Hello everyone.
This is my first time to share some newbie’s code. 
I am working on AI.
You can see my source below .
http://sites.google.com/site/mayumiyuu/Home/AI_mayu.zip?attredirects=0
I use 3 collision segments.
two collisions represent to Ralph’s hands to feel about the way he should go.
The 3rd collision is point to the another way when Ralph meet a dead end.
You can create a new own wall and load it to my application.
(But you must names it as ‘wall’.)
Hope this will help some newbies like me. ( ^ o^)
Enjoy.
Thanks Thaumaturge and David from this thread.
http://www.panda3d.net/phpbb2/viewtopic.php?t=4903