A comparison of different models of passive seat suspensions

Author(s):  
Raj Desai ◽  
Anirban Guha ◽  
P. Seshu

Long duration exposure to vehicle induced vibration causes various ailments to humans. Amongst the various components of the human-vehicle system, the seat suspension plays a major role in determining the level of vibration transferred to humans. However, optimising the suspension for maximising human comfort leads to poor vehicle handling characteristics. Thus, predicting human comfort through various seat suspension models is a widely researched topic. However, the appropriate seat suspension model to be used has not been identified so far. Neither has any prior work reported integrating models of all the components necessary for this analysis, namely human body, cushion, seat suspension and vehicle chassis, each with the appropriate level of complexity. This work uses a two-dimensional 12 DoF seated human body model with inclined backrest support, a nonlinear cushion model, a seat suspension model and a full vehicle model. Two kinds of road profiles – one with random roughness and one with a bump – have been used. It then compares the performance of five different seat suspension models based on a number of human comfort related parameters (seat to head transmissibility, suspension travel, seat acceleration, cushion contact force and head acceleration in both vertical and fore-aft directions) and vehicle handling parameters (vertical, rolling and pitching acceleration of chassis). The results clearly show the superiority of the configuration which involves a spring parallel to an inclined multi-stage damper. A separate analysis was also done to judge whether the integration of the vehicle model (with its associated complication) was necessary for this analysis. A comparison of the human body’s internal forces, moments, acceleration, and absorbed power with and without the vehicle model clearly indicates the need of using the former.

Author(s):  
Y-T Choi ◽  
N M Wereley

The mitigation of biodynamic response to vibratory and blast-induced shock loads using a magnetorheological (MR) seat suspension is addressed in this study. To this end, an MR seat suspension model for military vehicles including seated personnel is constructed in terms of a detailed lumped parameter model. The lumped parameter model of the human body consists of four parts: pelvis, upper torso, viscera, and head. From the model, the governing equation of motion of the MR seat suspension considering the human body is derived. Based on this equation, a semi-active nonlinear optimal control algorithm appropriate for the MR seat suspension is developed. The simulated control performance of the MR seat suspension is evaluated under three different excitations of sinusoidal and random vibration and tremendous shock load due to a mine explosion. In addition, the mitigation of injuries to humans due to such a shock load is evaluated and compared with a passive hydraulic seat suspension and a passive MR seat suspension with a constant yield force.


2005 ◽  
Vol 19 (07n09) ◽  
pp. 1689-1695 ◽  
Author(s):  
Y. M. HAN ◽  
J. Y. JUNG ◽  
S. B. CHOI ◽  
N. M. WERELEY

This paper presents robust control performances of a semi-active electro-rheological (ER) seat suspension incorporating vibration model of human-body. A cylindrical type of ER seat damper is manufactured for a commercial vehicle seat suspension system and its field-dependent damping force is experimentally evaluated. A human-body model is then derived and integrated with the governing equations of the ER seat suspension system. The integrated seat-driver model featured by a high order degree-of-freedom (DOF) is reduced through a balanced model reduction to design robust controller. By imposing semi-active actuating conditions, a sliding mode controller which is very robust to external disturbances and parameter uncertainties is synthesized and experimentally realized with the state observer. In the experimental configuration, a driver directly sits on the controlled seat. Control results for ride quality considering response of each human body segment are evaluated in both time and frequency domains. In addition, a comparison of the proposed semi-active ER seat suspension to a conventional passive seat suspension system is undertaken.


Aerospace ◽  
2003 ◽  
Author(s):  
Young-Tai Choi ◽  
Norman M. Wereley

This study investigates biodynamic response mitigation to three different excitations of sinusoidal and random vibrations and shock load using a magnetorheological (MR) seat suspension. In doing so, an MR seat suspension model for military vehicles, with a detailed lumped parameter model of the human body, was developed. The lumped parameter model of the human body consists of four parts: pelvis, upper torso, viscera and head. From the model, the governing equation of motion of the MR seat suspension considering the human body was derived. Based on this equation, a semi-active nonlinear optimal control algorithm appropriate for the MR seat suspension was developed. The simulated control performance of the MR seat suspension was evaluated under three different excitations of sinusoidal and random vibration and tremendous shock load due to a mine explosion. In addition, the mitigation of injuries to humans due to such shock load was also evaluated and compared with the passive seat suspension using a passive hydraulic damper.


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