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New(?) idea for RTH

Discussion in 'Phantom 2 Vision + Discussion' started by Foosy, Oct 30, 2014.

  1. Foosy

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    Seems like dji implemented a safety feature that sends the drone back home at a low speed.
    In reality, if there were obstacles in the way, a low speed would be a smaller impact, but would still be an impact, so there is no real gain achieved by slowing down the RTH route.

    Here is where I have an idea: have 2 RTH modes: direct and traceback.
    direct will fly straight line, as it does now;
    traceback will retrace your path in reverse, maintaining altitude history; All information is available in the logs that are used by tracking.

    Both could be flown at maximum speed. The selected return speed should be the one that yields the most distance traversed per amphour.
    The pilot will select traceback if he flew the drone around obstacles or direct if it was an open field.
     
  2. aseidman

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    Clever. Only issue will be battery. If your route there was long and windy you may not have sufficient battery to get home.
     
  3. Meta4

    Meta4 Moderator
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    Some good aspects in the idea but it could be difficult to tell your bird which route to take after it's lost connection.
     
  4. singapore_phantom

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    It could follow true-track and revert to straight-line once it has calculated that it has no choice, given low batt. You could still hit something in the end, but it's better than a no-hoper.
     
  5. MapMaker53

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    An interesting option, but I think "trace back" would almost always result in battery depletion before reaching home point -- at least for me. I generally don't lose control signal on my way out to a specific location. I've usually been flying around and filming a lot of different scenery at different points for different views and eventually may lose signal for one reason or another. By then my battery is usually approaching 30% and if my quad had to retrace its entire flight route back to every location it had been to during the flight it would never make it back to me. I think setting a safe RTH height is the only thing that is needed for a straight line home. I do agree the RTH speed should be optimized by the software.
     
  6. Foosy

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    The idea is that the user has a choice of which RTH mode to use.
    As to traceback not having enough battery: many times pilots lose control because there is an obstacle that prevent LOS, not necessarily because battery drained. You can fly it around a mountain, or around a real tall building and lose control.
    I would be more confident doing that, knowing that it could take the same route to return to me.

    As a matter of fact, most people that get into RTH because of battery are doing so to reach the farthest distance, and these are done in open fields with full LOS. For these missions I would always use the fastest direct mode of RTH.
     
  7. LeoS

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    Always best to KISS (Keep it Simple... Silly).

    Traceback issues:
    1. Will effectively half the effective flight time, you'll need to trace the exact way back to go home.
    2. The world may not be static. What was your initial path, may not be the same on the way back. (Assuming tracing back means following the attitude changes too).
    3. Technical issues? Need more memory to save the path.
     
  8. Foosy

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    Yes,
    Traceback is not optimal in certain conditions which is why I want the user to have control on the return mode.
    Obviously if we are looking for a solution that is completely autonomous then we would need a system with object avoidance that can calculate the shortest and safest route.

    By the way, the processor for this does not have to be on the bird. It could be your iPhone sending a continuously updating list of coordinates, in the same way that it now sends a dynamic RTH location. Just imagine it will send 3 coordinates, for a 3 hop trip. This is not traceback, it is an optimization route.
     
  9. LeoS

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    Once you have object avoidance, you probably can do away with traceback for 90% of the cases. Just fly straight back, and fly higher if there are objects until the phantom can clear it; or somethinig like that.

    I'd imagine something like this is most useful when you don't have control of your phantom, thus the requirement of the path to be stored on the bird. It would be silly to follow a path when the 'map' is not on the bird, because the path may involve blindspots that can cause the phantom to end up in irretrievable areas.

    Path optimization is a romantic concept, but the best path optimization is already done by DJI's current algorithm. Involves 3 points as well...
    1. Where you start
    2. How high to fly the course
    3. End point :)
     
  10. Foosy

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    Leos,
    I guess you did not understand my concept. I can understand that. I cannot understand why you have to be condescending...

    There is no need to store a map on the bird. There isn't one now and it can perfectly fly ground missions.
    maps applications calculate shortest routes all the time. Can we have a similar calculation done for drones? Absolutely. It may actually be easier, and yes most of the time the solution will be a straight path back.
    But, when I am flying my bird around a mountain that is 4500 ft high, going up is not an option. This hobby is about exploring. Eventually we will have also control without LOS. Right now we can venture around the corner. I want to do it, and for me getting a shot around the corner is worth it, especially if I could trust my bird to come back.

    Interestingly, I was filming above a river with trees on both sides. While I was close to the water, I did lose control and the phantom initiated an RTH. It went a straight line which meant going through trees that were in the LOS, as the river is not a straight line. I was petrified as I was seeing it come through the branches. I was lucky- it just happened to miss the branches and get to me. If I had traceback in that case, I would have avoided a few skipped heartbeats...
     
  11. MapMaker53

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    My method of avoiding those skipped heartbeats due to trees is to just lock the home point in at a high enough altitude for the RTH to pass above them. I don't have mountains where I live.
     
  12. LeoS

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    Well good luck then :)

    (ps: I meant coordinates rather than map stored on the phantom)

    Right now the phantom is capable of keeping a single dynamic coordinate (home) which can be updated on the fly every 2s and without the user doing anything. Once you want to increase the number of coordinates, you're bound to run into UI issues, not to mention logic errors.

    When dealing with such a dynamic and time sensitive system like flying a phantom... you need to make your logic as foolproof and requiring as little user intervention as possible.
     
  13. Meta4

    Meta4 Moderator
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    Or if you had anticipated the risk that RTH would have created in that situation and reset home point at a safe height, the operation would have been elegantly simple and caused no anxiety.