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Shichang Liu,Quanfeng Li,Xuanyu Hong,Yahui Zuo,Dingjiang Zou 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2
To effectively suppress the electromagnetic vibration generated by a permanent magnet motor at different frequency bands and to further improve the comprehensive control performance of the system, a new vector control strategy is proposed in this paper. The speed controller and current controller of the traditional vector control system of a permanent magnet synchronous motor (PMSM) are improved by means of an active disturbance rejection controller (ADRC) and a super-twisting sliding mode controller (STSMC). At the same time, random frequency space pulse width modulation (RFSVPWM) based on a periodic function is proposed to replace the traditional SVPWM. First, the expression of the radial electromagnetic force wave generated by motor supply current harmonics in low and medium frequency as well as high-frequency sideband is deduced by an analytical method, and the reason for the generation of the new radial electromagnetic force based on PI vector control is determined. Second, the ADRC, STSMC, and RFSVPWM are designed to suppress the power supply current harmonics and radial electromagnetic force components that greatly contribute to the electromagnetic vibration of the motor in different frequency bands. Finally, the superiority of the improved PMSM vector control system in terms of the comprehensive control performance and electromagnetic vibration is verified by multi-physics coupled finite element simulations.
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Lihua Li,Xuanyu Shen,Jiabei Liu,Wentao Li,Chuheng Zhong,Xinlong Zhou 대한토목학회 2023 KSCE JOURNAL OF CIVIL ENGINEERING Vol.27 No.2
For reusing the construction and demolition waste (C&DW) materials and solving waterloggingproblems, the feasibility of applying C&DW to the permeable pavement (PP) was investigated. The recycled brick aggregate (RBA) and recycled concrete aggregate (RCA) were used as PPbase materials under different mixing ratios and grades. Geotextiles were also used in thisstudy as filter contaminants. Modified compaction tests, rainfall model tests, and columnleaching tests were conducted on a total of 15 samples with three gradations and five RBA andRCA mix ratios. The specimens for the rainfall model test were compacted at around optimummoisture content, and the degree of compaction was 97%. Using the sub-layer compactionmethod, each group of samples is compacted in five layers in strict accordance with thespecifications. In general, C&DW has the potential to be used underground without pollutionto the groundwater. The heavy metal concentrations in C&DW are less than in the local soiland related to material resources. The water yield performance was the best when 100%concrete was used to build PP, and the total water storage was the most when 100% of brickswere chosen to make PP. Due to the excellent permeability, C&DW can be selected forpavement fillers. The geotextile reduces the permeability by about 13% but effectively filtersout more than 50% of the fine particles in the rainfall. The permeability performance ofconcrete aggregates may be better than that of bricks, and fine particles can reduce thepermeability.
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Topographic Evolution around Twin Piers in a Tandem Arrangement
Hao Wang,Hongwu Tang,Quanshuai Liu,Xuanyu Zhao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7
This laboratory study investigates the 2-D topographic evolution of a sand bed with cylindrical bridge piers arranged in tandem. The results of clear-water scouring experiments around two piers show that shapes of topography were similar for different spacing and scour duration. Fractal theory and statistical analysis were used to estimate the statistical properties of the evolution of the sandbed topography around the piers. The statistical properties of the bed surface contours remained almost stationary under continuing scouring action. Finally, the difference of local scour depth between two piers with scour time can be segregated into three regions: sheltering region, co-effect region and stabilizing region.
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