A new method is presented for determining far-field radiation patterns of an array by means of amplitude-only measurements performed on arbitrary surfaces in the array's near field. Based on the method of successi...
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A new method is presented for determining far-field radiation patterns of an array by means of amplitude-only measurements performed on arbitrary surfaces in the array's near field. Based on the method of successive projections, it is a significant generalisation of existing techniques where measurements are restricted to equally spaced points on canonical surfaces. The method has particular application to the airborne measurement of the large low-frequency arrays used in OTHR (over-the-horizon radar) systems, where direct determination of the far field is difficult if not impossible. Two examples illustrate the technique, showing its efficacy for both smooth and gross variations in array excitation.< >
This paper develops an adaptive controller for active vibration control. The method is based on the LQG approach via disturbance modelling given in De Nicolao et al. (1992b). This approach to the narrow band disturban...
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This paper develops an adaptive controller for active vibration control. The method is based on the LQG approach via disturbance modelling given in De Nicolao et al. (1992b). This approach to the narrow band disturbance rejection problem is then applied to the problem of eliminating the effects of roll eccentricity in steel-strip rolling mills.
The development of a periodic autoregressive spectral estimator which is insensitive to variations in period is considered. The extended Kalman filter is investigated for estimation of the period. This estimate is the...
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The development of a periodic autoregressive spectral estimator which is insensitive to variations in period is considered. The extended Kalman filter is investigated for estimation of the period. This estimate is then incorporated into a rotational framework to produce a time-varying spectral estimate for a nominally periodic system. It is expected that the method will be useful for monitoring the intracycle behaviour of rotating machinery such as diesel engines, compressors, gears and bearings. Use of the short time Fourier transform for variable speed envelope analysis is also shown to be a necessary tool for detection of faults in low, variable speed rotating machinery.
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