Junwei Xiong, Huanbin Chen, Fan Zhang, Zijun Qin, Junfeng Li
A bionic eye system driven by shape memory alloy (SMA) springs is designed for humanoid facial expression.• An antagonistic SMA spherical joint model enables precise multi-directional eyeball rotation with ±20° range and <1° error.• An SMA-PVC bias actuation mechanism with closed-loop PID control achieves eyelid motion with step tracking error <3.7%.