I plan to do what is called a "pull" to made changes to the custom code regarding custom shaped copters.
This change in code would only impacts irregular shaped quads, hexas, and octas when the pilot specifically opts to go custom versus the default (the standard X or +). You have a custom quad if the:
o aspect ratio <> 1 (length is different than width).
o rotors are non symmetric around the
- forward axis (y) going through the center of gravity (CG)
- sideways axis (x) going through the CG
- vertical axis (z) going through the CG
o has a front that is more open for a camera
o deviates from the pictures of a a + or X for the quad, hexa, or octa
o this includes ships described as spider, V, H, U, 88--88, C, etc.
o motor spin direction(s) are different than the pictures
o your CG is pushed somewhere else besides the centroid of the motors.
The advantages of going custom is that the motor factors will be tuned to the coordinate/spin system of your copter versus the coordinate/spin system of the regular copter. They will fly better. Pilots will probably not notice small deviations nor would they see significantly improved flight times. Large deviations might be noticed and provide noticeable changes in flight duration.
Please reply with the motor number (the out-pin number on the APM), coordinates of the motor, and rotation direction of each rotor. For example,
the owner of this copter would reply (motor number, x, y, CCW/CW):
o 1 (400, 200) CCW
o 2 (-250, -200) CCW
o 3 (-400, 200), CW
o 4 (250, -200 CW
[note: no need to tell us your units of measure just so long as you are consistent in measuring; say mm or inches]
Please note:
o The center of gravity of any quad spider or V is not necessarily where the bars cross. The bars typically cross behind the CG. .
o The CG is the center of the coordinates or (0,0) where x=0 and y=0
If you decide to participate by replying, the idea is that you will be able to access your custom motor factors without having to compile firmware. No promises at this point. First we see what's out there. But if you do reply, it's far more likely that your design will be implemented in the library.
If you have any questions or difficulties in doing this, let me know so I can help.
Replies
a lot of flyers like the H. the reason most of us like the X is for the same reasons we'd pick a triangle over a square ... it's much stronger and lighter. but there is a lot to be said about the beauty of a square or H. but a square or H have a lot of strength issues that are not apparent to even engineers--axial twist.
the X has the same benefits of the com at prop level. it's just about design and placement of the electronics platform.
on the other hand, my brother will choose sex appeal over weight efficiency every time. so go with your personal preference. it has to be fun.
yes and no.
H, I and square are typically the same. All suffer from issues with torsional twist (sort of the difference between a triangle and square).
Are they the same as the X if shear structures are added to the H, I, and square so they solve the axial twist issue? Yes in regard to turning sharp corners and not having the camera view wobble as the frame tries to twist and flex. But no in regard to the ship weighing about 40 grams more and not flying as long (between a few seconds of less flight time on typical quads to about 4 minutes on well engineered long-duration copters).
So if you are only trying to stay in the air for 15 minutes, an H, I or square is fine.
Can someone answer a question on the I or H design versus the X?
So obviously there is not difference in an I, H, or X in terms of motor location. All three frame types can locate the motors where ever you want them. So this question is in regard to frame design.
- H has two motor masts plus a central beam.
- I is simply a sideways H.
- X has two motor masts.
The advantages of the X over the H and I are:
- Frame weight as the motor positions can be supported with less frame material
- Motor to motor stiffness as lifting of one motor immediately lifts the two adjacent motors without the forces acting through a 90 degree joint.
- Wire weight as wire runs to the motors are shorter
- Frame stiffness as the X easily becomes, with the electronics platform, a series of triangles versus a series of rectangles.
So what are the advantages of the H and I?
Hi Forrest,
All the H I tried and have self-built were not behaving as good as the X :
-twist forces in the central body of the H
-yawing issues
So why H ? pure hype & fashion I guess (some say to have props out of the way when filming)
the spider or slanted X has the same benefits of the X's strength with only a small weight penalty for opening up the front for a center gimbal mounted camera. in fact, the camera Field of View (FOV) of an X will be greater than that of a H because of the structure required to spread the H gets in the way of the FOV.
for some, the H is cool and simple to build. and for others, like QAV owners, they are somewhat forced into it.
that is my impression too. guess they don't realize that changing the X angle does the same thing.
did this die or what?
In order to get the attention of the design team, we need to show them that there are many of us.
Currently the code doesn't allow you to modify the mix matrix directly, and also doesn't support a throttle factor in the table. I hacked the code to for my V-Tail design to add the throttle factor (since the rear props are angled) and am quite pleased with the result.
I think the best solution would be to have a custom frame mode in mission planner that lets you populate the mix matrix (including a throttle factor) to your liking. You could then use an external program to calculate the optimal factors based on geometry.
You photo above looks like it assumes all props are level and on the same plane. I think the general case would have a z axis value and a pair of angles to indicate tilt for each prop:
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