3 out of 4 GPS RTH Tries was not bad....just the last one!

Discussion in 'Walkera Cameras/Videos' started by cv_flyboy, Mar 11, 2016.

  1. cv_flyboy
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    cv_flyboy Member

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    Great video showing the Walkera Runner going berserk during a GPS RTH test. Had three successful return homes, but the last one resulted in a nasty crash. Watch how it accelerates to the ground. FYI...although the Runners are challenging, I do like them!



     
  2. cv_flyboy
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    cv_flyboy Member

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    I forgot to mention, if you want to see the details on the damage, if you are into that kind of gory thing.

     
  3. bjr981s
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    bjr981s Moderator Staff Member

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    Couple of things.

    I notice that you flew from a table, Did you level the table to perfect horizontal before trying to fly.

    The FC IMU calibrates at motor arm and will set the level position at this time. If it is not level the flight will be very erratic.

    The FC sets home position and altitude for RTH at motor arm. You need at least 3 left Led blinks before arming motors.
     
  4. cv_flyboy
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    cv_flyboy Member

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    Those are great points, but what was interesting is that RTH came back over head just find at the start of the flight. It was later in the flight where the RTH failed. I suspect the failure had more to do with our "location" of flight. In hindsight, although the field looked like a great location, we were pretty well surrounded by too many houses. I have seen erratic flights before that I have associated to too much WiFi on that 2.4ghz band. Watching the Runner, it just takes off. In most RTH videos that I have seen, the slowly fly either back where they should or slowly somewhere else. Mine was on a mission going somewhere fast.

    With all that said, it is rebuilt and hopefully next weekend I will take it out for another spin and definitely keep your points in mind. Thanks for the response.
     
  5. bjr981s
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    bjr981s Moderator Staff Member

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    So your video was the same battery charge?

    Do you know if the right rear LED was flashing when you attempted the RTH?

    In GPS mode as soon as the LED indicates low battery it attempts a programmed auto land.

    If you manually fight this or go to RTH it will have unpredictable results.

    As soon as LED indicates low battery it is best to switch to manual and land immediately.

    Cheers
     
  6. cv_flyboy
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    cv_flyboy Member

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    Great thoughts, but same charge, same flight, just a few minutes later. Battery was well within operating limits. The points you make are interesting in that at what voltage do you think the results become unpredictable?
     
  7. bjr981s
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    bjr981s Moderator Staff Member

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    Do not attempt to change settings on runner with MultiWii. It is not compatible.

    Only use the versions of MultiwiiWinGUI that is provided in the 1.2 Firmware version pack.

    Also GPS home location is set when you arm the motors.

    If you arm before a good lock is established it will fly away. make sure you have 5 left led blinks before arming.
     
  8. bjr981s
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    bjr981s Moderator Staff Member

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    Interesting question. I am not defensive of Walkera and I never assume that people don't know what they are doing. I do however assume that most people have no idea of the consequences of what they are doing. I'm usually correct 99.9% of the time.:) If I was wrong about this there would be no road deaths.

    I spend hours of my time here helping people fix problems with their Walkera products. Unfortunately most are beginners and don't have much experience so they look to people that "seem" to know what they are talking about.

    Unfortunately as they are new, they don't know how to interpret what experienced users are saying. They get confused and end up breaking their models as they try to emulate what advanced users are posting.

    Unfortunately the advanced users here are not posting information that can be interpreted by beginners.

    And some cases the experienced users are more confused than the beginners as they have learned the skills from random posts around the web and get things wrong.

    I Post the warnings everywhere I see a post that may lead a beginner into a bad situation. Posting you use Multiwii 2.2 to check your settings was what I was convened about.

    I am not defensive of Walkera. I am defensive of the members of this site that can go astray due to "advanced user speak".

    You can now confirm that this is not the case. This is not the way Failsafe is Implemented.

    Failsafe is a collaboration of the TX and RX. The TX transmits the Failsafe settings to the RX at regular intervals. How did you think the settings got to the RX in the first place?
    For Failsafe to be implemented the RX needs to interpret the failsafe settings information transmitted by the TX. Some do it at bind only. Some do it continually so it can be modified in flight. The Walkera drones that are GPS based have FW based settings for what to do in the event of a low battery, and loss of signal in the flight controller.

    As a loss of signal event triggers a RTH it is completely managed by the FW on the Flight Controller. It uses the stored GPS location set at motor arm. Not enough sats at motor arm could have a home position 20 miles away. The RX built for these is the same for GPS and Non GPS models. The RX has an RSSI signal that advises the FC that signal has been lost. The FC then ignores the RX PWM, PPM outputs.

    The only way that a flyaway can be initiated by the RX is if it fails to hold the RSSI signal lost to the FC.

    This is a possibility for all RXs in a very, very noisy environment where the RSSI signal is being sent, dropped, sent dropped or just not sent at all. e.g. RX signal dropping in and out quickly very high error rates but an RSSI that can be just coped with.

    The Rx procedure is to check the incoming packets for errors. If lots of consecutive packets have errors it keeps the PWM / PPM signal constant. Its only after a long error steam on no reception at all that it will set RSSI to connection lost, and pass control over to the FC. The FC will take control after about 2 seconds. If signal is again received the FC will use the PWM / PPM inputs again for 2 seconds etc. Depending on the stick positions at the time of the interference will define what the model does in the air.

    This is a generic issue with all GPS based FC and RX operations on bad RSSI.

    Its not Walkera or Spectrum brand related. Even the $3,000 DJI top end FCs suffer from this problem. Check out all the Inspire and Phantom flyaway videos.

    It may be counter intuitive but in the event of a Runner 250 Advance Flyaway. Turn off your radio?

    Also do not do more than 1 RTH per battery.

    Think of it as the FC reading a book. It starts on page 1 with the motor arm and ends when landed and unarmed. To land and then initiate flight and attempt a second RTH is fraught with danger. Like using a PC that has been left powered on and operating for over a year. It will crash due to memory leakage.

    The other condition is magnetic interference.

    When you are using GPS stabilise mode the compass direction is only useful for "holding the tail" in GPS RTH it is used to set the heading to the Home location.

    If the heading is incorrect. (It only uses the Mag compass not the GPS heading) the it will fly away as fast as it can in a random direction.

    The compass is a learned setting. (gets better over time) but can be "confused" by magnetic anomalies close to the flight location. e.g. Power lines or large metal structures.

    It also resets and needs to relearn if you start a calibration. Connect to Multiwii for FW update or settings inspection / update.

    These Walkera models are very reliable if you operate them in a sensible manner.

    So basically depending on when the flyaway occurs. In normal Flight or after RTH request. it will fall into one of the following categorises.

    • Not enough Sats at motor ARM. Bad home position lock.
    • Magnetic Compass issue Either uncalibrated or near magnetic anomaly.
    • Interference causing RX dropouts.

    There is one last thing that can cause erratic behaviour. Particularly on an Accelerometer And GPS based system.

    • Vibration. Badly balanced props,motor bearings etc will upset the delicate FC.

    Cheers.

    Now aren't you glad you asked that question. :D
     
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  9. Michael Moore
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    Michael Moore New Member

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    cv_flyboy. I assume you are the individual that showed us how to update the Walkera runner 250 advance to Multiwii 2.4???? GREAT series of videos.

    if so, i would like to ask some questions. if that is possible.

    It has nothing to do with this thread. it is related to connection issues.

    Thanks
     

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