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A robot does not see a spoon or fork or knife.
A robot does not see a cat or dog or child.
A robot only sees numbers coming from sensors.
The numbers are inaccurate and sometimes very wrong.
The numbers will be from some previous time, possibly
very out of date.
Here is an exercise you should do, in order to understand
what you have to program in your robot:
A robot is moving down the center of a hallway.
The hallway has doors.
The robot is to enter the first open door.
The robot has eight ultrasonic sensors (distance measuring):
#0 facing forward
#1 facing 45 degrees right
#2 facing 90 degrees right
#3 facing 135 degrees right
#4 facing to the rear (180 degrees)
#5 facing 135 degrees left
#6 facing 90 degrees left (270 degrees right)
#7 facing 45 degrees left
The very idealized data at time 1, 2, ... for each sensor follows.
99.9 means nor distance measured.
time #0 #1 #2 #3 #4 #5 #6 #7
t=1 47.5 4.2 3.0 0.7 0.5 0.7 3.0 4.2
t=2 46.5 4.2 3.0 2.1 1.5 2.1 3.0 4.2
t=3 45.5 4.2 3.0 3.5 2.5 3.5 3.0 4.2
t=4 44.5 4.2 3.0 4.2 3.5 4.2 3.0 4.2
t=5 43.5 4.2 3.0 4.2 4.5 4.2 3.0 4.2
t=6 42.5 4.2 3.0 4.2 5.5 4.2 3.0 4.2
t=7 41.5 4.2 3.0 4.2 6.5 4.2 3.0 4.2
t=8 40.5 4.2 3.0 4.2 7.5 4.2 3.0 4.2
t=9 39.5 4.2 3.0 4.2 8.5 4.2 3.0 4.2
t=10 38.5 4.2 3.0 4.2 9.5 4.2 3.0 4.2
t=11 37.5 4.2 3.0 4.2 10.5 4.2 3.0 4.2
t=12 36.5 4.2 3.0 4.2 11.5 4.2 3.0 4.2
t=13 35.5 4.2 3.0 4.2 12.5 4.2 3.0 5.7
t=14 34.5 4.2 3.0 4.2 13.5 4.2 3.0 5.7
t=15 33.5 4.2 3.0 4.2 14.5 4.2 3.0 4.9
t=16 32.5 99.9 3.0 4.2 15.5 4.2 4.0 4.2
t=17 31.5 99.9 3.0 4.2 16.5 4.2 4.0 4.2
t=18 30.5 99.9 3.0 4.2 17.5 4.2 4.0 4.2
t=19 29.5 4.2 99.9 4.2 18.5 4.9 3.0 4.2
t=20 28.5 4.2 99.9 4.2 19.5 5.7 3.0 4.2
t=21 27.5 4.2 99.9 4.2 20.5 5.7 3.0 4.2
t=22 26.5 4.2 3.0 99.9 21.5 4.2 3.0 99.9
t=23 25.5 4.2 3.0 99.9 22.5 4.2 3.0 99.9
t=24 24.5 4.2 3.0 99.9 23.5 4.2 3.0 99.9
t=25 23.5 4.2 3.0 4.2 24.5 4.2 99.9 4.2
t=26 22.5 4.2 3.0 4.2 25.5 4.2 99.9 4.2
t=27 21.5 4.2 3.0 4.2 26.5 4.2 99.9 4.2
t=28 20.5 4.2 3.0 4.2 27.5 99.9 3.0 4.2
t=29 19.5 4.2 3.0 4.2 28.5 99.9 3.0 4.2
t=30 18.5 4.2 3.0 4.2 29.5 99.9 3.0 4.2
t=31 17.5 4.2 3.0 4.2 30.5 4.2 3.0 4.2
t=32 16.5 4.2 3.0 4.2 31.5 4.2 3.0 4.2
t=33 15.5 4.2 3.0 4.2 32.5 4.2 3.0 4.2
t=34 14.5 5.7 3.0 4.2 33.5 4.2 3.0 4.2
t=35 13.5 5.7 3.0 4.2 34.5 4.2 3.0 4.2
t=36 12.5 4.9 3.0 4.2 35.5 4.2 3.0 4.2
t=37 11.5 4.2 4.0 4.2 36.5 4.2 3.0 4.2
t=38 10.5 4.2 4.0 4.2 37.5 4.2 3.0 4.2
t=39 9.5 4.2 4.0 4.2 38.5 4.2 3.0 4.2
t=40 8.5 4.2 3.0 4.9 39.5 4.2 3.0 12.0
t=41 7.5 4.2 3.0 5.7 40.5 4.2 3.0 10.6
t=42 6.5 4.2 3.0 5.7 41.5 4.2 3.0 9.2
t=43 5.5 4.2 3.0 4.2 42.5 4.2 12.0 7.8
t=44 4.5 4.2 3.0 4.2 43.5 4.2 12.0 6.4
t=45 3.5 4.2 3.0 4.2 44.5 4.2 12.0 4.9
t=46 2.5 3.5 3.0 4.2 45.5 4.9 12.0 3.5
t=47 1.5 2.1 3.0 4.2 46.5 6.4 12.0 2.1
t=48 0.5 0.7 3.0 4.2 47.5 7.8 12.0 0.7
Crudely drawn #7 #0 #1
\ | /
\|/
#6---o---#2
/|\
/ | \
#5 #4 #3
Actually the robot would not be moving in a straight line,
would not be in the exact center of the hallway,
would not get accurate distance readings (because of beam width
and partially open doors and physical irregularities of walls).
The robot must start its turn one time unit before it is
exactly opposite a door. Looking one data sample at a time,
you can assume you store past history. Determine at what time
the robot is given the "turn" command, and "right" or "left"?
No cheating allowed.
After you chose the time and direction, use the data to
draw a scale diagram of the hallway and the open doors.
From the idealized data you may even be able to indicate
the position of closed doors or windows. The sensors are
three feet above the floor, so you do not know which.
Hopefully you did not turn your robot and have it fall
out an open window. This exercise is intended to show the
difference between human perception and robot action based
on sensor data.
See the hallway, after you drew it or tried to draw it.
Detailed information Ultrasonic distance measuring sensors
Last updated 10/9/04