20 research outputs found
PWM-based Flux linkage estimation for permanent magnet synchronous machines
Monitoring of rotor temperature in permanent magnet
synchronous machines (PMSM) is of great importance as high
temperature could cause partial or even irreversible
demagnetization of the permanent magnets. Rotor temperature
measurement unfortunately is particularly difficult in practice,
since it is difficult to access temperature sensors on a rotating
shaft. Nevertheless, rotor temperature can be obtained
indirectly with the information of rotor magnet flux linkage, as
permanent magnet (PM) remanence decreases with rotor
temperature. In this paper, a simple and relatively accurate
method for online estimation of PM flux linkage is presented,
based on the measurement of current response to the standard
space-vector pulse width modulation (SV-PWM). This method
uses the already-existing PWM voltage as the excitation signal
in order to avoid any form of signal injection which produces
undesirable disturbance to the system. Knowledge of machine
parameters, such as inductances which may vary due to
saturation, is not required. The proposed methodology has been
verified in real-time simulation
Improved Fusion of Permanent Magnet Temperature Estimation Techniques for Synchronous Motors Using a Kalman Filter
In this paper, a new temperature observer topology is presented which overcomes the shortcomings of previous ones and achieves a higher accuracy, and a more robust disturbance rejection. It makes use of the Gopinath-style flux observer and combines a lumped-parameter thermal network operating at low speeds and a flux-based permanent magnet temperature observer operating at medium and high speeds. Simulation and experimental results on a 50 kW permanent magnet motor show a performance enhancement over standard topologies; particularly, a superior disturbance rejection to voltage estimation errors. A detailed analysis of the optimal controller tuning is also presented. Furthermore, a Kalman filter is incorporated to account for sensor noise and model uncertainties. Experimental results show an effective fusion of independent temperature estimation methods leading to a superior accuracy compared to the previously investigated approaches. Moreover, the Kalman filter-based fusion offers the capability of detecting temperature-related system failures, e.g., cooling circuit malfunctions
Vitamin A-Retinoic Acid Signaling Regulates Hematopoietic Stem Cell Dormancy
Dormant hematopoietic stem cells (dHSCs) are atop the hematopoietic hierarchy. The molecular identity of dHSCs and the mechanisms regulating their maintenance or exit from dormancy remain uncertain. Here, we use single-cell RNA sequencing (RNA-seq) analysis to show that the transition from dormancy toward cell-cycle entry is a continuous developmental path associated with upregulation of biosynthetic processes rather than a stepwise progression. In addition, low Myc levels and high expression of a retinoic acid program are characteristic for dHSCs. To follow the behavior of dHSCs in situ, a Gprc5c-controlled reporter mouse was established. Treatment with all-trans retinoic acid antagonizes stress-induced activation of dHSCs by restricting protein translation and levels of reactive oxygen species (ROS) and Myc. Mice maintained on a vitamin A-free diet lose HSCs and show a disrupted re-entry into dormancy after exposure to inflammatory stress stimuli. Our results highlight the impact of dietary vitamin A on the regulation of cell-cycle-mediated stem cell plasticity. VIDEO ABSTRACT
How nutrition and the maternal microbiota shape the neonatal immune system.
The mucosal surfaces of mammals are densely colonized with microorganisms that are commonly referred to as the commensal microbiota. It is believed that the fetus in utero is sterile and that colonization with microorganisms starts only after birth. Nevertheless, the unborn fetus is exposed to a multitude of metabolites that originate from the commensal microbiota of the mother that reach systemic sites of the maternal body. The intestinal microbiota is strongly personalized and influenced by environmental factors, including nutrition. Members of the maternal microbiota can metabolize dietary components, pharmaceuticals and toxins, which can subsequently be passed to the developing fetus or the breast-feeding neonate. In this Review, we discuss the complex interplay between nutrition, the maternal microbiota and ingested chemicals, and summarize their effects on immunity in the offspring
Neural G0: a quiescentâlike state found in neuroepithelialâderived cells and glioma
Singleâcell RNA sequencing has emerged as a powerful tool for resolving cellular states associated with normal and maligned developmental processes. Here, we used scRNAâseq to examine the cell cycle states of expanding human neural stem cells (hNSCs). From these data, we constructed a cell cycle classifier that identifies traditional cell cycle phases and a putative quiescentâlike state in neuroepithelialâderived cell types during mammalian neurogenesis and in gliomas. The Neural G0 markers are enriched with quiescent NSC genes and other neurodevelopmental markers found in nonâdividing neural progenitors. Putative glioblastoma stemâlike cells were significantly enriched in the Neural G0 cell population. Neural G0 cell populations and gene expression are significantly associated with less aggressive tumors and extended patient survival for gliomas. Genetic screens to identify modulators of Neural G0 revealed that knockout of genes associated with the Hippo/Yap and p53 pathways diminished Neural G0 in vitro, resulting in faster G1 transit, downâregulation of quiescenceâassociated markers, and loss of Neural G0 gene expression. Thus, Neural G0 represents a dynamic quiescentâlike state found in neuroepithelialâderived cells and gliomas