how to create a single-direction IK leg with a direction controller? One of the things i'd like to do is create an IK that only bends forward and backward on a single local axis. At the top, I want a control to change the direction of that axis.

so the ik goes only forward and back, no sideways movement. And I control which direction forward is.

I can't get this to work with Limit Location or constraint combination I've tried so far. It messes with the overall direction control or the placement of the foot after the chain :( 

I'm rigging a robot, and due to the (very specific) placement of his parts, his legs only bend one way, with a rotater cup as a hip socket. I can't quite figure out how to do this. Any help would be much appreciated!!

Thank you in advance,

Allen
In order to get it to work, the leg IK target bone  has a child of constraint to the rotater. The foot has an IK as well with a length of 1, and its target is parented to the leg IK.

Pretty tricky.