Impedance Model of the Interaction Between Environment and Human Body and Its Modification Design

This paper presents a model of environment-human body interaction, which is critical for us to perform balanced motions such as locomotion and activities of daily living while standing. Specifically, movement smoothness and stiffness are quantitatively represented by an impedance between environment and body (ENV-BODY impedance) based on the concept of mechanical impedance, which is commonly used in robotics. The ENV-BODY impedance model considers a spring and a damper to represent the behavior of the center of pressure with respect to the ground reaction force. The model parameters are obtained from experimentally measured motion data. In addition, real-time feedback is applied for intervening the ENV-BODY impedance model by either attenuating (in-phase mode) or amplifying (anti-phase mode) the displacement of the center of pressure. Experimental results show that the proposed ENV-BODY impedance model suitably reflects the relationship between ground reaction force and center of pressure during static standing, and reconstructs the center-of-pressure acceleration with average error of 4.1E-0l mm/s² Furthermore, the stiffness is smaller at the in-phase than at the anti-phase mode, thus being consistent with the expected mechanical stability. This model could be applied to training programs for evaluating movement smoothness and roughness using real-time motion measurement/analysis and environment control technology.