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 :)