Relaxed hand postures

Lee, Kyung-Sun; Mo, Seung-Min; Hwang, Jaejin; Wang, Hui; Jung, Myung‐Chul

doi:10.5100/jje.44.supplement_436

Cited by 3 publications

(3 citation statements)

References 8 publications

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“…We further increased the pinch force by an average 68% within this range by adding an initial bias of 15°. This accounted for the fact that the MCP angle of a relaxed human finger can be over 30° (Lee et al, 2008 ; Lee and Jung, 2014 ).…”

Section: Resultsmentioning

confidence: 99%

“…The custom prosthetic finger sacrifices higher blocked force for increased pinch force within the common grip range (24–55°) (Lee and Jung, 2016 ) and provides over twice the flexion range as the original design. The resting MCP angle of a human finger can be over 30°, so an initial bias of 15° was applied to further increase the fingertip force within the common grip range (Lee et al, 2008 ; Lee and Jung, 2016 ).…”

Section: Resultsmentioning

confidence: 99%

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Design of a High-Speed Prosthetic Finger Driven by Peano-HASEL Actuators

et al. 2020

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Current designs of powered prosthetic limbs are limited by the nearly exclusive use of DC motor technology. Soft actuators promise new design freedom to create prosthetic limbs which more closely mimic intact neuromuscular systems and improve the capabilities of prosthetic users. This work evaluates the performance of a hydraulically amplified self-healing electrostatic (HASEL) soft actuator for use in a prosthetic hand. We compare a linearly-contracting HASEL actuator, termed a Peano-HASEL, to an existing actuator (DC motor) when driving a prosthetic finger like those utilized in multi-functional prosthetic hands. A kinematic model of the prosthetic finger is developed and validated, and is used to customize a prosthetic finger that is tuned to complement the force-strain characteristics of the Peano-HASEL actuators. An analytical model is used to inform the design of an improved Peano-HASEL actuator with the goal of increasing the fingertip pinch force of the prosthetic finger. When compared to a weight-matched DC motor actuator, the Peano-HASEL and custom finger is 10.6 times faster, has 11.1 times higher bandwidth, and consumes 8.7 times less electrical energy to grasp. It reaches 91% of the maximum range of motion of the original finger. However, the DC motor actuator produces 10 times the fingertip force at a relevant grip position. In this body of work, we present ways to further increase the force output of the Peano-HASEL driven prosthetic finger system, and discuss the significance of the unique properties of Peano-HASELs when applied to the field of upper-limb prosthetic design. This approach toward clinically-relevant actuator performance paired with a substantially different form-factor compared to DC motors presents new opportunities to advance the field of prosthetic limb design.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Design of a High-Speed Prosthetic Finger Driven by Peano-HASEL Actuators

et al. 2020

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“…N f J denotes total number of joints of f th finger (N f J = 4 in this study), and N f is the total number of fingers (N f = 5 in this study). We used the statistics in (Lee et al 2008) to calculate the joint angle when the hand is at rest pose.…”

Section: Adaptation To Human Hand Modelmentioning

confidence: 99%

An inverse optimization approach to understand human acquisition of kinematic coordination in bimanual fine manipulation tasks

Yao

Billard

2020

Biol Cybern

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Tasks that require the cooperation of both hands and arms are common in human everyday life. Coordination helps to synchronize in space and temporally motion of the upper limbs. In fine bimanual tasks, coordination enables also to achieve higher degrees of precision that could be obtained from a single hand. We studied the acquisition of bimanual fine manipulation skills in watchmaking tasks, which require assembly of pieces at millimeter scale. It demands years of training. We contrasted motion kinematics performed by novice apprentices to those of professionals. Fifteen subjects, ten novices and five experts, participated in the study. We recorded force applied on the watch face and kinematics of fingers and arms. Results indicate that expert subjects wisely place their fingers on the tools to achieve higher dexterity. Compared to novices, experts also tend to align task-demanded force application with the optimal force transmission direction of the dominant arm. To understand the cognitive processes underpinning the different coordination patterns across experts and novice subjects, we followed the optimal control theoretical framework and hypothesize that the difference in task performances is caused by changes in the central nervous system's optimal criteria. We formulated kinematic metrics to evaluate the coordination patterns and exploit inverse optimization approach to infer the optimal criteria. We interpret the human acquisition of novel coordination patterns as an alteration in the composition structure of the central nervous system's optimal criteria accompanied by the learning process.

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