Substructured and analytical frameworks for the development of numerical-substructure-based and output-based substructuring controllers are proposed. The principle of numerical-substructure-based control systems utilises online parameters and signals related to numerical substructures for the control gain synthesis. Output-based controllers consider only online information related to transfer systems. The resulting linear feedforward and feedback controllers are synthesised using state-space and transfer-function techniques, assuming that the dynamics of tested specimens are to be completely unknown, and thus can cope with nonlinear substructuring tasks. Selection of the controllers for implementation depends on the synchronisation requirement and the dynamic properties of the controllers in real-time conditions. Experimental results of a two-mass-spring system verifying the controller designs are presented, which also show that the addition of feedback controllers can effectively reduce the synchronised errors.Accordingly, compared with (3) and (7), the procedure to obtain x e (s) in (16) is simplified and is independent of the Σ 2 parameters, resulting in a concise representation for x e (s).
SUMMARYExperimental techniques for testing dynamically substructured systems are currently receiving attention in a wide range of structural, aerospace and automotive engineering environments. Dynamic substructuring enables full-size, critical components to be physically tested within a laboratory (as physical substructures), while the remaining parts are simulated in real-time (as numerical substructures). High quality control is required to achieve synchronization of variables at the substructuring interfaces and to compensate for additional actuator system(s) dynamics, nonlinearities, uncertainties and time-varying parameters within the physical substructures. This paper presents the substructuring approach and associated controller designs for performance testing of an aseismic, base-isolation system, which is comprised of roller-pendulum isolators and controllable, nonlinear magnetorheological dampers. Roller-pendulum isolators are typically mounted between the protected structure and its foundation and have a fundamental period of oscillation far-removed from the predominant periods of any earthquake. Such semi-active damper systems can ensure safety and performance requirements, whereas the implementation of purely active systems can be problematic in this respect. A linear inverse dynamics compensation and an adaptive controller are tailored for the resulting nonlinear synchronization problem. Implementation results favourably compare the effectiveness of the adaptive substructuring method against a conventional shaking-table technique. A 1.32% error resulted compared with the shaking-table response. Ultimately, the accuracy of the substructuring method compared with the response of the shaking-table is dependent upon the fidelity of the numerical substructure.
In this paper, we propose a novel anti-windup (AW) framework for coping with input saturation in the disturbance rejection problem of stable plant systems. This framework is based on the one developed by Weston and Postlethwaite (W&P) [26].The new AW-design improves the disturbance rejection performance over the design framework usually suggested for the coprime-factorization based W&P-approach. The new AW approach is applied to the control of dynamically substructured systems (DSS) subject to external excitation signals and actuator limits. The benefit of this approach is demonstrated in the simulations for a small-scale building mass damper DSS and a quasi-motorcycle DSS.
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