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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.

In this paper, the performance of hydro-pneumatic limited bandwidth active suspension system is studied theoretically using a half car model. The bounce and pitch motions for the sprung mass and two vertical degrees of freedom for the unsprung mass's are considered (to permit for good suspension design). The linear optimal control theory is used to derive the full state feedback and feedforward control laws taking into account the correlation between the front and rear wheel excitation. The results are generated when the vehicle running on a statistically random road using a 6 Hz bandwidth analogue controller. A comparison between the conventional passive, limited bandwidth active suspensions with and without wheelbase correlation are presented and discussed. The results showed that there is a worthwhile improvement for the proposed active system over the passive, while incorporating wheelbase correlation added more benefits for the rear axle dynamics and pitch motion.

In this paper, the vehicle body attitude in response to low frequency dynamic loads experienced during braking, accelerating, cornering, aerodynamics or payload variations can be controlled using an electronically controlled active suspension. Using a four degree of freedom half vehicle model, a composite controller which consists of Linear Quadratic Regulator vibration controller (LQR) plus Proportional-Integral-Derivative controller (PID) has been designed to isolate the body vibration from the road surface irregularities and maintain the body static height constant as well as control the body pitch motion. Vertical step inputs and different longitudinal step braking forces were applied to the body C.G. to simulate the payload variations and emergency braking effects.