An ankle foot orthosis (AFO) provides assistance to individuals with lower limb muscle impairment to correct gait deficiencies [1]. Powered AFOs and exoskeletons have been developed to explored robotic gait assistance. The portable pneumatically powered ankle foot orthosis (PPAFO) is capable of providing plantarflexor and dorsiflexor torque at the ankle [2]. The PPAFO has three sensors: force resistive sensors (FSR) under the heel and ball of foot to detect foot contact, and a Hall effect sensor to record ankle angle.

Control of a powered AFO will be most effective, if we can successfully identify and actuate the AFO at specific times during the gait cycle, i.e., when to apply dorsiflexor or plantarflexor torque at the ankle. We define that one gait cycle has 101 gait states, which corresponds to 0–100% gait cycle (% GC). A simple approach for identifying gait events...

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