remove that servo etc.
I am currently completing my senior design and my project is a fixed wing (piper cub style) with vertical take-off and landing capability and a forward pulling traditional style motor. This is interesting because it's such a different approach from the previously mentioned Warwick university example. I would see this design being helpful at very slow speed but testing this to a slow flying fixed wing VTOL would be interesting to see what design is more efficient. could be useful for package delivery applications... maybe... as you mentioned high wind would be extremely detrimental to this design.
As the craft rotates forward, your wing is moving ahead of the CG and thus creating a pitch-up moment. If you set it further back, you would do better at higher speed (but worse at lower). Ideally you would have a way to move it back in response to the crafts pitch-angle to keep the center of lift closer to the CG.
I think just adding "flaps" to the masts that have limit stops would achieve higher efficiencies without adding much weight or stability issues. Make them delta shaped and have two sets of limiters so the "forward" surface (front flaps trailing the forward masts) is always at a higher angle than the rear ones; your center of lift should balance to the front two rotors and they can basically idle while the rear two provide forward thrust. This effect can be seen on your current iteration right before it goes into oscillation.
You are on the right track. Wings will increase the efficiency in forward flight. Based on a conversation with Ed Sweringen over 50 years ago, I think you have too much wing area for the aircraft. The wing flapping around makes it worse. Ed put small stub wings on a bell 209 HueyCobra Gunship that unloaded the rotor in forward flight and carried more armament. If wheels were added the wings increased the gross weight the helicopter would get off the ground with the lift from forward movement and air from the rotor in the ground effect. A much smaller fixed wing placed so the center of gravity and average center of effort don't induce isolation or proposing. Stating small and making the wing larger until it fails works much better than starting larger and cutting it down over and over until it works. good luck
I like the Opener/Blackfly concept a lot more. It's simpler because the wing doesn't have to rotate, the entire aircraft does, however it may not work well for some payloads.
Put a servo on the wing integrated with an accelerometer, and load the program on an arduino, regardless of the drone's inclination, the wing will always remain at the same angle. I believe it will work.
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The wings should have their center of drag in line with the center of mass of the craft to avoid introducing the pitch moment that caused the oscillations. This is tough because the wings would have to be mounted even farther outboard to avoid colliding with the rotors. If the front/rear motor pairs were moved more frontward/rearward instead, clearance for the wing could be introduced without elongating it and the available pitch moment from the motors pair would be increased, allowing it to more effectively counteract any pitch-wise disturbance.
that plus these wings are dead they have no control surfaces to combat aerodynamic forces like you would have in any real or model rc aircraft, adding this would likely fix it. ditch the homemade wing and get one for a rc plane that has all the control surfaces built in and intergrate it into the drone so that its software begins operating them to keep it in line with its stabilization programing. Also there's another way to improve efficiency , by changing out the rotors for the torodial design they not only improve flight BUT are near whisper quiet making the drone hardly noticable
Yes. It should have neutral static stability so the rotors have authority. I.e. the aero body must be orientation agnostic with respect to the relative wind and generate no torques about the cg. I don't know how close one can come to this in reality. None of these designs ever come close though because they don't even try.
You can technically solve this by just adding an equivalent system to the other side. Could try using smaller wings mounted top and bottom.
The other thing to consider is the fact that, not only is the wing causing a pitch moment due to induced forces, the center of mass is now shifted higher if not above the motors creating an unstable system. Even just adding a ballast below the quad could theoretically make the motor control play a little nicer.
I had a thought in a slightly different direction. How about 2 smaller wings, one in front of the front motors and staggered vertically but forward and out of the prop wash path, and the rear staggered slightly below the vertical rotation axis of the rear motors, behind the rear motors, again out of the wash path. So front and rear wings. This would of course require a landing gear to prevent awkward takeoff. But with the same pivoting wing with rotation stops would certainly have fair upward lift without the interference with prop flow paths. It should also equalize the load decrease across the motors..
The wing should be placed in the same way as it would be on an airplane, at the center of mass or further back.
to me it looks like the quad is fighting against the instability of its back heavy nature.
"A front heavy plane flies badly, a back heavy plane flies once"
- Some kerbal space program enjoyer
A front heavy plane flies badly unless it is flying very fast.
Move the wings down to the center of mass of the drone, to avoid having it add a speed-pitch feedback making it unstable. Control the wing AoA with a servo so that it's always correctly oriented relative the direction of travel through the air. Perhaps add a few degrees of dihedral to the wings to get a bit more stability. Use an airfoil section optimized for the very low speeds seen here, something appropriate for maybe 1-3 million Re.
The "dihedral=stability" equation is not so clear cut. the way dihedral works is by rolling the plane in the direction opposite sideslip at positive AOA, but with this arrangement that just adds more complexity for the control system to fight against.
it will the the blades
@@hazza2247 my in goes with pitch up free
@@brycering5989 what?
All the issues mentioned have been resolved and patented in US Patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones". We are scheduled for the release of our product line soon.
Maybe have the rod going through the wings be closer to the center of mass of the wing so it's easier to reach the edge case. This way, the drone uses less energy to keep the wing up
At Warwick university I saw a drone/fixed wing hybrid that had a stationary delta wing which was vertical when on the ground and then the drone completely turned horizontal during free flight thus turning into a fixed wing plane with a rotor above and below each side of the wing. I imagine this required custom software to calculate the best angle of attack for different speeds.
You could always abruptly transition to forward flight mode, stall, and recover
The RC aircraft X-Vert seems to be what you are describing, but with only a pair of motor. It uses pre-programmed maneuvers to transition to fixed wing and back again, while also changing the flight controls to be the standard for each.
Yep, they're known as Tailsitters.
Though there's not usually any custom programming required, Arduplane supports the configuration out of the box.
Tailsitters are efficient for long range, although as a camera drone the body interferes with the downward field of view at low speeds or hovering, and cannot fly sideways at higher speeds. The concept in this video has been patented in US patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones" and we are scheduled for the release of our product line soon.
PteroDynamics has released the video of their transwing drone the uses fold of wings with the props on to go from vertical to horizontal flight.
this is the kind development and testing I want to see more of.
mee too !!
For years we have been privately testing this exact concept with over 300 test flights on DJI and other drones and we filed a patent in 2019. All the issues mentioned in the comments have been resolved and patented in US Patent US20210107637A1 "Universally attachable hinged wing and vlos aid for multirotor drones". We are scheduled for the release of our product line soon.
100% 👍
@@dronedevices Will be watching for this release! ;)
@@AirtimeAerial Thank you for your interest!
With a properly tuned flight controler taking the wing into account, I think your preliminary data shows the wing it might have a significant efficiency gain in forward flight. I think for certain mission profiles you're onto something. As always great video Thanks
How do I increase the range of a helicopter
Google: Make a tiltrotor
Bing: Duct tape a wing on it lmfao
I'd really like to see this experiment repeated with the anomalous motor issue fixed. Like you said having one motor completely idled is really going to mess up the quads ability to stabilize itself and it might be a lot better without that problem present.
Flight controller: “u wot m8”
Don't think a motor was actually idle, just the motors and telemetry were not calibrated.
@@AerialWaviator he said it was idled and it looked idled.
The way you mounted the wing high above the quad puts the center of lift ahead of the CG when the quad pitches to translate forward. Thats almost certainly the main cause of your pitch instability in fast flight. The front motors are decreasing in speed to the point of idling because pitch moment from the forward positioned wing is so large it's taking all the load off them.
rctestflight your research is inspiring and see where you are going. Based on your RPM data showing distinct differences between 4 rotors perhaps prudent to try positioning 4 separate wings behind the thrustline (beneath) of each rotor. So as each rotor thrust will behave independently and observe any change in stall threads attached on low pressure surface of each wing in full throttle forward cruise. In turn cumulative lift may show where lift disparities exist. Good job of messing around so much with this, excellent!
There are still possibilities. I like that you illustrate the challenges and lessons learned. Great job!
A tail-sitter craft with four props in a quadcopter orientation, can easily make the transition to forward flight. The camera gimbal can be held on a swinging (pitch) axis. Keeping the entire camera assembly below the craft as it transitions back and forth between forward flight.
Wow this is so much fun and relaxing to watch these types of videos from you.
agreed. i have been watching his videos for years and its always fascinating yet informative along with his uniquely deep voice being chill to listen to lol
man i love this channel. cant wait for the PeterStripol colab
How about the sort of angle-of-attack control tail/elevator thing you used on your rigid wing sailboat? I think that would be a lot smoother than the hard stop on the wing angle.
Or an tuned progressive elastic resistance to the AOA? Like 3 different surgical tubing lengths in parallel, that way the AOA would be a function of the airspeed. You could still have a hard stop and the period of the oscillations may be longer as well. The tuning might be tricky, but maybe with force meter measurements on a hard stop for several AOA/airspeed combos you could tune the elastic dampening. Great video!
No way bud. The wing should be centered on the CG. Any aerodynamic stability, positive or negative, is going to fight the pid controllers. Aerodynamic stall is desirable in some cases and a normal part of the maneuvering flight regime. An AoA sensor should feed the FC to inform cruise efficiency. Get all these nasty aerodynamic flipperon things out of here. This is a quadcopter!
What if you put the wing fixed perpendicular to the rotors and in flight go full throttle and angle the quadcopter 90° forward and use it as a conventional aircraft. But then basically you've converted it into a VTOL
I love the idea and it apparently works a bit, extend the wings out beyond the rotors and mount it to the bottom of the frame of the unit. maybe make the size of the wings about 1/4 of the size that you have on there now. just a thought from my head.
Having the centre of lift below the centre of mass could cause issues, although the drone could probably keep it stable.
For a future video, try mounting the wing below the rotors, this may seem more unstable but it's highlighted to be just as viable as above aerodynamically by the drone pendulum fallacy. Having the wings below will allow them to rotate without the consequence of hitting the rotors, potentially allowing you to bring the CoL closer to the CoG (although, I'm not sure whether the downwash from the rotors will impact this).
Great idea but I think it would need a rewrite to the controller. Combining what Zipline does with being able to take off and land anywhere would be great
Have you considered a "freewing" system? Essentially, build the wing as a flying plank with a reflexed airfoil, or with a trim tab to adjust the reflex for different speeds, and then set the pivot so that it matches the flying plank's CG. With this setup the wing should hunt for the ideal angle of attack in the relative wind without needing a stop.
LOL why are there Hot Dogs on that Little VTOL?
Probably for stability. Hot dogs are great vibration dampeners. Some real science shit
Daniel, look into the “free-wing” concept. The wing adjusts the AOA automatically. Think you could build Rutans Scorpion as a model.
The drone is missing some kind of more effective pitch control like in standard airplanes, i think this is causing the oscillations.
Also fins below the rotors maybe would prevent the rotation of the airflow, which could boost efficieny as well
I agree. I think the flight controller program would need to be designed for this hybrid design and also include servo control for wing pitch, and then it should be able to effectively counter the instability.
I’ve been designing and flying RC planes for 40+ years. In order for this to have any chance of working, you need to do two things. First, get the center of mass (CG) of the drone about 35% back from the front of the wing. Second, use an accelerometer, servo, and small microcontroller that can adjust the wing’s angle of attack so regardless of the flight angle of the drone, you keep the wing’s angle of attack to the wind in the 0 to +3° range, depending on the airfoil. Otherwise, the wing just acts like a big sail.
Late to the party, but I think the performance would be better with the wing mounted just below the props instead of above them. It'll also be a more compact overall package.
the down wash of the props would keep pushing the wing down aswell as messing with the airflow over the wing so idk if it would be better, would like to see it tested still
@@hazza2247 Think it would be more drastic than the props pulling the air past the wing in the current configuration?
@@Stormclowe i mean both are bad, i don’t know enough about this stuff to have anymore of an opinion
Feedback: one way to avoid negative pitch moment at high speeds is mount a fixed-pitch wing forward of CG (1-3 degrees positive AoA); a slow climb is way better than a high speed crater
Next experiment: Place the wing below the rotors & fix the pitch (to eliminate oscillations). Test your theory regarding rotor wash. You might also want to experiment on wing placement (test forward of CG & aft of CG).
I'd love to see you push this idea a bit further. an idea I had would be to have 2 wings across with 2 rotors set into each wing. That might give you more stability.
in any case, love the vids and cant wait for the next one!
That is exactly what I have seen patented
In the hover (or "drone") orientation, having the wing above the center of mass increases stability. (In terms of forwards/backwards speed: going forward increases drag on the wing, which is above the center of mass, so it pitches you back, which decreases drag, and so on.) If your drone pitches forwards into "plane-like" orientation and tries to go fast, it is putting the wing in front of its center of mass - A very famous thing that is making a craft unstable.
There's 2 possible solutions:
*Either* move the pivot rod to *below the rotors* to get it to the same height as the center of mass or below it. In this case you'll loose the stabilization in drone-mode.
*Or* move the pivot rod further *towards the rear* of the drone. That will increase the stability in the airplane-like orientation. You can get away with keeping the wing above the propellers if your drone never pitches more than 35° or so down (which may _not_ be true, since I expect optimal efficiency gains close to 90° down pitch).
Here's my silly idea: Instead of large solid foam wings, use small spools of fabric and pairs of linear tracks to create the airfoil.
Winches made with continuous servos will be used to extend the fabric, while the spool will be tensioned back by coil springs.
This could provide more adjustments besides rotation, as there's total control over the airfoil's surface area. For example, to retract it partially or entirely when hovering or in turbulence.
Wait a minute, did I just reinvent sails and repurpose it as a motorized kite...? 🤔
Sounds like a fun project.
You essentially made a canard aircraft without the rest of the air frame and gave it some alternative form of P thrust. Thinking about how it all interacts is making my head spin, so keep going and make more iterations!
If you put a laser on it with longitudinal light, it will become one of the earth invasion films from before👽
Very interesting, even to a non mechanical/non engineer amateur drone enthusiast like me. I subscribed after watching your first Dyson vacuum engine powered airplane flight . The more I watch, the more I'm hooked on watching your RUclips videos. You're a very smart young whipper snapper.
And as I watch this video, it makes me proud to be from the Pacific Northwest. ( grew up in Bellevue) but live in downtown Seattle now.
Keep up the good work!
Hey I work only five min away from Freefly Systems. What an awesome place to work!
Ok now we need to send this to Ukraine
The high levels of Sketch is one of the main reasons I watch ths channel.
We need a RUclips X-Prize for guys like you to encourage this sort of thinking and building.
@@jcd-k2s Not necessarily. There are ways to filter out the big guys.
Wow, this idea looks great, but I would suggest to mount the wing further rearwards and with a fixed pitch angle because when the center of lift of the wing is behind the CG the wing actually provides positive pitch stability so it wont get into those oscillations. Also would negative angle of attack not cause the drone to crash because it would limit the maximum forward pitch of the quad. I really would like another video of this concept with some design improvements.
I was thinking the same thing about wing location. When the drone tilts forward, the wings move forward causing lift in the front so the drone tilts back, shifting lift to the back etc etc. I have no expertise though so was looking for a comment that was similar.
This is a fun experiment in seeing how positive you can possibly make Cm alpha.
Agreed with all the comments about the CG vs center of drag, but something else that might be worth trying is no stop on the AoA and then some kind of tail boom and stabilizer attached to the wing in the same way those drone sailboats get the perfect AoA on their sail
So, in my experience, drones often have to run their rear motors faster than their front motors when moving quickly because the faster they go the higher the righting moment in pitch due to aerodynamic forces. I don't know if that's universal, though. Maybe it depends on how your central body is shaped? But, as others have said, you are also getting a pitching moment from having the wings so high above the center of mass. Putting that all together, I'm impressed that it worked as well as it did.
Whenever I move to Washington in the future I hope I get to see your inventions getting tested around Seattle. How fun would that be to see some device and think "oh that's just rctestflight"
You are going to have to power the wings out of stall. Either by flying the drone fast to the point they pivot up out of stall or far, far more practical with active servo input, when forward velocity is achieved, raise the wing to +1-5* and revert the flight controller to attitude only. It will glide. If it glides, pivot forward slightly, add more power. Eventually, with the right config you should be able to get to nearly 90* with all 4 props providing 100% forward thrust!
The wings would be in front of the centre of mass by so much that it'd fall out of the sky long before 90 degrees.
Finally! I've been periodical searching online to see someone do this... I've been thinking of it as an attachment to dji drones that already have long flight times!
Drone programmer here, the wing seems way too complex system for the PID to handle, especially may be the following: at speed X, the wing is pushing you UP, and if this is more than the drone can compensate lowering motor speed, it goes crazy. Also sudden loss of lift (stalling) is something PID cannot handle.
Also, where is your center of lift?
PID are a more a final touch, the more the drone guidance know about its physic, the better result you have
Edit: if you would ask me how to start programming this, i think that first think you need to control electronically the pitch, or you cannot handle dynamic speed, you have one speed that is your most efficient and you cant exceed without keeping altitude requirements.
I would create a test in something like xplane, as it does actually simulate propeller physics and other aero property; and create a table to what best pitch give the best result. It is simply too many hour to properly create an optimizer , the lookup table is the best. Also while the wing are engaged, you probably want to use less motor and more wing control, as the wing itself will stabilize pitch roll and yaw.
Awesome idea to improve drone efficiency!
I think the main cause of instability is the aerodynamic pitch instability induced by the airfoil. As soon as the wing starts flying. Every normal aircraft needs to adress this problem. Usualy its done by choosing diferent agles of incident between main wing and tail wing. The simplest way to fix this on your drone would be probably by using a stable airfoil like its used for flying planks. No need for a tail anymore.
Check out the British designed Fairey Rotodyne from the late 1950s. A single rotor was used for take off and landing and which was then then put into auto-rotation during level flight. Lift also came from 2 short span conventional wings where the propeller engines were mounted. The system worked well but the biggest con was the noise made by the rotor tip jets on take of and landing. Not a good point as the aircraft was intended to be operated from city centres. There was a hush kit in design when the project was cancelled but by then it was too late to get any more government funding :(
Nice work. Look at the scorpion/stargazer freewing UAV and design your wing the same way. Use a pitch neutral airfoil (flying wing airfoil) and you can remove the stops and have the wing self align regardless of airspeed. Aurora flight sciences also had a vtol with this idea many years ago
I like the approach as I've made similar concepts some time ago. I used servo-like stabilized AoA of the wing to maintain constant angle regardless copter pitch and current sensor to get real power consumption. I notified significant gain in efficiency, however I dealt a lot on control algorithms as copter's autopilots does not like a wing to be attached and provide lift. It is bit misleading to autopilot, you increase the forward speed and you generate lift so it needs to decrease the thrust having less authority to control pitch, roll and yaw.
A wing mounted on top, like Chocolate Rocket commented, added a pitch moment because the drag force is acting a distance away from the center of mass. On top of that, the center of mass has been shifted upwards, creating even more instability. To counteract both of these points, you could try sizing down the airfoils and adding equivalent airfoils to both the top and the bottom of the quad. You technically don't know exactly where your center of mass is unless you're able to model all of the parts in CAD and use an assembly to let the computer figure it out for you, but you can use intuition to approximate where it is. Even if the top and bottom airfoil aren't the same distance from the center of mass, the resultant forces and moments will bring the system much closer to stability.
The travel locks would seem to create an unavoidable positive feedback loop. The control software of the copter is expecting the forward angle to increase as speed increases without increasing altitude. The drag from the wing being on top will always try and rotate the copter rearwards. If the control software detects an increase in altitude because of the extra lift, it's going to reduce throttle thus increasing the influence of that drag, pulling the copter back further, increasing the angle of attack + lift + drag working to convert forward velocity into even more altitude until the wing stalls.
Even so, I'm amazed you're able to see these efficiency numbers with the software being so confused. If the wing angle was controlled by the software and the software modeling was designed from the ground up to account for these effects, I think you'd certainly have something amazing here. Love this idea!
I don't want to give any suggestions but...The whole wing looks oversized. Try making it less wide (less wingspan) and possibly thinner with slightly reduced area and even 6 degrees dihedral. I believe it will help especially at 12+ m/s. I hope you can try again. Good Luck
Build one you can fly yourself around, everyone seems to place the pilot at or above the rotors, on a hard landing the pilot could be thrown down onto the rotors, and if the pilot is at rotor level a blade could snap and impale them, i'd like build my own with a fuel engine with two counter rotating props for the main lift, and four battery rotors for control. really enjoy your videos
okay this is super super cool. clearly needs some work but from these comments, it seems like there is A LOT of interest in this idea. I feel like this is going to be a huge innovation. super exciting. Initially, i thought it was going to be similar to a vtol and basically take it up like a normal drone, and then just rotate... i think if you put the wing under the rotors you could easily just convert to horizontal flight at a certain speed, but this is way cool too. either way, im excited to see this progress.
Cool idea. We went through this with the UAVforge spy drone project. Fixed wing VTOL planes do exist. Motors are mounted on the wings, but the whole wing can rotate so it effectively becomes a bi-copter.
As others have already pointed out, the problem is your center of lift is ahead of your CG. That is an inherently unstable configuration. This gets worse as it goes faster and pitches further forward. Will always be a problem with the wing mounted high above the center of the quad.
Your idling front motor was probably due to the angle of attack of one half of the wing being a little higher than the other so it was always trying to roll a bit.
FWIW, there is another way to get a fair bit of added efficiency with a multirotor like this, especially with large efficient props . Push it around horizontally. In other words, add a 5th motor mounted perpendicularly and push the aircraft around while it maintains a relatively level attitude with four main props just maintaining enough power for a hover (you'll find can actually reduce power below that a little). It's tricky to get prop clearance and it's generally loud as hell because that 5th prop is always cutting through the dirtiest air possible, but you can gain quite a lot of flight time. Foxtech FPV made the "Screamer" years ago, and even with five 5in props I could get almost double the flight time for a given forward velocity. The rear motor was larger and had > 1:1 power/weight ratio so I could pitch up to vertical and climb straight up at 50mph with the other 4 motors just idling.
Amazing that you had people at work filming you doing your thing. That's so rare from my experience.
Separate the wings by more so they are outside the area of the rotors . Also id lose the pitching of them. Not quite fixed but way less movent away from facing the way a wing should.... You know better than me AND know the quad but that still seems like what it wants..... Keep them coming dude! I love your videos. They're like mental chewimg gum.... 😎 Also.... It might be worth at least trying having the wing UNDER the rotors.... You never know it might add the low pressure needed above the wing if its at a helpful angle or something. In any case i think getting the wimgs outside of the rotor footprint would be a very good thing......
Two ideas that occurred to me watching this:
1.) Add four wings to a quadcopter where the propeller arms form the main spars. I think that with the right control algorithm you could directly control angle of attack (not just with ailerons/elevators), but could also purposely induce side slip/lateral motion without rolling or turning, which a conventional aircraft cannot really do.
2.) Create an aircraft with no control surfaces, that controls its orientation solely through rotating internal weights and conservation of angular momentum.
An idea I recently considered: Attaching helium filled balloons to a quadcopter to offset some of its weight and therefore reducing energy consumption for hovering. I have not gotten around to doing even some cursory math on how big these balloons would have to be to make any noticeable difference and so that the (volume of gas)/(weight of mount + balloon) works out to be at all productive, but I think it could be a fun thing to try. The attachment of the balloons would certainly have to be static, so that it is not a quadcopter swinging around helplessly on a cord below a balloon, and the large surface of a balloon could create some real problems with wind. Idk, maybe one could design a funky looking quadcopter airship.
I love the frequency of your video-output these days :)
Your projects are so unexpected.
Love your ideas.
A very interesting video. Surely, adding a tail with a depth rudder would greatly improve stability. Best regards.
I actually made something a lot like this a few years ago, but for a 4' quad style base, and rather than 1 wing in the middle, I had 2 wings front and back. They were automatically put level with 1 servo that was linked to both of them. It kinda worked for the lift aspect but the control algorithm had a ton of trouble with it. I never ended up getting a chance to fix that though.
@5:13! That's it! Nailed it! Not wrong. Right. That was the transition into lift. Freaked the FMC out though.
Now that was a creative way of finding new employees.
Kudos!
That was entertaining! :-) I would build a smaller wing to get a happy medium between efficiency and stability. Also make the carbon rods a couple of feet longer to build the wings further out so there's no wing directly above the rotors. I think the rotors decrease the pressure from under the wing and disrupt airflow so you lose lift and efficiency. I'd love to see a brand new build and test flight. Thank you for making great videos!
Try a reflexive foil allowed to pivot freely without any servo control around pivot at ~30% chord - basically kicked up at the trailing edge to function like an integrated tail plane, it will set an angle of attack relative to the airstream all the time. Alternatively employ a small tailplane at lower AOA mounted off of a still freely pivoting main wing. This reflexive foil approach has been used a lot by traction kites to overcome tendency to luff, but was also an effort years ago to make microlights under name 'freewing'. A servo control on the tail plane AOA would allow you to set main foil AOA independent of drone pitch. Something similar is done on speed sailing craft and sail drone craft, to precisely and rapidly control the foil lift in rapidly changing incipient air directions.
You need to set the angle of attack of the main wing to just below the stall angle of attack. The pivoting wing is great. So, to set the angle of attack to a fixed number, put a trailing trim tab on the wing, like a horizontal stabilizer. The angle of attack of the trim tab sets the angle of attack of the rotating wing.
Also, the Center of Lift should be at the CG of the drone. This is accomplished by putting the pivot point of the wing thru the CG. Without having Center of Lift aligned with the CG you are creating a pitching moment that will pitch the drone up or down. Lift is creating Pitching Moment, eliminate this by aligning lift thru the cg.
I think what's causing the drone to go unstable is the added speed is causing the wing to produce enough lift that causes the drone to start gaining altitude. This causes the drone to slow the motors down to maintain the proper altitude, thus causing an exponential drop in lift. Then the drone sees the altitude start to drop, so it speeds up the motors to regain altitude which then increases the airspeed over the wing causing it to produce more lift and quickly gaining more altitude than expected putting the drone in a positive feedback loop. I also think the changing of the angle attack might also be contributing this feedback loop.
Would be interesting to control the wing pitch with an AOA servo to keep the wing at +5deg relative to the quad pitch angle.
Put stabilize system into the wings to servo on either side
Also, the wing will be doing some crazy stuff to the airflow into the top and bottom pairs of rotors during the different flight regimes, potentially creating a negative feedback loop and reducing control authority - ie accelerating the air into the bottom rotors reducing their net thrust and slowing the air into the top rotors increasing their net thrust
One key difference with the flight testing in this video is the all-up-weight of the drone was not the same with and without the wing. When flying without the wing an equivalent amount of weight should have been carried by the drone. Expect we'll see much better efficiency when the challengers have same AUW. (12:28)
To avoid sketchy flight maneuvers, it would help to add a radius between waypoint legs. Those 180º turns are just asking for craziness. Not having a fixed wing (non-pivoting) would cause he centre of lift to vary as pitch angle varies. Location of centre of lift vs. centre of mass can effect stability.
Overall a fascinating experiment Daniel. Like how you totally skipped any testing with a robust 5-inch, or 7-inch freestyle quadcopter and went straight to flight testing on a 13-inch monster-copter.
The propellers below are creating a huge suction on the wings and the wing essentially is seeing an even larger angle of attack than what has already been provided, hence with an already higher aerodynamic centre of the wing from centre of gravity, its mostly in stall throughout the flight creating drag and instability. My suggestion would be lower the wings closer to centre of gravity (in case you have symmetrical airfoil on the wings), have a very low, almost zero angle of attack as the suction from propellers below manages to increase the angle of attack easily on the wings and also some roll instability I can see: Aerodynamics!
Seems to me this is a really good way to smoke really expensive esc's If you want more efficiency for long range then you should probably go with the standard H frame and go tilt rotor. Avoiding all the added weight and drag but not sacrificing any stability. I would think you could set it up where the front rotors go flat to act as the wing or slightly tilted like a Gyro copter and tilt the rear rotors more forward like an Osprey for higher air speed at the same or less power. Heck that may even be able to back feed current from the front rotors to do a little regenerative charging in flight.
I figured the possibility was likely, but it's nice to see such a clear difference in the data. Very cool. :)
I really appreciate the stall visualizations you showed, even if it was predictable that this wouldn't work too well as implemented. It was more of a science project than an engineering solution, and that's totally okay with me.
Loved this video. Loved your approach to the experiment and the way you analyze the results. Speaks really well for the company.
Still comeing back for this nice idea to see the performance. No clickbait bullshit. Top.
The best example to take inspiration from for fixed wing efficiency & Quadcopter type VTOL (vertical take-off & landing ) performance will be a US made military aircraft called V-22 osprey .
Hope some makes a RC drone based on it
the flight controller is probably doing weird things because it can't account for what it is happening because of the wing.
The software will probably need adjustment in order to account for the sudden lift when the wing starts taking effect.
Nice project!
if your quadcopter controller/software will support it, make it a BWB (Blended Wing Body) to house the camera and batteries, streamlined, tailsitter.
VTOL , with the props horizontal as designed, but attached to a fixed wing airframe. at altitude, it tilts further and further in the direction of travel until it's flying with the props vertical and the wings make 100% of the lift.
Thanks for the interesting test. As already mentioned in other comments, the wing position was not close enough to the center of gravity for that flight phase.
My assumption is that you could save the 24% much easier by using a more efficient propulsion concept: Larger propellers and adapted motors (lower KV, more torque). This also increases the area exposed to the wind and decreases stability in rough conditions - but much less than with wings added as in your example.
If the wings were located outboard the props, then they could provide lift more like a fixed wing aircraft. They could also be mounted lower to reduce drag related pitching moment. Interesting video.
Try Attaching a tail to the wing assembly that will hold the wing at the optimum angle of attack. Then allow the wing and tail assembly to rotate freely. A control surface on the horizontal stab could act as a trimming surface.
I think you should have a single divided wing. The wing should start outside the rotors. In the center part (within the rotors of the quadrocopter you might need an other stall. By that even turbulence up/downwinds can be better addressed.
Smart idea- an other approach is the gyrocopter principle in quadrocoptersas foam or carbon is not really so heavy.
Thank you for sharing
Wow , the exact idea that i even drawed it in my notes , thanks for creating it.
This channel has become my favorite out of nowhere.
It needs a tail with horizontal and verical stabilizers. 👍👍👍
Aeroespace engineering student here, those oscilations are caused by positive arch wings by definition having a positive pitch moment alpha derivative, thats why flying wings need to be delta shaped or atleast have some negative tip angle of atack so that the total pitching moment derivative is negative, crating a self stabilized flight
Oh, also, just a fun note, but the actual oscilations are caused by the angle of attack becoming so steep that the wing stalls and the nose falls back down and the cycle repeats again
nice video! keep it up!
Add the automatic angle of attack control vane from your wing-sailboat. This way, the angle of attack will be controlled to some reasonable angle automatically, won't go negative, and you can remove that servo etc.
I am currently completing my senior design and my project is a fixed wing (piper cub style) with vertical take-off and landing capability and a forward pulling traditional style motor. This is interesting because it's such a different approach from the previously mentioned Warwick university example. I would see this design being helpful at very slow speed but testing this to a slow flying fixed wing VTOL would be interesting to see what design is more efficient. could be useful for package delivery applications... maybe... as you mentioned high wind would be extremely detrimental to this design.
As the craft rotates forward, your wing is moving ahead of the CG and thus creating a pitch-up moment. If you set it further back, you would do better at higher speed (but worse at lower). Ideally you would have a way to move it back in response to the crafts pitch-angle to keep the center of lift closer to the CG.
I think just adding "flaps" to the masts that have limit stops would achieve higher efficiencies without adding much weight or stability issues. Make them delta shaped and have two sets of limiters so the "forward" surface (front flaps trailing the forward masts) is always at a higher angle than the rear ones; your center of lift should balance to the front two rotors and they can basically idle while the rear two provide forward thrust. This effect can be seen on your current iteration right before it goes into oscillation.
You are on the right track. Wings will increase the efficiency in forward flight. Based on a conversation with Ed Sweringen over 50 years ago, I think you have too much wing area for the aircraft. The wing flapping around makes it worse. Ed put small stub wings on a bell 209 HueyCobra Gunship that unloaded the rotor in forward flight and carried more armament. If wheels were added the wings increased the gross weight the helicopter would get off the ground with the lift from forward movement and air from the rotor in the ground effect. A much smaller fixed wing placed so the center of gravity and average center of effort don't induce isolation or proposing.
Stating small and making the wing larger until it fails works much better than starting larger and cutting it down over and over until it works.
good luck
I like the Opener/Blackfly concept a lot more. It's simpler because the wing doesn't have to rotate, the entire aircraft does, however it may not work well for some payloads.
*You NEED to put the wing on a SOLID Servo!!!*
Put a servo on the wing integrated with an accelerometer, and load the program on an arduino, regardless of the drone's inclination, the wing will always remain at the same angle. I believe it will work.