As a critical structure of aerospace equipment,aluminum alloy stiffened plate will influence the stability of spacecraft in orbit and the normal operation of the system.In this study,a GWO-ELM algorithm-based impact d...As a critical structure of aerospace equipment,aluminum alloy stiffened plate will influence the stability of spacecraft in orbit and the normal operation of the system.In this study,a GWO-ELM algorithm-based impact damage identification method is proposed for aluminum alloy stiffened panels to monitor and evaluate the damage condition of such stiffened panels of spacecraft.Firstly,together with numerical simulation,the experimental simulation to obtain the damage acoustic emission signals of aluminum alloy reinforced panels is performed,to establish the damage data.Subsequently,the amplitude-frequency characteristics of impact damage signals are extracted and put into an extreme learning machine(ELM)model to identify the impact location and damage degree,and the Gray Wolf Optimization(GWO)algorithm is employed to update the weight parameters of the model.Finally,experiments are conducted on the irregular aluminum alloy stiffened plate with the size of 2200 mm×500 mm×10 mm,the identification accuracy of impact position and damage degree is 98.90% and 99.55% in 68 test areas,respectively.Comparative experiments with ELM and backpropagation neural networks(BPNN)demonstrate that the impact damage identification of aluminum alloy stiffened plate based on GWO-ELM algorithm can serve as an effective way to monitor spacecraft structural damage.展开更多
A segmentation multi-dimensional crest factor reduction （SMD-CFR） algorithm is proposed for multi-service supporting digital radio over fibre （DRoF） system. Benefit from segmentation dynamic clipping threshold and...A segmentation multi-dimensional crest factor reduction （SMD-CFR） algorithm is proposed for multi-service supporting digital radio over fibre （DRoF） system. Benefit from segmentation dynamic clipping threshold and clipping factor got basing on characteristics of all service bands, the SMD-CFR is able to get better peak clipping and peak to average power ratio （PAPR） reduction for multi-band combined signal. Simulation results show that SMD-CFR gets more than 2.3 reduction in PAPR for two-bands combined signal of long term evolution （LTE） , which is much better than traditional one dimensional （1D）-CFR. Meanwhile, for 64-quadrature amplitude modulation （QAM） modulation and demodulation link, it has very small effect on bit error rate （BER） and error vector magnitude （EVM） , which are controlled less than 0. 1% and 0.2% respectively. For hardware experiment, SMD-CFR obtains 4.5% increase in drain efficiency and about 4 dBc increase in adjacent channel leakage ratio （ACLR）. These are very significant for the wide band power amplifier （PA） in multi-service supporting DRoF system.展开更多
基金supported by National Key Research and Development Project(2020YFE0204900)National Natural Science Foundation of China(Grant Nos.61903224,62073193,61873333)Key Research and Development Plan of Shandong Province(Grant Nos.2019TSLH0301,2021CXGC010204).
文摘As a critical structure of aerospace equipment,aluminum alloy stiffened plate will influence the stability of spacecraft in orbit and the normal operation of the system.In this study,a GWO-ELM algorithm-based impact damage identification method is proposed for aluminum alloy stiffened panels to monitor and evaluate the damage condition of such stiffened panels of spacecraft.Firstly,together with numerical simulation,the experimental simulation to obtain the damage acoustic emission signals of aluminum alloy reinforced panels is performed,to establish the damage data.Subsequently,the amplitude-frequency characteristics of impact damage signals are extracted and put into an extreme learning machine(ELM)model to identify the impact location and damage degree,and the Gray Wolf Optimization(GWO)algorithm is employed to update the weight parameters of the model.Finally,experiments are conducted on the irregular aluminum alloy stiffened plate with the size of 2200 mm×500 mm×10 mm,the identification accuracy of impact position and damage degree is 98.90% and 99.55% in 68 test areas,respectively.Comparative experiments with ELM and backpropagation neural networks(BPNN)demonstrate that the impact damage identification of aluminum alloy stiffened plate based on GWO-ELM algorithm can serve as an effective way to monitor spacecraft structural damage.
基金supported by the projects of ‘Smart in-building Wireless System using Flexible Digital Transmission Technology(SWIFT)’‘Research on in-building Signal Coverage System of Mobile IOT Based on Cloud’
文摘A segmentation multi-dimensional crest factor reduction （SMD-CFR） algorithm is proposed for multi-service supporting digital radio over fibre （DRoF） system. Benefit from segmentation dynamic clipping threshold and clipping factor got basing on characteristics of all service bands, the SMD-CFR is able to get better peak clipping and peak to average power ratio （PAPR） reduction for multi-band combined signal. Simulation results show that SMD-CFR gets more than 2.3 reduction in PAPR for two-bands combined signal of long term evolution （LTE） , which is much better than traditional one dimensional （1D）-CFR. Meanwhile, for 64-quadrature amplitude modulation （QAM） modulation and demodulation link, it has very small effect on bit error rate （BER） and error vector magnitude （EVM） , which are controlled less than 0. 1% and 0.2% respectively. For hardware experiment, SMD-CFR obtains 4.5% increase in drain efficiency and about 4 dBc increase in adjacent channel leakage ratio （ACLR）. These are very significant for the wide band power amplifier （PA） in multi-service supporting DRoF system.
