This thesis presents new approaches for control of semi-active vehicle suspension systems. In particular, towards optimizing the exploiting of the fast dynamic of modern devices, it focuses on three aspects: semi-active device modeling, damper control and optimal control for semi-active suspensions. At first, a new physical model of a semi-active damper is presented, which takes into account the fluid dynamics, the switching elements and the external valves. This model reproduces the real hardware with high precision. Nevertheless, because of its complexity and thus its high demand for computational time, it is not suitable for control in real-time applications. Therefore, a functional damper model, which emulates the main characteristics of the real device, is derived and validated by means of measurements. Next, the obtained model is integrated in a controller structure. Since the state of the art solution utilizes a feedforward approach based on static damper characteristics, the novelty of the presented model-based approach consists of introducing a dynamical feedforward path, which considers the hysteresis effects of the damper. This allows a better force tracking and, hence, a better exploitation of the semi-active hardware. In addition, the dynamical feedforward structure is extended by a force feedback path, which further reduces the control error and allows to increase the semi-active control performance. The low-level actuator control structure, meaning both the newly introduced feedforward and feedback structures, is analyzed by making use of state of the art suspension controllers. The commonly employed suspension controllers do not consider the working range, i.e. the state dependent constraints of the semi-active device in the controller design. Therefore, the third aspect addressed in this Thesis is an optimized high-level suspension controller, which takes the limitation of the controlling hardware into account. Based on the Principle of Optimality, two different suspension controller solutions for the nonlinear quarter-car model are compared in this Thesis. Although the high computational cost does not allow yet to utilize these methods for industrial applications, the importance of these approaches consists in the fact that the desired damper force always lies within the damper working range. Since the force can be continuously generated by the device, the control performance is further increased. The result for both the low-level and the high-level strategies have been experimentally confirmed on a semi-active quarter-car test rig, which has been designed and constructed by utilizing production vehicle components and sensors.


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    Title :

    Model-based damper control for semi-active suspension systems


    Contributors:

    Published in:

    Publication date :

    2013


    Size :

    172 Seiten, Bilder, Tabellen, 183 Quellen



    Type of media :

    Theses


    Type of material :

    Print


    Language :

    English






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