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← 08-05 Sensorless Vacumm Cleaner Problem

Unit 8 5 Sensorless Vacumm Cleaner Problem-

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Showing Revision 1 created 11/28/2012 by Amara Bot.

  1. [Narrator] This is the belief state space
  2. for the sensor-less vacuum problem.
  3. So we started off here.
  4. We drew the circle around this belief state.
  5. So we don't anything about where we are,
  6. but the amazing thing is,
  7. if we execute actions, we can gain knowledge
  8. about the world even without sensing.
  9. So let's say we move right,
  10. then we'll know we're in the right-hand location.
  11. Either we were in the left, and we moved right
  12. and arrived there, or we were in the right
  13. to begin with, and we bumped against the wall
  14. and stayed there.
  15. So now we end up in this state.
  16. We now know more about the world.
  17. We're down to 4 possibilities rather than 8,
  18. even though we haven't observed anything,
  19. and now note something interesting,
  20. that in the real world, the operations
  21. of going left and going right are
  22. inverses of each other, but
  23. in the belief state world
  24. going right and going left are not inverses.
  25. If we go right, and then we go left,
  26. we don't end up back where we were
  27. in a state of total uncertainty, rather
  28. going left takes us over here
  29. where we still know we're in 1 of 4 states
  30. rather than in 1 of 8 states.
  31. Note that it's possible to form a plan that
  32. reaches a goal without ever observing the world.
  33. Plans like that are called conform-it plans.
  34. For example, if the goal is to be
  35. in a clean location
  36. all we have to do is suck.
  37. So we go from one of these 8 states
  38. to one of these 4 states and,
  39. every one of those 4,
  40. we're in a clean location.
  41. We don't know which of the 4 we're in,
  42. but we know we've achieved the goal.
  43. It's also possible to arrive
  44. at a completely known state.
  45. For example, if we start here,
  46. we go left; we suck up the dirt there.
  47. If we go right and suck up the dirt,
  48. now we're down to a belief state
  49. consisting of 1 single state that is
  50. we know exactly where we are.
  51. Here's a question for you:
  52. How do I get from the state where I know
  53. my current square is clean,
  54. but know nothing else, to the belief state
  55. where I know that I'm in the right-hand side
  56. location and that that location is clean?
  57. What I want you to do is click on the
  58. sequence of actions, left, right, or suck
  59. that will take us from that start to that goal.