problem whlie making a solar car using

hi guys,
I'm making a solar powered car (303020) for my college project. I'm gonna use Arduino board for control. I've problem while making its code. I'm going to use 2 100 rpm dc motors and 2 sharp sensors to control speed whenever there is a hurdle on my way. condition is car have to run automatically.

please help me with this.. I want to write a code like:-

if there is a hurdle on any side of the car either left or right speed will decreased by 20-25%.

and suggest me some features for it .

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