This project started out as an experiment. Most multirotors have their rotors in a planar configuration. I noticed this is mostly true even when the props are titled in racing quads. (which is actually unnecessary). The idea is that if the moment arms do not change, standard flight controllers should be able to control non-planar shaped quadrotors as long as the control board is mounted near the center of gravity. I decided to try the idea out and it turns out it is able to fly pretty well.
- Basic Theory
Quadrotors control their attitude using thrust generated from each rotor on the arms. The torque which control the attitude can be calculated as the picture below.
Moving the rotors along the z axis of the quad does not change the moment arm which results in the same amount of torque. The moment of inertia may increase due to the displacement of the motors(further out from the center of gravity) but this can be controlled with a little more of P gain in the controller.
- Build
The configuration and part list is shown below.
– Motors : Turnigy Brushless motor Aerodrive 1200kv
– Props : 10X4.5 SF props
– ESC : Multistar 20A UBEC
– Flight Controller : KK2.1
– Battery : Zippy Flight Max 11.1V 3000mAh
– Frame : Tarrot carbon fiber quadrotor frame v2
Used two tarot quadrotor frames and mounted each frame using pennuts. Below is the picture of initial fitting the parts before wiring.
The battery was mounted just below the flight controller so that the center of graivity should be near the flight controller.
ESCs are mounted on different plates. I tied mounting everything symmetrically to prevent it from messing up the inertial moments.
I am so excited what I can do with this quad!
You can also view the project in the 404warehouse blog:
http://404warehouse.net/2015/09/22/symmetric-non-planar-quadrotor/
Comments
@Kay Fricke Thanks Kay, the flight controller does not need to be exactly on the CG but as the same as normal multirotors, if not placed on the cg I guess it will be much more sensitive to the movement as the controller assumes you have placed on c.g.
@Julian No yaw tendencies, Currently the configuration is symmetric. I guess I will get some kind of difference when the arms are asymmetrically placed!
Now can you make it like a T on top and bottom? So really, like a twisted capital I.
any interesting yaw tendencies? otherwise, way to think outside the X!
This could lead to intereting designs for cam copters.
My understanding is, that it is essential for this design, that the flight controller is positioned exactly on cg, or at least the imu, compass and gyro are?
Keep up the good work
Thanks for doing/posting this. There's lots of new opportunities for compoent layout with that configuration..
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