Subject:
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Re: Balancing robots
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 27 Jan 2004 19:48:52 GMT
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Viewed:
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968 times
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In lugnet.robotics, Scott Davis wrote:
> Just a thought.
>
> What if you were to set up a track for a steel ball to roll on and have some
> sort of sensor at the end that would tell the rcx that the robot is falling
> forwards/backwards.
>
> something like so:
> _______________________________________________
> |_/____________________________________________\_|
> _______________________________________________
> |_\____________________________________________/_|
>
> Where the rectangle is one of the studless beams. You would want something
> that was smooth so the ball wouldn't get stuck.
>
> The / & \ are pieces of metal connected to a wire with the 2x2 connector cut
> of one end and each wire is soldier to a metal piece. You would not want
> the metal pieces to be touching. When the ball rolled so that it was in
> contact with the metal pieces it would complete the circuit. setting the
> sensor port as a touch would work at monitoring if the ball was at either
> end of the track.
>
> If somebody wanted to get really creative you could put a resistor in the
> circuit and be able to use one sensor port to monitor both ends of the
> track.
>
> If somebody does try this or has tried something like this please let me
> know as I'm interested in how well this would work.
Scott,
I haven't tried that exact thing, but from the discussions I've had, I don't
think it would work very well.
The problem is that gravity is acting on the robot exactly the same as it's
acting on the ball. The robot is not just tilting, but falling. So, the ball
will fall at the same speed as the robot (and the sensor-track).
Meaning the ball will stay in the same place (relative to the robot) until an
external force (the floor) acts on one of them. (trust me on this) :)
Actually, there are some ways to make it work. The above statement assumes the
sensor is mounted near the center of mass of the robot. If you mount the sensor
very high, away from the center of the robot, the sensor track will travel
faster than the ball, so it will appear the robot is falling the other
direction. (not good)
But if you put the sensor below the center of mass (or below the axle) the
sensor track will move slower (or the opposite direction) than the ball.
However, if the sensor is mounted near the axle, you also have to take into
account the forward/back acceleration of the motors.
It gets messy.
My suggestion: it could work, if mounted below the axle, but then you still have
other forces to consider.
Steve
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Message is in Reply To:
 | | Re: Balancing robots
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| Just a thought. What if you were to set up a track for a steel ball to roll on and have some sort of sensor at the end that would tell the rcx that the robot is falling forwards/backwards. something like so: ___...___ |_/___...___\_| ___...___ (...) (20 years ago, 27-Jan-04, to lugnet.robotics)
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