mirror of https://github.com/ArduPilot/ardupilot
48 lines
2.3 KiB
Markdown
48 lines
2.3 KiB
Markdown
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# ExternalNav / Optical flow source switching
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Switches between AHRS/EKF sources based on the pilot's source selection switch or using an automatic source selection algorithm
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This script is intended to help vehicles automatically switch between ExternalNav and optical flow
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## Parmeter Descriptions
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-- ESRC_EXTN_THRESH : ExternalNav innovation threshold
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-- ESRC_EXTN_QUAL : ExternalNav quality threshold
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-- ESRC_FLOW_THRESH : OpticalFlow innovation threshold
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-- ESRC_FLOW_QUAL : OpticalFlow quality threshold
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-- ESRC_RNGFND_MAX : Rangefinder altitude threshold (in meters)
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## How to use
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Configure a downward facing lidar with a range of at least 5m
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Set RCx_OPTION = 90 (EKF Pos Source) to select the source (low=ExternalNav, middle=opticalflow, high=Not Used)
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Set RCx_OPTION = 300 (Scripting1). When this switch is pulled high, the source will be automatically selected
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Set SRC_ENABLE = 1 (enable scripting)
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Set EK3_SRCn_ parameters so that ExternalNav is the primary source, opticalflow is secondary
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- EK3_SRC1_POSXY = 6 (ExternalNav)
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- EK3_SRC1_VELXY = 6 (ExternalNav)
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- EK3_SRC1_VELZ = 6 (ExternalNav)
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- EK3_SRC1_POSZ = 6 (ExternalNav) or 1 (Baro)
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- EK3_SRC1_YAW = 6 (ExternalNav) or 1 (Compass)
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- EK3_SRC2_POSXY = 0 (None)
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- EK3_SRC2_VELXY = 5 (OpticalFlow)
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- EK3_SRC2_VELZ = 0 (None)
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- EK3_SRC2_POSZ = 1 (Baro)
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- EK3_SRC2_YAW = 1 (Compass)
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- EK3_SRC_OPTIONS = 0 (Do not fuse all velocities)
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When the 2nd auxiliary switch (300/Scripting1) is pulled high automatic source selection is used based on the following criteria:
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- ESRC_EXTN_THRESH holds the threshold for ExternalNav innovation threshold (around 0.3 is a good choice)
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- ESRC_EXTN_QUAL holds the ExternalNav quality threshold (about 10 is a good choice)
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- ESRC_FLOW_QUAL holds the optical flow quality threshold (about 50 is a good choice)
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- ESRC_FLOW_THRESH holds the threshold for optical flow innovations (about 0.15 is a good choice)
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- ESRC_RNGFND_MAX holds the threshold (in meters) for rangefinder altitude
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- If ExternalNav's quality is above ESRC_EXTN_QUAL and innovations are below ESRC_EXTN_THRESH, ExternalNav is used
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- Optical flow is used if the above is not true and:
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- Quality is above ESRC_FLOW_QUAL
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- Innovations are below ESRC_FLOW_THRESH
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- Rangefinder distance is below ESRC_RNGFND_MAX
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