Ankle Foot Orthosis for Patients with Drop Foot Using Shape-Memory-Alloy Actuators

Bohyun Lee, Ji Su Park, Shinsuk Park, Choong Hyun Kim

Research output: Contribution to journalArticlepeer-review


Gait disorders can lower the quality of life of patients. Drop foot, a causative factor of deviated gait patterns, renders patients unable to lift their forefoot towards the body. Hence, a light and compact ankle–foot orthosis (AFO), which is the most common treatment for drop foot, must be designed, especially for patients with impaired lower limb muscles as oxygen consumption increases by 30% per 1.96 N load on their foot. Furthermore, the limited range of ankle angles in the first 10% of the gait cycle (GC) is a major drawback for patients with drop foot compared to healthy individuals. This limited range of ankle angles can be improved by gaining support from an AFO composed of shape memory alloy (SMA) actuators (SMA-AFO). Therefore, in this study, an SMA was used to fabricate a soft actuator to reduce the weight of the AFO. An adaptive frequency oscillator (AO) was implemented in real time for continuous gait phase detection. Walk tests were performed on a treadmill with the SMA-AFO attached to the participants (N = 3). The experimental results showed that the participants could lift their forefoot in the dorsiflexion direction with an ankle angle of 8.75° in the first 10% of the GC. Furthermore, the current required to operate the SMA actuator can be supplied to only 45.3% of the GC, reducing the power consumption. Therefore, the proposed SMA-AFO can be used in patients with drop foot.

Original languageEnglish
Pages (from-to)2057-2072
Number of pages16
JournalInternational Journal of Precision Engineering and Manufacturing
Issue number11
Publication statusPublished - 2023 Nov

Bibliographical note

Publisher Copyright:
© 2023, The Author(s).


  • Actuator
  • Adaptive frequency Oscillator
  • Ankle foot orthosis
  • Drop foot
  • Gait assistance
  • Gait disorder
  • Gait phase detection
  • Shape memory alloy

ASJC Scopus subject areas

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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