In order to reduce structural vibrations in narrow frequency bands, tuned mass absorbers can be an appropriate measure. A quite similar approach which makes use of applied piezoelectric elements, instead of additional oscillating masses, are the well-known resonant shunts, consisting of resistances, inductances, and possibly negative capacitances connected to the piezoelectric element. This paper presents a combined approach, which is based on a conventional tuned mass absorber, but whose characteristics can be strongly influenced by applying shunted piezoceramics. Simulations and experimental analyses are shown to be very effective in predicting the behavior of such electromechanical systems. The vibration level of the absorber can be strongly attenuated by applying different combinations of resistant, resonant, and negative capacitance shunt circuits. The damping characteristics of the absorber can be changed by applying a purely resistive or resonant resistant shunt. Additionally, the tuning frequency of the absorber can be adapted to the excitation frequency, using a negative capacitance shunt circuit, which requires only the energy to supply the electric components.
Passive vibration control solutions are often limited to working reliably at one design point. Especially applied to lightweight structures, which tend to have unwanted vibration, active vibration control approaches can outperform passive solutions. To generate dynamic forces in a narrow frequency band, passive single-degree-of-freedom oscillators are frequently used as vibration absorbers and neutralizers. In order to respond to changes in system properties and/or the frequency of excitation forces, in this work, adaptive vibration compensation by a tunable piezoelectric vibration absorber is investigated. A special design containing piezoelectric stack actuators is used to cover a large tuning range for the natural frequency of the adaptive vibration absorber, while also the utilization as an active dynamic inertial mass actuator for active control concepts is possible, which can help to implement a broadband vibration control system. An analytical model is set up to derive general design rules for the system. An absorber prototype is set up and validated experimentally for both use cases of an adaptive vibration absorber and inertial mass actuator. Finally, the adaptive vibration control system is installed and tested with a basic truss structure in the laboratory, using both the possibility to adjust the properties of the absorber and active control.
This paper examines an approach used to design adaptive systems by means of Rapid-Prototyping on the basis of a simulation. The vibration behavior of mechanical systems including actuators, sensors, and an adaptive controller in the time domain will be modeled. This approach includes the calculation of the dynamic behavior of the mechanical structure with the help of the Finite Element Method (FEM). The FE model of the mechanical structure is transformed into modal space, then reduced and embedded as a state-space model in the MATLAB/Simulink environment. Thereby, a simple mechanical problem is solved analytically with the FEM as well as with the reduced MATLAB model. The comparison of the results shows a good agreement. Actuators and sensors are attached to the mechanical structure. Based on the resulting dynamical behavior of the mechanical structure, an adaptive control algorithm for the reduction of structural vibration is developed. Experimental tests are performed to verify and update the simulations. The hardware-in-the-loop simulations are carried out with a dSpace system. Some differences (with respect to speed-up, precision) between this simulation and other methods are presented later in the paper. This procedure allows the development and the evaluation of more complex adaptive mechanical structures.
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