Very Agressive Roll Move and Crash

PX4 Autopilot
1

Hello, I am trying to build my drone by using autopilot CUAV X7+ and Here 3 GPS. Firstly I want to use PX4 as a firmware but I have some issues. I have flashed the PX4 firmware to my CUAV X7+ and tried to fly but there was very agressive oscillations around the roll axis. I couldn’t solve this problem and I have tried the ArduPilot with the exactly same drone and it was a really successful flight.

Again I have flashed PX4 but same problem was there. I have done all the calibrations and ESC calibration. The main problem is that: When I take the propellers out of the motors and make it ARM in altitude or stabilize mode motors are turning great. I make the drone NOSEDOWN and fron 2 motors get faster as the rear 2 motors get slower. And I make it NOSEUP front 2 motors get slower and rear 2 motors get faster as they should.

BUT when I make it turn left around the roll axis left 2 motors get faster and one of the right motors gets slower however the other right motor is full throttle. Same thing is for right roll move. When I turn it right around the roll axis right 2 motors get faster and one of the left motor gets slower but the other left motor is full throttle either. because of that drone does not fly.

My gps is working all the sensors are good but i couldn’t solve this problem.

ArduPilot successful flight video: https://drive.google.com/file/d/1cJVV3C87RUx1AAi8QR635R7H_ZUN-FVQ/view?usp=sharing

PX4 Crash:

Drone: Quadcopter X
Frame: DJI F450 clone

Edit 1: I have just tried same tests with pixhawk 2.4.8 and get the same result. motors don’t get slower while the roll axis moves.

2

Hi there!

Could you provide the log in px4review for safety purposes?

Things that come to my mind:

  • Wrong geometry
  • Wrong turning direction
  • Too agressive tuninig
  • Faulty ground testing
3

Hi, motors directions are correct, i am sure. I haven’t tune it yet so I use default PID coefficients.

Log : https://review.px4.io/plot_app?log=eb34142b-abcd-4656-b229-9f44c9faee71

4

From the logs and the video, it seems that your PIDs need to be tuned. Also, you have a lot of noise in gyro and it propagate to the motors.

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Your motors are jumping from 0 to 100% during takeoff.
Not always will the default PID setting work fine with selected frame. You need to configure them to your platform.
Also don’t start with Position mode. It will accumulate errors from multiple controllers. Best to start in Stabilized mode (or Acro if you are familiar with it) and go from there.
It’s good practice to enable extended logs (SDLOG_PROFILE). It will help you diagnose problems without guessing.

5

Thank you so much i will try what you said.