Comfort Analysis of Occupant in Seat Suspension with Multiple Degrees of Freedom Human Biodynamic Modelling

To address the issue of occupant vibration comfort in vehicles under complex road conditions, this study establishes a vibration control system for a magnetorheological (MR) seat coupled with a four-degree-of-freedom human model and performs dynamic analysis. Through the transfer matrix method for multibody systems, the dynamic model and the corresponding topology of the MR seat-occupant system are established and occupant vibration response is obtained. Numerical simulation and comparative analysis reveal that the MR semi-active seat reduces the RMS values of acceleration for key human body parts (head and neck, upper trunk, viscera, and lower trunk) by the average of 25.5%–30.4% and the peak values by 9.8%–32.6%. Notably, the most substantial vibration reduction occurs in the regions of viscera and lower trunk, with RMS values decreased by up to 39.0%. Compared to a conventional passive system, the MR seat demonstrates superior vibration isolation performance in the low-frequency range based on acceleration frequency response characteristics. It effectively attenuates amplitudes within the occupant’s physiologically sensitive frequency bands, leading to the significant enhancement of ride comfort and ride quality.