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wshipley
Registered Member

Date Joined Oct 2009
Total Posts : 2

Posted 10/29/2009 9:39 PM (GMT -8)

First Question: Can I use the BOE-Bot Digital Encoder to automaticly adjust my servos to keep my BOE-Bot driving in a straight line?

Second Question: Does anyone have any guidance on how to do this, I have read most of the documentation on this site, and still don't know how to accomplist this. You see the servos that came with my BOE-Bot are serverly mis-matched.

Thanks

Mike Green
Registered Member

Date Joined Oct 2004
Total Posts : 13559

Posted 10/29/2009 10:10 PM (GMT -8)

1) Sort of. The encoders help, but they're not perfect. Remember that the wheels themselves can slip on the floor and the encoders won't catch that.

2) Have you looked at the "Downloads & Resources" part of the webpage for the wheel encoders? There's a quite involved discussion on using the encoders to correct for wheel motion and some sample code as well.

Servos have quite a bit of variation in manufacturing from manufacturer to manufacturer, model to model, and servo to servo within the same model. The control pulse width is used to set the servo speed (and direction) and it's expected that you might need to use a different pulse width (PULSOUT) for each servo to get approximately the same speed. You can calibrate them by writing a simple program to make the BoeBot move forward, then adjusting the PULSOUT values to get the BoeBot to move in a straight line, at least for some reasonable distance (a few feet).

wshipley
Registered Member

Date Joined Oct 2009
Total Posts : 2

Posted 10/29/2009 11:40 PM (GMT -8)

Thanks for the quick reply, I will try looking through the documentation again, now I just need to figure out ramping, with the unbalanced servos, but I will ask that in another thread.
Thanks.

C-Bob
Registered Member

Date Joined Oct 2009
Total Posts : 8

Posted 10/30/2009 11:28 AM (GMT -8)

1. maybe yes.
idea: boe bot have calibration routine, in calibration mode send some pulse to servo and measure distance betwen pulses from encoder, try it with variable pulse lenght - finding zaro and max speed, try it for both wheel, (calculated value store to flash and use in normal mode).

Output from this is also useable for ramping.

Sliping on the flor is standart random variable

you can minimalize this by ramping (start and stop slowly).

C-Bob

Every problem have at least one nice, simply and wrong solution.

erco
Registered Member

Date Joined Mar 2008
Total Posts : 664

Posted 11/3/2009 9:25 AM (GMT -8)

http://forums.parallax.com/forums/default.aspx?f=10&p=1&m=316092

"If you build it, they will come."

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