Abstract: A method comprises: sampling a current waveform of an induction machine to obtain sampled points; characterizing the sampled current over a selected first time window to obtain characterized points; subtracting the characterized points from respective sampled points to obtain a residual signal comprising residual points; obtaining a frequency spectrum representative of the residual signal over a selected second time window; and identifying a rotor bar pass frequency from the frequency spectrum. The method is typically carried out by a system comprising a computer, a computer-readable medium, or combinations thereof.

Abstract: A method comprises: sampling a current waveform of an induction machine to obtain sampled points; characterizing the sampled current over a selected first time window to obtain characterized points; subtracting the characterized points from respective sampled points to obtain a residual signal comprising residual points; obtaining a frequency spectrum representative of the residual signal over a selected second time window; and identifying a rotor bar pass frequency from the frequency spectrum. The method is typically carried out by a system comprising a computer, a computer-readable medium, or combinations thereof.

Abstract: A method for balancing a rotor of a rotatable machine such as a steam turbine-generator unit. A time-dependent equation is formulated for rotor vibration based on a rotordynamic computer model derived from finite element analysis of the machine's rotor vibration due to centrifugal forces caused by adding unbalance weights. The equation is repeatedly solved in the frequency domain as an optimizer program uses iteration to determine the unbalance weights which will cause the vibration of the rotor of the model to duplicate the measured vibration of the rotor of the machine. Then, balance weights are added to the rotor of the machine which are the inverse of the unbalance weights which were added to the rotor of the model.

Abstract: A diagnostic system and method for rotating machinery having mechanical problems combine AI-based interpretive reasoning with rotordynamic-based modeling and numerical optimization. A vibration response in the machinery to be diagnosed is first measured by machine sensors, and this measured response is used in a rule-based expert system to determine a probable cause of the machinery's mechanical problem. An appropriate finite element analytical model of the machinery is generated based on the probable cause. An optimizer computes the predicted response from the analytical model and compares it with the measured response. The model is automatically refined, guided by the expert system and numerical optimization, to match the predicted response with the measured response. The modifications to the model necessary to duplicate the measured response of the defective machinery are then indicative of the defects.

Abstract: An active noise control subassembly for reducing noise caused by a source (such as an aircraft engine) independent of the subassembly. A noise radiating panel is bendably vibratable to generate a panel noise canceling at least a portion of the source noise. A piezoceramic actuator plate is connected to the panel. A back plate is spaced apart from the first plate and the panel with the panel positioned between the source noise and the back plate. A pair of spaced-apart side walls each generally abut the panel and the back plate so as to generally enclose a back cavity. A mechanism is provided for varying the panel resonating frequency by varying the state of the back cavity (such as by varying its fluid pressure and/or volume) while the panel is undergoing bending vibrations.

Abstract: An active noise control subassembly for an aircraft engine. An aircraft engine noise radiating panel is bendably vibratable to generate a canceling noise generally opposite in phase to at least a portion of the discrete tonal noise produced by the engine. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the panel such that vibrations in the plate cause bending vibrations in the panel and such that the plate is compressively prestressed along the panel when the panel is free of bending vibrations. The compressive prestressing increases the amplitude of the canceling noise before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction to increase the amplitude of the canceling noise before the sum of the AC signal and DC bias exceeds the depolarization voltage in a direction opposite to the poling direction.

Abstract: An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied.