Improved cascade control structure for enhanced performance

In conventional single feedback control, the corrective action for disturbances does not begin until the controlled variable deviates from the set point. In this case, a cascade control strategy can be used to improve the performance of a control system particularly in the presence of disturbances. In this paper, an improved cascade control structure and controller design based on standard forms, which was initially given by authors, is suggested to improve the performance of cascade control. Examples are given to illustrate the use of the proposed method and its superiority over some existing design methods

PI CONTROLLER DESIGN FOR TIME DELAY SYSTEMS USING DIFFERENT MODEL ORDER REDUCTION METHODS

This study focuses on designing PI controllers for time-delay systems using various model order reduction techniques to reduce complexity. The stability boundary locus method was used to determine PI parameters that stabilizing reduced order models. After the PI parameters have been determined using the weighted geometric center method, the calculated controller parameters have been implemented in the original system. In this way, the efficiency of the controller design is effectively demonstrated through the reduction techniques. In addition, the study investigated the effectiveness of reduction methods with increasing time delay and adding an integrator to the system. The importance of these results is that they demonstrate the use of model order reduction techniques in the design of controllers for time-delay systems and reveal the advantages of these methods

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Comparison of Adaptation Mechanisms on MRAC

Model reference adaptive control (MRAC) could be designed using different adaptation mechanisms. An adaptation mechanism could affect the Model Reference Adaptive System (MRAS) performance. High adaptive gain increases the transient response performance while decreasing the robustness of the MRAS even under perfect conditions (no time delay, without unmatched uncertainty and absence of disturbance) and increasing control signal oscillation in classical MRAC. Classical MRAS do not perform satisfactorily on such time-delayed adaptive signals. This study presents and compares two different adaptation mechanisms in MRAS, which are the low-frequency learning method on MRAC and MRAC with PI adjustment mechanism. We have proposed a modification to the low-frequency learning method on MRAC to get a transient response as good as MRAC with a PI adjustment mechanism on the time delay system. The best performance is obtained from MRAS with PI adaptation mechanism

Analysis of Output Voltage Harmonics of Voltage Source Inverter used PI and PID Controllers Optimized with ITAE Performance Criteria

In this article, PI and PID controllers are designed using ITAE (Integral Time Absolute Error) Performance Criteria in order to obtain the controller parameters assuring improved response at selected load. The voltage source inverter (VSI) including PI and PID controllers whose parameters are estimated by minimizing errors using ITAE performance criteria are modeled in MATLAB environment. The stability analysis of the control system will be presented. VSI controlled with the PI-ITAE and the PID-ITAE controller are simulated for various loads and the results are analyzed using FFT analysis for observing and comparing the total harmonic distortion (THD) of the output voltage. The quality of the sinusoidal waveform is more important than the quantity and in order to achieve that, we need to reduce the harmonic content in the output

Analysis of Output Voltage Harmonics of Voltage Source Inverter used PI and PID Controllers Optimized with ITAE Performance Criteria

In this article, PI and PID controllers are designed using ITAE (Integral Time Absolute Error) Performance Criteria in order to obtain the controller parameters assuring improved response at selected load. The voltage source inverter (VSI) including PI and PID controllers whose parameters are estimated by minimizing errors using ITAE performance criteria are modeled in MATLAB environment. The stability analysis of the control system will be presented. VSI controlled with the PI-ITAE and the PID-ITAE controller are simulated for various loads and the results are analyzed using FFT analysis for observing and comparing the total harmonic distortion (THD) of the output voltage. The quality of the sinusoidal waveform is more important than the quantity and in order to achieve that, we need to reduce the harmonic content in the output

Analysis of PFC and THD with the Boost Converter

Boost konvertörün diğer topolojilere üstünlüğünden dolayı bu çalışmada güç katsayısı düzeltme ve harmonik bozulmayı düşürmek için boost konvertör topolojisi kullanılmıştır. Tek fazlı ortalama akım mod kontrollü devre simülasyonu ve sonuçları MATLAB/Simulinkte yapılmış ve doğrulanmıştırIn this paper, the boost converter topology which has advantages over other converter topologies is used to correct power factor and to reduce total harmonic distortion. Single Phase average current mode controlled PFC circuit is simulated by MATLAB/Simulink simulation tool and simulation results are verified. The input current and output voltage simulation waveforms are illustrated and analyzed

Stability and Performance Analysis in an Uncertain World

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Some Results on Control Systems with Mixed Perturbations

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Stability Margin Computation for Nonlinear Systems: A Parametric Approach

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