LP Wireless System

Discussion in 'Armory - Q&A' started by rudd, Jul 28, 2015.

  1. Mac A. Bee

    Mac A. Bee is a Verified Fencing ExpertMac A. Bee Podium

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    Fear.;)
     
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  2. mtwieg2

    mtwieg2 DE Bracket

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    I assumed this was sarcastic, but apparently some people feel very strongly about their colored shoes and masks...

    Another idea I've had for a while is to change the weapons such that when the weapon contacts conductive surface (lame/guard/sabre mask) the return current passes back through the weapon at the same point of contact. Simplest implementation would be a weapon with two contacts (or more) on the face of the tip. When hitting on a nonconductive circuit, pressure would be detected via normal means, but an open circuit between the two contacts would be detected. When hitting on a conductive surface with both contacts, a short circuit would be detected between the contacts. However this would not require currents to pass through the lame to the other fencer's wiring (the lame wouldn't even be connected to the scoring equipment), which would make wireless hit detection extremely easy.

    The same could be doable for sabre. I'd imagine the cutting edge of the blade having two (or more) circuits along its cutting edge, which must be shorted together to detect a touch.

    Again, if I were a mechanical engineer, I'd try to build such things by now.
     
    Last edited: Aug 12, 2016
  3. dcchew

    dcchew Podium

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    It would be a nightmare for the average fencer to maintain. For saber, having wire connections and insulated areas on the cutting edge, you must be kidding me. Making a saber blade to do what you describe would be very expensive.
     
  4. Zebra

    Zebra Podium

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    Flicks would be hard to detect too.
     
  5. Steve Khinoy

    Steve Khinoy DE Bracket

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    If a color sensing system works, change the rules about uniform and shoe colors.
     
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  6. mtwieg2

    mtwieg2 DE Bracket

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    Yeah everything is always harder with sabre...

    Not necessarily. I'd break each tip contact into many separate contacts and interleave the two around the circumference of the tip. That would allow detection of glancing contact anywhere around the tip.
     
  7. neevel

    neevel Armorer

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    But first Surprise, and then Ruthless Efficiency.
     
  8. Alex_Paul

    Alex_Paul Podium

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    This kind of micro engineering would have be very tricky. Maybe with the development of affordable 3d printing it will become possible for the tips of foil and epee. Splitting a sabre in two would be cost prohibitive with current technology.

    The idea of using colour sensors is not new and could work.

    I think making the argument that there are colours in fencing so it wouldn't work doesn't really wash. The range of colours are only allowed because the rules allow them. If the system would improve the sport then you could change the rules that allow colors and either remove or limit them very easily.

    Development on wireless has stopped while I am in Rio but I am back on it next week.
     
  9. irrationalexhuberous

    irrationalexhuberous Made the Cut

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    sabre aside, you think a photo sensor tip would be easier and cheaper to make than the alternating conductive face?
     
  10. EldRick

    EldRick Podium

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    Why not just use a piezo-electric pickup in the tip to sense the actual contact? This could work for epee.
     
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  11. brtech

    brtech Podium

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    Piezo is a kind of force sensor. You need that, but there may be better methods to integrate force sensing into a tip. But it isn't enough, because it wouldn't sense target/off-target/floor.

    The problem with an alternating conductive face is you can't detect ground vs target.
     
  12. St.Meow

    St.Meow Made the Cut

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    Couldn't it work in the same fashion as currently? Metallic piste creates a circuit between A and B of the tip, but there is then a grounding circuit for A-Piste and B-Piste.
     
  13. brtech

    brtech Podium

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    Nope. The basic problem of wireless with the current mechanisms, or any mechanisms that require metallic connections between any two elements that don't share a common ground is that there isn't a way to detect connections. You need two wires to get electrical contact. In wired fencing it's Left B and Right A, or Left B and Piste, or something similar. Wireless means no common connection (ground). Without it, you need some variation of "virtual ground", and that's hard. Color works. Any form of electrical contact doesn't.

    There is a notion that you can use the fact that the piste really can be earth grounded and use some form of capacitive coupling to detect that you are very near it. But that would only work with the piste. If you tried to also use metallic connections to lames, you would make it very hard to reliably detect the difference between piste and lame.

    You have to accept the fact that a lot of smart people have tried to make wireless work with metallic contacts for the past couple decades with, so far, no success. Alex says it's "almost ready". Could be, we'll see, but wireless using metallic contact is HARD.
     
  14. Privateer

    Privateer Podium

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    could the point face have two conductive surfaces that have to be bridged by the target?
     
  15. brtech

    brtech Podium

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    Yes, it could, and that would detect contact, but you could not detect the difference between contact with the strip and contact with the opponent's lame (or even your own lame, although we might be able to figure that out reliably).
     
  16. mtwieg2

    mtwieg2 DE Bracket

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    Good point brtech, so differentiating the lame from the piste/guard would be a problem. But those should be substantially easier to differentiate with true "wireless" methods. It's the lame that's very difficult due to the sweat and large surface area in contact with the body.

    Piezo sensors couldn't replicate the sort of response we're accustomed to now. Piezo crystals are quite hard so there would be almost no travel in the tip. They're useful for getting quantitative measurements of force, but all we need to know is if the force/displacement is past a certain threshold, and a spring+switch does that fine.
     
  17. SJCFU#2

    SJCFU#2 Podium

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    Wouldn't this require a complete redesign of the foil circuit (two wires running down the blade, with independent contacts inside of the tip)?
     
  18. mtwieg2

    mtwieg2 DE Bracket

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    Yeah it would be a hybrid of a foil and epee tip, with return current carried by both the blade and one of the wires. A relatively modest proposal compared to optical detection or piezo transducers.
     
  19. brtech

    brtech Podium

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    Nope. The problem is lack of ground. It's actually easier to detect the lame because of the capacitive couplng to the body. While you can connect the strip to true ground, it's harder to detect the contact, at least as far as I understand the work that has been published.

    I don't think that's really going to be a substantial barrier. It would feel different, but not that different. Having no moving parts would be much better than what we have now. I do think strain gauge sensors would be a better choice, mostly because it could be integrated into a single piece of silicon.
     
  20. mtwieg2

    mtwieg2 DE Bracket

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    What I mean is that it's difficult to differentiate the lame from the body. It's a big challenge specifically because of that large capacitance (plus sweat) between the two.

    It would still need to "move" by a few micrometers at least, so you wouldn't get away from tip screws, etc. And how would one adjust the sensitivity of a piezo crystal or strain gauge? You basically can't. Best you could do is have the scoring machine read the sensor output with the 500/750g weight applied and set that as its threshold.
     

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