Human Biodynamic Responses to Whole-Body Vehicular Vibration and Vibration Control

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Proposed study concerns characterization and modeling of seated human responses to whole-body vibration (WBV) in the sagittal plane when coupled with visco-elastic seats and prevention of potential vibration injuries through control of vibration. Off-road vehicles employed in the resource, construction and industrial sectors exhibit complex ride vibration and limited directional stability. Epidemiological studies have established strong correlations between magnitudes of vibration of many work vehicles and reported injuries among drivers, in addition to reduced work efficiency. Owing to increasing demand for higher load capacity and speeds, future vehicles are expected to exhibit more severe WBV and adverse stability limits. Considering the absorption of vibration energy by the body, characterization of biodynamics is vital for design of vibration control systems, namely secondary and primary suspensions, and to contribute to human-centered future work vehicles designs. Considerable efforts are thus continuing to characterize biodynamic measures for deriving: (i) frequency-weighting for assessing exposure risks; (ii) biodynamic models for applications in seating design and vibration control devices; and (iii) anthropodynamic manikins for efficient assessments of seats. The reported responses, however, have been invariably obtained with body coupled with rigid seats and idealized vibration, which are not representative of conditions that prevail in vehicles. The body coupling with an elastic seat substantially alters its mechanical properties and thereby affects the vibration absorption. Consequently, applications of reported biodynamic responses and models have met limited success thus far. This is mostly attributed to lack of body interactions with elastic seats and adequate measurement systems. Furthermore, the control of ride vibration through suspension designs cannot be conducted in an isolated manner due to adverse effects of suspension on vehicle stability. The primary objectives thus include: (i) experimental characterization and modeling of sagittal plane biodynamic responses of human body coupled with elastic seats and exposed to vertical and fore-aftl WBV; and (ii) designs of innovative suspensions through integrated ride, handling and stability vehicle models. The resistive pressure sensing grids will be used to measure body-seat interface forces and biodynamic responses to WBV. The frequency response of the measurement system, established in a recent study, will be applied to compensate for its limited bandwidth. Owing to strong dependence on body mass, back support and seat elasticity, the study will include subjects with body mass within three ranges and varying seat elastic property. The target biodynamic responses will be defined as functions of body mass and seat elasticity. The responses, obtained for a rigid seat, will be used to calibrate multi-body biodynamic models of the body of three masses. The calibrated models will be integrated with a finite element model of the seat so as to characterize the biodynamic responses of the body coupled with elastic seat. The feasibility of the models to reliably represent the seat-occupant response under typical vertical and fore-aft vehicle WBV will be established through experiments and simulations with suspension seats. The study will subsequently focus on innovative designs in primary suspensions involving inter-axle coupled hydro-pneumatic struts. An integrated ride and handling model of a frame-steer vehicle will be developed incorporating kineto-dynamics of the steering struts, different layouts of hydra-connected suspension and correlated tire-terrain interactions.