digitally controlled gears

sir, i am still novice to this field of robotics. we are designing micromouse. but we are facing problem in chasis designing. as
you can predict we need to change speed of micromouse during turning and make it to halt also when there is no forward path. for all this purpose i am thinking of gears. basically i have a 6 tyre design in which middle 2 is used to drive the wheel and rear and front tyres are for turning(for forward and reverse path). but i don't know how to command the gears through software. in my program micromouse would stop when there is no forward path. it means its speed gradually reduces to zero. then how do inform the motor that you have to change the gears to slow the speed. don't mind Is there any interfacing of gears with microcontrooler?
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snipped-for-privacy@gmail.com wrote:

The interface between gears and a microcontroller is called a Motor. It requires an additional interface, between the motor and the microcontroller, which is called a Motor Controller (or Speed Control, Electronic Speed Control, ESC, etc.).
JM
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snipped-for-privacy@gmail.com wrote:

No, you don't change gears to change speed. You just drive the motor differently. Get yourself a motor controller -- I recommend the Pololu Micro Dual Serial Motor Controller, reviewed here:
<http://www.strout.net/info/robotics/tutorials/Pololu0410.html>
You plug your motors into this board, and then your microcontroller (whatever's running your software) merely sends it the appropriate serial commands for how fast you want each motor to spin. It takes care of the rest.
Best, - Joe
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Joe Strout wrote:

No encoder. The wheels won't stay synchronized. Without an encoder, it's hard to get a two-wheel-drive device to go straight.
Pololu does make some motor controllers with encoder inputs, but wierdly, they just take single pulses, not quadrature. Jameco has a little motor controller with quadrature inputs. And Acroname has the WheelCommander, which is specifically designed for two-wheel drive robots.
http://www.acroname.com/robotics/parts/R279-WC-132.html
They also have all the other parts for this, at a moderately expensive but not outrageous price.
                John Nagle
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snipped-for-privacy@gmail.com wrote:

Do you mean something like this:
http://homepage1.nifty.com/hfd01577/MM3R/img/DSCN0213.JPG
If so, you don't need to change gears at all. Select an appropriate gear ratio (probably about 4:1) between the motor and the drive wheel and you can get perfectly good control just through the PWM drive to the main motor.
What you propose is intersting but seriously over-engineered for the problem you are trying to solve. in this case, there is a good reason why the vast majority of mice are simple two-wheel drive wheelchair designs.
Peter Harrison http://micromouse.cannock.ac.uk / http://www.micromouseonline.com/forum /
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