vgwit

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A way my failsafe works
« on: March 29, 2019, 11:24:43 am »
I'm trying to figure out how failsafe works and can not understand that.
I've got GCS 16.09, Flysky i6 radio and iA6b receiver sending IBus signal to Revo FC.
Failsafe settings in GCS are change to flight mode 6 (set to Rattitude) and all zeros to channel's values.
Failsafe setting for throttle in radio set to -51% and GCS shows that throttle goes to 1245 (1500 - 500*0.51) after radio switch off, hence RC keeps sending signal. Throttle neutral (minimal stable rotation) is 1028.

Then I arm the quad, rise throttle and switch the radio off. Motors stop, quad remains armed.
Questions: how FC guesses about radiooff (RC keeps sending) and why motors stop (not spinning at 1245 or 1028)?

Thanks.

Re: A way my failsafe works
« Reply #1 on: March 29, 2019, 05:04:30 pm »
There are two kinds of failsafe, RC and FC.

RC failsafe is when you have the RC programmed to certain stick positions when out of range.  In this case, the FC does not even know there is a failsafe.  It is the same as if you still had control and did it with the sticks and switches.

FC failsafe is when you have the RC programmed to stop sending pulses when out of range.  In this case, the FC does know and will set things to how you have failsafe set up in the FC.  To use this, you must set your RC failsafe mode to "stop sending pulses" when out of range.  Some RCs cannot do this.

vgwit

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Re: A way my failsafe works
« Reply #2 on: March 29, 2019, 08:10:29 pm »
Thank you for the reply.
I understand your explanation as well as description of RC and FC failsafe types from GCS user manual. I don't know how to change failsafe mode of my RC (not sure it is possible). But I see it keeps sending signal to FC after radio poweroff and this signal contains throttle 1245, not minimal or neutral. Then why Revo stops motors?

Re: A way my failsafe works
« Reply #3 on: March 29, 2019, 08:54:47 pm »
Start by looking at alarms on Flight Data page.  See what changes in the alarms when (within a few seconds after) you switch transmitter off.

Look at Input page to see what the values for all the channels are.  If any are invalid, it will cause an FC failsafe.  Actually, you may need to look at the raw data for this on the System page (DataObjects->ManualControlCommand->Channel).  If input page min-max is 1000-2000 and value is 0, it may show 1000.

Check to see what flight mode is selected by turning off the transmitter.  If it is a number greater than the allowed positions, etc.  There is code to keep you from using an FMS position for failsafe that is outside the normal operation range.  This is code that I personally like to change so that for instance I can have 3 normal flight positions on a 3 position switch, and have access to a 4th position that is only accessed during failsafe.  Switch the transmitter off to get this 4th position.
« Last Edit: March 29, 2019, 08:59:55 pm by TheOtherCliff »

vgwit

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Re: A way my failsafe works
« Reply #4 on: March 29, 2019, 11:25:19 pm »
Looking at the raw data page I see some out of range values after radio off. So it's clear now how FC detects failsafe. But still unclear why it stops motors despite throttle is mach bigger than 1000 ?

Re: A way my failsafe works
« Reply #5 on: March 30, 2019, 04:41:58 am »
For raw data, I recall that 0-65533 are legal but 65534-5 are illegal?

Try the other things I mentioned and report the results.

vgwit

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Re: A way my failsafe works
« Reply #6 on: March 30, 2019, 10:00:32 am »
On Flight Data page after TX poweroff green INPUT alarm turns to amber.

There are 65534 on two channels that are disabled, so they do not require attention.
But on channel 7 (which is potentiometer) RC sends to FC something like 5608 (I can't change it) and probably it is the reason FC decides of failsafe.

On throttle channel I can see values from 1000 to 2000 configured in transmitter setup for failsafe. But after it's poweroff motors always stop. Why?
« Last Edit: March 30, 2019, 10:19:56 am by vgwit »

Re: A way my failsafe works
« Reply #7 on: March 30, 2019, 04:57:22 pm »
Quote
On throttle channel I can see values from 1000 to 2000 configured in transmitter setup for failsafe. But after it's poweroff motors always stop. Why?
Input alarm green turning to amber says that the FC is going into failsafe if I recall correctly.  When it goes into FC failsafe it completely ignores all RC transmitter / receiver / Input->RemoteControlInput values and uses the values from Input->Failsafe page.

To fix the FC failsafe (I would do this):
So it is using the FC failsafe.  Just fix that to be what you want.  What failsafe FMS switch position are you using (it must be accessible with the real switch according to how many FMS switch positions you allow, usually 2 or 3) and how do you have the throttle set in FC failsafe.  Center (0) or left side (negative) is motors off.  Also beware that you should use the GUI (not System page) to set this because the number is off by one, zero on System page is the first switch position.

To stop it from failsafeing (but I would leave it as is and fix the FC failsafe):
Disable the inputs that are in question (65534, 5608) on the Input page.  Do this by setting that channel to Disabled or even None-Disabled.  I would start with ALL the inputs that go to 65534.  You will find that disabling the ones that go crazy with transmitter off will allow the Input alarm to stay green with transmitter off.

Google to learn about your RC:
Google for how to set the failsafe for that RC, including words in your search that describe the aux channels in question.

Parris

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Re: A way my failsafe works
« Reply #8 on: March 30, 2019, 06:09:16 pm »
With FlySky I think it depends on the receiver type . Whether it's AFHDS 2A or AFHDS frequency . AFHDS isn't failsafe capable . AFHDS 2A is failsafe capable . That is if I remember correctly .
Parris

Parris

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Re: A way my failsafe works
« Reply #9 on: March 30, 2019, 06:35:48 pm »
Go to page 14 on this Multi Rotors topics . I posted something about failsafe on the Flysky i6 that helped me . Failsafe on FS-i6 with ibus connection . Is the title .
Parris

vgwit

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Re: A way my failsafe works
« Reply #10 on: March 30, 2019, 10:13:29 pm »
Finally have clarified it for myself.
What misleaded me is that minimal stable motor rotation in output tab is not the same as neutral throttle value in input tab (last is bigger). So now I can get any desired rotation speed after TX poweroff. It works as expected.

I definately want to use FC failsafe for ReturnToBase mode. The way FC detects failsafe in my case is a little strange. It is based on channel7 reading (5608). I use this channel (don't want to disable it) so I'm willing to accept this way.

Thank all of you.