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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Thu, 22 Jan 2004 13:31:54 GMT
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Viewed:
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1772 times
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In lugnet.robotics, PeterBalch <PeterBalch@compuserve.com> wrote:
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> How does a balancing robot like Legway balance on a patterned floor? Or can
> it?
>
> But the Legway (for instance) can't measure the position of wheel or the
> wheel velocity. You can pretend that the motor commands correspond to the
> wheel velocity and smooth or integrate those numbers. That helps with
> balance but the results (in my simulation) are never as good as a robot
> that has wheel encoders. Is it possible to measure wheel velocity by
> measuring the motor back-emf?
I don't think there's a good source for this data (motor back-emf) using an RCX.
Yes, Legway just used the motor commands to simulate the wheel velocity. It
would have greatly increased the complexity of the wheel assembly to add
rotation sensors, including adding 'slop' into the drivetrain.
> On a patterened floor, maybe you can have several IR sensors and discard
> the measurements with the bigest changes on the assumption that they
> represent a change in the pattern.
>
> Has anyone tried it?
Legway uses two sensors to follow a line. So when one of the sensor readings
drop, it assumes the sensor is over the line, it ignores that sensor, and turns
the robot in that direction.
It also seems to work pretty well on wood grain (like a table top).
But it must have one of it's (two) sensors over a white (or light) area, or it
doesn't get usable readings from the EOPDs.
I think you could make the same scheme work on a patterned floor, if you can
mount the sensors so at least one of them is on a light area. Or, you may be
able to find sensors that are not affected by the surface color. For example,
an ultrasonic sensor may work well for that.
Steve
Steve
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Message has 1 Reply:
 | | Re: Balancing robots
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| (...) Um, the back-EMF of the motore isn't related to the motor load per se but rather the relaxation of the current in the coil when it moves off the stators. It's also very fast (ie E=Bc) so the RCX isn't likely to get good readings for this. It's (...) (20 years ago, 22-Jan-04, to lugnet.robotics)
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Message is in Reply To:
| | Balancing robots
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| How does a balancing robot like Legway balance on a patterned floor? Or can it? I've got some of the way there. My understanding from reading the web descriptions of various projects is that you _ought_ to measure - angle of tilt - rate of change (...) (20 years ago, 20-Jan-04, to lugnet.robotics)
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