A General Arthropod Joint Model and its Applications in Modeling Human Robotic Joints

Bearings are common rotational units, but these monocentric units do not realize high bio-imitability in exoskeleton robots. A common way to realize bionic motion is with an n-bar linkage mechanism within bearings, but the resultant joints can become complex. Herein, we propose a joint model based on the anatomy of grasshopper joints that consists of a pair of conjugate surfaces and a flexible connection body. An anatomical experiment involving crabs and lobsters reveals that the proposed joint model exists among crustaceans, which makes it a general joint structure for arthropods. After measuring the kinematic properties of crab and lobster joints, we have modified the joint model for robotics applications. An optimization algorithm is proposed for the design of the joint. A prototype of a bionic joint is fabricated and its kinematic characteristics are verified. The arthropod joint model is a promising mechanical unit in bionic robots.