Hexa center of gravity?

Hello, I'm designing a hexa to carry a 1.5 kg load. I'm trying to create the absolute lightest configuration possible, so it's mostly made from CF. My question is around CG. My intuition tells me that for horizontal stability, the CG should be as low as possible. I would also think that the motion sensors would be most effective if they were as close as possible to the thrust plane. Can of any of you that have built or modified multicopters educate me on whether my assumptions are correct? My current diameter from arm-to-arm is 675mm.

Thanks,

Mike

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –

Replies

  • Everyone here is sorta on the right track, except that we're relying on automated fast control response to stabilize the craft.  My experiments prove there is no way to ever get the response fast enough for manual piloting without either variable pitch or an inertial feedback system (both would be ideal, but the complexity of the former ought to give one pause).  Of course, I am far from alone in this conclusion.

    Therefore, the goal for a multicopter design is fast response, not necessarily inherent stability.  Reducing rotational inertia of the entire airframe about the control axes is of paramount concern.  A center of mass, (and as much of the mass as possible) nearest the pitch and roll axes intersection, or perhaps slightly below, is the ideal design target.  Dr. Paul Pounds does a good job of providing the mathematical justification for this in the following paper (if you don't mind staring at a bit of calculus):

    Pounds, et.al. - Modelling and Control of a Large Quadrotor Robot

    http://eprints.qut.edu.au/33732/1/cep2009_modelling_and_control_paper_sub_final.pdf
  • I plan on using my copter for aerial video so to compensate for the weight hanging underneath, I plan on putting the battery on top. Basically keeping the CG as close to the center of the airframe as possible. I'm not sure if this is correct or not, but I will be testing this weekend. I'll try a few scenarios of CG and report back.

This reply was deleted.

Activity

DIY Robocars via Twitter
Jan 28
DIY Robocars via Twitter
RT @Heavy02011: ⁦@diyrobocars⁩ : A Home-brew computer club* for Connected Autonomous Driving. talk at #piandmore ⁦@PiAndMore⁩ on Jan 23rd h…
Jan 23
DIY Robocars via Twitter
RT @a1k0n: New blog post! Deep dive into my ceiling light based localization algorithm which runs in 1ms on a Raspberry Pi 3: https://t.co/…
Jan 23
DIY Robocars via Twitter
Great new guide to using @donkey_car https://custom-build-robots.com/donkey-car-e-book-en
Jan 23
DIY Robocars via Twitter
RT @chr1sa: The next @DIYRobocars virtual AI race is tomorrow morn at 9:00am PT. You can watch live on Twitch https://www.meetup.com/DIYRobocars/events/275268196/
Jan 22
DIY Robocars via Twitter
New version of Intel OpenBot! This resolves many of the issues with the first version, including a much smoother tr… https://twitter.com/i/web/status/1352395636369313798
Jan 21
DIY Drones via Twitter
Using ArduRover with an RTK GPS https://ift.tt/2N9I3RO
Jan 18
DIY Drones via Twitter
Jan 18
DIY Robocars via Twitter
Jan 18
DIY Robocars via Twitter
Jan 15
DIY Robocars via Twitter
Jan 15
DIY Drones via Twitter
Jan 14
DIY Robocars via Twitter
RT @Heavy02011: @diyrobocars : A Home-brew computer club* for Connected Autonomous Driving on Jan 23rd, 2021 https://www.meetup.com/Connected-Autonomous-Driving/events/275728684/ #Meetu…
Jan 14
DIY Robocars via Twitter
Jan 14
DIY Robocars via Twitter
RT @Heavy02011: ⁦@diyrobocars⁩ Autonomous Driving Assembly at #rC3. join us at https://rc3.world/rc3/assembly/diyrobocars-f1tenth/ ⁦@f1tenth⁩ ⁦@DAVGtech⁩ ⁦@DWalmroth⁩…
Jan 11
DIY Robocars via Twitter
RT @chr1sa: New car designs coming for our next @DIYRobocars @donkey_car virtual race on the 23rd. Choose any one you want at race time Le…
Jan 11
More…