Simulation-based virtual driver fatigue prediction and determination of optimal vehicle seat dynamic parameters

Date

2013-08

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Abstract

Vehicle ride comfort plays an important role in the vehicle selection and customer satisfaction. It depends upon various factors including road irregularities, vehicle suspension, vehicle dynamics, tires, seat design and human body’s properties itself. For a given chassis, the seat design is one of important aspects in vehicle interior design. Vehicle seat design is a special example of product design process which takes multiple iterations. It is essential to reduce the total number of iterations in the early design stage to save time and money. How do the designers know the optimal seat parameters such as cushion, seat suspension, and etc. in the early design stage? What’s the fatigue level for drivers to drive this newly design vehicle? To answer these questions, simulation based biodynamic human model is the best choice to assess the designed seat instead of physical prototypes. This research work focuses on developing a simulation method to predict virtual driver fatigue and determine optimal seat dynamic parameters for cushion and seat suspension. These dynamic properties include the stiffness and damping values of cushion and seat suspension. A 14-degree of freedom (DOF) multibody biodynamic human model in 2D is selected from literature to assess three types of seat. The human model has total mass of 71.32 kg with 5 body segments. Backrest support and feet contact with the ground are included in this model. Three types of seat models are used in this research. The first seat has neither cushion nor seat suspension and is called as hard seat. The second type of seat has seat and backrest cushion but does not have seat suspension. Last seat model which is known as isolated seat has seat suspension and seat and backrest cushion. Transmissibility and absorbed power are derived and plotted in vertical and horizontal directions for all three types of seats. For given three types of seats, the seat with backrest and seat pan cushion and seat suspension has best performance compared to the hard seat or the seat without seat suspension based on transmissibility and absorbed power. It was shown that human body response depends on dynamic properties of seat suspension and cushion. Furthermore, optimization based method is used to determine the optimal dynamic seat parameters for seat suspension, and cushion. It was shown that biodynamic human simulation model is a useful tool to virtually assess the designed seats or design seats.

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Keywords

Ride comfort, Human biodynamic model, Seat model, Whole body vibration, Transfer function, Transmissibility, Absorbed power, Human body fatigue prediction, Optimal seat dynamic parameters, Simulation based method

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