Self-Adaptive Monolithic Anthropomorphic Finger with Teeth-Guided Compliant Cross-Four-Bar Joints for Underactuated Hands

This paper presents a novel approach for modeling one-degree-of-freedom human metacarpophalangeal/ interphalangeal joints based on a teeth-guided compliant cross-four-bar linkage. The proposed model allows developing self-adaptive anthropomorphic fingers able to be 3D printed in a single step without any accessories, except for simple tendon wiring after the printing process, using basic single-material additive manufacturing. Teeth-guided compliant cross-four-bar linkages as finger joints not only provide monolithic fabrication without assembly but also increase precision of anthropomorphic robot fingers by removing nonlinear characteristics, thus reducing the complexity of control for delicate grasping. Kinematic analysis of the proposed compliant finger joints is detailed and nonlinear finite element analysis results demonstrating their advantages are reported. A two-fingered underactuated hand with teeth-guided compliant cross-four-bar joints is also developed and qualitative discussion on grasping is conducted.