Bearings and their vibration play an important role in the performance of all motor systems. In many cases, the accuracy of the instruments and devices used to monitor and control the motor system is highly dependent on the dynamic performance of the motor bearings. In addition, many problems arising in motor operation are linked to bearing faults. Thus, fault detection of a motor system is inseparably related to the diagnosis of the bearing assembly. This paper presents an approach of using neural networks to detect common bearing defects from motor vibration data. The results show that neural networks can be an efective agent in the detection of various motor bearing faults through the measurement and interpretation of motor bearing vibration signals.
This paper describes the application of Active Fiber Composite actuators, a hybrid piezoelectric device, to the reduction of acoustic radiation from a cylindrical shell by active control methods. Active Fiber Composites were developed to provide a mechanically robust method for large-area, orthotropic actuation and sensing in active structures. The actuation layer is formed by small diameter piezoelectric fibers that are unidirectionally aligned and imbedded in a resin matrix system. By the nature of its structure, an Active Fiber Composite actuator allows use of the primary piezoelectric effect in the plane of the composite. A cylindrical shell testbed is used for this experiment due to the predominance of this structure, and the resulting general interest, within the field of underwater acoustics. To control acoustic radiation from the cylindrical shell, the Active Fiber Composite actuators, placed at optimal locations determined using numerical models, are used to generate a strain field that counteracts the strain associated with acoustically efficient shell motions. Using an end-mounted accelerometer as the error measurement, an adaptive LMS algorithm is used to minimize the error signal in real-time. Experimental are supplied to validate both the device and the methodology in a complex, real-world environment.
Active fiber composites were developed to provide a mechanically robust method for large-area, orthotropic actuation and sensing in active structures. This presentation will describe the application of active fiber composite actuators to the reduction of acoustic radiation from a cylindrical shell by active control. The composite actuation layer is formed by small diameter piezoelectric fibers that are unidirectionally aligned and imbedded in a resin matrix system. A separate, etched, interdigital electrode layer makes the electrical connections. By nature of its structure, an active fiber composite actuator or sensor allows use of the primary piezoelectric effect in the plane of the composite. Active fiber composites are inherently tolerant of damage and can be conformed to a wide range of structural shapes. To control acoustic radiation from a cylindrical shell, active fiber composite actuators are used to generate a strain field that counteracts the strain associated with acoustically efficient shell motions. Optimal placement of the actuators is determined using numerical models verified by an experimental characterization of the shell dynamics. The control signal applied to the actuator is determined, in real time, using adaptive control. Error sensing methods using accelerometers or active fiber composite sensors were considered. [Work supported by DARPA.]
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