Structural Optimization of Adaptive Soft Fin Ray Fingers with Variable Stiffening Capability

Soft and adaptable grippers are desired for their ability to operate effectively in unstructured or dynamically changing environments, especially when interacting with delicate or deformable targets. However, utilizing soft bodies often comes at the expense of reduced carrying payload and limited performance in high-force applications. Hence, methods for achieving variable stiffness soft actuators are being investigated to broaden the applications of soft grippers. This paper investigates the structural optimization of adaptive soft fingers based on the Fin Ray® effect (Soft Fin Ray), featuring a passive stiffening mechanism that is enabled via layer jamming between deforming flexible ribs. A finite element model of the proposed Soft Fin Ray structure is developed and experimentally validated, with the aim of enhancing the layer jamming behavior for better grasping performance. The results showed that through structural optimization, initial contact forces before jamming can be minimized and final contact forces after jamming can be significantly enhanced, without downgrading the desired passive adaptation to objects. Thus, applications for Soft Fin Ray fingers can range from adaptive delicate grasping to high-force manipulation tasks

Design and prototype of supernumerary robotic finger (SRF) inspired by fin ray® effect for patients suffering from sensorimotor hand impairment

In this paper, we present the design and prototype of a wearable supernumerary robotic finger, inspired by Fin Ray®, an underactuated device inspired by the physiology of fish fins. The application we propose has been designed for patients suffering from sensorimotor hand impairment, to compensate their missing grasping abilities. In this context Fin Ray® effect based closed-chain structure, effectively exploiting underactuation and compliance, are an interesting solution to meet the ergonomics and functional requirements, and to get a light but robust wearable device. The finger is actuated through a single linear actuator and it has a complaint structure with stiff crossbeams that buckle and deform in to conform around objects. We performed Finite Element Modeling (FEM) simulations to compare the soft-rigid structure with the Fin Ray® effect based closed-chain structure. We performed a set of tests to exploit the device potentialities in grasp compensation tasks through qualitative experiments based on activity daily living (ADL). Results showed that proposed robotic device can improve the autonomy of patients suffering from sensorimotor hand impairment in ADL and allow them to complete tasks which otherwise are impossible to perform