Hi All, Just pulled this image in from SUAS News (Thank you Gary) to illustrate a few really good concepts that it incorporates and talk about better Multicopter design a bit.
This copter has a lot of things right and is really a study in design excellence.
1. Most obvious is a sliding ball full enclosure camera Gimbal, very pro and really something we should be striving for.
2. The motors are on the bottom under the arms: More aerodynamically efficient with no prop wash interference and very little intake interference. Noticeably increased flight times and greater lift capability and much quieter.
3. Large slow high efficiency props and pancake motors: These are way more efficient than faster motors with smaller diameter more conventional props.
4. Carbon fiber aerodynamic frame arms: Again more aerodynamically efficient, light and strong.
5. Fully enclosed framework and a simple spring loaded landing gear that provides as little interference with the prop wash as possible.
Basically this quad incorporates the best design features I have seen so far and definitely provides food for thought.
I thought it might be worth soliciting comments and other thoughts about optimal multicopter design techniques.
Best Regards,
Gary
Comments
Andrew That is worth knowing as my coils are home made and are an integral part of the model. I like most people I expect, I have a few dead hard drives laying about.
Voice coil actuators are used in hard drives to control the read-write head. Now there's a source for some inexpensive hardware to play about with... ;)
I cant say how ecstatic I am about Jason Shorts Drift mode which I have yet to try. This will bring a new dimension to the way my system will work.
I forgot to mention that a typical inner axis stabilizer only moves about 2.5 degrees in all three axis. In my case it is 5 degrees. If you study the degree of disturbance from a good MR that has a fixed camera it is remarkable that the typical disturbance is rarely more than 1 degree which looks awful.
Having shown the reasons why a tri-copter is the most efficient lifter (and it flys nice too) We come to the camera stabilization. As weight is the enemy I cant see any good reason for duplicating the roll pitch and yaw functions that the model provides us with. so what we need is just the tilt function so that we can fly the camera single handedly and the model follow that track. The Phantom Vision is a nice simple example of how that works but it lacks stability. This is where the clever bit comes in. By making a sandwich plate that sits between the camera assy and the model we can stabilize that platform to an accuracy of .005 deg. this is about the same as a cineflex which is arguably the worlds best full size system. So how is this done? It is easier than you may think. Your Brushless gimbal struggles to maintain even .5 deg. accuracy because it has weak torque hold and importantly it is not a linear motor. You can however control another type of motor called the Voice Coil Actuator and you can do it with a normal brushless controller using two of the pins. The VCA is what you will find in every inner axis mil spec. gimbal and it is so fast it can attenuate most of the vibration frequencies that the model can produce. It does exist and I have it working as you will soon see. I would from a personal point of view say that this has to be regarded as a major step in the right direction.
Hi, interested to know on how do you test the prop/thrust efficiency, is there any software for it? I'm interested to test mine as well.TQ
something iv been studying over time is a small inflatable plastic sphere at the end of the arms for landing, with a side cylinder inflatable on the arms. iv done some research where I took an egg, put it in an envelope, and tied a air filled ballon, the experiment was also done with a helium balloon. The Air Balloon slowed the payload down much faster, further design testing is showing that if you have good material this can work as a suffeciant landing mechanism.
It is a controrversial point as MR's are different things to different people but after many years of developing heavy lift machines I finally reached the conclusion that If I wanted to lift a Red Epic camera then the best and most reliable solution was a single rotor heli. It has bullet proof electronics and mechanics and has better efficiency than any MR can ever have. It is beyond debate because the numbers don't lie and are not swayed by personal ideology. The only problem is that if your 190 kph Henseleit 700 does hit someone they will die.
So my own MR ideology is one of saving the planet from our own stupidity. The size of the camera sensor dictates the size and weight of everything that you will put in the air. So our future is in the hands of legislators who will soon wake up to the fact that sub 1.5 kilo machines can do the job perfectly well. In my case far better than any heavy lift contraption. This is not a red light to upset the community at large but some thoughts that I feel we should for our own good consider. Amen.... Sorry about that but this is what this discussion is all about is it not?
John, Graham.
It's about motor, prop and voltage. The response time. Not just how fast the prop spins up but how fast the prop can slow down. So a larger prop with more inercia will be harder to slow down. So it won't be as stable.
Pancake motors are more efficient in general, as they normally require a larger prop.
It comes down to what you want to do, if it's blasting around FPV then 6 - 10 inch is best. If you want to hover forever then 26inch is on 12S is better.
So it's almost impossible to answer that question unless we know the exact motor/prop volt combination. :-)
Have fun!
Simon
Someone mentioned broom sticks and the pendulum effect as an example of lower CoG and improved stability earlier.
I would just like to point out that this is the "Pendulum rocket fallacy". The pendulum stability affect is only true when the lift force is at a constant diagonal angle (hand pushing or pulling the stick upwards), regardless of the stick angle. But on a multicopter the lift angle is perpendicular to the angle of the "stick", invalidating the pendulum effect. Meaning that a neutral system where CoG = CoR, is the one that requires the least amount of energy to maintain stability.
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