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The blind modulation recognition (BMR) of high-order modulation types is a pressing task and needs to be raised in the calendar for the Beyond 5G (B5G) OSTBC-OFDM (Orthogonal Space-Time Block Coded-Orthogonal Frequency Division Multiplexing) system. In this letter, a BMR algorithm based on a project constellation vector which employs a temporal convolutional network (PCV-TCNet) is proposed to recognize 13 modulation formats, such as high-order 1024QAM and 2048QAM. Without any prior information, a zero-forcing blind equalization algorithm is leveraged to reconstruct the impaired signal. Furthermore, the learning content of PCV-TCNet is PCV features, which are transformed by the constellation diagram of the reconstructed signal. In addition, PCV-TCNet utilizes causal and dilated convolutions to accelerate the BMR process. The simulation results verify the proposed PCV-TCNet for recognizing the high-order modulation types in the B5G OSTBC-OFDM system and demonstrate its preferable recognition performance with the lowest complexity to existing methods.

Inspired by the experimental realization of lattice-porous graphene and mesoporous MXenes, the possibility of lattice-penetrated porous titanium nitride, Ti12N8, was proposed and verified by density functional theory calculations.

K9 optical glass is one of the typical components in optical systems. However, because of its poor fracture resistance, it is difficult to polish it with ultra-precision and high-efficiency and without any surface damage simultaneously. The emergence of the obliquely axial ultrasonic vibration-assisted polishing (UVAP) method can solve this problem which encounters in polishing efficiency and shape accuracy. However, due to the unclear material removal profile (MRP) mechanism, obliquely axial UVAP is not widely used in the processing field. This paper introduces the obliquely axial UVAP method in research processes, mainly focusing on the fixed point MRP analysis of the obliquely axial UVAP. Based on Hertz's contact theory, polishing pressure, the length of the semi-long axis (LLA) and the length of the semi-short axis (LSA) of the contact area are calculated under ultrasonic vibration conditions. Meanwhile, the relative linear velocity distribution of the oblique polishing tool in the instantaneous contact area is modeled by mathematical geometry method. A novel model of the MRP distribution for obliquely axial UVAP is proposed following the Preston equation. Subsequently, a series of polishing experiments were carried out to verify this model. The results show that the numerical model has good agreement with the experimental results on MRP, LLA, LSA, material removal depth and material removal rate (MRR). In addition, the material removal capability can be significantly improved by larger ultrasonic amplitude and larger oblique angle. This model not only more clearly elucidates the processing mechanism of obliquely axial UVAP, but also provides theoretical support for the polishing of free-form optical lenses.

Brittle materials such as glass and ceramics have fragile physical properties that result in poor stability in the machining process. Ultrasonic vibration-assisted polishing (UVAP) can improve the surface quality and machining efficiency of the workpiece, which is beneficial to solve the machining problems of brittle materials. In this paper, a theoretical model is established to predict the material removal rate (MRR), surface roughness, maximum contact radius, and maximum material removal depth of BK7 optical glass for different machining parameters. The new model mainly considers the following aspects: (1) Considering the randomness of the shape, the abrasive particle is modeled as a truncated polyhedron. (2) Due to the randomness of distribution, the abrasive particles are considered to be randomly distributed in the contact area between the polishing tool and the workpiece. (3) Based on the Preston equation, a material removal model is established which considers the micro-contact state of the abrasive particles with the workpiece. Compared with the experimental results of BK7 optical glass, the new model has high accuracy in predicting machining performance. It is meaningful to understand the mechanism of UVAP and improve the machining efficiency.

Atmospheric plasma discharges are finding increased applications in addressing environmental challenges including water purification, chemical synthesis and biotechnology. An effective means of interfacing the reactivity of plasma gas discharges with liquids is needed to enhance liquid phase chemical reactions. Plasma discharges in bubbles has been considered as an innovative solution for achieving this goal potentially offering electrically driven, sustainable chemistry with low energy consumption and the unique benefit of maintaining a large volume discharge under the liquid surface. Here we provide a concise review on the state-of-art for research on plasma-bubble interactions and a perspective for future research.

Purpose Laser cladding has been used in the field of repairing damaged parts of machine tools due to its advantages of less processing restrictions and easy formation of a good metallurgical bond with the base material. However, the mechanical properties of the coating sometimes cannot meet the process requirements. Therefore, the purpose of this paper is to prepare coatings with high microhardness and flexural strength. Design/methodology/approach The YCF102 alloy powder was mixed with different contents of Co and tested for laser cladding on AISI 1045 substrate under the same process parameters. The main phase composition of the coating was revealed by the XRD results. The main chemical composition of the coating was determined by the SEM and EDS results. In addition, the effect of Co content on the microstructure, microhardness and flexural strength of the coatings was investigated. Findings The results show that when the Co content is 2 wt% and 4 wt%, Co does not form compounds with other elements, but is uniformly distributed in the coating. And when the Co content is 6 wt% and 8 wt%, the Co reacts with Fe in the coating and generates Co3Fe7 in situ. The increase in Co did not result in a monotonic change in microhardness, but significantly improved the flexural strength and the flatness of the microstructure of the coating. When the Co content of the mixed powder is 8 wt%, the coating has high microhardness and flexural strength. Originality/value Co/YCF102 composite coating with high microhardness and flexural strength was prepared. This paper provides a theoretical and practical basis for research in the area of repairing damaged parts of machine tools by laser cladding.

Branched polymers have found utility in an array of fields due to the high density of functional groups combined with unique physical properties. Despite the abundant methods reported to synthesize various branched structures, controlling parameters such as the location of branch points and molecular weight distribution still remains a challenge. This report explores the ability of enyne-containing branching agents to synthesize star and miktoarm star polymers through a convergent synthesis pathway using ring-opening metathesis polymerization (ROMP). The branching agents contain an enyne metathesis terminator covalently linked to a norbornene monomer. When these agents are introduced into a living ROMP, macromonomers are generated in situ that continue to propagate via a grafting-through process with the remaining living chains. This strategy permits control over the degree of polymerization of the star arms, control of the number of star arms, and chain-extension with additional monomer to produce functional asymmetric miktoarm star polymers.

The stochastic resonance behavior of coupled stochastic resonance (SR) system with time-delay under mass and frequency fluctuations was studied. Firstly, the approximate system model of the time-delay system was obtained by the theory of small time-delay approximation. Then, the random average method and Shapiro-Loginov algorithm were used to calculate the output amplitude ratio of the two subsystems. The simulation analysis shows that increasing the time-delay and the input signal amplitude appropriately can improve the output response of the system. Finally, the system is applied to bearing fault diagnosis and compared with the stochastic resonance system with random mass and random frequency. The experimental results show that the coupled SR system taking into account the actual effect of time-delay and couple can more effectively extract the frequency of the fault signal, and thus realizing the diagnosis of the fault signal, which has important engineering application value.

Reversed-phase liquid chromatographic mass spectrometry (rpLC-MS) is a universal, platformed, and essential analytical technique within pharmaceutical and biopharmaceutical research. Typical rpLC method gradient times can range from 5 to 20 min. As monoclonal antibody (mAb) therapies continue to evolve and bispecific antibodies (BsAbs) become more established, research stage engineering panels will clearly evolve in size. Therefore, high-throughput (HT) MS and automated deconvolution methods are key for success. Additionally, newer therapeutics such as bispecific T-cell engagers and nucleic acid-based modalities will also require MS characterization. Herein, we present a modality and target agnostic HT solid-phase extraction (SPE) MS method that affords the analysis of a 96-well plate in 41.4 min, compared to the traditional rpLC-MS method that would typically take 14.4 h. The described method can accurately determine the molecular weights for monodispersed and highly polydispersed biotherapeutic species and membrane proteins; determine levels of glycosylation, glycation, and formylation; detect levels of chain mispairing; and determine accurate drug-to-antibody ratio values.

Gliomas are common and refractory primary tumors closely associated with the fine structures of the brain. Photothermal therapy (PTT) has recently shown promise as an effective treatment for gliomas. However, nonspecific accumulation of photothermal agents may affect adjacent normal brain structures, and the inflammatory response induced during PTT may result in an increased risk of brain tumor recurrence or metastasis. Here, the design and fabrication of an intelligent nanomachine is reported based on Gd

Astaxanthin is used extensively in the nutraceutical, aquaculture, and cosmetic industries. The current market necessitates higher astaxanthin production from Phaffia rhodozyma (P. rhodozyma) due to its higher cost compared to chemical synthesis. In this study, a bubble discharge reactor was developed to generate plasma-activated water (PAW) to produce PAW-made yeast malt (YM) medium. Due to oxidative stress induced by PAW, strains cultured in 15 and 30 min-treated PAW-made medium produced 7.9 ± 1.2 % and 12.6 ± 1.4 % more carotenoids with 15.5 ± 3.3 % and 22.1 ± 1.3 % more astaxanthin, respectively. Reactive oxygen species (ROS) assay results showed that ROS generated by plasma-water interactions elevated intracellular ROS levels. Proteomic analysis revealed increased expression of proteins involved in the cellular response to oxidative stress as well as carotenoid biosynthesis, both of which contribute to higher yields of astaxanthin. Overall, this study supports the potential of PAW to increase astaxanthin yields for industrial-scale production.

Methotrexate (MTX) and iguratimod (IGU) are conventional synthetic disease modifying antirheumatic drugs widely used in the treatment of Rheumatoid arthritis (RA) in China. Although MTX combined with IGU can significantly inhibit the progression of RA, some patients do not respond to the treatment. The purpose of this study is to explore the difference of serum protein expression between RA patients with good and poor response to the combined therapy by label-free quantitative proteomic approach. From the proteomics data, a total of 782 proteins in the serum of RA patients were detected, and of which 9 were upregulated and 18 were downregulated in the good response group compared to poor response group. Among them, four significantly differentially expressed proteins (RELN, LDHA, MRC1 and TKT) were further validated by multiple reaction monitoring (MRM)-based quantification approach, and three of them (RELN, LDHA and MRC1) were confirmed to be correlated with the response to MTX/IGU therapy. Logistic regression and ROC analysis indicated that the combination of RELN, LDHA and MRC1 had good performance in evaluating the response. This result proved the different serum proteins signature fingerprint between response group and non-response group; and highlighted the potential of the label-free and mass spectrometry-based quantitative proteomic approach in screening biomarkers for evaluating clinical response to MTX/IGU therapy in RA.

Osteoblasts play a key role in bone remodeling. Recent studies have reported that some hypertrophic chondrocytes co-expressing collagen I(Col I) and collagen X (ColX) could directly transdifferentiate into osteoblasts during endochondral ossification. However, whether nutrition intervention is beneficial to this transformation to improve osteoporosis (OP) remains unknown. In this study, ovariectomy (OVX)-induced OP mice were orally administered with docosahexaenoic acid (DHA) in different molecular forms for 13 weeks. The results showed that both DHA-triglyceride (DHA-TG) and DHA-phosphatidylcholine (DHA-PC) increased the bone mineral density and bone mineral apposition rate in ovariectomized mice, while DHA-ethyl esters (DHA-EE) had little effect. Interestingly, we found that both DHA-PC and DHA-TG increased the height of the growth plate, mainly increasing the number of hypertrophic chondrocytes. Further investigation by simultaneously labeling ColX and ColI indicated that DHA-PC and DHA-TG promoted the number of chondrocyte-transdifferentiated osteoblasts in the growth plate close to the diaphysis, in which DHA-PC performed better than DHA-TG. Apoptosis was not the only fate of hypertrophic chondrocytes. Western blot results showed that both DHA-TG and DHA-PC downregulated the Bax and cleaved-caspase3 expression and upregulated Bcl-2 expression in the growth plate, suggesting that chondrocyte apoptosis is inhibited. Runx2, the key regulator of chondrocyte-to-osteoblast transdifferentiation, was significantly increased by DHA-TG and DHA-PC, while DHA-EE had no effect on the above indicators. To our best knowledge, this is the first report that both DHA-PC and DHA-TG enhanced bone formation via promoting the chondrocyte-to-osteoblast transdifferentiation in the growth plate, contributing to the amelioration of OP. These activities depend on the molecular forms of DHA and their bioavailabilities. Our results provide guidance for the application of fish oil for bone health.

With the utilization of underground space, backward erosion piping (BEP) has been observed in many underground structures. Different from BEP in embankments or river dikes, the BEP in underground structures is usually triggered by a sudden flow of water and persists in a “progression phase,” in which the piping process can always reach an equilibrium before higher hydraulic loads are employed. In this study, the progression of BEP with sudden and gradual hydraulic loads was investigated using a radial Hele-Shaw cell. The test results indicated that the progression of BEP could be strongly influenced by the hydraulic loading speed. Once a faster hydraulic loading method was employed, the erodible medium could organize itself and show a greater resistance to erosion; additionally, the erosion pattern could be more uniform. These findings were included in a discussion of the erosion mechanism.

Surface functionalization or modification to introduce more oxygen-containing functional groups to biochar is an effective strategy for tuning the physico-chemical properties and promoting follow-up applications. In this study, non-thermal plasma was applied for biochar surface carving before being used in contaminant removal and energy storage applications. The results showed that even a low dose of plasma exposure could introduce a high number density of oxygen-functional groups and enhance the hydrophilicity and metal affinity of the pristine biochar. The plasma-treated biochar enabled a faster metal-adsorption rate and a 40% higher maximum adsorption capacity of heavy metal ion Pb2+. Moreover, to add more functionality to biochar surface, biochar with and without plasma pre-treatment was activated by KOH at a temperature of 800 °C. Using the same amount of KOH, the plasma treatment resulted in an activated carbon product with the larger BET surface area and pore volume. The performance of the treated activated carbon as a supercapacitor electrode was also substantially improved by > 30%. This study may provide guidelines for enhancing the surface functionality and application performances of biochar using non-thermal-based techniques.

Optical glass BK7 is widely used in optical lenses. It is a kind of hard and brittle material and thus difficult to machine. To solve the problems it has encountered in terms of polishing efficiency and quality, the axial ultrasonic vibration assisted polishing (UVAP) method is adopted in this study. A mathematical-prediction-model, firstly considering the effects of periodically changing pressure caused by ultrasonic vibration, is developed to predict the generated surface-profile. And for the first time, the concept of “Preston-coefficient distribution-function” is proposed to describe the effect of the abrasive-particle distribution on material-removal distribution-function. A series UVAP experiments on optical glass BK7 at different polishing parameters are conducted to validate the polishing efficiency and feasibility of the developed prediction model and proposed concept. The results confirm that UVAP method can realize a higher material removal rate (MRR) and a better surface quality. Compared to conventional method, the predictions are in good agreement with the experiments. The comparison of the obtained surface profiles proves the benefits of ultrasonic vibration as well. Moreover, the research results can be used to guide the adjustment of polishing parameters for deterministic material removal in straight feeding process of UVAP, and provide a valuable basis for trajectory planning of the global polishing of workpiece surfaces.

In terms of the traditional dynamic vibration absorber (DVA), the vibration damping effect improves with the mass ratio of DVA increasing, and the vibration level of target system is effectively controlled in the case that the mass ratio of DVA is large. This characteristic restricts the application of DVA to the track because of the limited available space. This study proposes one type of DVA with negative stiffness (NSDVA) applied to floating slab track to reduce the track vibration under the condition of small mass ratio and presents a design methodology of NSDVA attached on flexible system. Firstly, the mechanical model of floating slab with NSDVA is simplified to a two-degree-of-freedom system, and theoretical expressions of NSDVA’s optimal parameters, i.e., ratio of frequency, damping and stiffness are deduced according to the fixed-point expansion theory and stability condition. Secondly, with the combination of the multi-modal control theory and the finite element method, optimal parameters of NSDVA applied to a multi-degree of freedom (MDOF) system are calculated. 3-D finite element model of floating slab-NSDVA is built in ABAQUS software, and the modal analysis of floating slab is conducted to determine the target modal and equivalent mass. Compared with the traditional Voigt type DVA, the NSDVA adopted in this paper is proved to be more effective to reduce the both floating slab and rail vibration level. The design methodology of NSDVA attached to a MDOF system presented in this paper is feasible.

Graph convolutional networks (GCNs) have shown success in many graph-based applications as they can combine node features and graph topology to obtain expressive embeddings. While there exist numerous GCN variants, a typical graph convolution layer uses neighborhood aggregation and fully-connected (FC) layers to extract topological and node-wise features, respectively. However, when the receptive field of GCNs becomes larger, the tight coupling between the number of neighborhood aggregation and FC layers can increase the risk of over-fitting. Also, the FC layer between two successive aggregation operations will mix and pollute features in different channels, bringing noise and making node features hard to converge at each channel. In this article, we explore graph convolution without FC layers. We propose scale graph convolution, a new graph convolution using channel-wise scale transformation to extract node features. We provide empirical evidence that our new method has lower over-fitting risk and needs fewer layers to converge. We show from both theoretical and empirical perspectives that models with scale graph convolution have lower computational and memory costs than traditional GCN models. Experimental results on various datasets show that our method can achieve state-of-the-art results, in a cost-effective fashion.

Smart security is needed for complex scenarios such as all-weather and multi-scene environments, and visible–infrared person re-identification (VI Re-ID) has become a key technique in this field. VI Re-ID is usually modeled as a pattern recognition issue, which faces the problems of inter-modality and intra-modality discrepancies. To alleviate these problems, we designed the Local Features Leading Global Features Network (LoLeG-Net), a representation learning network. Specifically, for cross-modality discrepancies, we employed a combination of ResNet50 and non-local attention blocks to obtain the modality-shareable features and convert the problem to a single-modality person re-identification (Re-ID) problem. For intra-modality variations, we designed global feature constraints led by local features. In this method, the identity loss and hetero-center loss were employed to alleviate intra-modality variations of local features. Additionally, hard sample mining triplet loss combined with identity loss was used, ensuring the effectiveness of global features. With this method, the final extracted global features were much more robust against the background environment, pose differences, occlusion and other noise. The experiments demonstrate that LoLeG-Net is superior to existing works. The result for SYSU-MM01 was Rank-1/mAP 51.40%/51.41%, and the result for RegDB was Rank-1/mAP 76.58%/73.36%.

Structural inherent dynamic characteristics would change when damage occurs, and this fact is the theoretical basis of damage detection method based on vibration features. As one of structural inherent properties, frequency response function (FRF) contains rich information and has more potential in damage detection. On the basis of crack detection researches, a new method based on the change of FRF is proposed in this paper. First, the single-degree-of-freedom (SDOF) system is used to illustrated the change of dynamic features caused by cracks represented by changing stiffness, and it is found that the change of stiffness leads to the obvious nonlinear variation of frequency response function curvature (FRFC) and frequency response function curvature differentiation (FRFCD) near the natural frequency. To describe this phenomenon, the Pearson correlation coefficient is employed to analyze correlation relationship of FRF, FRFC and FRFCD between the undamaged and the damaged system. The results demonstrate that absolute values of these coefficients approach from 1 to 0 with the increase of stiffness change. The rail with cracks is taken as the research object, and relationships between the crack size and the correlation coefficients of FRF, FRFC and FRFCD are investigated through the combination of finite element simulation and frequency response experiment. The correlation coefficients of FRF, FRFC and FRFCD are close to 1 when the structure is intact. When cracks occur, the absolute value of the correlation coefficient will gradually trend from 1 to 0, and the sensitivity of FRFCD correlation coefficient to crack is much higher than that of FRF and FRFC. The selection of calculated frequency bands containing different modes and the damping of the structure would affect the absolute value of FRFCD correlation coefficient, but will not change the characteristics of high sensitivity of FRFCD and the relationship between the coefficient and crack size. Besides, noise signals would enhance the nonlinear relationship between responses of intact structure and the structure with cracks, and the FRFCD correlation coefficient value is influenced accordingly.

Cadmium (Cd) is a toxic heavy element for plant growth and development, plants have evolved many strategies to cope with Cd stress. However, the mechanisms how plants sense Cd stress and regulate the function of transporters remain very rudimentary. Here, we found that Cd stress induces obvious Ca

Accurate diagnosis and highly effective treatment of glioblastoma are still challenges in clinic. Near-infrared (NIR) light triggered fluorescence imaging and photodynamic therapy (PDT) showed the potential for theranostics of glioblastoma, but the presence of blood-brain barrier (BBB) and hypoxia limited treatment effect. Herein, the novel theranostic nanoagents with YOF:Nd

Light attenuation in large scale neutrino detectors like Theia is an important concern. Theia plans to use Water Based Liquid Scintillator as its detecting medium. At UC Davis, we develop a Scattering and Attenuation Measuring Device(SAMD) to measure light attenuation as well as the scattering parameters of the WBLS. The poster will present the initial pure water attenuation result to show the reliability of the system. A future update plan of light attenuation and scattering in WBLS will be discussed as well.

Due to the shortage of radio spectrum in the current 5G and upcoming 6G systems, the cognitive radio (CR) technique is indispensable for spectrum management and can put the unutilized spectrum to good use. As the core technology of CR, blind modulation recognition (BMR) plays a pivotal role in improving spectral efficiency. However, the BMR research on MIMO-OFDM systems still lacks enough attention. Given the prosperity of deep learning, we propose a series-constellation multi-modal feature network (SC-MFNet) to recognize the modulation types of MIMO-OFDM subcarriers. Without any prior information, a blind signal separation algorithm is employed to reconstruct the impaired transmitted signal. Considering the insufficient features of signal series, we propose a segment accumulated constellation diagram (SACD) strategy to produce the striking constellation features. Moreover, the proposed multi-modal feature fusion network is employed to collect the advantages of series and SACD features, which are extracted by one-dimensional convolution (Conv1DNet) branch and improved EfficientNet branch, respectively. Experimental results demonstrate that in a realistic non-cooperative cognitive communication scenario where prior information is exempted, the proposed SC-MFNet outperforms the traditional feature-based methods and the state-of-the-art neural networks which are based on either constellation features or series features.

To investigate the influencing factors of transcatheter arterial chemoembolization (TACE) on patients with hepatocellular carcinoma (HCC) for tumor response (complete and partial response, CR + PR).This research conducted a retrospective study of the hospital charts of patients treated with TACE successfully renewed from October 2014 to December 2015 at Sun Yat-sen University Cancer Center (Guangzhou, China). Univariate analysis (Chi-square test and repeated-measures ANOVA) selected nine influential tumor response factors from 22 core factors. The nine variables were included in a forward multiple logistic regression model predicting patients treated with TACE to achieve tumor response. Overall survival was calculated using the Kaplan-Meier method.Data of 277 of 282 patients were included in the analysis. Nine variables were analyzed by univariate analysis and independently associated with tumor response (tumor capsule integrity, nausea and vomiting, microwave ablation, liver dysfunction, the absolute value of lymphocyte (LYM), alpha-fetoprotein, and gamma-glutamyl transpeptidase (GGT). By multivariate analysis, GGT (odds ratio [OR] =0.996), liver dysfunction (OR = 0.395), combined with microwave ablation (OR = 0.503), and tumor capsule integrity (OR = 1.894) were the significant predictors of the tumor response group compared with the standard deviation group (P0.05).This study suggests that TACE combined with ablation on patients with complete tumor capsules may have a better prognosis in tumor response and OS; additionally, liver dysfunction and nausea and vomiting were the independent predictors of tumor response.

The aim of this study was to compare the safety and efficacy of radiofrequency ablation (RFA) with microwave ablation (MWA) for hepatocellular carcinoma (HCC) within the Milan criteria in challenging locations. This study retrospectively investigated 201 consecutive patients with Milan criteria HCCs who underwent RFA (RFA group, n = 150) or MWA (MWA group, n = 51) between January 2012 and December 2016. Overall survival (OS), recurrence-free survival (RFS), local tumor control, and treatment-related complications were compared between the two groups. Prognostic factors were analyzed using the Cox proportional hazard regression model. Median follow-up duration was 36.7 months (range: 6.2–64.0 months). Cumulative 1-, 3-, and 5-year OS rates were 97.9%, 92.3%, and 80.6% in the MWA group and 96.4%, 87.4%, and 78.2% in the RFA group, respectively, (P = 0.450). Cumulative RFS rates at 1, 3, and 5 years were 93.2%, 74.4%, and 63.7% in the MWA group and 80.3%, 57.3%, and 49.6% in the RFA group, respectively, (P = 0.097). Multivariate analyses showed that variable categories “patient age above 65 years” (P = 0.004) and “more than one tumor” (P = 0.004) were associated with overall mortality, and “patient age above 65 years” (P = 0.048) and “tumor size greater than 3 cm” (P = 0.009) were associated with inferior RFS. The incidences of major complications were not significantly different between the two groups (3.3% vs 3.9%, P = 0.843). RFA and MWA were associated with comparable safety and efficacy for HCC within the Milan criteria in challenging locations. Further study in a large, multi-center patient cohort is necessary to validate the results.

Ni204 cladding layers were prepared on the surface of 45# steel alloys via laser cladding under different overlap modes. The effects of overlap modes on microstructure evolution, microhardness, wea...

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 different periods. In the non-commutation period, a PWM cycle is divided into three regions, and the corresponding duration can be calculated by floating 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 effectiveness are verified by simulations and experiments under different conditions. In addition, the strategy can also be used to correct the installation error of Hall sensor.