coaxial axes / offset comp how to

the offset comp is +/- as i need... i think possible to do that in hal usig sum+gain(-1) .... but simply i have not clear the relationship of the signal (encoder-pos, encder.veocity, joint-cmp-pos, oint.os-fb,pid ec etc...) ....

The mechanical .... 2 shaft, every one is an axes. one rotate the end effector 360° around x plave, the second one rotate the end effector of 180° around Z plane. The hollow shaft A axes is external shaft, the normal shaft and inside to A axes is B axes. when rotate A and B is stopped, the end effector rotare around X and Z plane too. To avoid this I must rotate both at the same speed and position. So B axes is stopped in relation to A axes.
A very bad draw (real sorry) of mechanical schemas ...note the pulley reduction and motor is the same for axes A and B.

A-motor-position-cmd -> pid.A.command and B.offset.offset
A-encoder -> pid.A.feedback and axis.A.feedback

B-motor-position -> B.offset -> B.pid
B-encoder -> B.pid and B.offset.feedback
B.offset.feedback -> axis.B.feedback

thanks a lot .... this " code " I clarified many things ... thanks again

Regards
Giorgio

for anyone who had difficulty understanding offset.9 component and use with feedback signals and command, similar to what happened to me ...