Design of biomimetic robot-eye system with single vari-focal lens and winding-type SMA actuator

This paper presents a biomimetic robot-eye system with a single vari-focal lens and winding-type SMA actuator. Based on the biomechanics of the human eye, the proposed system consists of a biconvex PDMS lens, winding-type SMA actuator, and mechanical parts, such as grippers, load arms, an outer ring, and body. In contrast to other single vari-focal lenses, the proposed PDMS lens is a gel, thereby avoiding any deflection from gravity and external vibration. Plus, the PDMS lens is circularly enclosed and elongated by load arms joined to an outer ring that is operated by a winding-type SMA actuator. While the advantages of SMA wires are their light weight and high-power density, their deformation is small. Thus, to overcome this limitation, the lever principle is conversely applied to the load arms, allowing a large elongation of the PDMS lens to adjust its focal length, even though the SMA wire is only slightly deformed. The design of the proposed system is described in detail, and experimental results demonstrate the validity of the proposed system.