Tuesday, 29 January 2013

Why Wally loves Walls????

Make sure you read the previous post.

As i mentioned in the previous post, Wally keeps following the wall without any specific instructions to do so.  This is because the two motors used have slightly different speeds. Even though both are 200 rpm motors, it is impossible to have identical speed for both and there would be a small difference, owing to a variety of factors.

This is one of Wally's motors (Image courtesy NEX Robotics)


Wally's left motor is a wee bit faster than the right motor. So when she is told to go straight, she won't go exactly straight and would curve in to the right side. So when she goes near to the wall, with the wall being on the right side of Wally, the sensors on her right makes her turn away from the wall. Then when the wall is clear, though she is supposed to go straight, she curves in to the right. This triggers the sensors again. Over time this  keeps repeating, and it seems as if Wally is following the wall.

This also means that that Wally would follow a wall only if it is on her right side. That's good news!!! Now i'll never let a wall come to her right side!!!!! :P

So while I was searching for a solution:, i happened to 'stumbleupon' this cool site:
http://www.ikalogic.com/closed-loop-speed-and-position-control-of-dc-motors/

Thus all I needed was a pair of shaft encoders to fix Wally. But then there would be no meaning left for her name! So I'll be implementing these on probably on my next bot.

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