In order to achieve natural limb interaction, the American sex dollR&D center has reconstructed the human motion algorithm. The bionic joints of the full size sex doll use a liquid metal transmission system, which can perfectly reproduce the 49 core force points of human dance movements. When the user guides the full size sex doll to complete the waltz rotation, the center of gravity offset error does not exceed 0.3 mm. This precision control technology is being transplanted to the field of medical rehabilitation robots.