In this paper, the dynamic behavior of a non-linear eight degrees of freedom vehicle model having active suspensions and a fuzzy logic (FL) controlled passenger seat is examined. The non-linearity occurs due to dry friction on the dampers. Three cases of control strategies are taken into account. In the first case, only the passenger seat is controlled. In the second case, only the vehicle body is controlled. In the third case, both the vehicle body and the passenger seat are fully controlled at the same time. The time responses of the non-linear vehicle model due to road disturbance and the frequency responses are obtained for each control strategy. At the end, the performances of these strategies are compared. Nomenclature a, b = distances of axle to the center of gravity of the vehicle body c, d = distances of unsprung masses to the center of gravity of the axles e, f = distances of passenger seat to the center of gravity of the vehicle body c s i = ith damping coefficient of suspension c s5 = damping coefficient of passenger seat f(V r i ) = ith dry friction force k s i = ith spring constant of suspension k s5 = spring constant of passenger seat k t i = ith stiffness coefficient of tire m i = ith mass of axle m 5 = mass of the passenger x i = ith state variable z i (t) = ith road excitation I x 7 = mass moment of inertia of the vehicle body for pitch motion I x 8 = mass moment of inertia of the vehicle body for roll motion M = mass of the vehicle body
A high standard service must be provided in rail transportation for passenger safety and comfort. With this need in mind, data are collected on vibration problems in rail systems and control. In this study, a rail vehicle system in use in Istanbul traffic is studied and a physical model in the form of a 22-degrees-of-freedom half light rail transport vehicle and differential equations created for analyzing vibrations. A computer simulation is also been carried out. In the simulation, real parameters for the modeled vehicle are employed. In an effort to minimize displacement and acceleration of the vibrations obtained in the end of simulations based on time and frequency domains, a fuzzy logic controller is used to actively control vibrations in the simulation environment.
In this paper, the problem of active vibration control of multi-degree-of-freedom structures is considered. Fuzzy logic and PID controllers are designed to suppress structural vibrations against earthquakes under the non-linear soil-structure interaction. The advantage of the fuzzy logic approach is the ability to handle the non-linear behavior of the system. Non-linear behavior of the soil is modeled in the dynamics of the structural system with non-linear hysteric restoring forces. The simulated system has fifteen degrees of freedom, which is modeled using spring-mass-damper subsystems. A structural system was simulated against the ground motion of the destructive Kocaeli earthquake (M w = 7.4) in Turkey on 17 August 1999. At the end of the study the time history of the storey displacements and accelerations, the control voltages and forces, and the frequency responses of both the uncontrolled and the controlled structures are presented. The performance of designed fuzzy logic control is checked using the changing mass parameters of each storey and the results are discussed. These results show that the proposed fuzzy logic controller has great potential in active structural control.
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