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In this paper, a fractional order economic system is studied. An active control technique is applied to control chaos in this system. The stabilization of equilibria is obtained by both theoretical analysis and the simulation result. The numerical simulations, via the improved Adams-Bashforth algorithm, show the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a method for active vibration isolation of frequency varying tonal disturbances in an engine mounted on a raft is presented. An adaptive nonlinear control algorithm with frequency tracking is introduced to tackle this problem. The studied process is a true MIMO-system with strong cross-couplings and high background noise level. The controller performance is first validated by extensive simulations and then by test bed implementation. It is shown that the proposed method is robust to measurement noise and additional output disturbances, while yielding a high level of vibration suppression with fast convergence rate. [Copyright &y& Elsevier]

Reducing the vibration of marine power machinery can improve warships' capabilities of concealment and reconnaissance. Being one of the most effective means to reduce mechanical vibrations, the active vibration control technology can overcome the poor effect in low frequency of traditional passive vibration isolation. As the vibrations arising from operation of marine power machinery are actually the frequency-varying disturbances, the H∞ control method is adopted to suppress frequency-varying disturbances. The H∞ control method can solve the stability problems caused by the uncertainty of the model and reshape the frequency response function of the closed loop system. Two-input twooutput continuous transfer function models were identified by using the system identification method and are validated in frequency domain of which all values of best fit exceeds 89%. The method of selecting the weighting functions on the mixed sensitivity problem is studied. Besides, the H∞ controller is designed for a multiple input multiple output (MIMO) system to suppress the single-frequency-varying disturbance. The numerical simulation results show that the magnitudes of the error signals are reduced by more than 50%, and the amplitudes of the dominant frequencies are attenuated by more than 10 dB. Finally, the single excitation source dual-channel control experiments are conducted on the floating raft isolation system. The experiment results reveal that the root mean square values of the error signals under control have fallen by more 74% than that without control, and the amplitudes of the error signals in the dominant frequencies are attenuated above 13 dB. The experiment results and the numerical simulation results are basically in line, indicating a good vibration isolation effect. [ABSTRACT FROM AUTHOR]

Techniques for optimal control to increase system security attract a great deal of interest from industry. The presence of transversal cracks can considerably modify the dynamics of a system. In the case of closed-loop systems, i.e. controlled systems, these faults can cause the destabilization and variation of control performance. Consequently, such variations can be used to detect transversal cracks. Therefore, the present study proposes an investigation into the possibility of detecting structure modification based on estimated control performance by using the Rational Fraction Polynomial algorithm. This method is applied numerically to a multi-cracked controlled truss. Both the optimal control of the cracked structure and the possibility of detecting the presence of cracks by monitoring the evolution of control performance are studied. The efficiency of the proposed method is demonstrated through numerical simulations corresponding to different crack orientations and locations. [ABSTRACT FROM PUBLISHER]