It has been shown that piezoelectric materials can be used as passive electromechanical vibration absorbers by shunting them with electrical networks. Semi-active piezoelectric absorbers have also been proposed for suppressing harmonic excitations with varying frequency. However, these semi-active devices have limitations that restrict their practical applications. The approach presented here is a high performance active-passive alternative to semi-active absorbers. By utilizing a combination of a passive electrical circuit and active control actions, the system is synthesized for adaptive variable frequency narrowband disturbance rejection. The active control consists of three parts: an inductor tuning action, a negative resistance action, and a coupling enhancement action. In the current paper (Part 1), the control algorithm is developed and analyzed. Part 2 of the paper contains experimental investigations and parametric studies of the new absorber design.
Previous studies have shown that piezoelectric materials can be used to provide passive damping by shunting them with an electrical network, such as a series RL circuit. This same configuration can also be used in conjunction with an active voltage source as an active-passive hybrid vibration control method. This active-passive piezoelectric network (APPN) concept, which combines the advantages of passive damping and active control, has proven to be very effective for vibration suppression, especially in narrow-band applications. It has also been recognized that the resistor element in these devices, which is necessary to provide passive damping, can reduce the authority of the active control action by dissipating a portion of the control power. One possible method to improve upon this situation is to use a variable resistor in the shunt circuit and on-line adjust the resistance based on feedback. However, the concurrent design method previously synthesized for APPN systems becomes difficult to implement when such a state-dependent and time-varying resistor is used. In this research, an effective and simple active-parametric control law is developed for an APPN system with variable resistance. The active control law uses a simple but effective rate feedback law along with a feedback linearization technique to compensate for the dynamics of the variable resistor. The parametric control law is designed to turn the resistor off when the active source is supplying power to the actuator and turn the resistor on when necessary to dissipate power from the structure. With this variable resistance action it is possible to retain the passive damping abilities of the APPN circuit while minimizing the amount of control power that is dissipated in the circuit. A series of simulations are conducted in order to demonstrate the increased efficiency due to the variable resistance action. The effects of excitation bandwidth and controller gain on the performance of the system are also examined.
In Part 1 of the paper, a new high-performance active-passive hybrid piezoelectric absorber concept was presented. This design is an attractive alternative to semi-active absorbers for the purpose of suppressing harmonic excitations with variable frequency. In this paper (Part 2), the effectiveness of the new absorber design is first demonstrated through experimental investigations. Parametric studies are then carried out to illustrate how the performance of the new design is affected by the design parameters and excitation characteristics. In these studies, two state-of-the-art control methods are used as baselines for comparison with the new absorber design, and it is shown that the proposed design offers superior performance and efficiency compared to these methods.
Active-passive hybrid piezoelectric networks (APPN) have been shown to be effective devices for vibration suppression. It has also been recognized that the resistor element in these devices, which is necessary to provide passive damping, can reduce the authority of the active control action. One possible method to improve upon this situation is to use a variable resistor in the RL shunt and on-line adjust the resistance based on feedback. However, the concurrent design method previously synthesized for APPN systems becomes difficult to implement when such a state-dependent and time-varying resistor is used. In this research, an effective and simple control law is developed for an APPN system with variable resistor. It is shown that by proper on-line adjustment of the variable resistor, the efficiency of the APPN system can be significantly increased.
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