Tuning vertical movements in Ardupilot

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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.

 

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