Lost transmitter connection: what happens?

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lucaszanella
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Lost transmitter connection: what happens?

Post by lucaszanella »

What happens when the quadcopter losts the transmitter signal? I was testing with my quadcopter (motors activated) and when I turned off the Tx the quad stayed at the same velocity but after some seconds the motors speeded up so hard that I turned the Tx on again.

Can someone explain me what happened? What is supossed to happen when the quad losts it signal?

Thanks!

Katch
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Re: Lost transmitter connection: what happens?

Post by Katch »

You can set up failsafe in the config.h.

Basically you have a motor idle speed (the speed they run at when the quad is armed and throttle at zero)

When flying if you lose Tx signal after a few seconds failsafe kicks in which is usually idle speed + X (X being a variable you set up in the config.h) - this should give the quad enough throttle to descend safely and land (relatively) harm free. After a further few second the motors with stop and disarm.

If you were testing on the ground and your motors were idling this would explain why they sped up when you turned off your Tx - after a few seconds the throttle would increase to idle+X for a safe descent.

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Hamburger
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Re: Lost transmitter connection: what happens?

Post by Hamburger »

if you use a modern tx/rx, then the rx failsafe will kick in first and do its failsafe. In that case MWii will never know the rx lost signal and the MWii failsafe will _not_ kick in.

With those better tx/rx, the MWii failsafe only comes to life if rx gets disfunctional (broken wire etc.)

What your rx does for failsafe depends on the vendor's implementation.
What MWii does for failsafe, Katch described it well.

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UndCon
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Re: Lost transmitter connection: what happens?

Post by UndCon »

I triggered the failsafe the hard way - I turned off the transmitter in mid flight.
The MultiWii failsafe kicks in and drops the Quad - albeit a bit fast descend (I increased the motor value since then)

Now to a problem.

try to fly away again when you power up your TX...
To recover from a failsafe you have to turn off your motors and then restart them again - only then you can fly off.


Here is the scenario I was thinking of:

Flying about and suddenly your connection breaks - the MultiWii starts failsafe descend.
You regain connection while MultiWii is still in air.
Now you have to turn off the motors and start frefalling without control. Now you will not be able to turn motor back on again as the MultiWii is not level enough to be armed.

CRASH - due to failsafe routine.

As is you must let MultiWii land in failsafe - you cannot regain control.
if connection is restored I want to be able to have full control again - just power up the darn motors again to stop falling.

The approach to solve a broken connection/failsafe in multiWii is totally messed up!
Compare to a glitch in Spektrum TX/RX - even if you drop connection for a while it is restored as soon as possible

Just my 2cents...

//UndCon

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Hamburger
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Re: Lost transmitter connection: what happens?

Post by Hamburger »

UndCon wrote:I triggered the failsafe the hard way - I turned off the transmitter in mid flight.
The MultiWii failsafe kicks in and drops the Quad - albeit a bit fast descend (I increased the motor value since then)

you sure?
As you mentioned Spektrum, with Sektrum (and other modern tx/rx), when you turn off tx, the rx will recognize this and start its rx-failsafe. With Spektrum that means throttle signal goes to trained failsafe value (set in binding process) and all other channels to min-value (or center?). MWii will not detect this, because it gets sane rx signals still -> _no_ MWii failsafe.

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UndCon
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Re: Lost transmitter connection: what happens?

Post by UndCon »

HI!

Spektrum is just an example in this case. - When I tested failsafe I used my TGY9X with Frsky module

my concerns are still the behaviour that once failsafe - always failsafe - until motor are powered off - recovery does not exists

PatrikE
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Re: Lost transmitter connection: what happens?

Post by PatrikE »

UndCon wrote:Once failsafe - always failsafe - until motor are powered off - recovery does not exists


Exactly...
I dont use the failsafe function Only the failsafe in the Frsky reciver.

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Hamburger
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Re: Lost transmitter connection: what happens?

Post by Hamburger »

I agree.
The MWii failsafe was more useful if it could detect tx-rx failure.

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

Believe it or not, this is one of my pet peeves and the reason I love the cheap FlySky 6 channel Receivers. When there is no signal, it stops outputting and the MWC's failsafe will engage. In this situation, the dumber the RX, the better in my opinion.

Pyrofer
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Re: Lost transmitter connection: what happens?

Post by Pyrofer »

Most RX have a signal LED, could we take a wire off that to an input pin on the Flight controller to tell it when its got signal?
Then we would have a sane way to detect RX loss on all receivers (that have a LED).

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

If you turn tx on or regain connection the failsafe will stop immeadietly.
Nils

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

Pyrofer wrote:Most RX have a signal LED, could we take a wire off that to an input pin on the Flight controller to tell it when its got signal?
Then we would have a sane way to detect RX loss on all receivers (that have a LED).


It has been done here but not incorporated into the main code.

viewtopic.php?f=13&t=1615

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

jevermeister wrote:If you turn tx on or regain connection the failsafe will stop immeadietly.
Nils


within the set time, yes.

#define FAILSAVE_DELAY 10 // Guard time for failsafe activation after signal lost. 1 step = 0.1sec - 1sec in example

Alexinparis
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Re: Lost transmitter connection: what happens?

Post by Alexinparis »

Failsafe was added because Shirka lost his multicopter. (a runaway to the sky in stable mode...)
The cause was a bad connection between FC board and the RX.
In this case the failsafe detects there is a signal loss and takes actions to land.

Failsafe can do nothing if the TX-RX link is lost and if the RX continues to feed good signals to FC board.
Failsafe is not here to check if RC channels are static due to a TX connection loss.

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

copterrichie wrote:
jevermeister wrote:If you turn tx on or regain connection the failsafe will stop immeadietly.
Nils


within the set time, yes.

#define FAILSAVE_DELAY 10 // Guard time for failsafe activation after signal lost. 1 step = 0.1sec - 1sec in example


In my current software it even works after the landing has been dtarted. at least for a sum signal.

Btw.: best thing to do is to shut down everthing on signal loss. so nothing can go haywire and hurt people.

Nils

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

jevermeister wrote:
copterrichie wrote:
jevermeister wrote:If you turn tx on or regain connection the failsafe will stop immeadietly.
Nils


within the set time, yes.

#define FAILSAVE_DELAY 10 // Guard time for failsafe activation after signal lost. 1 step = 0.1sec - 1sec in example


In my current software it even works after the landing has been dtarted. at least for a sum signal.

Btw.: best thing to do is to shut down everthing on signal loss. so nothing can go haywire and hurt people.

Nils


I strongly agree!!!

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Hamburger
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Re: Lost transmitter connection: what happens?

Post by Hamburger »

Alexinparis wrote:Failsafe was added because Shirka lost his multicopter. (a runaway to the sky in stable mode...)
The cause was a bad connection between FC board and the RX.
In this case the failsafe detects there is a signal loss and takes actions to land.

same thing happened to me.
The RX was attached directly, piggy-packed with connectors on top of an early jussi board, secured only with adhesive tape. During excessive copter flying the RX took off & went flying on its own :) . In my case, failsafe did land the copter (more or less) intact.

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

Alexinparis wrote:Failsafe was added because Shirka lost his multicopter. (a runaway to the sky in stable mode...)
The cause was a bad connection between FC board and the RX.
In this case the failsafe detects there is a signal loss and takes actions to land.

Failsafe can do nothing if the TX-RX link is lost and if the RX continues to feed good signals to FC board.
Failsafe is not here to check if RC channels are static due to a TX connection loss.


I recall when this happened and as stated, the cheap Flysky RX'es will stop all output on lost signal. I agree that if the RX continue to output a signal, there is nothing the FC can do EXCEPT, measure the time between the last received command, example if, last command is greater than 3 seconds, then shutdown.

Katch
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Re: Lost transmitter connection: what happens?

Post by Katch »

copterrichie wrote:
Alexinparis wrote:Failsafe was added because Shirka lost his multicopter. (a runaway to the sky in stable mode...)
The cause was a bad connection between FC board and the RX.
In this case the failsafe detects there is a signal loss and takes actions to land.

Failsafe can do nothing if the TX-RX link is lost and if the RX continues to feed good signals to FC board.
Failsafe is not here to check if RC channels are static due to a TX connection loss.


I recall when this happened and as stated, the cheap Flysky RX'es will stop all output on lost signal. I agree that if the RX continue to output a signal, there is nothing the FC can do EXCEPT, measure the time between the last received command, example if, last command is greater than 3 seconds, then shutdown.


This would need exceptions; like when in Alt hold or GPS Pos Hold - I could see a lot of broken copters due to failsafe kicking in when not required

mr.rc-cam
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Re: Lost transmitter connection: what happens?

Post by mr.rc-cam »

On R/C systems that have *programmable* Failsafe, you could assign a spare RX channel to change states upon a R/C link failsafe and use it to control the MWC's failsafe. This same channel could also be used to control auto RTH using a switch on the TX (just setup the travel mix differently than what is used in a R/C signal loss). I don't use the GPS feature yet, and I haven't looked at the code, but maybe this is already implemented?

- Thomas

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UndCon
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Re: Lost transmitter connection: what happens?

Post by UndCon »

Seems I expect something from the so called failsafe that is not its intentions.
I suggest renaming it into something else to stop further mishaps.

I'm glad I tested the "failsafe" so I know its behavior - I will never do it again.
When the RC link dies I'm doomed

BTW - similar scenarios happened to me when flying FPV with my Skywalker
Flying far away and very low made RC link die -I reached up in the air to regain control and it worked 2 times and I could continue flying - 1 time I crashed and had to drive my car to pick up the plane

This will not happen with "failsafe" MultiWii...it will always land

//UndCon

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

So what should we call a function that will iniate a SAFE landing if there is a FAIL in transmission ;-)


I think you misunderstand the function:

It is a way to set how the copter should react to a lost transmitter signal.
You can set it to just shut down, or try to land for a few seconds.
If you want something else you should try:
Panic "Return home" and "Land" (ACC, Baro, Mag, GPS, Sonar)
Panic Position Hold (ACC,Baro, MAG, GPS)
Panig Landing (ACC, Sonar)
etc etc.

It is up to you what the reaction to a signal loss is.
I think the best solution is to shut down the engines as soon as transmission is lost or at least try to land.

If there are receivers, that always repeat the last signal after signal loss then those are crap and we have to find another approch on finding a solution.

Panic Handler would be a nice name btw...

copterrichie
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Re: Lost transmitter connection: what happens?

Post by copterrichie »

IMO, people judge Failsafe based upon expensive radio gear used on an Airplane. When in fact, most of the external failsafe devices I have seen such as the one below, simply shutdown the throttle to prevent a runaway. This is what I believe the original thoughts were behind the Failsafe contained within the FC. Others have tried to incorporate auto-landing viewtopic.php?f=8&t=1356 but it is not working very well in my opinion.


Image

http://www.rctimer.com/index.php?gOo=go ... oductname=

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UndCon
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Re: Lost transmitter connection: what happens?

Post by UndCon »

Yes - when I hear failsafe I always refer to how receivers react when they loose signal from transmitter

In order to program a failsafe (possible on some models) you usually rebind the RX/TX again.

//UndCon

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

shall we call it panic handler? ;-)

Nils

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Hamburger
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Re: Lost transmitter connection: what happens?

Post by Hamburger »

this is all about some tech failure. But 'panic' is something you do not see in tech equipment too often, so no. :)

bill516
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Re: Lost transmitter connection: what happens?

Post by bill516 »

Fail safe is a generic term not just an RC term. Fail safe means, if a fault occurs then fail to safe condition, be that switch off, shutdown, switch to low power, etc.

In our case fail safe reduces power to motors to descend copter. Maybe a condition could be added that if baro fitted and current alt = to power on alt, then shutdown motors, if current alt greater than power on alt reduce motor power. If no baro then we would have to leave failsafe condition as it is, motors will power up to fail safe throttle value until they shut down. You could even extend it to GPS, if signal loss then return home, descend, shut down motors.

I am more than happy with the term fail safe as I know that is the safe condition.

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UndCon
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Re: Lost transmitter connection: what happens?

Post by UndCon »

Of course Fail safe is used outside the RC world.
The name is not important - it is the intended features that are relevant.

//UndCon

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

bill516 wrote:Fail safe is a generic term not just an RC term. Fail safe means, if a fault occurs then fail to safe condition, be that switch off, shutdown, switch to low power, etc.

In our case fail safe reduces power to motors to descend copter. Maybe a condition could be added that if baro fitted and current alt = to power on alt, then shutdown motors, if current alt greater than power on alt reduce motor power. If no baro then we would have to leave failsafe condition as it is, motors will power up to fail safe throttle value until they shut down. You could even extend it to GPS, if signal loss then return home, descend, shut down motors.

I am more than happy with the term fail safe as I know that is the safe condition.


I like that.

bill516
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Re: Lost transmitter connection: what happens?

Post by bill516 »

jevermeister wrote:
bill516 wrote:Fail safe is a generic term not just an RC term. Fail safe means, if a fault occurs then fail to safe condition, be that switch off, shutdown, switch to low power, etc.

In our case fail safe reduces power to motors to descend copter. Maybe a condition could be added that if baro fitted and current alt = to power on alt, then shutdown motors, if current alt greater than power on alt reduce motor power. If no baro then we would have to leave failsafe condition as it is, motors will power up to fail safe throttle value until they shut down. You could even extend it to GPS, if signal loss then return home, descend, shut down motors.

I am more than happy with the term fail safe as I know that is the safe condition.


I like that.


Good get coding :D

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jevermeister
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Re: Lost transmitter connection: what happens?

Post by jevermeister »

bill516 wrote:
jevermeister wrote:
bill516 wrote:Fail safe is a generic term not just an RC term. Fail safe means, if a fault occurs then fail to safe condition, be that switch off, shutdown, switch to low power, etc.

In our case fail safe reduces power to motors to descend copter. Maybe a condition could be added that if baro fitted and current alt = to power on alt, then shutdown motors, if current alt greater than power on alt reduce motor power. If no baro then we would have to leave failsafe condition as it is, motors will power up to fail safe throttle value until they shut down. You could even extend it to GPS, if signal loss then return home, descend, shut down motors.

I am more than happy with the term fail safe as I know that is the safe condition.


I like that.


Good get coding :D


Lool. Will try this weekend...

lool. I will try it this weekend...

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