This article proposes an enhanced version of the deadbeat flux vector controller (DBFC) as a one single control law that can operate in the entire torque-speed plane. The operation at any feasible ...modulation index can be accomplished by adequate determination of the flux trajectories at the different operating regions (e.g., PWM, overmodulation (I and II), and six-step). Continuous and seamless transition between the four operating regions is guaranteed, where the modulation index changes linearly with speed between PWM and six-step (without abrupt change in torque or acoustic problems). With the proposed strategy, undesirable torque dynamics, stability problems, and increased computational efforts associated with using multiple control laws are avoided. The transient performance of DBFC at the maximum voltage limit is analyzed in detail in the flux plane. A time-optimal torque control algorithm is developed to achieve the fastest possible torque dynamics and to considerably reduce the settling time, without the use of a voltage margin. The torque can be controlled with high accuracy and high robustness to machine parameter variations. With DBFC, no tradeoff between good steady state six-step behavior and good transient performance is needed due to the decoupling of switching and calculation frequencies. The proposed DBFC controller offers valuable features, and it is simple to implement. Simulation and experimental results are provided to validate the proposed control algorithm, which is implemented on an automotive microcontroller with a high-power/high-performance automotive traction machine.
Through a combination of flux and current observers, deadbeat-direct torque and flux control for interior permanent magnet synchronous machines has preferred features comparing to the existing ...current vector control (CVC). These include simpler flux weakening control, less parameter sensitivity with increasing speed due to the Gopinath-style flux observer and evading of anti-windup strategies at the inverter voltage limit. The operation throughout the entire torque-speed range can be accomplished with a single control law. For the second flux weakening region, the algorithm inherently achieves the maximum torque per flux (MTPF) operation by applying the square-root-condition (SRC). In contrast to CVC, no look-up-table nor solving the parameter-dependent MTPF equation is required. In this article, the equivalence of the SRC method to the conventional MTPF strategy is demonstrated analytically, graphically, in simulation, and through experimental results without any stability problems. A sensitivity analysis regarding the machine parameters and iron losses compares and evaluates both methods. Superior performance of the SRC algorithm compared to the conventional method is proven.
For traction drives, the operation in the overmodulation and six-step regions is crucial to increase the torque-speed range and the drive's efficiency. Deadbeat flux-control (DBFC) shows superior ...dynamic performance as compared to current-vector-controllers in these regions. In this paper, an overmodulation strategy for DBFC is presented. This technique, named minimum flux-phase error (MFPE), permits a smooth transition from the linear to the six-step regions. Consequently, abrupt changes of the modulation index are prevented which results in smoother transients and a closer operation to the maximum-torque-per-ampere (MTPA) line. DBFC can be combined with DB-DTFC (deadbeat direct torque and flux control) to ensure controllability throughout the entire torque-speed range. The complete control strategy is shown in this paper. Results from a 300kW IPMSM hardware-in-the-loop (HiL) testbench are shown to validate the strategy. Challenging caveats of the method are also discussed.
Six-step operation of interior permanent magnet synchronous machines (IPMSMs) has many advantages such as the full utilization of the DC-link voltage and the minimization of the switching losses. ...Deadbeat Flux Control (DBFC) is a control strategy designed to achieve overmodulation and six-step operation with competent dynamic performance. This paper presents an upgraded implementation of the DBFC controller. One unique control law can operate in the entire torque-speed plane with a simple methodology for continuous and smooth transition between the four different operating regions (i.e., linear, overmodulation I, overmodulation II, and six-step), and under voltage and current limitations. Combining multiple controllers and switching between different control laws is completely avoided. This paper presents an approach for closed-loop torque regulation that has high dynamic performance, high accuracy, and is robust against parameter variations. The proposed controller is evaluated in simulation and experimentally. It is implemented on an automotive microcontroller for a 300 kW IPMSM traction drive.
Accurate flux linkage estimation is essential for Direct Torque and Flux Control (DTFC) of interior permanent magnet synchronous machines (IPMSMs). For this, a discrete-time Gopinath flux observer is ...used by combining the current and voltage models of the IPMSM. The factors affecting the flux estimation accuracy such as inverter nonlinearities, iron loss, discretization errors, and encoder offset-angle are analyzed in this paper with simulation and experimental results. Usually, the accuracy of the flux observer is evaluated by comparing the estimated and measured torques. However, this method is unreliable. Hence, this paper presents the Square-Root-Condition (SRC) as a more reliable and precise methodology to tune the flux observer and determine the flux estimation accuracy without measuring the flux or the voltage. SRC is an extension to Deadbeat-Direct Torque and Flux Control (DB-DTFC) that calculates the Maximum Torque per Flux (MTPF) solution based on the estimated flux. SRC does not rely on pre-calculated data or solving the parameter-dependent MTPF equation. Moreover, it has a minimum sensitivity to machine parameters.
Deadbeat-control is a well-established control technique that uses the inverse machine model to determine the voltage commands required to achieve the desired torque and flux commands. Its classic ...implementation requires solving a quadratic equation with an extensive number of terms. Moreover, it can be only solved in the dq-reference frame. In this paper, two novel implementations are presented. The first methodology, in the dq-reference frame, reduces the algorithm's complexity and computation time. Moreover, it is immune to estimation errors of the permanent magnet flux. A second methodology based on the flux vector orientation is also presented. As opposed to the classic implementation, the proposed method does not require solving a quadratic equation; this reduces its complexity and computation time. Furthermore, the proposed methodology can be solved both in the dq and αβ frames since it relies only on the stator flux's magnitude and angle. Up to date and to the best of the author's knowledge, DB-DTFC in the stationary frame has not been presented before for salient machines. DB-DTFC in the stationary frame reduces the reliance on the position observer and facilitates the implementation of overmodulation techniques and six-step operation. The proposed methodology can operate in the MTPF line without any adjustments and it shows an adequate dynamic performance. Simulation and experimental results validate the methodologies. Caveats regarding their implementation are also discussed.
Through a combination of flux and current observers, Deadbeat-Direct Torque and Flux Control (DB-DTFC) for Interior Permanent Magnet Synchronous Machines (IPMSMs) has preferred features comparing to ...the existing Current Vector Control (CVC). These include simpler flux weakening control, less parameter sensitivity with increasing speed due to the Gopinath-style flux observer and evading of anti-windup strategies at the inverter voltage limit. The operation throughout the entire torque speed range can be accomplished with a single control law. For the second flux weakening region, the algorithm inherently achieves the Maximum Torque per Flux (MTPF) operation by applying the Square-Root-Condition (SRC). In contrast to CVC, no Look-Up-Table (LUT) nor solving the parameter-dependent MTPF equation is required. The equivalence of the SRC method to the conventional MTPF strategy is demonstrated analytically, in simulation and through experimental results. A parameter sensitivity analysis compares and evaluates both methods. Superior performance of the SRC algorithm compared to the conventional method is proven.
A huge-amount of citrus by-products is being wasted every-year. There is a high-need to utilize these by-products with high-efficiency. This study focuses on the essential oil (EO) isolation from the ...zest of Citrus sinensis (CS) by-products, using a novel dual-function gas-chromatography mass-spectrometry optimized ultrasound-assisted hydrodistillation-prototype (DF-GC/MS-HUS). The CS-EO was GC-analyzed by MS-detector (GC/MS) and optimized by flame-ionization detector (GC/FID). Ultrasound-assisted hydrodistillation (HUS) had a dual-function in CS-EO isolation by utilizing an adequate-energy to break-open the oil-containing glands, and by functioning-as a dispersing-agent to emulsify the organic-phase. The most effective DF-GC/MS-HUS optimized-conditions were isolation under 38 °C and 10 min of 28.9 Hz sonication. The main-components of CS-EO were limonene, β-myrcene, and α-pinene (81.32%, 7.55%, and 4.20%) in prototype, compared to (60.23%, 5.33%, and 2.10%) in the conventional-method, respectively. The prototype CS-EO showed natural antibacterial-potentials, and inhibited the bio-film formation by Staphylococcus aureus, Listeria monocytogenes, and E. coli more-potent than the conventional-method. Compared to conventional-method, the prototype-method decreased the isolation-time by 83.3%, lowered energy-consumption, without carbon-dioxide production, by reducing isolation-temperatures by more-than half, which protected the thermolabile-components, and increased the quantity by 2514-folds, and improved the quality of CE-EO composition and its antibacterial-potentials. Therefore, the DF-GC/MS-HUS prototype method is considered a novel green-technique that minimized the energy-utilization with higher-efficiency.
Nuclear medicine (NM) started in Qatar in the mid-1980s with a 1-head γ-camera in Hamad General Hospital. However, Qatar is expanding, and now Hamad Medical Corp. has 2 NM departments and 1 PET/CT ...Center for Diagnosis and Research, with several hybrid SPECT/CT and PET/CT cameras. Furthermore, 2 new NM departments will be established in Qatar in the coming 3 y. Therefore, there is a need to optimize radiation protection in NM imaging and establish diagnostic reference levels (DRLs) for the first time in Qatar. This need is not only for the NM part of the examination but also for the CT part, especially in hybrid SPECT/CT and PET/CT.
Data for adult patients were collected from the 3 SPECT/CT machines in the 2 NM facilities and from the 2 PET/CT machines in the PET/CT center. The 75th percentile values (also known as the third quartile) were considered preliminary DRLs and were consistent with the most commonly administered activities. The results for various general NM protocols were described, especially
Tc-based radiopharmaceuticals and PET/CT protocols including mainly oncologic applications.
The first DRLs for NM imaging in Qatar adults were established. The values agreed with other published DRLs, as was the case, for example, for PET oncology using
F-FDG, with DRLs of 258, 230, 370, 400, and 461-710 MBq for Qatar, Kuwait, Korea, the United Kingdom, and the United States, respectively. Similarly, for cardiac stress or rest myocardial perfusion imaging using
Tc-methoxyisobutylisonitrile, the DRLs were 926, 976, 1,110, 800, and 945-1,402 MBq for Qatar, Kuwait, Korea, the United Kingdom, and the United States, respectively.
The optimization of administered activity that this study will enable for NM procedures in Qatar will be of great value, especially for new departments that adhere to these DRLs.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a rapidly evolving RNA virus that mutates within hosts and exists as viral quasispecies. Here, we evaluated the within-host diversity ...among vaccinated and unvaccinated individuals (n = 379) infected with different SARS-CoV-2 Variants of Concern. The majority of samples harbored less than 14 intra-host single-nucleotide variants (iSNVs). A deep analysis revealed a significantly higher intra-host diversity in Omicron samples than in other variants (p value < 0.05). Vaccination status and type had a limited impact on intra-host diversity except for Beta-B.1.315 and Delta-B.1.617.2 vaccinees, who exhibited higher diversity than unvaccinated individuals (p values: <0.0001 and <0.0021, respectively). Three immune-escape mutations were identified: S255F in Delta and R346K and T376A in Omicron-B.1.1.529. The latter 2 mutations were fixed in BA.1 and BA.2 genomes, respectively. Overall, the relatively higher intra-host diversity among vaccinated individuals and the detection of immune-escape mutations, despite being rare, suggest a potential vaccine-induced immune pressure in vaccinated individuals.
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•Higher within-host diversity among omicron-positive samples•Higher within-host diversity among vaccinated individuals regardless of virus lineage•Limited impact of vaccine type on within-host diversity of SARS-CoV-2
Immunology; Immune response; Virology; Genomics
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