algorithm - How to plot a room outline from range finder sensors in a toy car? -


i have toy car has arduino , 4 ultrasonic range finder sensors in front, rear , both sides, give me distance wall if exist within range sensor covers, sensors give me data in short intervals, car has move around room , plot outline, rooms can have columns , kind of irregular, don't know algorithms involved in plotting, insight appreciated.

heh once did robot same :)
bud turn around @ 1 place (no turning radius)
easy drive , map environment
in case hard because not see car kinematics

anyway hints:

1.while doing ultrasonic listening should have motors quiet

  • i used stepper motors pulses heard in receiver
  • if use dc motor tricky (may need full stop)
  • or determine echo echo , commutator noise
  • with brushless (bldc) , sinusoidal driving ok
  • but pwm or other impulse driving create same problems
  • so need synchronize listening times , pulse noisse times
  • without proper measure equipment extremly hard (oscilloscope ideal this)

2.ultrasound emitters

  • to avoid many confusions
  • either use 1 @ time
    • this easy slow
  • or @ once , wait first receive
    • in way not data far echoes
  • it possible receive sides need complex filtering
  • try optimize receiving loop as can
  • i did in few t of mcu give me 4 mm resolution
  • but long time ago , atmel used old 51 clone running on 20 mhz only
  • dont know arduino (preffer uc3) todays mcus more 10 times faster better timings.

3.movement

  • you need code movement manoeuvres
  • forwad/backward constant step
  • turn left/right 90 degrees
  • their must accurate can code
  • in suitable environment can use ultrasound more accurate (need perpendicular sides , no problematic material inside)
  • with these can start mapping 2d maze

4.mapping room

  • create 2d map of environment
  • you can cell or vector approach
  • i recommend cell access (it less accurate easier starters)
  • map can 2d array

  • with values unknown,space,wall

    1.init

    • place car perpendicular wall
    • clear map unknown
    • set position in middle of map (x,y)

    2.echo-locate sides

    • if wall found mark in map on (x,y)+(distance * side vector)
    • and mark space between x,y , wall mark space
    • if no wall found mark space cells in map x,y (x,y)+(safe range*side vector)
    • side vectors can be: front(0,+1), back(0,-1), left(-1,0), right(+1,0)
    • safe range distance car wall detected in [cells]
    • distance measured distance of wall in [cells]
    • do not forget add emitter/receiver offsets car position account
    • also mark current position (x,y) space

    3.find or closest or fastest move cell marked unknown neighbouring space cell

    • if none such found mapping finished (blink led or crazy move signal it)
    • if found plan path , move car it
    • set position x,y it

    4.goto 2

now mine data mcu pc , view it

[notes]

  • there can added improve ...
  • beware fabric/cloth materials
  • they hard detect ultrasound
  • for emitters use required frequency maximize performance
  • for impulse echolocation the best power/accuracy/range ratio emitting 7 pulses
  • no 1 knows why best (at least applications , equipment know of)

have fun :)


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