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Multiwii 2.4 fail safe?

Posted: Tue Apr 07, 2015 11:37 pm
by Droontje
Hello all,
I have been using multiwii on my quadcopter (own design foldable) for more than a year now, but have recently updated the system with a new pro board (readytoflyquads) with GPS.
I was testing the GPS mission functionality a few days ago and thought to find out how the quadcopter would react on RC transmitter outage. I think i have read somewhere that failsafe is something on the todo list for 2.4, but I wanted to see what the behaviour was. So I uploaded a small mission (4 waypoints, via EZ-GUI GS), put the quadcopter in the air, started the mission and during the mission I turned the RC transmitter off. Beforehand I made sure that the mission 'switch' would stay on (mission 'on' at aux-switch-states 'mid' and 'high', mid is what the receiver gives when transmitter is off). After turning off the transmitter, the mission was neatly continued (as i expected). But then when i switched the transmitter back on (simulating the quadcopter returning within reach), the quadcopter went into a fast spiral. After two complete turns (radius about 3-5 meter) i was able to regain control only after quickly turning the mission switch off. Oeff.
OK, i know I was testing a feature not yet available, but i have some questions:
- has anybody allready tested the same procedure and with what results?
- is the uncontrolled spiral (i imagine that the mag sensing is confused) expected, or even explainable behaviour?
- am i right in expecting the failsafe function for a quadcopter that is performing a mission would be to finish the mission first (on a well planned mission this would be near the home position), and after that perhaps hold position, or land.
I have seen some videos on youtube where, with other flightcontroller, during a preplanned mission the RC connection was lost and later re-established while the mission continued, so this could be a reasonable aproach.
Any thoughts, answers?
Greetings, Dirk

Re: Multiwii 2.4 fail safe?

Posted: Sun Jul 05, 2015 11:06 pm
by Droontje
Ok, I figured this one out by myself. The problem that was causing my quadcopter to crash was caused by my Turnigy 6XS FHSS RC transmitter. When you turn the radio on with the throttle stick in another than the lowest position, it will sound an alarm and will not work. In the mean time the receiver is giving max values on yaw and roll, causing the bird to crash. I should have tested this without props before trying it live. EZ-GUI helped me in finding this out by presenting the radio values.
Therefore when you want to test your failsafe routine with this radio, be sure to put throttle in low position before turning it on again!!

This also helped me to find the proper FAILSAFE_DETECT_THRESHOLD (at 1015) for this receiver; when connection is lost the receiver gives throttle channel a value of 1010, and all others 1500 (mid position).

Greetz, Dirk