PX4 v1.13 MAVLink parachute support #1943
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hamishwillee
commented
Jul 13, 2022
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| ### MAVLink Parachute Setup | ||
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@ThomasDebrunner @MaEtUgR Can you please check this section.
I've looked at the code in PX4/PX4-Autopilot#18589 and I want to confirm my understanding
The big picture is clear - the MAV_CMD_DO_PARACHUTE is emitted if the parachute is detected and healthy on failsafe. The COM_PARACHUTE parameter is checked an will warn if a parachute is expected but not present/healthy.
The small picture is less clear:
- PX4 appears to base its health checks on getting the heartbeat - that then sets
SYS_STATUS.onboard_control_sensors_present_extendedand.onboard_control_sensors_health_extendedfor the recovery system bit. Is that right? - What about the enabled flag? (
onboard_control_sensors_enabled_extended) - doesn't seem to be set. I would kind have expected enabled to be based on theCOM_PARACHUTEparameter. - I guess we're assuming that a parachute is always "in a good state". Otherwise we need a mechanism for it to actually tell the flight stack it is OK.
- What is
COM_PARACHUTEsupposed to do other than be a trigger for sending events when the heartbeat is lost? - Should
COM_PARACHUTEbe set for a PWM parachute? In this case how would you know if it is "healthy" etc? Presumably you will still want to emit this info for a GCS? - Is the
MAV_CMD_DO_PARACHUTEsent to the specific component that emits the MAV_TYPE_PARACHUTE? What if two are connected? Or is it just sent to current system ID and component 0 (broadcast). - Is the
MAV_CMD_DO_PARACHUTEcommand forwarded? i.e. can a GCS trigger the parachute? Should it?
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Merging as this is, I think correct. I still need the detail in ^^^ and that request is tracked in #1977
hamishwillee
commented
Jul 13, 2022
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bkueng
reviewed
Jul 21, 2022
hamishwillee
commented
Jul 27, 2022
| MAVLink parachute support is enabled by setting the parameter [COM_PARACHUTE=1](../advanced_config/parameter_reference.md#COM_PARACHUTE). | ||
| PX4 will then indicate parachute status using the [MAV_SYS_STATUS_RECOVERY_SYSTEM](https://mavlink.io/en/messages/common.html#MAV_SYS_STATUS_RECOVERY_SYSTEM) bit in the [SYS_STATUS](https://mavlink.io/en/messages/common.html#SYS_STATUS) extended onboard control sensors fields: | ||
| - `SYS_STATUS.onboard_control_sensors_present_extended`: MAVLink parachute present (based on heartbeat detection). | ||
| - `SYS_STATUS.onboard_control_sensors_enabled_extended`: ? |
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This updates parachute support docs for MAVLink and (partially) for actuators.
It follows on from the work in PX4/PX4-Autopilot#18589