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Heavy trucks are becoming more common in use for international transportations, with longer highways and long driving hours contributing corresponding increases in driver's fatigue that is related to accidents. In this paper a detailed procedure is proposed to improve a highway truck seat. A dynamic model of an on-highway truck seat is simulated using Simulink toolbox in MATLAB. The seat suspension including the cushion is mounted on the cab floor of a half truck model and excited by a rapid excitation of step input. The seat suspension system controller is designed to improve the ride quality of the driver. Genetic Algorithms (GA) is used to obtain the coefficients of the control parameters. In addition, model outputs comparison of the proposed design to a conventional passive seat suspension using the maximum overshoot and the root mean square (RMS) values of both, the driver acceleration and the seat suspension working space.

One of the main causes of the torsional and bending fluctuations of the driveline is the angularity of the driveshaft and its universal joints. Most of the previous studies of the driveline vibrations have considered constant and equal angularities of these joints. However, the exact equality of the angularity is very difficult to maintain for ground vehicles under different ride vibration modes. This paper is concerned with the coupling between the driveline fluctuations and the ride vibrations of the rear drive vehicles. The coupled motions, which are; drive axle suspension deformation and vehicle body pitch angle and their derivatives, have been used to study the driveshaft and output shaft bending and torsional fluctuations. The results have showed that the fluctuations of the driveshaft due to the base angularity of the joints are superimposed by another fluctuation due to the bounce and pitch of the vehicle body.