Soft Robotic Haptic Interface with Variable Stiffness for Rehabilitation of Neurologically Impaired Hand Function

In this paper, the modeling, design, and characterization of the passive discrete variable stiffness joint (pDVSJ-II) are presented. The pDVSJ-II is an extended proof of concept of a passive revolute joint with discretely controlled variable stiffness. The key motivation behind this design is the need for instantaneous switching between stiffness levels when applied for remote exploration applications where stiffness mapping is required, in addition for the need of low-energy consumption. The novelty of this work lies in the topology used to alter the stiffness of the variable stiffness joint. Altering the stiffness is achieved by selecting the effective length of an elastic cord with hook's springs. This is realized through the novel design of the cord grounding unit (CGU), which is responsible for creating a new grounding point, thus changing the effective length and the involved springs. The main features of CGU are the fast response and the low-energy consumption. Two different levels of stiffness (low, high) can be discretely selected besides the zero stiffness. The proposed physical-based model matched the experimental results of the pDVSJ-II in terms of discrete stiffness variation curves, and the stiffness dependency on the behavior of the springs. Two psychophysiological tests were conducted to validate the capabilities to simulate different levels of stiffness on human user and the results showed high relative accuracy. Furthermore, a qualitative experiment in a teleoperation scenario is presented as a case study to demonstrate the effectiveness of the proposed haptic interface.

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Design and Evaluation of Haptic Interface Wiggling Method for Remote Commanding of Variable Stiffness Profiles

10.1109/icar53236.2021.9659476 ◽

2021 ◽

Author(s):

Jasper Schol ◽

Jelle Hofland ◽

Cock J.M. Heemskerk ◽

David A. Abbink ◽

Luka Peternel

Keyword(s):

Variable Stiffness ◽

Haptic Interface

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A Variable-Stiffness Straight-Line Compliant Mechanism

Volume 5A: 39th Mechanisms and Robotics Conference ◽

10.1115/detc2015-46650 ◽

2015 ◽

Cited By ~ 2

Author(s):

Jeffrey C. Hawks ◽

Mark B. Colton ◽

Larry L. Howell

Keyword(s):

Force Feedback ◽

Compliant Mechanism ◽

Variable Stiffness ◽

Effective Length ◽

Haptic Interface ◽

Element Analysis ◽

Straight Line ◽

Rigid Body Model ◽

Straight Line Mechanism ◽

Force Displacement

In this research a variable-stiffness compliant mechanism was developed to generate variable force-displacement profiles at the mechanism’s coupler point. The mechanism is based on a compliant Robert’s straight-line mechanism, and the stiffness is varied by changing the effective length of the compliant links with an actuated slider. The force-deflection behavior of the mechanism was analyzed using the Pseudo-Rigid Body Model (PRBM), and two key parameters, KΘ and γ, were optimized using finite element analysis (FEA) to match the model with the measured behavior of the mechanism. The variable-stiffness mechanism was used in a one-degree-of-freedom haptic interface (force-feedback device) to demonstrate the effectiveness of varying the stiffness of a compliant mechanism. Unlike traditional haptic interfaces, in which the force is controlled using motors and rigid links, the haptic interface developed in this work displays haptic stiffness via the variable-stiffness compliant mechanism. One of the key features of the mechanism is that the inherent return-to-zero behavior of the compliant mechanism was used to provide the stiffness feedback felt by the user. A prototype haptic interface was developed capable of simulating the force-displacement profile of Lachman’s Test performed on an injured ACL knee. The compliant haptic interface was capable of displaying stiffnesses between 4200 N/m and 7200 N/m.

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Fingers and Thumbs: Toys and Activities for Children with Hand-Function Problems - (Play can help)

Australian Occupational Therapy Journal ◽

10.1046/j.1440-1630.2001.00221-3.x ◽

2001 ◽

Vol 48 (1) ◽

pp. 52-52

Author(s):

Christina Chittleborough

Keyword(s):

Hand Function

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Clinical Update: Assessing Maximum Medical Improvement in Carpal Tunnel Syndrome

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2003.julaug02 ◽

2003 ◽

Vol 8 (4) ◽

pp. 4-5

Author(s):

Christopher R. Brigham ◽

James B. Talmage

Keyword(s):

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Proper Time ◽

Carpal Tunnel Release ◽

Hand Function ◽

Factors Affecting ◽

Early Results ◽

Medical Evaluation ◽

Nerve Recovery ◽

Tunnel Syndrome

Abstract Permanent impairment cannot be assessed until the patient is at maximum medical improvement (MMI), but the proper time to test following carpal tunnel release often is not clear. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) states: “Factors affecting nerve recovery in compression lesions include nerve fiber pathology, level of injury, duration of injury, and status of end organs,” but age is not prognostic. The AMA Guides clarifies: “High axonotmesis lesions may take 1 to 2 years for maximum recovery, whereas even lesions at the wrist may take 6 to 9 months for maximal recovery of nerve function.” The authors review 3 studies that followed patients’ long-term recovery of hand function after open carpal tunnel release surgery and found that estimates of MMI ranged from 25 weeks to 24 months (for “significant improvement”) to 18 to 24 months. The authors suggest that if the early results of surgery suggest a patient's improvement in the activities of daily living (ADL) and an examination shows few or no symptoms, the result can be assessed early. If major symptoms and ADL problems persist, the examiner should wait at least 6 to 12 months, until symptoms appear to stop improving. A patient with carpal tunnel syndrome who declines a release can be rated for impairment, and, as appropriate, the physician may wish to make a written note of this in the medical evaluation report.

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