ECU Failsafe feature.
11-30-2013, 08:06 PM
#1
Thread Starter
ECU Failsafe feature.
I know many ECU's have a failsafe feature built in to them to shut the engine
down if the ECU cannot make sense of the receiver signal to them.
When checking a model this morning (Kingtech 140/Futaba MZ14 radio) at
first attempt at testing the failsafe (turning transmitter off) the engine continued
at the idle setting. We found the failsafe setting in the radio set to hold so the
owner made the failsafe active then set the failsafe position to the idle setting of
the engine. When the transmitter was turned off the engine slowed from about 1/2
throttle to idle & continued to idle but did not shut down.
We could have set the failsafe to the stop position on the transmitter (stick down, trim down)
but didn't want the engine to cut because of a minor glitch.
Is this because the ECU interprets the receiver failsafe setting as a legitimate signal &
therefore does not initiate it's own failsafe?
- John.
down if the ECU cannot make sense of the receiver signal to them.
When checking a model this morning (Kingtech 140/Futaba MZ14 radio) at
first attempt at testing the failsafe (turning transmitter off) the engine continued
at the idle setting. We found the failsafe setting in the radio set to hold so the
owner made the failsafe active then set the failsafe position to the idle setting of
the engine. When the transmitter was turned off the engine slowed from about 1/2
throttle to idle & continued to idle but did not shut down.
We could have set the failsafe to the stop position on the transmitter (stick down, trim down)
but didn't want the engine to cut because of a minor glitch.
Is this because the ECU interprets the receiver failsafe setting as a legitimate signal &
therefore does not initiate it's own failsafe?
- John.
11-30-2013, 09:05 PM
#2
From Futabas manual.
"The Failsafe function is used to set up positions that the servos will move to in the case of radio interference. Defines servo position when signals are lost and when receiver battery voltage becomes low."
I believe your understanding is correct. In some cases, so easy use such as jet can allow the operator to set A timeframe before failsafe occurs. The idea here is that a transient condition would not immediately command the turbine to shut down if that indeed was the preset failsafe condition. We are required to set them up this way in the states. However I agree with you. The risk is that you have a greater risk of fire, post crash, by leaving a turbine running in failsafe (at idle).
The king tech ECUs may allow for this but I am unaware if they have the capability. If they do it would most likely be in a hidden submenu.
You might check with Barry at KingTech or Gaspar at Xicoy.
"The Failsafe function is used to set up positions that the servos will move to in the case of radio interference. Defines servo position when signals are lost and when receiver battery voltage becomes low."
I believe your understanding is correct. In some cases, so easy use such as jet can allow the operator to set A timeframe before failsafe occurs. The idea here is that a transient condition would not immediately command the turbine to shut down if that indeed was the preset failsafe condition. We are required to set them up this way in the states. However I agree with you. The risk is that you have a greater risk of fire, post crash, by leaving a turbine running in failsafe (at idle).
The king tech ECUs may allow for this but I am unaware if they have the capability. If they do it would most likely be in a hidden submenu.
You might check with Barry at KingTech or Gaspar at Xicoy.
12-01-2013, 01:08 AM
#4
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An ecu can only failsafe if there is no servo signal or a signal that is outside the normal pulse width. This was for the days when people didn't have failsafe radio or didn't set a failsafe. The radio failsafe sends a valid servo pulse to the ecu so the ecu never knows that anything is wrong. If you want it to shutdown then you need to set the radio failsafe to shutdown.
12-01-2013, 01:50 AM
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Boomerang
If you want the ecu to shut down with failsafe you must set the radio fail-safe correctly to shut down. If failsafe conditions are encountered the ECU will go to idle after 0.5 secs and then to stop after another 1.5 secs. This is explained in the Kingtech 140 manual. This will deal with your concern about a minor glitch affecting the engine. You should have set the engine stop position when the ECU learns the transmitter settings as set out in the manual. You should go through the learn process again exactly as the manual.
John
If you want the ecu to shut down with failsafe you must set the radio fail-safe correctly to shut down. If failsafe conditions are encountered the ECU will go to idle after 0.5 secs and then to stop after another 1.5 secs. This is explained in the Kingtech 140 manual. This will deal with your concern about a minor glitch affecting the engine. You should have set the engine stop position when the ECU learns the transmitter settings as set out in the manual. You should go through the learn process again exactly as the manual.
John
12-01-2013, 02:10 AM
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You should set the failsafe position to a signal below STOP setting, I mean, if when the stick and trim are set to low the throttle output is -100%, then set that in failsafe the throttle output is below -100% (-110% ... -125%)
If in flight the radio enter in failsafe, the ecu will "see" this signal below STOP, and will wait 2s before shutting down the engine, and will record the cause of shutdown as failsafe. If the failsafe position is set same a STOP position, the system will work the same, but the recorded cause of shutdown will be recorded as a normal shutdown, and the receiver error counter will not count the failsafe time, so you will loose this information for future diagnostic.
To test the failsafe delay the engine should be at higher than idle setting. If the ecu receive a command of IDLE for over than 2s, then the failsafe timer is set to zero, shutting down the engine immediately.
Gaspar
If in flight the radio enter in failsafe, the ecu will "see" this signal below STOP, and will wait 2s before shutting down the engine, and will record the cause of shutdown as failsafe. If the failsafe position is set same a STOP position, the system will work the same, but the recorded cause of shutdown will be recorded as a normal shutdown, and the receiver error counter will not count the failsafe time, so you will loose this information for future diagnostic.
To test the failsafe delay the engine should be at higher than idle setting. If the ecu receive a command of IDLE for over than 2s, then the failsafe timer is set to zero, shutting down the engine immediately.
Gaspar
12-01-2013, 12:09 PM
#10
Thread Starter
So, if I understand this correctly:
When the ECU 'learns' the receiver signals during set-up the range of settings
from the STOP setting, to the FULL THROTTLE setting (the IDLE setting would
be somewhere in the middle), that range is considered 'normal' parameters.
If the radio failsafe is set anywhere within that range the ECU considers that to
be normal parameters & does not see anything unusual & will not go into failsafe.
If, as Gaspar explains, you set the radio failsafe to a figure outside the range from stop
to full throttle (his example was -110% to -125%, stop being -100%) the failsafe recognises
this as outside the parameters it learned during set up & starts it's own failsafe procedures
including the 2S delay & record it in the ECU memory as a failsafe.
Correct?
Thanks guys, John.
When the ECU 'learns' the receiver signals during set-up the range of settings
from the STOP setting, to the FULL THROTTLE setting (the IDLE setting would
be somewhere in the middle), that range is considered 'normal' parameters.
If the radio failsafe is set anywhere within that range the ECU considers that to
be normal parameters & does not see anything unusual & will not go into failsafe.
If, as Gaspar explains, you set the radio failsafe to a figure outside the range from stop
to full throttle (his example was -110% to -125%, stop being -100%) the failsafe recognises
this as outside the parameters it learned during set up & starts it's own failsafe procedures
including the 2S delay & record it in the ECU memory as a failsafe.
Correct?
Thanks guys, John.
12-01-2013, 12:19 PM
#11
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No!
The ecu still recognises it as a valid signal. The invalid signal limits are outside what your tx can generate with travels turned up to max.
Gaspars ecu will shutdown the engine with anything from the normal shutdown signal onwards. The only difference is what reason the display shows to explain the shutdown. If it gets a shutdown signal further on from the normal because your radio falsafe is programmed to send that extreme signal then the ecu will say failsafe instead of user shutdown. That way when you glide back and land or stare at the wreckage and wonder why the engine stopped in flight you can find out if it was because the radio went into failsafe.
The ecu still recognises it as a valid signal. The invalid signal limits are outside what your tx can generate with travels turned up to max.
Gaspars ecu will shutdown the engine with anything from the normal shutdown signal onwards. The only difference is what reason the display shows to explain the shutdown. If it gets a shutdown signal further on from the normal because your radio falsafe is programmed to send that extreme signal then the ecu will say failsafe instead of user shutdown. That way when you glide back and land or stare at the wreckage and wonder why the engine stopped in flight you can find out if it was because the radio went into failsafe.
12-01-2013, 12:20 PM
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Correct, but please note that when you say:
anywhere between the stop and max includes the range where the ecu stop the engine, so if you set the failsafe position in your radio to output a STOP signal, the engine will be shut down the same as if the ecu receive a signal outside the normal operating window, the only difference will be the data recorded by the ecu, but the engine operation will be exactly the same.
Gaspar
If the radio failsafe is set anywhere within that range the ECU considers that to
be normal parameters & does not see anything unusual & will not go into failsafe.
be normal parameters & does not see anything unusual & will not go into failsafe.
Gaspar
12-02-2013, 03:28 PM
#14
No!
The ecu still recognises it as a valid signal. The invalid signal limits are outside what your tx can generate with travels turned up to max.
Gaspars ecu will shutdown the engine with anything from the normal shutdown signal onwards. The only difference is what reason the display shows to explain the shutdown. If it gets a shutdown signal further on from the normal because your radio falsafe is programmed to send that extreme signal then the ecu will say failsafe instead of user shutdown. That way when you glide back and land or stare at the wreckage and wonder why the engine stopped in flight you can find out if it was because the radio went into failsafe.
The ecu still recognises it as a valid signal. The invalid signal limits are outside what your tx can generate with travels turned up to max.
Gaspars ecu will shutdown the engine with anything from the normal shutdown signal onwards. The only difference is what reason the display shows to explain the shutdown. If it gets a shutdown signal further on from the normal because your radio falsafe is programmed to send that extreme signal then the ecu will say failsafe instead of user shutdown. That way when you glide back and land or stare at the wreckage and wonder why the engine stopped in flight you can find out if it was because the radio went into failsafe.
