Yifan David Li

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Ankle foot orthoses (AFOs) are widely used as assistive/rehabilitation devices to correct the gait of people with lower leg neuromuscular dysfunction and muscle weakness. We have developed a portable powered ankle-foot orthosis (PPAFO), which uses a pneumatic bi-directional rotary actuator powered by compressed CO<sub>2</sub> to provide untethered(More)
A portable powered ankle-foot orthosis (PPAFO) was previously developed using off-the-shelf pneumatic components to explore new opportunities for fluid power in human assist devices. The untethered pneumatically powered ankle-foot orthosis provides both motion control and torque assistance at the ankle via a binary, event-based control scheme that uses(More)
One of the challenges that any powered lower limb orthotic or prosthetic device must address for activities in the real world is its ability to recognize gait modes (level ground walking, stairs, ramps, etc.) and adapt to mode changes promptly. There are two critical aspects of this problem. First, the gait mode has to be recognized at the earliest possible(More)
A Portable Powered Ankle-Foot Orthosis (PPAFO) has been designed for gait assistance. The PPAFO can supply assistive torque at the ankle joint in plantarflexion and dorsiflexion using a bidirectional pneumatic actuator. Two control schemes have been developed to regulate timings of the assistive torques during different phases in the gait cycle. The Direct(More)
Ankle-foot orthoses (AFOs) ameliorate the impact of impairments to the lower limb neuromuscular motor system that affect gait. Emerging technologies provide a vision for fully powered, untethered AFOs. The portable powered AFO (PPAFO) provides both plantarflexor and dorsiflexor torque assistance via a bi-directional pneumatic rotary actuator. The system(More)
Ankle-foot orthoses (AFOs) are used to assist persons with lower-limb neuromuscular impairments. We have developed the portable powered AFO (PPAFO). This device uses a bidirectional pneumatic actuator powered by a CO2 bottle to provide dorsiflexor and plantarflexor torque assistance. The PPAFO operates tether-free, allowing for use outside of the(More)
0957-4158/$ see front matter 2012 Elsevier Ltd. A http://dx.doi.org/10.1016/j.mechatronics.2012.09.002 ⇑ Corresponding author. Tel.: +1 217 333 3415. E-mail address: ethw@illinois.edu (E.T. Hsiao-Wec This paper presents a model-based approach to control design for an existing lower-limb robotic assist device, the portable powered ankle–foot orthosis(More)
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