Abstract
This study employed a resettable variable stiffness TMD (RVS-TMD) to alleviate detuning effect. The RVS-TMD is composed of a TMD and a resettable variable stiffness device (RVSD), which consists of a resettable element and a controllable stiffness element. By varying the stiffness element of RVSD, the detuning effect can be mitigated. While, by actuating the resettable element, the hysteresis loop of the RVSD can cover all four quadrants in the force-deformation diagram and thus result in more energy dissipation. However, to adjust the stiffness of the TMD system, the problem of time-delay is inevitable. For an active control system, time is consumed in data acquisition, data processing, on-line calculation, and control force execution. There is always a delay between the time at which the control force is assumed to be applied and actually applied, which may cause degradation in control efficiency. Therefore, the control design of a RVS-TMD system should take into account the effect of time delay. This study applied delayed control gains to alleviate the time delay effect based on the LQR optimal output feedback control algorithm. A parametric study was conducted to demonstrate the relationships of delayed gains with intentionally-added delay time. The results of numerical simulation show the application of optimally-delayed gains significantly alleviates the time delay effect and assure the desired control efficacy.
