Powering my pi2 and my components at the same time

Hey guys,

I am looking to build a raspy powered bot and use some computer vision to make interact with objects and I am being halted by a very simple problem.

I can’t seem to power everything correctly.
I am using a couple DC motors, an ultrasonic and servo for moving around the camera and they work nicely off 4xAA batteries.
However if I try to power the Pi off of the same supply, it can’t provide enough and the pi reboots.

If I try to run the pi off a supply of its own (4XAA through a regulator) it works fine.

But if I try to power both the components off of a power supply and the pi of off a separate supply with a common ground, the pi gets very hot (down by the normal use powersupply) and I have to turn it off in fear of blowing something (which I think happened to my previous pi that no longer turns on while testing)

Anybody achieved this nicely, perhaps with a motor driver or something (currently just using a L293D) I would appreciate a wire diagram or links to components that might help with this.