Grip and grasp: lizard claw inspired robotic manipulators

Abstract

This paper considers the selection of a lizard claw to apply as an end effector on a bioinspired robotic manipulator, to improve grasping efficiency. Our work draws on morphological parameters that influence mechanical grip. By considering geometrical ratios that are built on parameters such as the arm-to-tip angle, the claw inner radius, and the slip distance, our research identifies optimal parameters that influence grip strength and stability. We demonstrate that these parameters, when combined to form two specific indices (the geometric mean, IGM, and the arithmetic mean of deviations, IAMD), provide a basis for more extensive comparisons between the different claw morphologies researched. The claw of Crotaphytus collaris is deduced as being the most suitable candidate for application as a bioinspired end effector in a robotic manipulator used for grasping objects, as it closely aligns with our optimal design criteria. To practically demonstrate gripping and grasping, we use a lightweight ping pong ball as well as larger and heavier objects such as an abalone shell, boxing mitts and a printer spool. Our robotic manipulator integrates dual grasping strategies. These include pinching for delicate objects and scooping for larger, irregular objects, thus enhancing its versatility across different environments and for different applications. Overall, this paper offers valuable new insights into biomimetic manipulator design using claws as end effectors, highlighting the importance of lizard claw selection based on morphology.