Commutation Compensation Strategy for Brushless DC Motor Based on Terminal Voltage Reconstruction

Li Guidan,Zhang Tianqi,Li Bin,Fu Tongling,Duan Peihua 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4

In the sensorless brushless DC (BLDC) motor control system, the commutation signal is the key to measure the system performance. To improve the commutation accuracy, a commutation compensation strategy based on terminal voltage reconstruction is proposed. By analyzing the commutation process, the integral of ideal terminal voltage is adopted to determine the commutation error. Then considering the voltage clamping of the freewheel diode, the actual terminal voltage is analyzed in diff erent periods. In the non-commutation period, a PWM cycle is divided into three regions, and the corresponding duration can be calculated by fl oating phase current, and then the equality of actual and ideal terminal voltage integrals is revealed. In the commutation period, the instantaneous value of back-electromotive force (back-EMF) at commutation point is used to construct the ideal terminal voltage and the commutation time is determined by the edge detection. In this way, the integral of terminal voltage can be calculated precisely. Then the error index is introduced and the relationship between the commutation error and the error index is presented. To eliminate the commutation error, the PI controller is adopted which outputs the compensation angle. The proposed strategy avoids the phase shift errors and the accumulation of integral errors, moreover the feasibility and eff ectiveness are verifi ed by simulations and experiments under diff erent conditions. In addition, the strategy can also be used to correct the installation error of Hall sensor

Highly flame-retarding cotton fabrics with a novel phosphorus/nitrogen intumescent flame retardant

Peihua Zhao,Yaqing Liu,Xinhang Li,Mei Zhang,Shengnan Liu,Wenjun Liang 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.9

A novel phosphorus/nitrogen intumescent flame retardant, namely 6-chloro-4-(diethylamino phosphoratephosphoryl chloride)-2-(sodium 4-aminobenzensulfonate)-1,3,5-triazine (APPCABT), has been synthesized and charac-terized by elemental analysis, FT-IR,1H-NMR and31P{H}-NMR spectroscopies. To investigate the flame-retardingproperties of the treated cotton fabrics, APPCABT was applied to the chemical treatment of the cotton fabrics surface. The flame-retarding performance of the treated samples with APPCABT was evaluated by limiting oxygen index (LOI). The thermal degradation behavior of the treated samples was studied using thermogravimetric analysis (TGA). Thesurface morphology of the treated samples was observed by scanning electron microscopy (SEM). These results showthat APPCABT is both an intumescent flame retardant with high efficiency and an excellent char-forming agent forthe flame-retarding treatment of cotton fabrics.

Effect of Knitting Structure and Polyethylene Content on Thermalwet Comfort and Cooling Properties of Polyethylene/polyester Fabrics

Juan Qian,Ting Xie,Liqun Chen,Zhijiang Li,Ning Guo,Shaoju Fu,Peihua Zhang 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

Polyethylene is getting tremendous attention in personal thermal management textiles for summer, but there is lackof systematical coolness and thermal-wet comfort research in wearing knitting fabrics. In this work, two group of knittingstructure were designed following a sandwich structure model that consisted of a middle layer of multifilament and twoasymmetric outer layers. Nine bi-layer samples interknitted with polyester were fabricated with one face composed ofpolyester filaments and the other face built of polyethylene and polyester filaments. Textile parameters, such as knittingstructure, polyethylene fractions and distribution in the inner layer, yarn composition and relative porosity, were considered. Breathability, thermal transfer properties, moisture management performance and dynamic cooling performance wasmeasured and evaluated to investigate the thermal-wet and coolness relevant comfort properties of these fabrics. It was foundthat the fabrics knitted with tuck stitches have better air permeability, contact coolness, overall moisture management anddynamic cooling performance in comparison to the fabrics knitted with float stitches. The air permeability became better withthe increasing proportion of polyethylene and the decreasing ratio of tuck stitch. The effective contact area of polyethylenewith skin was beneficial to promote the transient thermal conductivity and dynamic cooling performance of fabric. The resultalso suggested that an asymmetric structure with meshes in the inner layer were beneficial to promote moisture management. Meanwhile, when the proportion of tuck stitch in inner layer was 6.25 %, the air permeability and heat transfer properties offabric were the best. Moreover, independent tests had proved that the performance of transient and steady thermalconductivity of polyethylene/polyester fabric was the best when the mass ratio of polyethylene was 49.3 % in this study.

Potato tillage method is associated with soil microbial communities, soil chemical properties, and potato yield

Ma Haiyan,Xie Chen,Zheng Shunlin,Li Peihua,Cheema Hafsa Nazir,Gong Jing,Xiang Zhuqing,Liu Juanjuan,Qin Jiahao 한국미생물학회 2022 The journal of microbiology Vol.60 No.2

Intensive potato continuous cropping (IPCC) results in low potato yields compared with non-intensive potato continuous cropping (PCC) and potato-maize rotation (PMRC). However, it is still unclear whether the degree of potato continuous cropping obstacle is related to the soil environment formed by the previous crop. To investigate the effect of planting potatoes and planting maize after harvesting the spring potatoes on soil chemical properties and soil microbial community structure, an experiment was carried out in the same origin soil environment over a period of seven years: (a) PCC, i.e., spring planting; (b) IPCC, i.e., autumn and spring planting (IPCC); (c) PMRC, i.e., spring potatoes and summer maize (PMRC), and (d) fallow (CK). We confirmed that the potato yield under PMRC was significantly higher than that under PCC and IPCC. Under IPCC, soil total phosphorus content was significantly higher than other treatments, whereas ammonium nitrogen content was the lowest. Compared with PCC and IPCC, PMRC had a higher ammonium nitrogen content and lower total phosphorus content. The significantly different fungal taxa in IPCC (Glomerellales, Plectosphaerella, Thelebolales) may threaten the health of the plant and positive correlated with soil total phosphorus, while other microbial taxa in PMRC (Bacillales, Polythrincium, Helotiales) can mainly promotes plant nitrogen uptake and protects plants against diseases. The PMRC-promoting taxa were positively correlated with the ammonium nitrogen content and negative correlated with soil total phosphorus content. In summary, the cropping systems might have affected potato yields by changed soil microorganism community structures – especially fungal community structures – and by the chemical properties of the soils that also depends on microbes.

Effect of Sc Content on the Microstructure and Properties of Al–Mg–Sc Alloys Deposited by Wire Arc Additive Manufacturing

Lingling Ren,Huimin Gu,Wei Wang,Shuai Wang,Chengde Li,Zhenbiao Wang,Yuchun Zhai,Peihua Ma 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.1

Despite showing considerable potential, wire arc additive manufacturing (WAAM) has been limited to producing Al–Mgalloys. As the addition of Sc can improve the mechanical properties of Al–Mg alloys, in this study, Al–Mg–Sc alloy depositswith different Sc contents were prepared by a WAAM process. The porosity, microstructure, and mechanical properties ofthe deposits were studied. At Sc contents less than 0.15%, Sc was completely dissolved in the Al matrix without grain refinement,and the mechanical properties were slightly improved. At a Sc content of 0.3%, the primary Al3Scphase precipitatedout of the as-deposited body, resulting in an abrupt change in the microstructure, significant grain refinement, significantlyincreased tensile strength and yield strength, with a tensile strength, yield strength, and elongation of 372 MPa, 270 MPa,and 22.5%, respectively. Following heat treatment at 350 °C for 1 h, the grain boundaries were refined and the secondaryAl3Scphase was precipitated. Furthermore, the tensile strength and yield strength were significantly increased to 415 MPaand 279 MPa, respectively, and elongation decreased to 18.5%. At a Sc content of 0.45%, due to the aggregated precipitatedphase, the coarsened grain boundaries and the limited solid solution amount of Sc in the α(Al) matrix (~ 0.25%), themechanical properties were not further improved compared with the deposit with Sc content of 0.3%. Thus, based on economicconsiderations, the optimal Sc content was 0.3%. Owing to their enhanced mechanical properties, WAAM-producedAl–Mg–Sc alloys are expected to have a wide range of applications in aviation, aerospace.