counter balance mechanism.
for me, it sounds like mechanical design to reduce the required torque.
i was thinking to power each joint with a big torque servo, like 180kgcm servo, to make the arm move smoothly. even i'm thinking to use double servo to move the shoulder part, expecting 70-90% of total torque in shoulder.
until i read about CBM, then... i'm dizzy now although i do have a hope if anyone here can give me a clue about that smart arm design or CBM.