Design of a Reconfigurable Robotic System for Flexoextension Fitted to Hand Fingers Size

Abstract

Due to the growing demand for assistance in rehabilitation therapies for hand movements, a robotic system is proposed to mobilize the hand fingers in flexion and extension exercises. The robotic system is composed by four, type slider-crank, mechanisms that have the ability to fit the user fingers length from the index to the little finger, through the adjustment of only one link for each mechanism. The trajectory developed by each mechanism corresponds to the natural flexoextension path of each finger. The amplitude of the rotations for metacarpophalangeal joint (MCP) and proximal interphalangeal joint (PIP) varies from 0 to 90° and the distal interphalangeal joint (DIP) varies from 0 to 60°; the joint rotations are coordinated naturally. The four R-RRT mechanisms orientation allows a 15° abduction movement for index, ring, and little fingers. The kinematic analysis of this mechanism was developed in order to assure that the displacement speed and smooth acceleration into the desired range of motion and the simulation results are presented. The reconfiguration of mechanisms covers about 95% of hand sizes of a group of Mexican adult population. Maximum trajectory tracking error is less than 3% in full range of movement and it can be compensated by the additional rotation of finger joints without injury to the user.

Experimental Characterization of A-AFiM, an Adaptable Assistive Device for Finger Motions

“…The point of contact between the screw and link 4 is achieved through a nut; that L 4 varies when the screw turns. Similar triangles are formed by points EFG, and AFB, and they modify the angle δ as reported in [33][34][35][36][37].…”

“…The point of contact between the screw and link 4 is achieved through a nut; that 𝐿 varies when the screw turns. Similar triangles are formed by points EFG, and AFB, and they modify the angle 𝛿 as reported in [33][34][35][36][37]. The mechanism can be reconfigured using variable C, proposed in Figure 5, whose length L 1 between its external nodes A and B varies in the proportion of length, L 4 [34].…”

“…The synthesis of flexor and extensor mechanisms was performed from a trajectory generation method using three precision points based on the curves of the coupler link [33]. The Rotation-Rotation, Rotation, and Translation (R-RRT), and type slider-crank mechanisms are selected since the extension of the coupler link develops a very similar trajectory to that presented in Figure 3 [34]. The range of movement of the R-RRT mechanism is mechanically limited to avoid finger hyper-extension.…”

“…The mechanism can be reconfigured using variable C, proposed in Figure 5, whose length L 1 between its external nodes A and B varies in the proportion of length, L 4 [34]. The C is composed of a passive rotational joint, point F, and a screw whose end is attached to the G point of link 5 through a ball joint [34][35][36][37]. The point of contact between the screw and link 4 is achieved through a nut; that L 4 varies when the screw turns.…”

Design and Development of 3d Printed Myoelectric Robotic Exoskeleton for Hand Rehabilitation

“…According to the kinematic model of the human hand [27], illustrated by Figure 3, the mechanical design must ensure the coincidence of the center of rotation because any conflict between the center of rotation of the user's hand and that of the exoskeleton device can damage both the user's hand as well as the mechanical structure. Next section details the mechatronic design by respecting the anatomical range of motion and center of rotation.…”