Low-frequency vibration analysis of human body in semi-supine posture exposed to vertical excitation

Abstract

In the new space vehicle architecture, the astronauts in semi-supine posture would be exposed to elevated vibration level. The present study is focused to develop a multi-body model of human in a semi-supine posture to analyze their biodynamic responses due to vertical excitation. The study proposes a linear 15-DOF model of a semi-supine human in the sagittal plane. The human body model is represented by five body segments as head-neck, torso-arm, pelvis, thigh, and legs. Each segment is interconnected with the translational and rotational spring-damper elements to simulate the relative motion. The tissues in contact with the rigid vibrating support are modeled using translational spring-damper elements. The model parameters were identified using optimization scheme by minimizing the least square error between normalized magnitude and phase of predicted and target vertical apparent mass in the frequency domain. The parameter sensitivity analysis shows that vertical stiffness and damping of underneath tissue of torso has substantial influence on peak modulus of apparent mass and corresponding resonance frequency. The modal analysis reveals that the principal resonance frequency for human body in semi-supine posture is greater as compared to seated and standing posture.