Recently I upgrade the firmware on my custom Quadcopter firmware from 1.10.1 to 1.12 stable. And flight in position mode become very unstable.
While using 1.10.1, I’ve tuned my PID using QGC, where only rate Controller xRate_P, I, D are shown. The drone flies stable and responsive in both manual and position mode. No Jerk or overshoot.
When upgrade to 1.12 stable, with my previous PID value, manual flight performs as usual, while flying in Position mode, the behavior become supper unstable: overly sensitive for input, and a lot of overshoot, if I gave a step input, the drone will almost flip over due to overshoot.
I don’t understand why a firmware update leads to unstable flight in position mode?
I notice the firmware introduced rate_K, meanwhile, the latest QGC also shows “Velocity Controller” and “Position controller”. Including some new parameters like Proportional gain (MPC_XY_VEL_P_ACC), how is this different than the old P.I.D values? Can someone help me understand how to tuning these new params to have a stable flight as before?
It looks like the developers have changed the controller design a little since v1.10 . The new parameters (MPC_XY_VEL_P_ACC … etc.) are designed to make the position control response independent of the throttle required to maintain altitude.
I suggest re-tuning you UAV under the new controller structure to find stable PID values. You could probably start with the parameter defaults and go from there.
You only need to tune the MPC_XY_VEL_<P,I,D>ACC and MPC_Z_VEL<P,I,D>_ACC parameters.
And then probably the position XY and Z PID parameters too, because they depend on the velocity controller response, but this might not be necessary if your new velocity controller reponse is very similar to your previous velocity controller in v1.10.
