As part of the overall project 'Active Steering Systems in a Modular Structure for Different Vehicle Topologies,' in collaboration with Hydraulik Nord Fluidtechnik GmbH & Co. KG, a novel active steering system is to be developed, which, due to its modularity, can be adapted to various vehicle topologies. This project is co-financed by the European Union through the European Regional Development Fund and by Hydraulik Nord Fluidtechnik GmbH & Co. KG. The work is carried out by several partners through subprojects.

The goal of the subproject 'Creation of a Development Environment for Active Steering Systems' at the Chair of Engineering Mechanics/Dynamics is the development and validation of real-time capable multibody simulation models for different vehicle topologies.

The phenomenon of synchronization, also known as the lock-in effect, has been known for centuries and is a subject of research in recent times in fields such as physics, biology, chemistry, and psychology, among others. In a mechanical sense, two oscillators with different fundamental frequencies can synchronize to the same frequency through coupling. Energy is transferred from the faster oscillator to the slower one. The oscillators considered here represent nonlinear self-excited oscillators.

The mathematical description of synchronization involves two basic tasks: determining the existence and stability conditions. For nonlinear systems, these must be approximated analytically. If the coupling between two oscillators satisfies the existence conditions, self-synchronization is possible, but it may be physically unstable. If both the existence and stability conditions are met, the stability of self-synchronization depends on the chosen initial conditions, as self-synchronization is generally not asymptotically stable. However, additional control of one of the coupled oscillators can ensure asymptotic stability. With appropriate control, the phase angle and vibration amplitude of the controlled oscillator in the synchronized state can be set.

Initial studies at the Chair have shown that controlled oscillators are well-suited for vibration reduction in dynamically loaded structures. The oscillators can operate energy-independently at most operating points. Input variables for the control include, among other things, the measured excitation force. A measurement of the system state is not necessary.

The findings obtained at the Chair will be further explored and experimentally verified in the following studies.

Wind turbines are generally designed for a service life of 20 to 25 years. The mechanical structure is designed for this reference service life on a site-specific basis. However, the sites are only roughly classified by the certification guidelines with regard to the loads to be expected there. As a result, the actual loads on the turbines may be lower than assumed during planning. For this reason, many wind turbines have structural reserves even after the end of their reference service life. This means that dismantling the turbines after the end of the reference service life makes neither economic nor ecological sense. At present, wind turbines are being dismantled which, under certain circumstances, could have remained standing and generating electricity for a few more years.

The aim of the project is to determine the individual service life of the mechanical structures of a wind turbine. To do this, it is first necessary to record the actual stress history of the wind turbine support structure during operation. Direct measurement of the stresses on a wind turbine during operation is only possible at accessible points and requires an extremely high level of metrological effort. In this context, it makes more sense to indirectly derive the cyclic stresses from movement variables of the wind turbine that are relatively easy to measure. The functional relationship between the measured variables and the stresses must be determined using suitable numerical structural models. The cyclic stresses determined during the operating time of the wind turbine can be used to derive service life predictions adapted to the respective stress history. The difference between the individual service life prediction and the reference service life then results in the service life reserve that can be used beyond the reference service life.