Motivation: Human assist devices such as hand tools and orthotics require high force, low speed, compact size, and light weight, which match hydraulics. Traditionally, hydraulic systems are used in applications that require large amounts of power so components are large and heavy. To apply hydraulic technologies to human assist devices, traditional hydraulic components must be scaled down to appropriate power levels, that is, from thousands of watts to about 100 W. To apply small-scale (10–100 W) hydraulics to human assist devices, three steps were taken. First, a hydraulic ankle foot orthosis (AFO) was built and tested to understand the feasibility of using small-scale hydraulics in human assist devices. Second, a small-scale electrohydraulic actuator (EHA) system was built to identify the gaps between the desired small-scale hydraulic components and the smallest off-the-shelf hydraulic components. Third, basic fluid mechanics and structural equations were used to model the efficiency of small-scale hydraulic components, which is the key to miniaturize traditional hydraulic systems. Results: The AFO platform showed that sufficient torque and range of motion can be realized with a hydraulic system but confirmed the need for small hydraulics to reduce the weight and bulk. The EHA system showed that the smallest off-the-shelf components are oversized for a small-scale hydraulic system and identified the need for custom small-scale hydraulic components. The efficiency models showed that reasonable efficiencies are achievable for small-scale hydraulic components, but different design rules are required.
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Design Of Medical Devices Conference Abstracts
Small-Scale Hydraulics for Human Assist Devices
Jicheng Xia,
Jicheng Xia
University of Minnesota
, Twin Cities
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Katherine L. Braun,
Katherine L. Braun
University of Minnesota
, Twin Cities
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William Durfee
William Durfee
University of Minnesota
, Twin Cities
Search for other works by this author on:
Jicheng Xia
University of Minnesota
, Twin Cities
Katherine L. Braun
University of Minnesota
, Twin Cities
William Durfee
University of Minnesota
, Twin CitiesJ. Med. Devices. Jun 2011, 5(2): 027530 (1 pages)
Published Online: June 14, 2011
Article history
Online:
June 14, 2011
Published:
June 14, 2011
Citation
Xia, J., Braun, K. L., and Durfee, W. (June 14, 2011). "Small-Scale Hydraulics for Human Assist Devices." ASME. J. Med. Devices. June 2011; 5(2): 027530. https://doi.org/10.1115/1.3590872
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