Fluid Power Research: Hydraulic Powered Orthoses

The Center for Compact and Efficient Fluid Power (CCEFP) is a network of researchers, educators, students and industry working together to transform fluid power—how it is researched, applied and taught.  CCEFP fluid power research is creating hydraulic and pneumatic technology that is compact, efficient, and effective.  We are pleased to share an update on the Hydraulic Powered Orthoses, led by Professor Will Durfee at the University of Minnesota.


Hydraulic Powered Orthoses

Submitted by:  Brett Neubauer, PhD Candidate, University of Minnesota

fluid power research - hydraulic powered orthosis

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The hydraulic ankle-foot orthosis is a powered orthosis that provides the user’s ankle with torque assistance during plantar flexion and dorsiflexion. The first generation hydraulic-powered orthosis is composed of the hydraulic power supply positioned at the lower back and the orthosis actuator secured to the shin and slid into a shoe. The hydraulic power supply uses a re-chargeable lithium polymer battery to power a DC brushless electric motor driving an axial piston pump. The hydraulic power supply is capable of generating pressures up to 2000 psi at a maximum flowrate of 13.3 cc/s.  The fluid power is transported in small hoses to the ankle where a lightweight aluminum cable hydraulic cylinder converts the fluid power into 90 Nm of torque assistance.

A research collaboration between Gillette Children’s Hospital, Oak Ridge National Lab (ORNL), National Institute of Health (NIH), and Center for Compact and Efficient Fluid Power (CCEFP) has spawned the design and construction of a second child-sized orthosis. Currently prescribed ankle-foot orthoses are passive devices that use different mechanical methods to provide support and stiffness to the ankle. The stiffness is an important parameter in prescribing an orthosis, and the current methods for selecting the most appropriate stiffness for a user is trial and error. This can be a costly and time-consuming process that requires the production of several orthoses. The prescription hydraulic orthosis we are designing will be a hydraulic-powered orthosis that can emulate the dynamics of a passive orthosis. The stiffness can be easily adjusted electronically, allowing a clinician to use this orthosis as a prescription tool. In an effort to reduce the weight of the actuator at the ankle to less than a 1 kg, the design uses state-of-the-art additive manufacturing processes electron beam melting and stereolithography.

To learn more about this activity, connect with Brett Neubauer (at neub0070@umn.edu) or Prof. Will Durfee (at wkdurfee@umn.edu).

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