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In this paper, we explain the process of designing a fuzzy based controller which can be installed in a vehicle. This controller uses sensors and actuators to coordinate suspension, brakes and steering system in critical situations to help a driver maintain the kinetic balance of the vehicle. An advantage of this controller is that it doesn't interfere with the driver's habit in vehicle control and it resumes functioning only in critical moments. Using various actuators and sensors, we introduce a new approach to detect instability and the turnover threshold. This makes the proposed fuzzy analyzer a novel one.

In this paper road damage caused by heavy vehicles is studied. The effects of passive, semi-active and active suspension designs on dynamic road loading are compared. Attention is given to develop an accurate vehicle model with useful tandem suspension behavior. A nonlinear two-dimensional model of tractor-semitrailer is considered. The model includes nonlinear behavior of leaf spring and tandem suspension in the trailer axles. To obtain accurate results, a realistic road profile model is considered. The control scheme of the semi-active suspension system is based on the modified skyhook damper model. For the active suspension control system design, due to nonlinearity in the vehicle model, a linear quarter vehicle model is considered. Then linear quadratic optimal technique is employed to design the control law. Two road damage criteria were applied to assess the vehicle performance: The dynamic road stress factor and the 95th percentile dynamic loads.