Altitude PID

Requirements

Here are some notes for achieving a good altitude hold:

• protect the barometric sensor from light and air turbulence (a black plastic tube glued on the pcb with some foam inside or anything else).
• tune your multirotor with proper Acc calibration , radio and Acc trims
• consider that you should activate baro only when a stable hover is reached
• Once you activate the baro DO NOT touch anymore throttle
• Once with baro on you should not notice any differences in behavior between Acro and Acc mode.
• When changing PID values begin with P, I and D values at zero,

Altitude PID tuning

• Take notes, record which values cause desirable/undesirable effects, this will be useful in future!
• Set Altitude P, I and D to 0.
• Slowly increase D from 0 in increments of 1-2 until you start to get a slow yo yo movement. (When I tried this step, I don't really get a yo-yo motion, with low D values the copter shoots up when alt hold is enabled, as it increases it holds with drift, then if increased further it drops to the ground)
• Reduce D a little until yo yo movement stops (or, if no yoyo motion, reduce D until the hover sounds smoother!).
  • At this point the multicopter will start to hold altitude for a short time with drift
• Increase P slowly now in small increments (0.1-0.2), and you will find that the multicopter will begin to hold altitude better, until it starts the yo yo movement again,
• reduce P until yo yo movement goes away. The multicopter will now hold altitude with less drift.
• I is now increased gradually to reduce the drift when the battery runs down and the throttle needed to keep the copter at hover changes.
• If copter moves with an incremental sinusoidal from altitude point (point when you activate baro) decrease P value little by little, when you reach a good result increase D parameter.