ISAR imaging of moving satellite based on GO–PO scattering model

2017 ◽  
Vol 9 (7) ◽  
pp. 1499-1507
Author(s):  
Jiakun Wang ◽  
Min Zhang ◽  
Pengbo Wei ◽  
Panpan Jiang
Keyword(s):  
Electromagnetic Scattering ◽  
Great Influence ◽  
Multiple Reflections ◽  
Antenna Structure ◽  
Time Frequency ◽  
Large Size ◽  
Isar Imaging ◽  
Compensation Technique ◽  
Complex Target ◽  
Scattering Characteristic

An efficient algorithm is proposed for the radar cross-section (RCS) prediction of complex target with electronically large size, which is a combination of geometrical optics and physical optics (GO–PO) method. The method taking the multiple reflections into account is applied to the electromagnetic scattering analysis of a satellite model. Then RCS curves of entire satellite model and the model without antenna structure are figured out. Based on the simulated echoes, the traditional inverse synthetic aperture radar (ISAR) images are discussed. Moreover, an application of motion compensation technique based on the joint time-frequency analysis is presented for ISAR imaging of the moving satellite that has both translational and rotational movements. Numerical results show good performance of GO–PO method in accuracy and efficiency and the great influence of the antenna with corner structures on the scattering characteristic of the satellite.

High Resolution ISAR Imaging for Maritime Targets by Encoder-Decoder Network Combined with the Time-Frequency Attention

2021 ◽  
Author(s):  
Jianyang Wang ◽  
Di Cheng ◽  
Shiyuan Li ◽  
Chang Chen ◽  
Lingyun Zhou ◽  
...  
Keyword(s):  
High Resolution ◽  
Time Frequency ◽  
Isar Imaging

Incipient Surge Detection in Large Volume Energy Systems Based On Wigner-Ville Distribution Evaluated On Vibration Signals

2021 ◽  
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Paolo Silvestri ◽  
Mario L. Ferrari ◽  
Aristide Fausto Massardo
Keyword(s):  
Research Field ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Rolling Bearings ◽  
Time Frequency ◽  
Rotating Machine ◽  
Large Size ◽  
Critical Issues ◽  
Volume Energy ◽  
Transient Operations

Abstract Compressor response investigation in nearly unstable operating conditions, like rotating stall and incipient surge, is a challenging topic nowadays in the turbomachinery research field. Indeed, turbines connected with large-size volumes are affected by critical issues related to surge prevention, particularly during transient operations. Advanced signal-processing operations conducted on vibrational responses provide an insight into possible diagnostic and predictive solutions which can be derived from accelerometer measurements. Indeed, vibrational investigation is largely employed in rotating-machine diagnostics together with time-frequency analysis such as smoothed pseudo-Wigner Ville (SPWVD) time-frequency distribution (TFD) considered in this paper. It is characterized by excellent time and frequency resolutions and thus it is effectively employed in numerous applications in the condition monitoring of machinery. The aim and the innovation of this work regards SPWVD utilization to study turbomachinery behavior in detail in order to identify incipient surge conditions in the centrifugal compressor starting from operational vibrational responses measured at significant plant locations. To this aim, an experimental campaign has been conducted on a T100 microturbine connected with different volume sizes to collect significant data to be analyzed. The results show that SPWVD is able to successfully identify system evolution towards an unstable condition, by recognizing different levels and features of the particular kind of instability that is going to take place within the plant. Instability phenomena regarding rolling bearings have also been identified and their interaction with surge onset has been investigated for diagnostic purposes.

scholarly journals Improvement of Intake Structures in a Two-Way Pumping Station with Experimental Analysis

2020 ◽  
Vol 10 (19) ◽  
pp. 6842
Author(s):  
Yanjun Li ◽  
Rong Lu ◽  
Huiyan Zhang ◽  
Fanjie Deng ◽  
Jianping Yuan
Keyword(s):  
Frequency Domain ◽  
Great Influence ◽  
Operating Conditions ◽  
Stable Operation ◽  
Pressure Pulsations ◽  
Pump Unit ◽  
Measuring Point ◽  
Time Frequency ◽  
Pumping Station ◽  
Bell Mouth

Pumping stations are important regulation facilities in a water distribution system. Intake structures can generally have a great influence on the operational state of the pumping station. To analyze the effects of the bell mouth height of the two-way intake on the performance characteristics and the pressure pulsations of a two-way pumping station, the laboratory-sized model pump units with three different intakes were experimentally investigated. To facilitate parameterized control, ellipse and straight lines were used to construct the profile of the bell mouth. The frequency domain and time-frequency domain of the pressure pulsations on the wall of intakes were analyzed by the Welch’s power spectral density estimate and the continuous wavelet transform (CWT) methods, respectively. The results showed that the bell mouth height (H) has significant influences on the uniformity of the impeller inflow and the operation stability of the pump unit. When H = 204 mm, the data fluctuated greatly throughout the test process and the performance curves are slightly lower than the other two schemes. As the bell mouth height gradually decreases, the average pressure difference of each measuring point began to decrease, more homogeneous velocity distribution of impeller inflow can be ensured. The amplitude of blade passing frequency is obvious in the spectrum. While when (H) is more than 164 mm, the main frequency of pressure pulsations at three points fluctuates with the rotation of the impeller. When H decreases to 142 mm, pressure pulsations will be independent of the operating conditions and positions which contributes to the long-term stable operation of the pump unit.

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