Search

With reference to speed controlled induction motor drives, an algorithm which allows the on-line estimation either of the speed and one motor parameter or, alternatively, of two motor parameters, is presented in the paper. The results obtained by simulation fully confirm the validity of the proposed algorithm. At last, the problems arising from the implementation of the proposed algorithm on a DSP-based control hardware are analysed. Keywords: induction motor drives, velocity control.

In this paper, a torque control algorithm of a Permanent Magnet Synchronous Generator (PMSG) for Direct Drive Wind Turbines (DDWTs) is proposed. In particular, a twelve- phase PMSG with four independent three-phase output subsystems has been considered with the aim of improving the DDWT torque management, energy efficiency, power generation and reliability; these goals are achieved by means of the decoupled control of each three-phase subsystem which the generator is split in. Hence, a novel coordinate transformation and the synthesis of the proposed master control algorithm are introduced: this last one allows the independent management of the reference currents of each subsystem and, thus, permits the development of an efficient variable speed wind turbine control. In addition, using the proposed DDWT, a novel topology of Continuous Medium Voltage Distribution system (CMVD) for a wind power plant is presented. In particular, the DC subsystems power outputs are connected by means the proposed CMVD to a centralized cascaded H-Bridge inverter structure, which is the only interface between the electric power transmission network and the wind power plant. The goodness of the proposed control algorithm is verified by means of a simulation study carried out in the Matlab Simulink environment, whose results are presented in the paper. [ABSTRACT FROM AUTHOR]

In this paper, a predictive Direct Torque Control (DTC) of an Induction Motor (IM) drive is presented. Although the control uses stator flux and current vectors as state variables, a novel set of variables have been introduced in order to directly manage torque, stator flux and current magnitude variations in each sampling time interval. Then, the existence domain of the above mentioned variables in each sampling time interval is determined and depicted graphically, together with the inverter voltage saturation and current limitation constraints. As a result, the proposed predictive control algorithm allows a better tracking of the IM reference torque profile than that achievable by means of the traditional DTC technique, especially in terms of current and torque ripple. The effectiveness of the proposed predictive DTC algorithm is verified by simulating an IM drive by means of the Matlab Simulink tool. The simulation results, which also refer to the case of the traditional constant switching frequency DTC, highlight the good performance of the drive, especially referring to torque ripple and to low speed operation. [ABSTRACT FROM AUTHOR]

An EMI modelling of heat sinks employed in Switching Mode Power Supplies (SMPSs) is presented in this paper. In fact, the capacitive coupling between electronic power devices and their heat sinks generally lead to impulsive current circulation in the latter, making them able to generate conducted electromagnetic noise and/or to emit as antennas. Such electromagnetic noise may give rise to the incorrect electronic circuits and control system operations. Hence, the proposed heat sinks model is developed in order to evaluate these effects, aiming to be an useful tool in order to avoid system faults and to guarantee the compliance to EMC standards. In particular, the proposed model allows the achievement of the resonance frequency of a heat sink in a closed analytical form. The results obtained by employing the proposed modelling procedure is properly compared with those achieved by means of finite element investigations, highlighting the effectiveness of the proposed method. This is also corroborated by the experimental studies carried out in an EMC laboratory. [ABSTRACT FROM AUTHOR]

The paper deals with a high performance single-stage three phase inverter for grid connected PV systems. In the paper a current control algorithm is developed so that the proposed configuration can convert the solar dc power into high quality ac power while tracking the maximum power from the PV array, ensuring active and reactive power flow control, higher efficiency, low cost and compact size. Moreover total harmonic distortion of the current fed into the grid is very low with respect to the IEEE standard. In the paper a full analysis of the proposed system is presented and numerical results for different reference values of active and reactive power have been shown and discussed. [ABSTRACT FROM AUTHOR]

A predictive control of a brushless DC generator is presented in this paper. The tracking characteristic of the prime-mover is considered for setting the reference value of the electromagnetic torque developed by the generator. This reference is assumed in order to determine the switching pattern of the AC/DC converter, at each sampling period, under minimum Joule losses and minimum torque ripple constraints. In order to highlight the improved performances achievable by means of the proposed predictive control algorithm, two cases are considered: in the first one, the generator supplies a resistive load as in standalone applications, whereas, in the second one, it is connected to a constant voltage DC grid. Hence, the respective conversion systems are computer simulated in the Matlab Simulink environment and the results are compared to those of the traditional systems. The comparison reveals that, in both cases, the torque ripple minimization is achieved and more power can be delivered by using the proposed control technique with respect to those of traditional systems. [ABSTRACT FROM AUTHOR]

In the paper an interleaved soft switching dc-dc converter for applications in electric vehicle is proposed. The used topology raises the efficiency and the power density of the dc/dc converter minimizing switching losses by adopting a simple auxiliary active clamping circuit. Such auxiliary circuit is operational regardless of boost or buck mode of operation. The configuration guarantees fixed switching frequency, active clamped zero voltage switching operations of the main switches and bidirectional power flow. ZVS operations are guaranteed with wide load range. In the paper the operating principle, soft-switching conditions and steady state analysis are presented. A 27 kW prototype is designed and simulation results to verify the theoretical analysis are provided. [ABSTRACT FROM AUTHOR]

In the paper two control techniques are compared respect to the traditional field oriented approach (F.O.), in order to define the range of applicability of each one. Targets of the different controls are to achieve a vector control and to generate firing commands for the quasi resonant inverter (QRI), that guarantee soft switching of the inverter switch, improving the dynamic response of the whole system. These targets will be obtained by means of a state feedback approach. [ABSTRACT FROM AUTHOR]

A novel modulation technique suitable for the current control of brushless DC drives under commutation is presented in the paper. The pulse width of the chain voltages are determined by means of a predictive algorithm under the constraints of minimum Joule losses and torque ripple free commutation. At maximum speed the torque ripple appears but is lower than that of six step operation. The proposed technique leads also to higher mean torque than that of traditional six step operation. Simulation results highlight the better performance of the drive controlled by the propose algorithm with respect to that of the traditionally controlled drive. [ABSTRACT FROM AUTHOR]

Background: Assessment of regional ventilation/perfusion (V'/Q) mismatch using electrical impedance tomography (EIT) represents a promising advancement for personalized management of the acute respiratory distress syndrome (ARDS). However, accuracy is still hindered by the need for invasive monitoring to calibrate ventilation and perfusion. Here, we propose a non-invasive correction that uses only EIT data and characterized patients with more pronounced compensation of V'/Q mismatch., Methods: We enrolled twenty-one ARDS patients on controlled mechanical ventilation. Cardiac output was measured invasively, and ventilation and perfusion were assessed by EIT. Relative V'/Q maps by EIT were calibrated to absolute values using the minute ventilation to invasive cardiac output (MV/CO) ratio (V'/Q-ABS), left unadjusted (V'/Q-REL), or corrected by MV/CO ratio derived from EIT data (V'/Q-CORR). The ratio between ventilation to dependent regions and perfusion reaching shunted units ( V D ' /Q SHUNT ) was calculated as an index of more effective hypoxic pulmonary vasoconstriction. The ratio between perfusion to non-dependent regions and ventilation to dead space units (Q ND / V DS ' ) was calculated as an index of hypocapnic pneumoconstriction., Results: Our calibration factor correlated with invasive MV/CO (r = 0.65, p < 0.001), showed good accuracy and no apparent bias. Compared to V'/Q-ABS, V'/Q-REL maps overestimated ventilation (p = 0.013) and perfusion (p = 0.002) to low V'/Q units and underestimated ventilation (p = 0.011) and perfusion (p = 0.008) to high V'/Q units. The heterogeneity of ventilation and perfusion reaching different V'/Q compartments was underestimated. V'/Q-CORR maps eliminated all these differences with V'/Q-ABS (p > 0.05). Higher V D ' / Q SHUNT correlated with higher PaO 2 /FiO 2 (r = 0.49, p = 0.025) and lower shunt fraction (ρ =  - 0.59, p = 0.005). Higher Q ND / V DS ' correlated with lower PEEP (ρ =  - 0.62, p = 0.003) and plateau pressure (ρ =  - 0.59, p = 0.005). Lower values of both indexes were associated with less ventilator-free days (p = 0.05 and p = 0.03, respectively)., Conclusions: Regional V'/Q maps calibrated with a non-invasive EIT-only method closely approximate the ones obtained with invasive monitoring. Higher efficiency of shunt compensation improves oxygenation while compensation of dead space is less needed at lower airway pressure. Patients with more effective compensation mechanisms could have better outcomes., (© 2024. The Author(s).)

Patient self-inflicted lung injury (P-SILI) is a major challenge for the ICU physician: although spontaneous breathing is associated with physiological benefits, in patients with acute respiratory distress syndrome (ARDS), the risk of uncontrolled inspiratory effort leading to additional injury needs to be assessed to avoid delayed intubation and increased mortality. In the present review, we analyze the available clinical and experimental evidence supporting the existence of lung injury caused by uncontrolled high inspiratory effort, we discuss the pathophysiological mechanisms by which increased effort causes P-SILI, and, finally, we consider the measurements and interpretation of bedside physiological measures of increased drive that should alert the clinician. The data presented in this review could help to recognize injurious respiratory patterns that may trigger P-SILI and to prevent it.

Purpose: In the acute respiratory distress syndrome (ARDS), decreasing Ventilation-Perfusion [Formula: see text] mismatch might enhance lung protection. We investigated the regional effects of higher Positive End Expiratory Pressure (PEEP) on [Formula: see text] mismatch and their correlation with recruitability. We aimed to verify whether PEEP improves regional [Formula: see text] mismatch, and to study the underlying mechanisms., Methods: In fifteen patients with moderate and severe ARDS, two PEEP levels (5 and 15 cmH 2 O) were applied in random order. [Formula: see text] mismatch was assessed by Electrical Impedance Tomography at each PEEP. Percentage of ventilation and perfusion reaching different ranges of [Formula: see text] ratios were analyzed in 3 gravitational lung regions, leading to precise assessment of their distribution throughout different [Formula: see text] mismatch compartments. Recruitability between the two PEEP levels was measured by the recruitment-to-inflation ratio method., Results: In the non-dependent region, at higher PEEP, ventilation reaching the normal [Formula: see text] compartment (p = 0.018) increased, while it decreased in the high [Formula: see text] one (p = 0.023). In the middle region, at PEEP 15 cmH 2 O, ventilation and perfusion to the low [Formula: see text] compartment decreased (p = 0.006 and p = 0.011) and perfusion to normal [Formula: see text] increased (p = 0.003). In the dependent lung, the percentage of blood flowing through the non-ventilated compartment decreased (p = 0.041). Regional [Formula: see text] mismatch improvement was correlated to lung recruitability and changes in regional tidal volume., Conclusions: In patients with ARDS, higher PEEP optimizes the distribution of both ventilation (in the non-dependent areas) and perfusion (in the middle and dependent lung). Bedside measure of recruitability is associated with improved [Formula: see text] mismatch., (© 2022. The Author(s).)

Rationale: Unilateral ligation of the pulmonary artery may induce lung injury through multiple mechanisms, which might be dampened by inhaled CO 2 . Objectives: This study aims to characterize bilateral lung injury owing to unilateral ligation of the pulmonary artery in healthy swine undergoing controlled mechanical ventilation and its prevention by 5% CO 2 inhalation and to investigate relevant pathophysiological mechanisms. Methods: Sixteen healthy pigs were allocated to surgical ligation of the left pulmonary artery (ligation group), seven to surgical ligation of the left pulmonary artery and inhalation of 5% CO 2 (ligation + Fi CO 2 5%), and six to no intervention (no ligation). Then, all animals received mechanical ventilation with Vt 10 ml/kg, positive end-expiratory pressure 5 cm H 2 O, respiratory rate 25 breaths/min, and Fi O 2 50% (±Fi CO 2 5%) for 48 hours or until development of severe lung injury. Measurements and Main Results: Histological, physiological, and quantitative computed tomography scan data were compared between groups to characterize lung injury. Electrical impedance tomography and immunohistochemistry analysis were performed in a subset of animals to explore mechanisms of injury. Animals from the ligation group developed bilateral lung injury as assessed by significantly higher histological score, larger increase in lung weight, poorer oxygenation, and worse respiratory mechanics compared with the ligation + Fi CO 2 5% group. In the ligation group, the right lung received a larger fraction of Vt and inflammation was more represented, whereas CO 2 dampened both processes. Conclusions: Mechanical ventilation induces bilateral lung injury within 48 hours in healthy pigs undergoing left pulmonary artery ligation. Inhalation of 5% CO 2 prevents injury, likely through decreased stress to the right lung and antiinflammatory effects.

Background: In acute respiratory distress syndrome (ARDS), non-ventilated perfused regions coexist with non-perfused ventilated regions within lungs. The number of unmatched regions might reflect ARDS severity and affect the risk of ventilation-induced lung injury. Despite pathophysiological relevance, unmatched ventilation and perfusion are not routinely assessed at the bedside. The aims of this study were to quantify unmatched ventilation and perfusion at the bedside by electrical impedance tomography (EIT) investigating their association with mortality in patients with ARDS and to explore the effects of positive end-expiratory pressure (PEEP) on unmatched ventilation and perfusion in subgroups of patients with different ARDS severity based on PaO 2 /FiO 2 and compliance., Methods: Prospective observational study in 50 patients with mild (36%), moderate (46%), and severe (18%) ARDS under clinical ventilation settings. EIT was applied to measure the regional distribution of ventilation and perfusion using central venous bolus of saline 5% during end-inspiratory pause. We defined unmatched units as the percentage of only ventilated units plus the percentage of only perfused units., Results: Percentage of unmatched units was significantly higher in non-survivors compared to survivors (32[27-47]% vs. 21[17-27]%, p < 0.001). Percentage of unmatched units was an independent predictor of mortality (OR 1.22, 95% CI 1.07-1.39, p = 0.004) with an area under the ROC curve of 0.88 (95% CI 0.79-0.97, p < 0.001). The percentage of ventilation to the ventral region of the lung was higher than the percentage of ventilation to the dorsal region (32 [27-38]% vs. 18 [13-21]%, p < 0.001), while the opposite was true for perfusion (28 [22-38]% vs. 36 [32-44]%, p < 0.001). Higher percentage of only perfused units was correlated with lower dorsal ventilation (r =  - 0.486, p < 0.001) and with lower PaO 2 /FiO 2 ratio (r =  - 0.293, p = 0.039)., Conclusions: EIT allows bedside assessment of unmatched ventilation and perfusion in mechanically ventilated patients with ARDS. Measurement of unmatched units could identify patients at higher risk of death and could guide personalized treatment.

Rationale: Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs. Objectives: We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO. Methods: Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmH 2 O, Vt 10 ml/kg, I:E = 1:2, FiO 2 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO 2 . Measurements and Main Results: At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions ( p = 0.009 and p = 0.018). Intrapulmonary shunt increased ( p < 0.001) and arterial PaO 2 decreased ( p < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow ( r = 0.555, p = 0.011). Conclusions: Progressive decrease of respiratory rate coupled with increasing CO 2 removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation., Competing Interests: TM received personal fees from Fisher & Paykel, Drager, Mindray, and BBraun outside of the present work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Spinelli, Colussi, Dal Santo, Scotti, Marongiu, Garbelli, Mazzucco, Dondossola, Maia, Battistin, Biancolilli, Rosso, Gatti and Mauri.)

Background: Nasal high flow delivered at flow rates higher than 60 L/min in patients with acute hypoxemic respiratory failure might be associated with improved physiological effects. However, poor comfort might limit feasibility of its clinical use., Methods: We performed a prospective randomized cross-over physiological study on 12 ICU patients with acute hypoxemic respiratory failure. Patients underwent three steps at the following gas flow: 0.5 L/kg PBW/min, 1 L/kg PBW/min, and 1.5 L/kg PBW/min in random order for 20 min. Temperature and FiO 2 remained unchanged. Toward the end of each phase, we collected arterial blood gases, lung volumes, and regional distribution of ventilation assessed by electrical impedance tomography (EIT), and comfort., Results: In five patients, the etiology was pulmonary; infective disease characterized seven patients; median PaO 2 /FiO 2 at enrollment was 213 [IQR 136-232]. The range of flow rate during NHF 1.5 was 75-120 L/min. PaO 2 /FiO 2 increased with flow, albeit non significantly (p = 0.064), PaCO 2 and arterial pH remained stable (p = 0.108 and p = 0.105). Respiratory rate decreased at higher flow rates (p = 0.014). Inhomogeneity of ventilation decreased significantly at higher flows (p = 0.004) and lung volume at end-expiration significantly increased (p = 0.007), but mostly in the non-dependent regions. Comfort was significantly poorer during the step performed at the highest flow (p < 0.001)., Conclusions: NHF delivered at rates higher than 60 L/min in critically ill patients with acute hypoxemic respiratory failure is associated with reduced respiratory rate, increased lung homogeneity, and additional positive pressure effect, but also with worse comfort.

There is increasing recognition that traumatic brain injury (TBI) may initiate long-term neurodegenerative processes, particularly chronic traumatic encephalopathy. However, insight into the mechanisms transforming an initial biomechanical injury into a neurodegenerative process remain elusive, partly as a consequence of the paucity of informative pre-clinical models. This study shows the functional, whole brain imaging and neuropathological consequences at up to one year survival from single severe TBI by controlled cortical impact in mice. TBI mice displayed persistent sensorimotor and cognitive deficits. Longitudinal T2 weighted magnetic resonance imaging (MRI) showed progressive ipsilateral (il) cortical, hippocampal and striatal volume loss, with diffusion tensor imaging demonstrating decreased fractional anisotropy (FA) at up to one year in the il-corpus callosum (CC: -30%) and external capsule (EC: -21%). Parallel neuropathological studies indicated reduction in neuronal density, with evidence of microgliosis and astrogliosis in the il-cortex, with further evidence of microgliosis and astrogliosis in the il-thalamus. One year after TBI there was also a decrease in FA in the contralateral (cl) CC (-17%) and EC (-13%), corresponding to histopathological evidence of white matter loss (cl-CC: -68%; cl-EC: -30%) associated with ongoing microgliosis and astrogliosis. These findings indicate that a single severe TBI induces bilateral, long-term and progressive neuropathology at up to one year after injury. These observations support this model as a suitable platform for exploring the mechanistic link between acute brain injury and late and persistent neurodegeneration., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: The efficacy of epidural spinal cord stimulation on chronic neuropathic pain due to failed back surgery syndrome or nerve root lesions is well reported. There is even literature reporting the effects of spinal cord stimulation in controlling peripheral vascular lesions as in peripheral arteriopathies or diabetic neuropathies and in complex regional pain syndrome type II. This is probably due to an effect of epidural spinal cord stimulation, mainly on the parasympathetic nervous system., Case Description: A 14- year-old boy affected, since birth, by a quickly growing widespread lymphangioma at the pelvis and right thigh, underwent repetitive surgical procedures to try to reduce its extension. Recurrence always occurred. Due to a massive swelling of his right lower limb and a wide painful area all over the pelvis and right lower limb, the patient lost his autonomy and was almost bedridden or wheelchaired. On January 2015 the patient underwent the implant of a low dorsal epidural 8-lead magnetic resonance imaging (MRI)-compatible electrode connected to an MRI-compatible stimulator. The patient, 1 month after the implantation, had a complete recover of his autonomy, with a marked shrinkage of his right lower limb and a near disappearance of pain. He resumed the activity of the daily living. One year later, a hip MRI showed partial reduction of the lesion. The patient is still nearly free from pain., Conclusions: This is the first case report of severe chronic pain syndrome due to a widespread lymphangioma successfully treated by means of epidural spinal cord stimulation., (Copyright © 2016 Elsevier Inc. All rights reserved.)