Optimal seat dynamic parameters determination for minimizing virtual driver's fatigue

In vehicle driving environment, the driver is subjected to the vibrations in horizontal, vertical, and fore-aft directions. The human body is very much sensitive to whole body vibration and this vibration transmission to the body depends upon various factors including road irregularities, vehicle suspension, vehicle dynamics, tires, seat design and the human body's properties. The seat design plays a vital role in the vibration isolation as it is directly in contact with human body. Vibration isolation properties of a seat depend upon its dynamic parameters which include spring stiffness and damping of seat suspension and cushion. In this paper, an optimization-based method is used to determine the optimal seat dynamic parameters for seat suspension, and cushion based on minimizing occupant's body fatigue (occupant body absorbed power). A 14-degree of freedom (DOF) multibody biodynamic human model in 2D is selected from literature to assess three types of seat arrangements. The human model has total mass of 71.32 kg with 5 body segments. Backrest support and feet contact with the vehicle floor are included in this model. The weighted absorbed power plots from translational and rotational motions of the occupant body are obtained and its values are calculated to predict virtual body fatigue for three types of seat models. Out of these models, the seat with backrest and seat pan cushion and seat suspension has the best performance compared to the hard seat or the seat without seat suspension. Results have also shown that with optimal seat dynamic parameters, there is substantial reduction in the human body's virtual fatigue.