7 inch quadcopters fly like shit? Well, kind of, yes…

So, you got yourself a 7-inch quadcopter drone, you try to tune it, and you finally discovered that something is bloody wrong? Whatever you do, no matter how long you tune the PID gains and filtering, you can not get rid of jello and some strange vibrations? Welcome to the club mate!

Apparently, scaling 5-inch frames to 7-inch ones in XY axes does not work! Longer arms equal lower modal frequencies. Bigger propellers equal lower vibration frequency. After combining both factors, we have frame oscillations that are happening on the hardware level. No way you can tune that thing out. To make thing worse, 2205 and 2206 (even 2207) motors does not have enough torque to quickly change 7-inch propeller rotation speed.

For the details, watch the video.

Detecting Cleanflight PID tuning issues with Blackbox: excess P gain

Almost all quadcopter PID tuning tutorials can be summarized into one sentence: “Increase P until you see oscillations, then lower it”. Plus some thoughts about I and very vague advices about D and that is all. When I got into the hobby, I’ve read all of those tutorials. And I did know more about PID tuning than before that. I even had more questions than before. How to recognize high frequency oscillations, how to recognize low frequency oscillations. Lower P? OK, but how much? And D? How to tune this bloody D? As a result, every time I tried, I ended up with very snappy but shaky quadcopter that maybe responded very quickly to commands, but was very shaky and was making strange noises.

And then came Cleanflight and Blackbox. Live became simpler. What I’ve learned from Blackbox logs is that I wanted high P so much, I had too much of it in the end. Actual oscillations begins before we see or hear them and excess D introduces jello. Blackbox simplified things, but still, logs analysis is something like an art. You have to know what to look for. Continue reading Detecting Cleanflight PID tuning issues with Blackbox: excess P gain

Reptile 500 PID values for Cleanflight

After few test flights I have to admit, that PID values for Reptile 500 quadcopter frame I posted here are too aggressive. Way too aggressive. Specially D coefficient was too big and was main source of high frequency vibrations visible as camera jello. Reducing P and D, and slight increase of I improved quadcopter behavior. Current settings:

  • Raptile 500 frame, EMAX GT2218/09 motors, APC 10×4.5MR propellers,
  • Flip32+,
  • Cleanflight 1.10,
  • PID controller: LuxFloat,
  • Looptime: 2000
  • PIDs:
    • Roll (P / I / D): 1.8 / 0.07 / 30
    • Pitch (P / I / D): 1.8 / 0.07 / 30
    • Yaw (P / I / D): 2.5 / 0.1 / 0

Video has been processed with slight software camera stabilization. Standard settings from iMovie.