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49983RE: [beam] snakes, inchworms, sidewinders and slithery thingies

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  • David Walker
    Jul 1, 2005
      hey group,
      I had a look over the oism website and I've been bitten by the slithery
      things bug. I would like to know,i know i can't make the oism circuitry, but
      is there information out there about tilden's 3 motor snake that he built,
      or inchworm information (i can't get to the page in solarbotics.net)
      any information would be great

      I've wanted to build a gPIM style slithery thing for a while now, but I
      can't find the right sort of motors to use for it.
      Anyway, in terms of the circuitry I started off with master - slave - slave
      bicores. (I don't know if you have read the Living Machines papers- if you
      haven't, make sure you do!) If you looked at this in 3D, you would see a
      tube, with the master bicore making up the rim on one end (imagine in this
      case that the bicore is a circle with a pulse travelling round it. tricores,
      ucores etc also work) and the second slave would be on the other rim.
      Pulses travel around the circumference of the cross section with a delay
      along its length. It might look a bit like a candy cane or those things
      outside a barber's.
      After this I made the tube into a doughnut - this involves un-grounding
      the master bicore and hooking its resistors to the last slave. you end up
      with a slave - slave - slave architecture. This, in my opinion is better at
      driving a robot like this because it shouldn't 'really' have a head to speak
      of. Also, assuming you have some way of measuring and reacting to feedback,
      the affects can be felt globally. in an m-s-s bicore if a slave's
      frequency/duty cycle/period (sorry, I can't remember which one!) is altered
      any effects can only be passed "downstream", away from the master. In the
      torus/donut s-s-s bicore the effects pass all the way round, a but like what
      Tom Jenner was (I think) saying about closed loop systems of OISMs compared
      to an open loop chain, although they are a little different since it seems
      information can travel both ways in a branch of OISMs. Such alteration to
      the circuit could be acheived using the ABcore just like a bicore doughnut.
      I have another way that I'm experimenting with that may be better, but I'll
      post more when I've finished to save embarrassing myself if it fails!
      As far as light seeking goes, I'm not sure I have the most effective
      method; I've replaced the bicore resistors controlling the end motors with
      LDRs. This means four LDRs are necessary where I assume MWT used two.
      However it seems to allow the end sections to act a bit like localised heads
      when pointing at a light source. I'm pretty sure you can simply remove one
      LDR from each end - something Tilden was saying about the controller being
      robust, removing couplng resistors etc.
      The best way to go about building this is to make seperate bicore
      sections ie: perfboard or PCB - I've just started making PCBs and I made
      myself some quite convincing hextiles for this purpose! This helps in that
      its easy to visualise the circuit and unplug & change resistors.
      Good luck!
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