A compliant modular robotic hand with fabric force sensor for multiple versatile grasping modes

This paper presents the development of a compliant, modular, reconfigurable, and sensorized robotic hand with multiple grasping capabilities. Each finger consists of a soft pneumatic actuator with embedded fabric force sensor and a detachable casing. The casing has a through hole for housing the actuator and special connectors for attachment to other casings. One casing each from the thumb and finger parts has a protrusion for connecting both parts together via a screw tightening system. The through-hole design allows different grasping length to be achieved and the inflated pneumatic channel of the actuator locks it in place. The modular robotic hand is capable of various versatile grasping tasks by simply changing the bending direction of the actuator, the distance between the thumb and finger parts, the grasping length of the actuator, or attaching/detaching additional fingers to the hand. (1) Hook grasping with single finger, (2) pinching with pad opposition, (3) reverse grasping for holding a pipe-like object, (4) wrap grasping with palm opposition, as well as (5) picking up an object through its handle with one thumb and two or more fingers were illustrated. These studies show the capability of the compliant modular robotic hand in performing various types of grasping by simply using different configurations of the casings. The excellent payload-to-weight ratio of the robotic hand was demonstrated. Also, the fabric force sensor that was embedded in the soft actuator indicated the difference in grasping forces that were applied to different objects during hook grasping. The modular robotic hand has the potential to broaden or substitute the usage of existing robotic hands, especially in applications where soft versatile configurable grasping is desired.