A multi-purpose control and power electronic architecture for active magnetic actuators

This paper shows the results related with the design and implementation of a multi-purpose electronic architecture used to drive magnetic actuators by means of a three-phase independent-legs module in place of the commonly used H-bridge modules. The typical application is the magnetic actuators drive used in active magnetic bearings. The architecture is composed of a control unit with a floating point Digital Signal Processor (DSP), a power board with six independent phase legs and a carrier board to interconnect them. When more than one module is required by the application, the communication between them is guaranteed by means of CAN bus interconnection. The proposed system allows to drive two pairs of opposite electromagnets, such as those typically used to control active magnetic bearings. The study is motivated by the opportunity of reducing the amount of power and control electronic components resulting in a more straightforward, efficient and cost reduction design

Bayesian multinomial probit modeling of daily windows of susceptibility for maternal PM2.5 exposure and congenital heart defects

Epidemiologic studies suggest that maternal ambient air pollution exposure during critical periods of pregnancy is associated with adverse effects on fetal development. In this work, we introduce new methodology for identifying critical periods of development during post-conception gestational weeks 2–8 where elevated exposure to particulate matter less than 2.5 µm (PM2.5) adversely impacts development of the heart. Past studies have focused on highly aggregated temporal levels of exposure during the pregnancy and have failed to account for anatomical similarities between the considered congenital heart defects. We introduce a multinomial probit model in the Bayesian setting that allows for joint identification of susceptible daily periods during pregnancy for 12 types of congenital heart defects with respect to maternal PM2.5 exposure. We apply the model to a dataset of mothers from the National Birth Defect Prevention Study where daily PM2.5 exposures from post-conception gestational weeks 2–8 are assigned using predictions from the downscaler pollution model. This approach is compared with two aggregated exposure models that define exposure as the average value over post-conception gestational weeks 2–8 and the average over individual weeks, respectively. Results suggest an association between increased PM2.5 exposure on post-conception gestational day 53 with the development of pulmonary valve stenosis and exposures during days 50 and 51 with tetralogy of Fallot. Significant associations are masked when using the aggregated exposure models. Simulation study results suggest that the findings are robust to multiple sources of error. The general form of the model allows for different exposures and health outcomes to be considered in future applications

Associations between PM2.5 and risk of preterm birth among liveborn infants

Purpose: Studies suggest exposure to ambient particulate matter less than 2.5 μg/m3 in aerodynamic diameter (PM2.5) may be associated with preterm birth (PTB), but few have evaluated how this is modified by ambient temperature. We investigated the relationship between PM2.5 exposure during pregnancy and PTB in infants without birth defects (1999–2006) and enrolled in the National Birth Defects Prevention Study and how it is modified by concurrent temperature. Methods: PTB was defined as spontaneous or iatrogenic delivery before 37 weeks. Exposure was assigned using inverse distance weighting with up to four monitors within 50 kilometers of maternal residence. To account for state-level variations, a Bayesian two-level hierarchal model was developed. Results: PTB was associated with PM2.5 during the third and fourth months of pregnancy (range: (odds ratio (95% confidence interval) = 1.00 (0.35, 2.15) to 1.49 (0.82, 2.68) and 1.31 (0.56, 2.91) to 1.62 (0.7, 3.32), respectively); no week of exposure conveyed greater risk. Temperature may modify this relationship; higher local average temperatures during pregnancy yielded stronger positive relationships between PM2.5 and PTB compared to nonstratified results. Conclusions: Results add to literature on associations between PM2.5 and PTB, underscoring the importance of considering co-exposures when estimating effects of PM2.5 exposure during pregnancy

Paternal genetic variants and risk of obstructive heart defects: A parent-of-origin approach

Previous research on risk factors for obstructive heart defects (OHDs) focused on maternal and infant genetic variants, prenatal environmental exposures, and their potential interaction effects. Less is known about the role of paternal genetic variants or environmental exposures and risk of OHDs. We examined parent-of-origin effects in transmission of alleles in the folate, homocysteine, or transsulfuration pathway genes on OHD occurrence in offspring. We used data on 569 families of liveborn infants with OHDs born between October 1997 and August 2008 from the National Birth Defects Prevention Study to conduct a family-based case-only study. Maternal, paternal, and infant DNA were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR), 95% confidence interval (CI), and likelihood ratio tests from log-linear models were used to estimate the parent-of-origin effect of 877 SNPs in 60 candidate genes in the folate, homocysteine, and transsulfuration pathways on the risk of OHDs. Bonferroni correction was applied for multiple testing. We identified 3 SNPs in the transsulfuration pathway and 1 SNP in the folate pathway that were statistically significant after Bonferroni correction. Among infants who inherited paternally-derived copies of the G allele for rs6812588 in the RFC1 gene, the G allele for rs1762430 in the MGMT gene, and the A allele for rs9296695 and rs4712023 in the GSTA3 gene, RRs for OHD were 0.11 (95% CI: 0.04, 0.29, P = 9.16x10-7), 0.30 (95% CI: 0.17, 0.53, P = 9.80x10-6), 0.34 (95% CI: 0.20, 0.57, P = 2.28x10-5), and 0.34 (95% CI: 0.20, 0.58, P = 3.77x10-5), respectively, compared to infants who inherited maternally-derived copies of the same alleles. We observed statistically significant decreased risk of OHDs among infants who inherited paternal gene variants involved in folate and transsulfuration pathways

Rotor on cone-shaped active magnetic bearings with three-phases power drivers

This paper presents the modeling, the control design and the experimental results obtained on a rotor suspended by means of cone-shaped active magnetic bearings controlled by an innovative three-phases drive technique. The machine reproduces a turbo-compressor group of a conditioning unit used in high performance jet aircrafts. The conical geometry of magnetic bearings allows to perform a compact design of actuation stage which is composed of only four pairs of electromagnets instead of five of conventional cylindrical solution, resulting of great interest for the application in small machines. The modeling phases of the system are illustrated along with the drive technique and control design procedure. The mechanical subsystem has been reproduced starting from the finite element (FE) model, reduced to its first bending modes. The electromechanical interaction has been modeled considering each electromagnet as a two-port element (electrical and mechanical) exerting a force expressed as function of displacement and current in equations linearized around the working point. The control design takes into account the axial and radial coupled actions of the actuators and performs a SISO decentralized technique with five PID filters. The overall system results to be compact in the actuation subsystem as well as in the power divers equipment, being this performed with an innovative technique based on a three-phases configuration to drive a couple of electromagnets instead of standard H-bridge configuration. The control and drive schemes are presented and the reference generation for power drivers switches is illustrated in details. This approach allows to save 25% of power electronics components and reduce losses on the switches although the design phases result quite more complex than classical solutions. The paper concludes on the exposition of experimental results aiming to validate and prove the correctness of drive technique and control design approache

Rotor on cone-shaped active magnetic bearings with three-phases power drivers

This paper presents the modeling, the control design and the experimental results obtained on a rotor suspended by means of cone-shaped active magnetic bearings controlled by an innovative three-phases drive technique. The machine reproduces a turbo-compressor group of a conditioning unit used in high performance jet aircrafts. The conical geometry of magnetic bearings allows to perform a compact design of actuation stage which is composed of only four pairs of electromagnets instead of five of conventional cylindrical solution, resulting of great interest for the application in small machines. The modeling phases of the system are illustrated along with the drive technique and control design procedure. The mechanical subsystem has been reproduced starting from the finite element (FE) model, reduced to its first bending modes. The electromechanical interaction has been modeled considering each electromagnet as a two-port element (electrical and mechanical) exerting a force expressed as function of displacement and current in equations linearized around the working point. The control design takes into account the axial and radial coupled actions of the actuators and performs a SISO decentralized technique with five PID filters. The overall system results to be compact in the actuation subsystem as well as in the power divers equipment, being this performed with an innovative technique based on a three-phases configuration to drive a couple of electromagnets instead of standard H-bridge configuration. The control and drive schemes are presented and the reference generation for power drivers switches is illustrated in details. This approach allows to save 25% of power electronics components and reduce losses on the switches although the design phases result quite more complex than classical solutions. The paper concludes on the exposition of experimental results aiming to validate and prove the correctness of drive technique and control design approaches