Subject:
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Re: RCX & RIS, a fading glory?
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 31 Jan 2003 02:24:41 GMT
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Viewed:
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1522 times
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In lugnet.robotics, Eric Sophie writes:
> But frankly, I have
> only seen a couple of hand fulls of Lego Robots that really use the RCX to
> its fullest. Dont's get me wrong. I say that statement very carefully.
> If one were to look at the range of RCX Creations. I would say it is far
> more difficult to make a Robot or device that really uses the RCX to its
> fullest,
> than it is to simply offer conjecture on expanding the current RCX.
> I say let me see the MOCs!
All right, you asked for it :)
http://www.ecf.toronto.edu/~stehlik/images/robots/projX/top1.jpg
The amount of wires connected to the RCX should give you an idea of how
fully I used the RCX. Overall, there were 5 motors and 7 sensors connected
to it :)
The main page describing this robot can be seen here:
http://www.ecf.toronto.edu/~stehlik/projX.html
Let me explain a bit. Last year rtlToronto put on an extremely challenging
robotics competition.
http://peach.mie.utoronto.ca/events/lego/lego-022302-index.html
The task was based on a 16 cell grid with eight randomly placed blocks. Your
robot had to figure out the location of the blocks and place them in an X
pattern as quickly as possible. This task was very similar to a real world
'pick and place' robot. The emphasis was on both accuracy and speed. The
software was challenging because the robot had to scan the board and
determine the optimal solution that would require the least amount of moves.
Some people used the strategy of scanning the entire board first, but the
fastest robots used a type of 'solve on the fly' approach which made for
some really tricky coding. Having only 32 variables in the standard firmware
made this even more challenging. I used LegOS, so this wasn't an issue.
Anyway, enough about the code. The mechanics of the robot were difficult as
well. First and foremost, two motors are required for positioning the robots
gripper over any given cell. This leaves one motor to both grip and lift the
block. Some people used a second RCX, but many in the group didn't have that
option, and there were many clever gripper solutions. I used pneumatics for
my gripper because of the speed advantage. I was able to control the gripper
and lift cylinder with one motor via a directional splitter device. As well,
considering the robot had to move as quickly as possible, the lighter you
could build it the better. Usually this type of robot has is motors mounted
on its axes, which limits speed because it has to carry around more weight.
Several of the entries (including myself) used a type of string drive which
allowed the motors to be mounted offboard. Now onto sensors... Since the
object was to have the robot move as quickly and accurately as possible, it
was a challenge to incorporate the appropriate type of sensors. Rotation
sensors tend to lose count and so there were accuracy problems. Most people
used light sensors with light/dark targets along the axes of their robot.
Each axis of the robot requires a sensor to track its position, so this left
one sensor to scan for the blocks and track the gripper. I'm not sure how
the others accomplished this, but I used a light sensor to scan the blocks,
and a touch sensor to keep track of the position of my two pneumatic valves,
both connected to the same port.
What were the results? Some very fast and spectacular robots. Many of the
robots could solve the worst case scenario (all blocks misplaced) in
approximately 30 seconds. The fastest time was 16 seconds. That means a
block was picked up, moved to the correct cell, and placed every 2 seconds.
If you ask me, thats pushing the limits of the RCX.
I would say that ALL of the 12 robots entered pushed the limits. Now if you
are still reading this far, have a look at this video on rtlToronto:
http://peach.mie.utoronto.ca/events/lego/video/lego-071902-demoreel.mpg
It shows clips from a bunch of the compeitions we have done. Many of them
have pushed the limits of what is possible with the RCX. There is some
footage of the project X competition near the end of the video.
Sorry for bragging, but Eric asked for it :)
Rob
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Message has 1 Reply:
 | | Re: RCX & RIS, a fading glory?
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| (...) You RTL'ers are amazing! Absolutly fantastic. I could just imagine the complexity of the programming either that or the beauty of its simplicity! Just great! wow! Thanks! e (URL) (22 years ago, 31-Jan-03, to lugnet.robotics)
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Message is in Reply To:
| | Re: RCX & RIS, a fading glory?
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| (...) I was thinking that if TLC links these two devices closely....well let's say I think that while they share simular characteristics they are really very different. I would hope that the fate of Mindstorms and Sybotics lay on different roads. (...) (22 years ago, 30-Jan-03, to lugnet.robotics)
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