TY - GEN
T1 - Environment-Dependent Modulation of Human Ankle Stiffness and its Implication for the Design of Lower Extremity Robots
AU - Nalam, Varun
AU - Lee, Hyunglae
N1 - Funding Information:
This study was completed by a support of Virginia G. Piper Foundation, adidas-ASU Global Sport Alliance, and Ira A. Fulton Schools of Engineering at the Arizona State University.
Publisher Copyright:
© 2018 IEEE.
PY - 2018/8/20
Y1 - 2018/8/20
N2 - Understanding how human ankle mechanics are modulated during interaction with a wide range of environments is essential to develop reliable and robust lower extremity robots such as prosthetics and exoskeletons that mimic the behavior of the human ankle. This paper investigates the effect of mechanical environment on the modulation of human ankle stiffness and its underlying mechanisms. A novel multi-axis robotic platform, capable of actuating the ankle in both dorsiflexion-plantarflexion (DP) and inversion-eversion (IE), was used to quantify ankle stiffness in 2 degrees-of-freedom, while human subjects maintain upright posture in a range of stiffness-defined haptic environments. Ankle stiffness in DP increased with increasing compliance of haptic environment, but it was significantly lower than the stiffness measured in a rigid mechanical environment. On the other hand, ankle stiffness in IE was relatively constant in both compliant and rigid environments. Analysis of muscle activation and center of pressure of the ground reaction force provided an explanation for the underlying mechanisms of these observations. Notably, the analysis confirmed that modulation of ankle stiffness cannot be solely explained by activation of superficial ankle muscles. Implications for the design and control of lower extremity robots mimicking human ankle impedance are discussed.
AB - Understanding how human ankle mechanics are modulated during interaction with a wide range of environments is essential to develop reliable and robust lower extremity robots such as prosthetics and exoskeletons that mimic the behavior of the human ankle. This paper investigates the effect of mechanical environment on the modulation of human ankle stiffness and its underlying mechanisms. A novel multi-axis robotic platform, capable of actuating the ankle in both dorsiflexion-plantarflexion (DP) and inversion-eversion (IE), was used to quantify ankle stiffness in 2 degrees-of-freedom, while human subjects maintain upright posture in a range of stiffness-defined haptic environments. Ankle stiffness in DP increased with increasing compliance of haptic environment, but it was significantly lower than the stiffness measured in a rigid mechanical environment. On the other hand, ankle stiffness in IE was relatively constant in both compliant and rigid environments. Analysis of muscle activation and center of pressure of the ground reaction force provided an explanation for the underlying mechanisms of these observations. Notably, the analysis confirmed that modulation of ankle stiffness cannot be solely explained by activation of superficial ankle muscles. Implications for the design and control of lower extremity robots mimicking human ankle impedance are discussed.
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U2 - 10.1109/URAI.2018.8442204
DO - 10.1109/URAI.2018.8442204
M3 - Conference contribution
AN - SCOPUS:85053494280
SN - 9781538663349
T3 - 2018 15th International Conference on Ubiquitous Robots, UR 2018
SP - 112
EP - 118
BT - 2018 15th International Conference on Ubiquitous Robots, UR 2018
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 15th International Conference on Ubiquitous Robots, UR 2018
Y2 - 27 June 2018 through 30 June 2018
ER -