how to tune vertical movements for Copter (multirotors):

✅ Key Parameters for Vertical Tuning

1. Altitude Hold / Loiter / Auto Modes

These rely on a stable vertical control system.

• PSC_ACCZ_P
  Proportional gain for vertical acceleration (Z-axis).
  → Try increasing if the copter feels sluggish going up/down.
  → Reduce if it overshoots or oscillates vertically.

• PSC_ACCZ_I
  Integral gain for vertical acceleration.
  → Helps maintain steady altitude in the presence of bias (e.g., battery sag).
  → Increase carefully to improve holding, but too much causes oscillations.

• PSC_ACCZ_FF
  Feedforward gain for throttle control.
  → Helps the copter respond immediately to altitude changes.
  → Typical value is 0.5–1.0. Higher = faster vertical response.

✅ Throttle Response and Stability

• THR_MID
  Defines the throttle level for hover (0–1000).
  → Set this using data logs or in-flight tuning (CH6) so the autopilot knows what throttle to use when maintaining altitude.

• MOT_THST_HOVER (Copter 3.6+)
  Automatically estimated by the system or manually set.
  → Accurate value is essential for stable altitude control.

• MOT_SPIN_MIN
  Minimum throttle to keep motors spinning.
  → Should be just above the minimum where motors start spinning.

✅ Rate of Climb/Descent

• WPNAV_SPEED_UP / WPNAV_SPEED_DN
  Max climb and descent speed in cm/s during Auto modes.
  → Adjust based on how aggressive you want vertical motion in missions.

• WPNAV_ACCEL_Z
  Maximum vertical acceleration in cm/s².
  → Lower for smoother flight, higher for faster response.

🔧 Tuning Steps

1. Set MOT_THST_HOVER correctly using logs or hover flight.

2. Start with default PSC_ACCZ_P/I/FF. Use:

   • P = 0.5

   • I = 1.0

   • FF = 0.5

3. Test in AltHold mode. See if altitude is stable.

4. Adjust PSC_ACCZ_P/I/FF:

   • If slow to respond: increase FF

   • If steady hover drifts: increase I

   • If aggressive bounce: reduce P and I

🧪 Optional: Use CH6 Tuning

• Assign PSC_ACCZ_P or FF to CH6 tuning knob to adjust it live during flight.

• Helps find the sweet spot without repeated reuploads.

📈 Use Dataflash Logs

• Look at BARO.Alt, GPS.Alt, CTUN.ThO, and IMU.AccZ logs to analyze vertical performance.

• Use Mission Planner or LogAnalyzer to plot.