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Research Papers

A Novel Reconfigurable Gravity Balancer for Lower-Limb Rehabilitation With Switchable Hip/Knee-Only Exercise

[+] Author and Article Information
Tzu-Yu Tseng

Department of Mechanical Engineering,
National Taiwan University of
Science and Technology,
43, Section 4, Keelung Road,
Taipei 106, Taiwan

Yi-Jia Lin, Wei-Chun Hsu

Graduate Institute of Biomedical Engineering,
National Taiwan University of
Science and Technology,
43, Section 4, Keelung Road,
Taipei 106, Taiwan

Li-Fong Lin

Department of Physical
Medicine and Rehabilitation,
Shuang Ho Hospital,
Taipei Medical University,
291, Zhongzheng Road, Zhonghe District,
New Taipei City 235, Taiwan;
School of Gerontology and Health Management,
Taipei Medical University,
291, Zhongzheng Road, Zhonghe District,
New Taipei City 235, Taiwan

Chin-Hsing Kuo

Department of Mechanical Engineering,
National Taiwan University of
Science and Technology,
43, Section 4, Keelung Road,
Taipei 106, Taiwan
e-mail: chkuo717@mail.ntust.edu.tw

1Corresponding author.

Manuscript received February 15, 2016; final manuscript received March 1, 2017; published online April 27, 2017. Assoc. Editor: Aaron M. Dollar.

J. Mechanisms Robotics 9(4), 041002 (Apr 27, 2017) (9 pages) Paper No: JMR-16-1039; doi: 10.1115/1.4036218 History: Received February 15, 2016; Revised March 01, 2017

In lower-limb rehabilitation, there is a specific group of patients that can perform voluntary muscle contraction and visible limb movement provided that the weight of his/her leg is fully supported by a physical therapist. In addition, this therapist is necessary in guiding the patient to switch between hip-only and knee-only motions for training specific muscles effectively. These clinic needs have motivated us to devise a novel reconfigurable gravity-balanced mechanism for tackling with the clinical demands without the help from therapists. The proposed mechanism has two working configurations, each leading the patient to do either hip-only or knee-only exercise. Based on the principle of static balancing, two tensile springs are attached to the mechanism to eliminate the gravitational effect of the mechanism and its payload (i.e., the weight of the patient's leg) in both configurations. The gravity balancing design is verified by a numerical example and adams software simulation. A mechanical prototype of the design was built up and was tested on a healthy subject. By using electromyography (EMG), the myoelectric signals of two major muscles for the subject with/without wearing the device were measured and analyzed. The results show that the myoelectric voltages of the stimulated muscles in both hip-only and knee-only motion modes are reduced when the subject is wearing the device. In summary, the paper for the first time demonstrates the design philosophy and applications by integrating the reconfigurability and static balancing into mechanisms.

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Figures

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Fig. 1

A reconfigurable mechanism for hip/knee flexion/extension training: (a) knee-only exercise and (b) hip-only exercise

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Fig. 2

Gravity balancing design for the reconfigurable mechanism: (a) knee-only motion and (b) hip-only motion

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Fig. 3

Position vectors of the mass centers of the links and the limb segments

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Fig. 4

Implementation of the ideal zero-free-length spring

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Fig. 5

Potential energies simulated by adams: (a) knee-only motion configuration and (b) hip-only motion configuration

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Fig. 6

CAD model of the new assistive device (see figure online for color)

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Fig. 7

Prototype of the proposed assistive device

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Fig. 8

Changes of fixation positions for adjusting the assistive forces

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Fig. 9

EMG pattern of VL during knee extension and flexion movement without (no use, thick line) and with (middle position, thin line) the device

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Fig. 10

EMG pattern of RF during hip flexion and extension movement without (no use, thick line) and with (middle position, thin line) the device

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Fig. 11

Effects of changing fixation positions on EMG pattern of VL during knee extension and flexion movement

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Fig. 12

Effects of changing fixation positions on EMG pattern of RF during hip flexion and extension movement

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