# Automatic Decentralized Vibration Control System Based on Collaborative Stand-Alone Smart Dampers
## 6 Conclusions  
This work has been focused on the evaluation of modal parameters and the development of a feasible control strategy. The modified EMC strategy represents a solution that improves the vibration reduction performance with respect to a totally decentralized control system, since the global control action can be focused on some specific vibration modes according to a desired target. The goal was to reduce as much as possible the vibrations, considering also the damping that each actuator can introduce. Good results have been obtained by means of the numerical simulations, which have been validated through the experimental tests on the test rig.  
The proposed solution can be customized considering also different targets with respect to the one fixed in this work. For example, a different goal could be the increase of the damping as much as possible, by using the maximum damping potential of the overall control system regardless the state of vibration. In this case, only the damping weights should be considered in the final gains setting.  
The solution presented in this paper fits the project requirements, since a low computational effort and no real-time data sharing are required. This latter feature leads to an important consideration, since the main advantage of this control strategy is the scalability of the controlled system. The number of actuators can be easily increased without a reduction on the control performance, since no real-time data exchange is required to compute the control action, as centralized control architectures actually requires. To date, no fault-tolerant algorithms have been defined. Then, the control system is not robust to sensor faults, but the features of the smart devices allow the implementation of a diagnostic protocol to get information about the status of the sensors. This aspect could be addressed in future works.  
Moreover, all the information needed to apply such control strategy can be obtained in the previous identification phases. Closed forms formulas, to calculate the maximum  
Figure 7: Comparison between uncontrolled (blue line) and controlled (red line) system for the three sensors in the experimental test.  
applicable gains and the weighting factors, have been derived. In particular, besides the information about structure natural frequencies and vibration state, control gains calculation requires also the knowledge of the non-dimensional damping ratio and structural gain. For this reason, a modal parameter damping estimation has been developed. In order to evaluate the damping ratio, a time-domain decay method has been applied and acceptable results have been obtained.  
Validation, formal analysis and algorithms implementation, N.D.; conceptualization, methodology and investigation, S.C.; writing-review and editing, visualization, all authors; supervision, project administration, F.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no public data available.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} AVC & Active Vibration Control \\ DOF & Degree Of Freedom \\ DVF & Direct Velocity Feedback \\ SNDF & Selective Negative Derivative Feedback \\ FFT & Fast Fourier Transform \\ FRF & Frequency Response Function \\ PCB & Printed Circuit Board \\ PMA & Proof-Mass Actuator \\ CCU & Central Control Unit \\ \end{tabular}