Improve wall detection algorithm

General tasks

• Make use of the ping sensor when looking in front (e.g. for differentiating ramps from walls - #6 (closed))
• Logic for wall overrides when new readings do not match previous ones (linked to #20 (closed)) new issue: #26
• Be able to differentiate ramps from walls on sides (#6 (closed))

Wall detection logic

Front

•  

• all sensors agree

  • nothing special (duh)

• ping detects but both IRs do not

  • possibilites:
    • could be bump detected - ping may be able to detect flat faces normal to it
      • bumps likely to be detected only past about 20cm
      • threshold: above 10cm
      • ignore ping & mark no wall
    • below 10cm - object (obstacle) directly in-front of robot
      • mark wall and (potentially) mark cell in-front as black (no victims allowed in cell with obstacle
    • narrow object (obstacle) in front - mark as wall
    • bumps very unlikely

• both IRs detect but ping does not

  • most likely ramp detected - ping does not get reading back from ramp
  • ignore IRs & mark no wall
    • no need to mark as ramp because algorithm will traverse there next and mark
    • marking would not help the algorithm out anyways

• only one IR detects a wall

  • mark no wall
  • possibilities:
    • obstacle - only detected by IR sensor on corresponding side
    • robot misaligned next to wall (not likely) - detecting edge of wall
      • both cases: should move away from side IR detecting wall to avoid whatever is there

• only one IR does not detect a wall

  • possibilities:
    • obstacle in front of robot
      • mark as wall
    • robot misaligned in front of wall (not likely) - one sensor not seeing wall (mark as wall)

Side

•  

• both IRs agree - possibilities:

  • readings are close (too close to be ramp)
    • mark as wall
  • ambiguous readings (could be wall or ramp or obstacle)
    • turn to check with front sensors
  • readings are far - no wall

• IRs disagree

  • possibilities:
    • obstacle
      • mark as no wall
    • robot misaligned in front of wall or edge of wall
      • ❓ check with front?
  • ❓ overall: check with front?