Articles written in Sadhana

    • Fuzzy logic control of vehicle suspensions with dry friction nonlinearity

      L Emir Sakman Rahmi Guclu Nurkan Yagiz

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      We design and investigate the performance of fuzzy logic-controlled (FLC) active suspensions on a nonlinear vehicle model with four degrees of freedom, without causing any degeneration in suspension working limits. Force actuators were mounted parallel to the suspensions. In this new approach, linear combinations of the vertical velocities of the suspension ends and accelerations of the points of connection of the suspension to the body have been used as input variables. The study clearly demonstrates the effectiveness of the fuzzy logic controller for active suspension systems. Suspension working space degeneration is the most important problem in various applications. Decreasing the amplitudes of vehicle body vibrations improves ride comfort. Body bounce and pitch motion of the vehicle are presented both in time domain when travelling over a ramp-step road profile and in frequency domain. The results are compared with those of uncontrolled systems. At the end of this study, the performance and the advantage of the suggested approach and the improvement in ride comfort are discussed.

    • Different control applications on a vehicle using fuzzy logic control

      Nurkan Yagiz L Emir Sakman Rahmi Guclu

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      In this paper, the active suspension control of a vehicle model that has five degrees of freedom with a passenger seat using a fuzzy logic controller is studied. Three cases are taken into account as different control applications. In the first case, the vehicle model having passive suspensions with an active passenger seat is controlled. In the second case, active suspensions with passive passenger seat combination are controlled. In the third case, both the passenger seat and suspensions have active controllers. Vibrations of the passenger seat in the three cases due to road bump input are simulated. At the end of the study, the results are compared in order to select the combination that supplies the best ride comfort.

    • Design of a fuzzy robust-adaptive control law for active suspension systems


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      This paper outlines a new approach in control of active vibration systems to make the system robust to parametric uncertainties, unmodeled dynamic effects and external disturbances. Namely, it is aimed to ensure robustness of the system towards all kind of disturbances such as road surface inputs and unexpected system parameter changes. So, a new robust-adaptive controller is designed as a vibration isolator and then applied on a full car active suspension system to improve the ride comfort of a vehicle in the presence of structured parameteruncertainties and unstructured unknown parameters or unmodeled dynamics. For this purpose, new parametric uncertainty upper bound adaptation algorithm is developed to isolate any platform from vibrations. Using adaptive laws, the controller can operate properly under changing conditions. The robustness of controller is also ensured by robust control law. This new approach represents a groundbreaking solution to eliminate any disturbance on a vehicle. Stability of the system is guaranteed by using Lyapunov theory, thus uniform boundedness error convergence is achieved. Afterwards, fuzzy logic controller is used to achieve the optimum values of controller gains. Also, comparative numerical solution using a fuzzy logic controlled suspension is performed on the same full-car model, both in time and frequency domain since classical FLC is an effective control method for active suspensions. At the end, it has been verified that the designed fuzzy robust-adaptive controller improves ride comfort more successfully than fuzzy logic one.

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