Control Reference Parameter for Stance Assistance Using a Passive Controlled Ankle Foot Orthosis—A Preliminary Study

• Main Authors: Dimas Adiputra, Mohd Azizi Abdul Rahman, Ubaidillah, Saiful Amri Mazlan, Nurhazimah Nazmi, Muhammad Kashfi Shabdin, Jun Kobayashi, Mohd Hatta Mohammed Ariff
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Applied Sciences
• Subjects: control parameter reference; stance assistance; magnetorheological brake; body mass index; walking speed; ankle torque; ankle angular velocity
• Online Access: https://www.mdpi.com/2076-3417/9/20/4416

This paper aims to present a preliminary study of control reference parameters for stance assistance among different subjects and walking speeds using a passive-controlled ankle foot orthosis. Four young male able-bodied subjects with varying body mass indexes (23.842 ± 4.827) walked in three walking speeds of 1, 3, and 5 km/h. Two control references, average ankle torque (aMa), and ankle angular velocity (aω), which can be implemented using a magnetorheological brake, were measured. Regression analysis was conducted to identify suitable control references in the three different phases of the stance. The results showed that aω has greater correlation (p) with body mass index and walking speed compared to aMa in the whole stance phase (p1(aω) = 0.666 > p1(aMa) = 0.560, p2(aω) = 0.837 > p2(aMa) = 0.277, and p3(aω) = 0.839 > p3(aMa) = 0.369). The estimation standard error (Se) of the aMa was found to be generally higher than of aω (Se1(aMa) = 2.251 > Se1(aω) = 0.786, Se2(aMa) = 1.236 > Se2(aω) = 0.231, Se3(aMa) = 0.696 < Se3(aω) = 0.755). Future studies should perform aω estimation based on body mass index and walking speed, as suggested by the higher correlation and lower standard error as compared to aMa. The number of subjects and walking speed scenarios should also be increased to reduce the standard error of control reference parameters estimation.