Biodynamic response of the seated human body to a vibrating environment: Effect of seat backrest support

Abstract

This paper introduces the feature that the backrest of an ergonomic chair can provide effective support to the head, chest and waist into the vibration environment, and conducts research on whether the backrest can provide the reduction to the vibration, and the influence of its stiffness and damping on the vibration reduction influence. Four-degree-of-freedom (4-DOF) human-chair coupling models are constructed to characterize the different contact modes between the head, chest, waist and backrest. The simulation results of the biodynamic response curves of the seat-to-head (STH) transfer ratio of the model agree with the trend of the experimental results, proving its validity. With backrest support, the peak of STH curve will be reduced (the effect of supporting the waist is not obvious) and its resonance frequency will be changed. When the upper torso is in full contact with the backrest, the peak value and resonant frequency of STH curve are positively correlated with the contact stiffness of the chair surface and negatively correlated with the contact damping. For periodic and nonperiodic excitation, selection methods of the contact stiffness and damping of the backrest are proposed to reduce the transmission rate and improve comfort.