This work deals with active vibration control of a rotating machine in both steady state and transient motion. Two stacks of piezoelectric ceramic orthogonally arranged in a plane localized at one of the bearings were used as the control actuators, using a modal control strategy. The optimal controller LQR was used to calculate the control gain, working together with an LQE observer that estimates the modal state. Simulation carried out on FEM model suggested the feasibility of the control strategy, and experimental tests using a physical test rig show good agreement with the numerical results, and confirm the efficiency of the strategy.

Active magnetic bearings (AMBs) can actively control the on-board rotor to reduce excessive vibration caused by base motion and improve the system's ability to withstand base excitation. Current active controllers for base motions require additional sensors or complex robust designs, making it difficult to balance reliability and applicability. In this article, a disturbance observer (DOB) approach is developed, numerically and experimentally, to observe and suppress disturbance caused by base motions, which can achieve vibration control without adding additional sensors or replacing the commonly used proportional-integral-derivative controller. Specifically, an AMB-rotor system model considering base motions is established based on general equation of motion. The effect of base motions on the system is considered as disturbance, including additional external forces, stiffness forces, and gyroscopic forces. The working principle, robust stability analysis, and design process of the DOB are presented. Simulation and experiments are conducted on a lab-scale AMB-rotor test rig. The DOB exhibits satisfactory behaviors under harmonic and shock excitations. The impact of the observation bandwidth of the DOB on vibration suppression is also analyzed.

The aim of this work is to propose a methodology for the experimental determination of the matrix relating unbalance forces to measured displacements for a rotating machine. The goal is to obtain an alternative solution to special situations found in the industrial context, especially for highly flexible rotors that may lead to a nonlinear behavior of the system. The trial-weights-based techniques, such as the influence coefficients method or the modal method, cannot be applied in such configurations. The proposed balancing method is based on the use of an identified model for the system. A pseudo-random optimization technique using genetic algorithms was applied for the identification process. The basic idea is to obtain the flexible rotor unbalance response, which is then mimicked by using a finite element method model in which the unbalance masses and their corresponding angular positions are the design variables from the optimization viewpoint. This way, an inverse problem is solved and the corrective masses are obtained. The model characteristics of the system are adjusted experimentally. Experimental investigations were carried out and the results show the efficiency of the method developed; the limitations and improvements are finally discussed.

The benefits of angular sampling when measuring various signals in rotating machines are presented and discussed herein. The results are extracted from studies on transmission error measurements with optical encoders in the field of power transmissions and can be broadened to include phase difference measurements, such as torsional vibrations, and applied to control, monitoring and measurement in rotating machines with discrete geometry. The main conclusions are primarily that the use of angular sampling enables the exact location of harmonics and, consequently, the obtaining of spectral amplitude components with precision. This is always true even if the resolution of encoders is not directly related to the studied discrete geometry. It then becomes possible to compare these harmonics under different operating conditions, especially when speed varies, without changing any parameters in spectral analysis (window length, spectral resolution, etc.). Moreover, classical techniques of improving signal to noise ratio by averaging become fully efficient in the detection of defective elements. This study has been made possible thanks to the technique of transmission error measurement with optical encoders that allows the comparison of sampling procedures, based on the same raw data.The intensive use of such transducers and the development of an original transmission error measurement technique lead to advocate the use of angular sampling in experimental measurements in rotating machines with discrete geometry.