Newsgroups: comp.robotics
Path: brunix!sgiblab!spool.mu.edu!agate!iat.holonet.net!bsmall
From: bsmall@iat.holonet.net (Brad Smallridge)
Subject: Re: Robot Sumo Contest Announcement
Message-ID: <CH4C0J.HuI@iat.holonet.net>
Organization: HoloNet National Internet Access System: 510-704-1058/modem
References: <HATTORI.93Nov25120529@gaea.csrd.nkk.co.jp>
Date: Fri, 26 Nov 1993 21:36:18 GMT
Lines: 84

hattori@csrd.nkk.co.jp (Mato Hattori) writes:
: Yes, it seems that the robot started first has an advantage.  So that
: judges are severely watching the starting time in order to keep
: fairness of the game.  Robots in stand alone category should have at
: lease a start button and 5 sec timer.  We, operator will push the
: button as soon as the judge's signal.  The robots must keep their
: starting position for exactly 5 sec.  Robots may not move or even
: spread their arms during that period.  Then, we have to leave at least
: 1 meter away from the ring during that period.  No one can be inside
: the area until game ends.  If robot moved before 5 sec past since
: judge's signal, the robot will lose a half point.
:
 
Is half a point a lot? You get only one point if you win, am I right?
: 
: >   The other concern is one of friction. It would appear to me that a machine
: >   that sensed when its wheels were slipping, and could adjust the power to
: >   the motors accordingly, would have the advantage. The static coefficient
: >   of friction is more than the dynamic coefficient of friction. 
: 
: 
: Hmmm ... Interesting idea.  Let's try.  I have never seen robot
: wrestler with precise revolution control.  All I saw was just turnning
: on or off the motors.
: 

Gee, I'm surprised. It seems like an obvious strategy.

: >   The robots that ran off the ring, were they braking or using their motors
: >   in reverse?
: 
: I made two Sumo robots so far.  They are braking when they want to
: stop.  One uses 2 sets of MOS H bridge IC to control each motor, the
: another uses 2 sets of discreet H-bridge with 4 transistors and 4
: opt-isolator for each motor.  I just signaled the H bridge to be
: electrically shorten turning on bottom 2 transistors and off above 2
: transistors.  Reversing would be better if the robot has much inertia.
: But take care of inverse voltage of inductors.  H bridge could be
: easily broken with the spike voltage generated by the motors.  If you
: made very-easy-maintenance robot wrestler, you may have a chance to
: repair during the game.  In most case, you should consider there's no
: time to exchange H bridge during the game.
: 
: 
: For example, how would you make control program for your robot?  Using
: PC and cross compiler/assembler?  Yup, it would be a general way.  So,
: how would you load the program onto the robot's CPU?  Burning UV-EPROM
: every time you changed the program?  OK, do it if you have enough time
: to develop the program.  In most case, we should have more efficient
: way to download the program.  Using serial interface?  Well then, how
: to load the program for serial interface?  This is an interesting
: boot-strap problem, isn't it?

Well, I'm set up to make a sophisticated robot if I wanted too. I have
developed a board with a DS5000 as the micro and the TC211 as a CCD input
device. I could use one of those boards and then I'd be programming in C
and downloading it using the DS5000 serial port. The DS5000 already has
the downloader circuitry and software.
 
This seems like overkill however. I wanted to do it with just
electro-mechanics. I will probably start with the mechanics and work from
there. I'll leave room for the vision board however.
 
I think I can sense the slipping of the wheels mechanically by having
another wheel spinning on the axle of the drive motors and coupled to the
drive wheels with a spring also on the axle. I use this technique a lot in
my robotic projects. If the senseing wheel is not moving forward, it holds
the spring open, and the drive wheel is not being driven. If the senseing
wheel is moving forward, the spring tightens on the axle (the axle is
constantly being driven) and the drive wheel is driven forward. That's my
mechanical idea; sounded more interesting to me than trying to encode the
wheels and so forth.

: 
: Sensors, interface, algorithm, ....  there're many interesting
: technical points in making robots.
: 

You bet! Are you coming to San Jose?

Yours,
Brad Smallridge
bsmall@holonet.net

