Top/bottom refers to the robot being forward or flipped backward. Picture a robot configured with the base at the center of a clock and the EOA at 12:00 and then same robot flipped up and over to 6:00 without ever moving J1, and that is a simplified explanation. I don't at what exact joint values it switches from top to bottom.The top and bottom nomenclature is a little confusing personally, the only way it seem to work is for the gantry robots that mount at 90 degrees and don't have a J1 axis. Well technically they do, but J1 isn't a joint, but is the axis moving along the gantry. So since the robot cant rotate at the waist, so to speak, it can only flip over itself. Since it is mounted at 90 degrees then technically one configuration would be "top" and one would be "bottom".
Also some more info here:
Hi there,
Thanks for your reply, but I think I may not make myself very clear which leads your confusion.
So "Top" and "Bottom" is a type of configuration defined in fanuc robot system. As you said, this nomenclature is terribly confusing since other robot system may call it "Left/Right shoulder" or "Front/Back" configuration. This is caused by the intended mechanical design of the articulated robot system which shifted shoulder (usually J2) joint horizontally in order to avoid singularity point while robot arm is in vertical pose.
I know how to solve this problem in inverse kinematics but I could not figure out the rule to identify configuration by just looking at the joint values, thanks.
Pan