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eug_titles/BallBot/Part1

This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.

Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.

Tape/disk: Home » Personal collection » Acorn hard disk » misc » misc3
Filename: eug_titles/BallBot/Part1
Read OK: ✔
File size: 21DD bytes
Load address: 0000
Exec address: 0000
Duplicates

There is 1 duplicate copy of this file in the archive:

File contents
BallBot Update

Artificial Intelligence Module

The Artificial Intelligence module is the computer program which will run
in the final robot to drive it around the tennis court to collect any
balls, and then dump them in a "home" position. The AI module's technique
is easiest viewed if you imagine that you are a small robot on a tennis
court, and imagine what strategy you would adopt. It is important to
decide what action you would take when confronted with all of the
following objects:

1. ME - Never visable from the ultrasonic sensors, because its always
behind them (when did you last see your face without using a mirror?), but
it is very important to know where you are relative to the rest of the
court.
2. THE BALL - The target. How could such a small thing be so important? Go
for it, but only if its safe to do so without the risk of colliding with
anything on the way.
3. THE  PLAYER - Nasty thing this... Keeps on moving around, but gets
annoyed if you collide with it. Keep away from this at all costs,
otherwise you will find yourself being recycled in the local scrapyard.
4. THE NET - An area where balls often collect, but be VERY careful when
maneovreing close to the net - you don't want to get caught up in it,
because that would be embarrassing.
5. THE CROWD - Large thing which surrounds the court. Don't collide with
it, or you will be in trouble. One wrong move when close to the crowd
could find you a place in that scrapyard again...

I found that the easiest method of performing this task was to split it
up. First the robot enters one of the two sides of the court. It then
begins slowly rotating around, scanning the court for balls. If it sees
one straight ahead, it drives forward to get it. If it sees one to one
side, it steers towards that side to line up with the balls. Once it has
collected the ball, it begins rotating again to try and find another
ball. If it manages to rotate through 360 degrees without seeing a ball,
it knows that this side of the court is clear of balls.

The robot then looks for a net post, and steers towards it. When it gets
very close, it steers away from the net to go around the post onto the
other side of the court. This maneovre required much attention in the
development of the module - if it steers too much it tends to get lost off
the court, and if it steers too little it collides with the post.

When this maneovre has been completed, the robot return to the first stage
of the process, and scans the court for balls again. Once again, the robot
only finishes when it successfully rotates through 360 degrees without
seeing a ball.

This time, the robot heads off towards the point where it is to dump the
balls - currently in the middle of one of the sides of the court, although
this will probably be changed later. Then it dumps the balls here, before
heading off towards one of the net posts, where it sits dormant until
asked to do another collection.

The Computer Simulation

The BallBot artificial intelligence module was developed in BASIC on an
Acorn Archimedes, using a computer simulation of a tennis court. The
simulation takes the robot is being at a point with co-ordinates (x,y) on
the court, and facing a direction of bearing d. To find the ultrasonic
data to pass to the AI module, it systematically cycles through every
object on the court: the balls, the net posts, the net, and any humans.
For each it finds the distance that the object is from the robot, using
Pythagoras' theorum, and the bearing using trigonometry:

It then decides which sensors that particular object would be detected by.
If it is out of sight of all of the sensors, it is ignored, and the
simulation moves onto the next object. This object will not affect
BallBot's input from any of the sensors. If it is in sight of one of the
sensors, it compares the distance of the object with any others which are
already logged as being detected by that sensor. If it is closer, the
previous entry for that sensor is removed, as it would be hidden behind
the new object. If it is further away, the object currently being
considered is ignored, as it would be hidden from sight. This way, the
closest object to the robot is found.

When the simulation has finished processing all of the objects in this
way, the ultrasonic inputs are completed. They are passed to the
artificial intelligence module for processing. Based upon this data, the
module decides what to do next, and the output data to the motors is
calculated. Although the AI module is running on the same computer as the
simulation, it only accesses the ultrasonic data passed to it, and does
not use any data concerning the co-ordinates of itself or any other object
on the court. This would be cheating, and would make the module useless in
any real life situation. The output data is returned to the simulation,
which uses it to update the values of x, y and d (the position of the
robot). It first has to find the speed at which the robot is travelling,
and then uses trigonometry to update x and y:

It then calculates whether or not the robot is turning at all, and if it
is, it updates the value of the bearing d by adding or subtracting a certain number of
degrees from it. When this is completed, the cycle begins again. The same
cycle will also be used by the final robot. The only difference is that
the manipulation of the motors and the calculation of ultrasonic data will
be carried out by hardware, not software.

This simulation allowed me to develop the simulation very easily, and as
the AI module was in BASIC it could be adapted to overcome faults with
little difficulty. At first I placed tennis balls on the court by clicking
with the mouse, and then watched the robot move round to collect them.
Later, when the robot was more reliable, I added a feature to the
simulation which allowed the computer to randomly place balls on the court
itself, without the user, and then set the AI module to try to collect
them. The simulation produced a log of all of the runs, with a judgement
of how well it went. If the AI module successfully collected all of the
balls, and returned the, to the "home" spot, it gave a "PASS". If it
failed to collect all the balls it returned "FAIL". Other responses were
given for crashing into the net or reaching a point of indecision (i.e.
the robot just froze up). Later I could watch the failed runs myself, and
study them to find out what went wrong. I found it useful to develop the
AI module's code during the daytime, and then leave the computer
simulation running on its own overnight so that I could see what areas
still needed attention.

This computer simulation runs in real-time, so that the robot on the
screen moves around in the same time-scale as would the real robot in
reality. This gives me a better judgement as to whether or not the speed
is acceptable than would statistics alone. In order to make the simulation
real-time, I had to research the exact dimensions of a tennis court to
know how fast the robot will move relative to landmarks on the court.

When I had developed the AI module in BASIC so that it was working
consistently, I had to translate the module into 6502 machine code.
Although BASIC is easier to work with, it would not be feasable to run the
code in the final robot or the prototype in BASIC. Machine code not only
runs faster, but is also the only language which microprocessors
can interpret without special software being present (which will not be
the case in the the final robot).

When the module had been converted into machine code, I began testing it
on a BBC, as opposed to an Archimedes, as this computer runs on a 6502
processor, and so accepts this form of machine code. First I used a
conversion of the simulation to check that the conversion had been
successful. I found that even without having to run the AI module in
BASIC, the BBC simulation ran slowly at only 1/20th of real speed. Even
so, I was able to use it to find a few bugs which had cropped up during the
transfer, and remove them from the code.

Development of the BallBot MOS

When the AI module had been successfully converted to the BBC, I began
developing a MOS (Machine Operating System) under which it would operate.
This reads input from an Ultrasonics module, and then passes the data to
the AI module. When the AI module has finished processing the data, it
takes the motor control data and sends it to the BBC's output ports to be
acted upon by the hardware.

This small module is actually a very simple piece of code - its sole
purpose is to pass data from one module to another, and to keep all of the
modules working together in time with one another.

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00000010  41 72 74 69 66 69 63 69  61 6c 20 49 6e 74 65 6c  |Artificial Intel|
00000020  6c 69 67 65 6e 63 65 20  4d 6f 64 75 6c 65 0d 0d  |ligence Module..|
00000030  54 68 65 20 41 72 74 69  66 69 63 69 61 6c 20 49  |The Artificial I|
00000040  6e 74 65 6c 6c 69 67 65  6e 63 65 20 6d 6f 64 75  |ntelligence modu|
00000050  6c 65 20 69 73 20 74 68  65 20 63 6f 6d 70 75 74  |le is the comput|
00000060  65 72 20 70 72 6f 67 72  61 6d 20 77 68 69 63 68  |er program which|
00000070  20 77 69 6c 6c 20 72 75  6e 0d 69 6e 20 74 68 65  | will run.in the|
00000080  20 66 69 6e 61 6c 20 72  6f 62 6f 74 20 74 6f 20  | final robot to |
00000090  64 72 69 76 65 20 69 74  20 61 72 6f 75 6e 64 20  |drive it around |
000000a0  74 68 65 20 74 65 6e 6e  69 73 20 63 6f 75 72 74  |the tennis court|
000000b0  20 74 6f 20 63 6f 6c 6c  65 63 74 20 61 6e 79 0d  | to collect any.|
000000c0  62 61 6c 6c 73 2c 20 61  6e 64 20 74 68 65 6e 20  |balls, and then |
000000d0  64 75 6d 70 20 74 68 65  6d 20 69 6e 20 61 20 22  |dump them in a "|
000000e0  68 6f 6d 65 22 20 70 6f  73 69 74 69 6f 6e 2e 20  |home" position. |
000000f0  54 68 65 20 41 49 20 6d  6f 64 75 6c 65 27 73 20  |The AI module's |
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00000110  69 65 73 74 20 76 69 65  77 65 64 20 69 66 20 79  |iest viewed if y|
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00000130  79 6f 75 20 61 72 65 20  61 20 73 6d 61 6c 6c 20  |you are a small |
00000140  72 6f 62 6f 74 20 6f 6e  20 61 20 74 65 6e 6e 69  |robot on a tenni|
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00000160  67 69 6e 65 20 77 68 61  74 20 73 74 72 61 74 65  |gine what strate|
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000001c0  6e 66 72 6f 6e 74 65 64  20 77 69 74 68 20 61 6c  |nfronted with al|
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000001e0  6e 67 20 6f 62 6a 65 63  74 73 3a 0d 0d 31 2e 20  |ng objects:..1. |
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00000260  77 69 74 68 6f 75 74 20  75 73 69 6e 67 20 61 20  |without using a |
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000002a0  20 79 6f 75 20 61 72 65  20 72 65 6c 61 74 69 76  | you are relativ|
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000002d0  48 45 20 42 41 4c 4c 20  2d 20 54 68 65 20 74 61  |HE BALL - The ta|
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00000350  20 63 6f 6c 6c 69 64 69  6e 67 20 77 69 74 68 0d  | colliding with.|
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000009c0  6c 6c 73 20 61 67 61 69  6e 2e 20 4f 6e 63 65 20  |lls again. Once |
000009d0  61 67 61 69 6e 2c 20 74  68 65 20 72 6f 62 6f 74  |again, the robot|
000009e0  0d 6f 6e 6c 79 20 66 69  6e 69 73 68 65 73 20 77  |.only finishes w|
000009f0  68 65 6e 20 69 74 20 73  75 63 63 65 73 73 66 75  |hen it successfu|
00000a00  6c 6c 79 20 72 6f 74 61  74 65 73 20 74 68 72 6f  |lly rotates thro|
00000a10  75 67 68 20 33 36 30 20  64 65 67 72 65 65 73 20  |ugh 360 degrees |
00000a20  77 69 74 68 6f 75 74 0d  73 65 65 69 6e 67 20 61  |without.seeing a|
00000a30  20 62 61 6c 6c 2e 0d 0d  54 68 69 73 20 74 69 6d  | ball...This tim|
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00000a50  64 73 20 6f 66 66 20 74  6f 77 61 72 64 73 20 74  |ds off towards t|
00000a60  68 65 20 70 6f 69 6e 74  20 77 68 65 72 65 20 69  |he point where i|
00000a70  74 20 69 73 20 74 6f 20  64 75 6d 70 20 74 68 65  |t is to dump the|
00000a80  0d 62 61 6c 6c 73 20 2d  20 63 75 72 72 65 6e 74  |.balls - current|
00000a90  6c 79 20 69 6e 20 74 68  65 20 6d 69 64 64 6c 65  |ly in the middle|
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00001f20  65 77 20 62 75 67 73 20  77 68 69 63 68 20 68 61  |ew bugs which ha|
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00001f60  6d 20 66 72 6f 6d 20 74  68 65 20 63 6f 64 65 2e  |m from the code.|
00001f70  0d 0d 44 65 76 65 6c 6f  70 6d 65 6e 74 20 6f 66  |..Development of|
00001f80  20 74 68 65 20 42 61 6c  6c 42 6f 74 20 4d 4f 53  | the BallBot MOS|
00001f90  0d 0d 57 68 65 6e 20 74  68 65 20 41 49 20 6d 6f  |..When the AI mo|
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00002010  20 69 74 20 77 6f 75 6c  64 20 6f 70 65 72 61 74  | it would operat|
00002020  65 2e 0d 54 68 69 73 20  72 65 61 64 73 20 69 6e  |e..This reads in|
00002030  70 75 74 20 66 72 6f 6d  20 61 6e 20 55 6c 74 72  |put from an Ultr|
00002040  61 73 6f 6e 69 63 73 20  6d 6f 64 75 6c 65 2c 20  |asonics module, |
00002050  61 6e 64 20 74 68 65 6e  20 70 61 73 73 65 73 20  |and then passes |
00002060  74 68 65 20 64 61 74 61  20 74 6f 0d 74 68 65 20  |the data to.the |
00002070  41 49 20 6d 6f 64 75 6c  65 2e 20 57 68 65 6e 20  |AI module. When |
00002080  74 68 65 20 41 49 20 6d  6f 64 75 6c 65 20 68 61  |the AI module ha|
00002090  73 20 66 69 6e 69 73 68  65 64 20 70 72 6f 63 65  |s finished proce|
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000020b0  69 74 0d 74 61 6b 65 73  20 74 68 65 20 6d 6f 74  |it.takes the mot|
000020c0  6f 72 20 63 6f 6e 74 72  6f 6c 20 64 61 74 61 20  |or control data |
000020d0  61 6e 64 20 73 65 6e 64  73 20 69 74 20 74 6f 20  |and sends it to |
000020e0  74 68 65 20 42 42 43 27  73 20 6f 75 74 70 75 74  |the BBC's output|
000020f0  20 70 6f 72 74 73 20 74  6f 20 62 65 0d 61 63 74  | ports to be.act|
00002100  65 64 20 75 70 6f 6e 20  62 79 20 74 68 65 20 68  |ed upon by the h|
00002110  61 72 64 77 61 72 65 2e  0d 0d 54 68 69 73 20 73  |ardware...This s|
00002120  6d 61 6c 6c 20 6d 6f 64  75 6c 65 20 69 73 20 61  |mall module is a|
00002130  63 74 75 61 6c 6c 79 20  61 20 76 65 72 79 20 73  |ctually a very s|
00002140  69 6d 70 6c 65 20 70 69  65 63 65 20 6f 66 20 63  |imple piece of c|
00002150  6f 64 65 20 2d 20 69 74  73 20 73 6f 6c 65 0d 70  |ode - its sole.p|
00002160  75 72 70 6f 73 65 20 69  73 20 74 6f 20 70 61 73  |urpose is to pas|
00002170  73 20 64 61 74 61 20 66  72 6f 6d 20 6f 6e 65 20  |s data from one |
00002180  6d 6f 64 75 6c 65 20 74  6f 20 61 6e 6f 74 68 65  |module to anothe|
00002190  72 2c 20 61 6e 64 20 74  6f 20 6b 65 65 70 20 61  |r, and to keep a|
000021a0  6c 6c 20 6f 66 20 74 68  65 0d 6d 6f 64 75 6c 65  |ll of the.module|
000021b0  73 20 77 6f 72 6b 69 6e  67 20 74 6f 67 65 74 68  |s working togeth|
000021c0  65 72 20 69 6e 20 74 69  6d 65 20 77 69 74 68 20  |er in time with |
000021d0  6f 6e 65 20 61 6e 6f 74  68 65 72 2e 0d           |one another..|
000021dd

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