| Exposure of seated drivers to long term vibration can impair their ability to drive and can lead to health disorders. This is particularly true for millions of professional drivers of trucks, buses, tractors, off-road vehicles, and earth-moving equipment. A study of the ride comfort with two-state suspension design was carried out using computational methods of multibody dynamics. Models of heavy vehicle with secondary suspensions at both cab and seat levels were developed to simulate the dynamic response of the driver when the vehicle was driven through a very poor road surface. Ride comfort due to different suspension configurations were compared and evaluated by ISO Standard in order to assess the efficiency of the proposed suspension system.; A semi-active suspension system, also known as sky-hook suspension, was studied and applied at the seat suspension and cab suspension of the tractor semi-trailer model. The working theory of the sky hook suspension is based upon an active damper whose damping coefficient is capable to be varied quickly in a working bandwidth. The control algorithm and its key parameters were discussed and sought for the optimal reduction on the transmitted vibration to driver's body.; The sky-hook seat suspension and sky-hook cab suspension reduced the vertical root - mean-square acceleration of the driver's body by 20% when they worked individually. The combined effects of the two suspensions reduced the transmitted vibration by 40%, which prolonged the exposure limits recommended by the ISO Standard up to six times longer than a traditional suspension system. The simulation results suggest the two-state suspension design has strong potential on the ride comfort improvement. |
