MAVLINKHUD
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Full Parameter PDF

Overview

The QUAL parameter group (specifically QUAL_MIN or FLOW_QUAL_MIN) defines the confidence requirements for visual sensors.

Key Concepts

1. Optical Flow Quality

Optical Flow sensors (like the PX4Flow or HereFlow) output a "Quality" score (0-255) for every sample. This score indicates how many distinct features the camera can see and track on the ground.

  • QUAL_MIN: The minimum acceptable quality score.
  • Action: If the live quality drops below this threshold (due to low light or flying over water/sand), the autopilot will reject the flow data and trigger a failsafe (usually falling back to AltHold mode).

Developer Notes

  • Library: libraries/AP_OpticalFlow.
  • Tuning: If you find your drone constantly dropping out of Loiter indoors, check the logs for QUAL. You may need to lower the threshold or improve lighting.

QUAL_MIN

Default 10
Range 0 255

QUAL_MIN: FlowHold Flow quality minimum

Description

Minimum flow quality to use flow position hold.

Values

  • Range: 0 to 255
  • Default: 10

Description

This parameter sets the reliability threshold for the Optical Flow sensor in FlowHold mode.

  • Function: The optical flow sensor reports a "quality" metric (0-255) with each reading, indicating how confident it is in the surface texture it sees.
  • Below Threshold: If quality drops below QUAL_MIN (e.g., flying over water, low light, or featureless concrete), FlowHold stops trying to hold position and behaves like AltHold (drift with wind) to prevent runaway accumulation of errors.
  • Above Threshold: FlowHold actively fights drift using the flow sensor data.
View Source
QuadPlane Configuration (Q) QuickTune Configuration (QWIK)