Variable Pitch Tricopter Using APM

I have been building a variable pitch tricopter and wanted to share my results so far.

Basically - I chose a tri and not a quad, because the tri geometry is the same as a traditional heli 120 deg swash plate. Since I can't write a firmware on my own, I wanted to use an off the self solution.

I used a home made simple frame

3 e-flite park 370 hollow shaft motors with their variable pitch props

3 castle ESCs that I had laying around.


Here is a video of the tri on a table

https://www.youtube.com/watch?v=XI_8KCJyjcA


Here is a list of my various attempts

  1. radio programed as 120 deg swash and used airplane stabilizer - worked but not great
  2. used a commercial heli flybarless system - it flew , but could not set gains low enough
  3. used my ardupilot mega - with traditional heli firmware - worked, but could not remove oscillations
  4. I retried the APM with heli firmware and reduced the swash upper and lower limits to 1400 to 1550 and lowered rate p to 0.8 and stabilize p to 3.5 no I term and stabilize D of 0,07

 This allowed me to fly and hover, but very touchy

Check out the video above - and now I need suggestions .

I think one point is I need to redesign the pitch servo so that I use more of the servo throw, but mechanically reduce the movement - I have lost a lot of resolution using such a narrow pitch range in mission planner

suggestions welcome

Al

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Comments

  • Hardware is really simple

    home made tri - frame sandwiched using PCB.

    motors are park 370 hollow shaft - http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLM1210HS

    e-flight variable pitch kit http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLPVPP100.

    Pitch servos are hitech high speed digital tail servos - HSG-5084MG (unfortuantely non programmable)

    Agree regarding servo horn. If I move control rod to toward the centre I can reduce travel. My problem is my scratch build servo base needs some work to allow the servo to more closer to the centre of the motor shaft.

    Al

  • Have you tried moving the servo ball link closer to the servo horn screw. i know mechanically that will take some travel out. can you provide more information about your hardware?
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