MAVLINKHUD
Download Android App Professional ArduPilot Ground Station
Full Parameter PDF

Overview

The STILL parameter group (specifically STILL_THRESH or INS_STILL_THRESH) defines the sensitivity of the autopilot's Motion Detection logic.

The system needs to know if the vehicle is physically stationary for critical operations like gyro calibration on boot or performing pre-arm checks.

Key Concepts

1. Stillness Detection

The autopilot monitors the raw variance of the accelerometers.

  • Stationary: If the variance is below STILL_THRESH, the system assumes it is on the ground and still.
  • Moving: If vibrations or movement exceed this value, the system assumes it is being handled or is on a moving platform.

Parameter Breakdown

  • STILL_THRESH: Acceleration variance threshold.
    • Typical: 0.1 for fixed-wing, 2.5 for multicopters (to account for motor vibration).

Integration Guide

  • Boat Starts: If you are launching from a moving boat, the autopilot may refuse to calibrate its gyros because it thinks it is moving. In this case, you must increase STILL_THRESH to allow the calibration to finish despite the deck's motion.

Developer Notes

  • Library: libraries/AP_InertialSensor.

Stillness threshold for detecting if we are moving

STILL_THRESH: Stillness threshold for detecting if we are moving

Description

Threshold to tolerate vibration to determine if vehicle is motionless.

Values

  • Range: 0.05 to 50
  • Default: 0.1 (Plane/Rover), 2.5 (Copter/Heli)

Description

This parameter sets the sensitivity of the "Motion Detection" logic used by the EKF (Extended Kalman Filter) and the calibration routines.

  • Function: The autopilot monitors the accelerometer noise. If the total acceleration variance is below this threshold, it assumes the vehicle is sitting still on the ground.
  • Usage:
    • Calibration: When calibrating the gyros on boot, the vehicle must be "still." If you are on a boat or a windy platform, you may need to increase this threshold so the calibration can complete.
    • Arming: Some arming checks require the vehicle to be motionless.
  • Tuning: Increase if you have trouble passing pre-arm checks on a moving platform. Decrease for high-precision calibration on a solid bench.
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Stick Mixing Configuration (STICK) Stopping Distance Configuration (STOP)