Design and Simulation of a 3-DOF Dexterous Joint Actuator Based on Multi-Drive Hierarchical Output and Spherical Rotation Mechanism

Series-type and ball-and-socket are currently two typical architectures of hip joint actuators. However, they either rely on advancements and applications in materials science or compromise on structural design, failing to accurately mimic the motion of the human hip joint. Therefore, we designed a three-degree-of-freedom (3-DOF) dexterous joint actuator based on multi-drive hierarchical output and spherical rotation mechanism for better kinematics performance, high power density, and high load-withstand capability. Three identical motors were installed in parallel on the motor mounting frame, with two motors coupled and controlled a pair of differential bevel gears, while another motor transmitted torque through two spherical gears, coupled with a secondary frame mounted on a large bevel gear, ultimately achieving spherical rotation with a fixed point as the center. 3D simulations demonstrated that this new design could achieve a 120-degree rotation range across three degrees of freedom, with high load-withstand capability, successfully meeting project expectations and demonstrating its usability. This design closely approximated the overall performance of the human hip joint in terms of driving performance, motion characteristics, and control logic. It provides theoretical support for addressing existing engineering bottlenecks in joint actuators and has promising potential for various robotic applications.