Any ideas on how to stabilize a robot (keep it from falling backwards) ??
having something the slides out the back of the robot should help a lot
A simple way is to add weight to counter balance the robot. The closer to the ground the better.
the downside to adding weight is, well, it adds weight :P. A much better solution is something that flips out or slides out that way you don’t have to add weight and slow the robot down.
You can add a flip/slide out mechanism, with elastics, a stopper, and a triggering method or bolt a sheet of plate steel underneath near the wheels. Both a viable options and both add weight :p.
Just determine what makes the most sense to your design.
a flip out/slide anti-tip requires less weight than a counterweight, and works at least as well. though weight distribution is important, having the batteries closer to the front and closer to the ground helps a lot, so does having a lift that’s mounter closer the front of the drive.
Thankyou all for ur help
you’re welcome
I have just recently posted my anti-tip system in This Conversation. Hopefully this can unleash your creativity in some way, shape, or form 
But adding anti-tipping mechanisms increase your footprint, making maneuvering the field more difficult, especially with the large game objects this year. While it’s less relevant with an experienced driver, it still makes a difference. If re-balancing the robot with batteries, remounting the lift farther forwards, pneumatics forwards, etc. solves the issue, there’s no reason to add anti-tips.