Micromouse w/o encoders URGENT please

  1. OK, the rule of the micromouse is quite simple: build a self-running robot and solve the maze, for each maze, you have three times to attempt. The goal is to solve the maze as fast as possible.

  2. I forgot to type this in: guiding wheel x1
    (though this doesn't help much)

3,4: To salvage this, I've stay up almost all night for this (It's now 3:30 in the morning here)

For the approach part:
The section of straight line is OK, but for the turning process, it's not quite accurate as I want. (I'm still working on this part)
And what I'm looking for is how to know how far it goes if I don't use any encoder. Because as it started to run, the voltage might drop, and I'm afraid that if I hard code the PWM value for every action, it might get inaccurate at last.

And...Sorry that I can't take pictures of it. My teammates don't let me do so (Don't know the reason...)