Vibration Output Research Articles

Artificial Neural Network Approach ForMultiple Fault Diagnosis: A Case Study

A method is presented for multiple fault diagnosis by means of an Artificial Neural Network (ANN). The major advantage of using an ANN as opposed to any other technique for fault diagnosis in condition ba:-ed maintenance is that the network produces an immediate decision with minimal computation for a given input vector, whereas conventional techniques like spectral analysis require complete processing of an input signal to reach a diagnosis. The basic strategy is to train a neural network to recognize the behavior of the machine condition as well as the behavior of the possible system faults. The multi-layer feed forward network is used in this paper with back propagation learning algorithm. The network is trained by giving training examples, which have known input vector of vibration signatures and output vector of membership of possible faults. Field data of a lubricating oil pump for a residual gas compressor from a LPG recovery plant is used for training and testing the network. For diagnosis purpose, five different states are considered. The correct classification rate during training and testing is very high. On the basis of the results presented it is felt that the application of neural network shows superior performance in fault diagnosis. Transactions on Information and Communications Technologies vol 6, © 1994 WIT Press, www.witpress.com, ISSN 1743-3517

Reduction of errors in vibratory gyroscopes by double modulation

Vibratory drive, vibratory output instruments for sensing angular rates, such as tuning forks, potentially offer certain advantages over conventional gyroscopes. The theoretical performance of these devices has not been realized experimentally because of zero-rate errors attributed to mass unbalance, driving force unbalance and other imperfections. By separating the driving and sensing frequencies through a process called double modulation, obtained through an additional rotation or vibration of the basic sensing element, zero-rate errors may be diminished. Theoretical and experimental evidence in support of the double modulation concept is presented. A tuning-fork type of instrument has been used in the initial experiments and a substantial improvement over the performance of the same instrument without double modulation has been realized.

Evaluation of a New Artificial Mastoid as an Instrument for the Calibration of Audiometer Bone-Conduction Systems

A basic problem in obtaining dependable bone-conduction thresholds in pure-tone audiometry has been the attainment of an objective measure of the vibrational output of the system. In the past, several different artificial-mastoid designs have been reported, but none has proved entirely satisfactory as a standard calibration instrument, largely because of the problems involved in devising a stable and reproducible method of terminating the bone vibrator with a mechanical impedance that simulates that of the average human mastoid. In the present study, a new artificial mastoid, Beltone model 4, was analyzed for stability of response and for its potential use as a calibration instrument. Two bone vibrators were used for repeated measurements over a period of time to establish the reliability and linearity of the measuring instrument. Normative data were then derived from a suitable sample of normal-hearing subjects for one of the vibrators. These data were then transferred to other vibrators of the same type via the artificial mastoid, and bone-conduction thresholds were measured for the criterion sample of normal-hearing subjects and for subjects with sensorineural hearing impairments. Results suggest that the new artificial mastoid has good stability and that it shows excellent promise as an instrument for the calibration of bone-conduction audiometers.

Field Installation Acoustic Treatment of Air Conditioning Equipment

Attainment of acceptable air conditioning noise levels results from (a) low vibration and noise output, and (b) acoustic enevironment at installation. Commercially available equipment requires extraneous acoustic treatment for 5 to 50% of domestic installations (depending on building construction) in order to eliminate annoyance. Acoustical surveys of site conditions prior to installation permit most economical application of acoustic treatment and constructions. Classification of installation features and identification of respective transmission paths facilitate prior analysis of site conditions and assessment of treatment requirements. The most important transmission paths are through (a) the foundations, (b) the air discharge and return openings and ducting, and (c) the equipment casings. Effective methods for blocking transmission along each path by means of field applied treatments are discussed.

A Clinical Method For Calibrating the Bone-Conduction Audiometer

The clinician who wishes to make full use of pure-tone audiograms needs a valid and simple method for ensuring that the calibration for his bone-conduction system is adequate. Unfortunately, we lack a standard procedure whereby the physicist can specify for us the vibrational output representing bone-conduction norms. * For the time being the clinician must therefore rely upon his own efforts to assure himself that his bone measurements are acceptable. Even after a physical standard is established, the need will remain for an easy and adequate method of checking calibration in a clinical situation. There are three calibrational methods from which the clinician can choose. The first method utilizes loudness balancing, the second is based on thresholds yielded by normal listeners, while the third relies on the responses of cases with sensorineural (or nerve-type) loss. The loudness-balance method is advocated by Beranek as a means of transferring air-conduction norms to a