1,721,140 research outputs found
Artificial Pancreas: In Silico Study Shows No Need of Meal Announcement and Improved Time in Range of Glucose with Intraperitoneal vs. Subcutaneous Insulin Delivery
Full text linkContemporary Artificial Pancreas (AP) consists of a subcutaneous (SC) glucose sensor, a SC insulin pump and a control algorithm. Even the most advanced systems are far from optimal, in particular due to the non-physiologic nature of SC route. While SC insulin delivery is convenient and minimally
invasive, it introduces delays to insulin action that make tight control difficult, particularly during meals. In addition frequent
patient interventions are needed, e.g., at mealtime. The intraperitoneal (IP) insulin delivery could address this major challenge since it exhibits a faster pharmacokinetics/pharmacodynamics, hence making easier to quickly respond to glycemic disturbances. A 1-day hospital closed-loop study has shown significant improvements of IP glucose control vs SC AP, and that meal announcement is not necessary. However, the IP AP has not been tested in more realistic everyday life conditions. In this work we have performed an in silico study of 14 days of an IP AP by using the UVA/Padova simulator which includes intra- and inter-day variability of insulin sensitivity and several real life scenarios. We show superiority of IP AP vs SC AP in terms of quality of glucose control (time in range 87% IP vs 80% SC) without the need of a meal announcement
A gain scheduling approach to improve pressure control in water distribution networks
No full textReal time pressure control is a common technique adopted to face the problem of leakage reduction in water distribution networks. Recently, in the context of Water 4.0, the spread of wired water distribution networks has opened new possibilities in terms of sensing and communication, resulting in the possibility of adopting higher sampling rates and consequently higher closed-loop bandwidths for the control system. While this could be exploited to improve the performance, it has also drawn the attention of the fundamental question of closed-loop stability, which was seldom considered in a systematic way, especially in the hydraulic community. This works aims to combine some recent results in term of design of frequency domain controllers with a gain scheduling approach, to account and compensate for the main nonlinearities affecting the system under control, and to preserve stability and robustness of the closed-loop in a wide operating region. The approach is validated by means of simulated experiments performed on a detailed dynamic model of the water distribution network. In addition, the gain scheduling approach can improve the overall performance of the control scheme and allows avoiding heavy retuning of the regulator when applied to the nonlinear system
The in situ approach to model identification and control design for pressure regulation in Water Distribution Networks: An in silico evaluation
No full textIn the context of Water Distribution Networks, service pressure regulation is an important technique that allows reductions in leakage, risk of pipe bursts and mechanical stress to the infrastructure. Recent works demonstrated in silico, i.e. numerically, that linear control systems can be effectively adopted for this task, provided that a careful tuning is performed. Specifically, the tuning should be based on high order, linear models, which describe the system dynamics around a nominal working point. These models can be straightforwardly derived in a simulated environment, but their in situ identification may be challenging due to the presence of non-measurable, exogenous disturbances. This work moves a step forward towards the application of service pressure regulation in situ, by proposing an effective model identification approach for the linear models, based on spectral analysis. The novel approach can cope with exogenous, non-measured disturbances acting during the identification experiments, and considers possible constraints limiting the experimental design. Moreover, the models identified in the in situ conditions are exploited to synthesise linear regulators and assess the closed-loop performances of the overall control methodology. Though being presented and tested in silico, this work assumes a strong practical relevance in view of the results achieved. It in fact demonstrates that novel control schemes, previously designed in nominal conditions only, can be actually designed and implemented in a real scenario, thus making pressure control safer, more reliable and more effective. Finally, the numerical analysis allows for a comparison of both identification and control results with to those obtained in nominal conditions, to provide further insight and stress the reliability of the proposed methodology
Sum-of-delay models for pressure control in Water Distribution Networks
No full textService pressure control is a powerful tool to reduce leakage and risk of pipe bursts in Water Distribution Networks (WDNs). However, to obtain good control performances, it is essential to rely on a good model of the plant. A typical approach consists of the identification of a linear, local model of the system around the desired working point. Previous works relied on black-box, high order models to demonstrate that WDNs are characterised by a very complex dynamic behaviour, which should be properly modelled to avoid stability issues resulting from poor regulator design. This work aims at providing a physical justification for such complex dynamic behaviour, by means of a particular grey-box model structure, with pure delays as its fundamental blocks. Moreover, this works demonstrates that the new model structure can be very effective and efficient in modelling the WDN dynamics. Finally, to proper exploit the new model, this work proposes a bi-objective optimisation based procedure for the regulator design. The potentialities of both model identification and regulator design phases are assessed by means of simulated experiments performed on a detailed unsteady flow model of three different WDNs
Stability and Robustness of Real-Time Pressure Control in Water Distribution Systems
No full textThis paper deals with the fundamental requirement of stability of real-time control algorithms for water distribution systems. Loss of stability may in fact generate strong pressure waves that cause damages to the structure and increase leakage and maintenance costs. In addition, since the system under control is characterized by complex, nonlinear dynamic behavior, it is very important to guarantee that stability is preserved even when the water distribution system is working very far from its nominal working point. The aim of this work is therefore to apply tools and methodologies of control system theory to analyze both nominal and robust stability of real-time control algorithms in a case study framework. This allows quantitative understanding of the cause of possible instability of the control scheme and suggests how to prevent it. Finally, this work proposes a possible way to improve the design of the control algorithms under investigation, to reduce the risk of instability events, and, at the same time, reduce the cost of control
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bi-objective optimisation based tuning of pressure control algorithms for water distribution networks
No full textWith the application to water industry of the Industry 4.0 approach (i.e. the Water 4.0 approach), Real Time Control is gaining attention as a strategic tool for the management of Water Distribution Networks. Moreover, this approach favours the installation of a wired communication infrastructure, which guarantees new standards in communication between sensors, actuators and control units. This work focuses on the particular task of service pressure regulation, obtained by means of a closed-loop control based on Pressure Control Valves and frequency domain control algorithms. While the topics of the identification of proper control structures, and the analysis of their stability and robustness properties were covered in previous works, this paper is aimed at improving the design phase of such algorithms by formulating the regulator tuning problem as a bi-objective optimisation one. Its solution leads to a Pareto front that captures the typical design trade-off between regulation performances and control effort and robustness, and helps the designer selecting the favoured tunings to be tested on the plant. Simulations performed on a detailed model of two different WDNs highlight the benefits of the approach and the reliability of the obtained tunings
Neural Network Implementation of Nonlinear Receding Horizon Control of Nonlinear Discrete-Time Systems
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