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Subject: 
Balancing robots
Newsgroups: 
lugnet.robotics
Date: 
Tue, 20 Jan 2004 21:19:20 GMT
Original-From: 
PeterBalch <peterbalch@(StopSpammers)compuserve.com>
Viewed: 
1566 times
  
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 of tilt
        - position of wheel
        - rate of change of wheel

If you have only IR sensors then you can measure the rate of change of tilt
on a plain floor. If you assume that when the robot is turned on, the IR
measurement is "upright" then you can estimate absolute tilt. If you
integrate the motor commands over a few seconds and you're mostly heading
"forwards" then you adjust the "upright" estimate.

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?

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?

Peter



Message has 3 Replies:
  Re: Balancing robots
 
Hello PeterBalch, Tuesday, January 20, 2004, 9:19:20 PM, you wrote: P> How does a balancing robot like Legway balance on a patterned floor? Or can P> it? P> I've got some of the way there. P> My understanding from reading the web descriptions of (...) (20 years ago, 20-Jan-04, to lugnet.robotics)
  Re: Balancing robots
 
(...) 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 (...) (20 years ago, 22-Jan-04, to lugnet.robotics)
  Re: Balancing robots
 
Hi all We've just returned from holiday and our Lego is locked up for the summer but For what its worth I have added a version of my code to (URL) You can see what I did to mod Steve's program to work with two standard Lego light sensors. The output (...) (20 years ago, 26-Jan-04, to lugnet.robotics)

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